Merge pull request #1 from dan200/master

update 7/8

LICENSE

@@ -36,7 +36,7 @@ This mod is provided 'as is' with no warranties, implied or otherwise. The owner
 of this mod takes no responsibility for any damages incurred from the use of
 this mod. This mod alters fundamental parts of the Minecraft game, parts of
 Minecraft may not work with this mod installed. All damages caused from the use
-or misuse of this mad fall on the user.
+or misuse of this mod fall on the user.
 
 3. Play rights
 --------------

build.gradle

@@ -31,7 +31,7 @@ minecraft {
     version = "1.9.4-12.17.0.1959"
     runDir = "run"
     replace '${version}', project.version
-    
+
     // the mappings can be changed at any time, and must be in the following format.
     // snapshot_YYYYMMDD   snapshot are built nightly.
     // stable_#            stables are built at the discretion of the MCP team.
@@ -46,7 +46,7 @@ dependencies {
     // or you may define them like so..
     //compile "some.group:artifact:version:classifier"
     //compile "some.group:artifact:version"
-      
+
     // real examples
     //compile 'com.mod-buildcraft:buildcraft:6.0.8:dev'  // adds buildcraft to the dev env
     //compile 'com.googlecode.efficient-java-matrix-library:ejml:0.24' // adds ejml to the dev env
@@ -78,23 +78,25 @@ processResources {
     inputs.property "mcversion", project.minecraft.version
 
     def grgit = Grgit.open(dir: '.')
-    inputs.property "commithash", grgit.log(maxCommits: 1)[0].id
+    inputs.property "commithash", grgit.head().id
 
     def blacklist = ['GitHub', 'dan200', 'Daniel Ratcliffe']
     Set<String> contributors = []
-    
+
     grgit.log().each {
-        if (!blacklist.contains(it.committer.name))
-            contributors.add(it.committer.name)
+        if (!blacklist.contains(it.author.name)) contributors.add(it.author.name)
+        if (!blacklist.contains(it.committer.name)) contributors.add(it.committer.name)
     }
 
     from(sourceSets.main.resources.srcDirs) {
         include 'mcmod.info'
         include 'assets/computercraft/lua/rom/help/credits.txt'
 
-        expand 'version':project.version, 'mcversion':project.minecraft.version, 'gitcontributors':contributors.sort().join('\n')
-    }        
-    
+        expand 'version':project.version,
+               'mcversion':project.minecraft.version,
+               'gitcontributors':contributors.sort(false, String.CASE_INSENSITIVE_ORDER).join('\n')
+    }
+
     from(sourceSets.main.resources.srcDirs) {
         exclude 'mcmod.info'
         exclude 'assets/computercraft/lua/rom/help/credits.txt'

src/main/java/dan200/computercraft/ComputerCraft.java

@@ -18,6 +18,7 @@ import dan200.computercraft.api.permissions.ITurtlePermissionProvider;
 import dan200.computercraft.api.pocket.IPocketUpgrade;
 import dan200.computercraft.api.redstone.IBundledRedstoneProvider;
 import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.core.apis.AddressPredicate;
 import dan200.computercraft.core.filesystem.ComboMount;
 import dan200.computercraft.core.filesystem.FileMount;
 import dan200.computercraft.core.filesystem.JarMount;
@@ -60,6 +61,7 @@ import net.minecraft.util.EnumHand;
 import net.minecraft.util.SoundEvent;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
+import net.minecraftforge.common.config.ConfigCategory;
 import net.minecraftforge.common.config.Configuration;
 import net.minecraftforge.common.config.Property;
 import net.minecraftforge.fml.common.FMLCommonHandler;
@@ -105,8 +107,18 @@ public class ComputerCraft
     public static final int pocketComputerGUIID = 106;
 
     // Configuration options
+    private static final String[] DEFAULT_HTTP_WHITELIST = new String[] { "*" };
+    private static final String[] DEFAULT_HTTP_BLACKLIST = new String[] {
+        "127.0.0.0/8",
+        "10.0.0.0/8",
+        "172.16.0.0/12",
+        "192.168.0.0/16",
+        "fd00::/8",
+    };
+    
     public static boolean http_enable = true;
-    public static String http_whitelist = "*";
+    public static AddressPredicate http_whitelist = new AddressPredicate( DEFAULT_HTTP_WHITELIST );
+    public static AddressPredicate http_blacklist = new AddressPredicate( DEFAULT_HTTP_BLACKLIST );
     public static boolean disable_lua51_features = false;
     public static String default_computer_settings = "";
     public static boolean logPeripheralErrors = false;
@@ -185,6 +197,7 @@ public class ComputerCraft
 
         public static Property http_enable;
         public static Property http_whitelist;
+        public static Property http_blacklist;
         public static Property disable_lua51_features;
         public static Property default_computer_settings;
         public static Property logPeripheralErrors;
@@ -252,10 +265,28 @@ public class ComputerCraft
         Config.config.load();
 
         Config.http_enable = Config.config.get( Configuration.CATEGORY_GENERAL, "http_enable", http_enable );
-        Config.http_enable.setComment( "Enable the \"http\" API on Computers (see \"http_whitelist\" for more fine grained control than this)" );
+        Config.http_enable.setComment( "Enable the \"http\" API on Computers (see \"http_whitelist\" and \"http_blacklist\" for more fine grained control than this)" );
 
-        Config.http_whitelist = Config.config.get( Configuration.CATEGORY_GENERAL, "http_whitelist", http_whitelist );
-        Config.http_whitelist.setComment( "A semicolon limited list of wildcards for domains that can be accessed through the \"http\" API on Computers. Set this to \"*\" to access to the entire internet. Example: \"*.pastebin.com;*.github.com;*.computercraft.info\" will restrict access to just those 3 domains." );
+        {
+            ConfigCategory category = Config.config.getCategory( Configuration.CATEGORY_GENERAL );
+            Property currentProperty = category.get( "http_whitelist" );
+            if( currentProperty != null && !currentProperty.isList() ) category.remove( "http_whitelist" );
+
+            Config.http_whitelist = Config.config.get( Configuration.CATEGORY_GENERAL, "http_whitelist", DEFAULT_HTTP_WHITELIST );
+
+            if( currentProperty != null && !currentProperty.isList() )
+            {
+                Config.http_whitelist.setValues( currentProperty.getString().split( ";" ) );
+            }
+        }
+        Config.http_whitelist.setComment( "A list of wildcards for domains or IP ranges that can be accessed through the \"http\" API on Computers.\n" +
+            "Set this to \"*\" to access to the entire internet. Example: \"*.pastebin.com\" will restrict access to just subdomains of pastebin.com.\n" +
+            "You can use domain names (\"pastebin.com\"), wilcards (\"*.pastebin.com\") or CIDR notation (\"127.0.0.0/8\")." );
+
+        Config.http_blacklist = Config.config.get( Configuration.CATEGORY_GENERAL, "http_blacklist", DEFAULT_HTTP_BLACKLIST );
+        Config.http_blacklist.setComment( "A list of wildcards for domains or IP ranges that cannot be accessed through the \"http\" API on Computers.\n" +
+            "If this is empty then all whitelisted domains will be accessible. Example: \"*.github.com\" will block access to all subdomains of github.com.\n" +
+            "You can use domain names (\"pastebin.com\"), wilcards (\"*.pastebin.com\") or CIDR notation (\"127.0.0.0/8\")." );
 
         Config.disable_lua51_features = Config.config.get( Configuration.CATEGORY_GENERAL, "disable_lua51_features", disable_lua51_features );
         Config.disable_lua51_features.setComment( "Set this to true to disable Lua 5.1 functions that will be removed in a future update. Useful for ensuring forward compatibility of your programs now." );
@@ -327,7 +358,8 @@ public class ComputerCraft
     public static void syncConfig() {
 
         http_enable = Config.http_enable.getBoolean();
-        http_whitelist = Config.http_whitelist.getString();
+        http_whitelist = new AddressPredicate( Config.http_whitelist.getStringList() );
+        http_blacklist = new AddressPredicate( Config.http_blacklist.getStringList() );
         disable_lua51_features = Config.disable_lua51_features.getBoolean();
         default_computer_settings = Config.default_computer_settings.getString();
 

src/main/java/dan200/computercraft/core/apis/AddressPredicate.java

@@ -0,0 +1,168 @@
+package dan200.computercraft.core.apis;
+
+import com.google.common.net.InetAddresses;
+import dan200.computercraft.ComputerCraft;
+
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Pattern;
+
+/**
+ * Used to determine whether a domain or IP address matches a series of patterns.
+ */
+public class AddressPredicate
+{
+    private static class HostRange
+    {
+        private final byte[] min;
+        private final byte[] max;
+
+        private HostRange( byte[] min, byte[] max )
+        {
+            this.min = min;
+            this.max = max;
+        }
+
+        public boolean contains( InetAddress address )
+        {
+            byte[] entry = address.getAddress();
+            if( entry.length != min.length ) return false;
+
+            for( int i = 0; i < entry.length; i++ )
+            {
+                int value = 0xFF & entry[ i ];
+                if( value < (0xFF & min[ i ]) || value > (0xFF & max[ i ]) ) return false;
+            }
+
+            return true;
+        }
+    }
+
+    private final List<Pattern> wildcards;
+    private final List<HostRange> ranges;
+
+    public AddressPredicate( String... filters )
+    {
+        List<Pattern> wildcards = this.wildcards = new ArrayList<Pattern>();
+        List<HostRange> ranges = this.ranges = new ArrayList<HostRange>();
+
+        for( String filter : filters )
+        {
+            int cidr = filter.indexOf( '/' );
+            if( cidr >= 0 )
+            {
+                String addressStr = filter.substring( 0, cidr );
+                String prefixSizeStr = filter.substring( cidr + 1 );
+
+                int prefixSize;
+                try
+                {
+                    prefixSize = Integer.parseInt( prefixSizeStr );
+                }
+                catch( NumberFormatException e )
+                {
+                    ComputerCraft.log.warn( "Cannot parse CIDR size from {} ({})", filter, prefixSizeStr );
+                    continue;
+                }
+
+                InetAddress address;
+                try
+                {
+                    address = InetAddresses.forString( addressStr );
+                }
+                catch( IllegalArgumentException e )
+                {
+                    ComputerCraft.log.warn( "Cannot parse IP address from {} ({})", filter, addressStr );
+                    continue;
+                }
+
+                // Mask the bytes of the IP address.
+                byte[] minBytes = address.getAddress(), maxBytes = address.getAddress();
+                int size = prefixSize;
+                for( int i = 0; i < minBytes.length; i++ )
+                {
+                    if( size <= 0 )
+                    {
+                        minBytes[ i ] &= 0;
+                        maxBytes[ i ] |= 0xFF;
+                    }
+                    else if( size < 8 )
+                    {
+                        minBytes[ i ] &= 0xFF << (8 - size);
+                        maxBytes[ i ] |= ~(0xFF << (8 - size));
+                    }
+
+                    size -= 8;
+                }
+
+                ranges.add( new HostRange( minBytes, maxBytes ) );
+            }
+            else
+            {
+                wildcards.add( Pattern.compile( "^\\Q" + filter.replaceAll( "\\*", "\\\\E.*\\\\Q" ) + "\\E$" ) );
+            }
+        }
+    }
+
+    /**
+     * Determine whether a host name matches a series of patterns.
+     *
+     * This is intended to allow early exiting, before one has to look up the IP address. You should use
+     * {@link #matches(InetAddress)} instead of/in addition to this one.
+     *
+     * @param domain The domain to match.
+     * @return Whether the patterns were matched.
+     */
+    public boolean matches( String domain )
+    {
+        for( Pattern domainPattern : wildcards )
+        {
+            if( domainPattern.matcher( domain ).matches() ) return true;
+        }
+
+        return false;
+    }
+
+    private boolean matchesAddress( InetAddress address )
+    {
+        String addressString = address.getHostAddress();
+        for( Pattern domainPattern : wildcards )
+        {
+            if( domainPattern.matcher( addressString ).matches() ) return true;
+        }
+
+        for( HostRange range : ranges )
+        {
+            if( range.contains( address ) ) return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Determine whether the given address matches a series of patterns
+     *
+     * @param address The address to check.
+     * @return Whether it matches any of these patterns.
+     */
+    public boolean matches( InetAddress address )
+    {
+        // Match the host name
+        String host = address.getHostName();
+        if( host != null && matches( host ) ) return true;
+
+        // Match the normal address
+        if( matchesAddress( address ) ) return true;
+
+        // If we're an IPv4 address in disguise then let's check that.
+        if( address instanceof Inet6Address && InetAddresses.is6to4Address( (Inet6Address) address )
+            && matchesAddress( InetAddresses.get6to4IPv4Address( (Inet6Address) address ) ) )
+        {
+            return true;
+        }
+
+        return false;
+    }
+}

src/main/java/dan200/computercraft/core/apis/ArgumentHelper.java

@@ -0,0 +1,246 @@
+package dan200.computercraft.core.apis;
+
+import dan200.computercraft.api.lua.LuaException;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.Map;
+
+/**
+ * Various helpers for arguments
+ */
+public final class ArgumentHelper
+{
+    private ArgumentHelper()
+    {
+        throw new IllegalStateException( "Cannot instantiate singleton " + getClass().getName() );
+    }
+
+    @Nonnull
+    public static String getType( @Nullable Object type )
+    {
+        if( type == null ) return "nil";
+        if( type instanceof String ) return "string";
+        if( type instanceof Boolean ) return "boolean";
+        if( type instanceof Number ) return "number";
+        if( type instanceof Map ) return "table";
+
+        Class<?> klass = type.getClass();
+        if( klass.isArray() )
+        {
+            StringBuilder name = new StringBuilder();
+            while( klass.isArray() )
+            {
+                name.append( "[]" );
+                klass = klass.getComponentType();
+            }
+            name.insert( 0, klass.getName() );
+            return name.toString();
+        }
+        else
+        {
+            return klass.getName();
+        }
+    }
+
+    @Nonnull
+    public static LuaException badArgument( int index, @Nonnull String expected, @Nullable Object actual )
+    {
+        return badArgument( index, expected, getType( actual ) );
+    }
+
+    @Nonnull
+    public static LuaException badArgument( int index, @Nonnull String expected, @Nonnull String actual )
+    {
+        return new LuaException( "bad argument #" + (index + 1) + " (" + expected + " expected, got " + actual + ")" );
+    }
+
+    public static double getNumber( @Nonnull Object[] args, int index ) throws LuaException
+    {
+        if( index >= args.length ) throw badArgument( index, "number", "nil" );
+        Object value = args[ index ];
+        if( value instanceof Number )
+        {
+            return ((Number) value).doubleValue();
+        }
+        else
+        {
+            throw badArgument( index, "number", value );
+        }
+    }
+
+    public static int getInt( @Nonnull Object[] args, int index ) throws LuaException
+    {
+        if( index >= args.length ) throw badArgument( index, "number", "nil" );
+        Object value = args[ index ];
+        if( value instanceof Number )
+        {
+            return (int) ((Number) value).longValue();
+        }
+        else
+        {
+            throw badArgument( index, "number", value );
+        }
+    }
+
+    public static double getReal( @Nonnull Object[] args, int index ) throws LuaException
+    {
+        return checkReal( index, getNumber( args, index ) );
+    }
+
+    public static boolean getBoolean( @Nonnull Object[] args, int index ) throws LuaException
+    {
+        if( index >= args.length ) throw badArgument( index, "boolean", "nil" );
+        Object value = args[ index ];
+        if( value instanceof Boolean )
+        {
+            return (Boolean) value;
+        }
+        else
+        {
+            throw badArgument( index, "boolean", value );
+        }
+    }
+
+    @Nonnull
+    public static String getString( @Nonnull Object[] args, int index ) throws LuaException
+    {
+        if( index >= args.length ) throw badArgument( index, "string", "nil" );
+        Object value = args[ index ];
+        if( value instanceof String )
+        {
+            return (String) value;
+        }
+        else
+        {
+            throw badArgument( index, "string", value );
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    @Nonnull
+    public static Map<Object, Object> getTable( @Nonnull Object[] args, int index ) throws LuaException
+    {
+        if( index >= args.length ) throw badArgument( index, "table", "nil" );
+        Object value = args[ index ];
+        if( value instanceof Map )
+        {
+            return (Map<Object, Object>) value;
+        }
+        else
+        {
+            throw badArgument( index, "table", value );
+        }
+    }
+
+    public static double optNumber( @Nonnull Object[] args, int index, double def ) throws LuaException
+    {
+        Object value = index < args.length ? args[ index ] : null;
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Number )
+        {
+            return ((Number) value).doubleValue();
+        }
+        else
+        {
+            throw badArgument( index, "number", value );
+        }
+    }
+
+    public static int optInt( @Nonnull Object[] args, int index, int def ) throws LuaException
+    {
+        Object value = index < args.length ? args[ index ] : null;
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Number )
+        {
+            return (int) ((Number) value).longValue();
+        }
+        else
+        {
+            throw badArgument( index, "number", value );
+        }
+    }
+
+    public static double optReal( @Nonnull Object[] args, int index, double def ) throws LuaException
+    {
+        return checkReal( index, optNumber( args, index, def ) );
+    }
+
+    public static boolean optBoolean( @Nonnull Object[] args, int index, boolean def ) throws LuaException
+    {
+        Object value = index < args.length ? args[ index ] : null;
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Boolean )
+        {
+            return (Boolean) value;
+        }
+        else
+        {
+            throw badArgument( index, "boolean", value );
+        }
+    }
+
+    public static String optString( @Nonnull Object[] args, int index, String def ) throws LuaException
+    {
+        Object value = index < args.length ? args[ index ] : null;
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof String )
+        {
+            return (String) value;
+        }
+        else
+        {
+            throw badArgument( index, "string", value );
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    public static Map<Object, Object> optTable( @Nonnull Object[] args, int index, Map<Object, Object> def ) throws LuaException
+    {
+        Object value = index < args.length ? args[ index ] : null;
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Map )
+        {
+            return (Map<Object, Object>) value;
+        }
+        else
+        {
+            throw badArgument( index, "table", value );
+        }
+    }
+
+    private static double checkReal( int index, double value ) throws LuaException
+    {
+        if( Double.isNaN( value ) )
+        {
+            throw badArgument( index, "number", "nan" );
+        }
+        else if( value == Double.POSITIVE_INFINITY )
+        {
+            throw badArgument( index, "number", "inf" );
+        }
+        else if( value == Double.NEGATIVE_INFINITY )
+        {
+            throw badArgument( index, "number", "-inf" );
+        }
+        else
+        {
+            return value;
+        }
+    }
+}

src/main/java/dan200/computercraft/core/apis/BitAPI.java

@@ -11,6 +11,8 @@ import dan200.computercraft.api.lua.LuaException;
 
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
+
 // Contributed by Nia
 // Based on LuaBit (http://luaforge.net/projects/bit)
  
@@ -23,25 +25,6 @@ public class BitAPI implements ILuaAPI
     private static final int BRSHIFT                  = 4;
     private static final int BLSHIFT                  = 5;
     private static final int BLOGIC_RSHIFT              = 6;
- 
-    private static int checkInt( Object o, int count ) throws LuaException
-    {
-        if( o instanceof Number )
-        {
-            return (int)(((Number)o).longValue());
-        }
-        else
-        {
-            if( count == 2 )
-            {
-                throw new LuaException( "Expected number, number" );
-            }
-            else
-            {
-                throw new LuaException( "Expected number" );
-            }
-        }
-    }
     
     public BitAPI( IAPIEnvironment _environment )
     {
@@ -82,31 +65,28 @@ public class BitAPI implements ILuaAPI
     @Override
     public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
-        Object a = args.length>0?args[0]:null;
-        Object b = args.length>1?args[1]:null;
- 
         int ret = 0;
         switch(method) {
             case BNOT:
-                ret = ~checkInt(a, 1);
+                ret = ~getInt( args, 0 );
                 break;
             case BAND:
-                ret = checkInt(a, 2) & checkInt(b, 2);
+                ret = getInt( args, 0 ) & getInt( args, 1 );
                 break;
             case BOR:
-                ret = checkInt(a, 2) | checkInt(b, 2);
+                ret = getInt( args, 0 ) | getInt( args, 1 );
                 break;
             case BXOR:
-                ret = checkInt(a, 2) ^ checkInt(b, 2);
+                ret = getInt( args, 0 ) ^ getInt( args, 1 );
                 break;
             case BRSHIFT:
-                ret = checkInt(a, 2) >> checkInt(b, 2);
+                ret = getInt( args, 0 ) >> getInt( args, 1 );
                 break;
             case BLSHIFT:
-                ret = checkInt(a, 2) << checkInt(b, 2);
+                ret = getInt( args, 0 ) << getInt( args, 1 );
                 break;
             case BLOGIC_RSHIFT:
-                ret = checkInt(a, 2) >>> checkInt(b, 2);
+                ret = getInt( args, 0 ) >>> getInt( args, 1 );
                 break;
         }
         

src/main/java/dan200/computercraft/core/apis/BufferAPI.java

@@ -13,6 +13,9 @@ import dan200.computercraft.core.terminal.TextBuffer;
 
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getString;
+import static dan200.computercraft.core.apis.ArgumentHelper.optInt;
+
 public class BufferAPI implements ILuaAPI
 {
     private static class BufferLuaObject implements ILuaObject
@@ -55,81 +58,25 @@ public class BufferAPI implements ILuaAPI
                 case 2:
                 {
                     // read
-                    int start = 0;
-                    if( arguments.length >= 1 && (arguments[0] != null) )
-                    {
-                        if( !(arguments[0] instanceof Number) )
-                        {
-                            throw new LuaException( "Expected number" );
-                        }
-                        start = ((Number)arguments[1]).intValue() - 1;
-                    }
-                    int end = m_buffer.length();
-                    if( arguments.length >= 2 && (arguments[1] != null) )
-                    {
-                        if( !(arguments[1] instanceof Number) )
-                        {
-                            throw new LuaException( "Expected number, number" );
-                        }
-                        end = ((Number)arguments[1]).intValue();
-                    }
+                    int start = optInt( arguments, 0, 0 );
+                    int end = optInt( arguments, 1, m_buffer.length() );
                     return new Object[] { m_buffer.read( start, end ) };
                 }
                 case 3:
                 {
                     // write
-                    if( arguments.length < 1 || !(arguments[0] instanceof String) )
-                    {
-                        throw new LuaException( "Expected string" );
-                    }
-                    String text = (String)(arguments[0]);
-                    int start = 0;
-                    if( arguments.length >= 2 && (arguments[1] != null) )
-                    {
-                        if( !(arguments[1] instanceof Number) )
-                        {
-                            throw new LuaException( "Expected string, number" );
-                        }
-                        start = ((Number)arguments[1]).intValue() - 1;
-                    }
-                    int end = start + text.length();
-                    if( arguments.length >= 3 && (arguments[2] != null) )
-                    {
-                        if( !(arguments[2] instanceof Number) )
-                        {
-                            throw new LuaException( "Expected string, number, number" );
-                        }
-                        end = ((Number)arguments[2]).intValue();
-                    }
+                    String text = getString( arguments, 0 );
+                    int start = optInt( arguments, 1, 0 );
+                    int end = optInt( arguments, 2, start + text.length() );
                     m_buffer.write( text, start, end );
                     return null;
                 }
                 case 4:
                 {
                     // fill
-                    if( arguments.length < 1 || !(arguments[0] instanceof String) )
-                    {
-                        throw new LuaException( "Expected string" );
-                    }
-                    String text = (String)(arguments[0]);
-                    int start = 0;
-                    if( arguments.length >= 2 && (arguments[1] != null) )
-                    {
-                        if( !(arguments[1] instanceof Number) )
-                        {
-                            throw new LuaException( "Expected string, number" );
-                        }
-                        start = ((Number)arguments[1]).intValue() - 1;
-                    }
-                    int end = m_buffer.length();
-                    if( arguments.length >= 3 && (arguments[2] != null) )
-                    {
-                        if( !(arguments[2] instanceof Number) )
-                        {
-                            throw new LuaException( "Expected string, number, number" );
-                        }
-                        end = ((Number)arguments[2]).intValue();
-                    }
+                    String text = getString( arguments, 0 );
+                    int start = optInt( arguments, 1, 0 );
+                    int end = optInt( arguments, 2, m_buffer.length() );
                     m_buffer.fill( text, start, end );
                     return null;
                 }
@@ -184,23 +131,11 @@ public class BufferAPI implements ILuaAPI
         {
             case 0:
             {
-                if( arguments.length < 1 || !(arguments[0] instanceof String) )
+                String text = getString( arguments, 0 );
+                int repetitions = optInt( arguments, 1, 1 );
+                if( repetitions < 0 )
                 {
-                    throw new LuaException( "Expected string" );
-                }
-                String text = (String)(arguments[0]);
-                int repetitions = 1;
-                if( arguments.length >= 2 && arguments[1] != null )
-                {
-                    if( !(arguments[1] instanceof Number) )
-                    {
-                        throw new LuaException( "Expected string, number" );
-                    }
-                    repetitions = ((Number)arguments[1]).intValue();
-                    if( repetitions < 0 )
-                    {
-                        throw new LuaException( "Expected positive number" );
-                    }
+                    throw ArgumentHelper.badArgument( 1, "positive number", Integer.toString( repetitions ) );
                 }
                 TextBuffer buffer = new TextBuffer( text, repetitions );
                 return new Object[] { new BufferLuaObject( buffer ) };

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -21,6 +21,8 @@ import java.io.OutputStream;
 import java.util.HashMap;
 import java.util.Map;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getString;
+
 public class FSAPI implements ILuaAPI
 {
     private IAPIEnvironment m_env;
@@ -89,11 +91,7 @@ public class FSAPI implements ILuaAPI
             case 0:
             {
                 // list
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     String[] results = m_fileSystem.list( path );
                     Map<Object,Object> table = new HashMap<Object,Object>();
@@ -110,32 +108,20 @@ public class FSAPI implements ILuaAPI
             case 1:
             {
                 // combine
-                if( args.length != 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof String) )
-                {
-                    throw new LuaException( "Expected string, string" );
-                }
-                String pathA = (String)args[0];
-                String pathB = (String)args[1];
+                String pathA = getString( args, 0 );
+                String pathB = getString( args, 1 );
                 return new Object[] { m_fileSystem.combine( pathA, pathB ) };
             }
             case 2:
             {
                 // getName
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 return new Object[]{ FileSystem.getName( path ) };
             }
             case 3:
             {
                 // getSize
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try
                 {
                     return new Object[]{ m_fileSystem.getSize( path ) };
@@ -148,11 +134,7 @@ public class FSAPI implements ILuaAPI
             case 4:
             {
                 // exists
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     return new Object[]{ m_fileSystem.exists( path ) };
                 } catch( FileSystemException e ) {
@@ -162,11 +144,7 @@ public class FSAPI implements ILuaAPI
             case 5:
             {
                 // isDir
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     return new Object[]{ m_fileSystem.isDir( path ) };
                 } catch( FileSystemException e ) {
@@ -176,11 +154,7 @@ public class FSAPI implements ILuaAPI
             case 6:
             {
                 // isReadOnly
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     return new Object[]{ m_fileSystem.isReadOnly( path ) };
                 } catch( FileSystemException e ) {
@@ -190,11 +164,7 @@ public class FSAPI implements ILuaAPI
             case 7:
             {
                 // makeDir
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     m_fileSystem.makeDir( path );
                     return null;
@@ -205,12 +175,8 @@ public class FSAPI implements ILuaAPI
             case 8:
             {
                 // move
-                if( args.length != 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof String) )
-                {
-                    throw new LuaException( "Expected string, string" );
-                }
-                String path = (String)args[0];
-                String dest = (String)args[1];
+                String path = getString( args, 0 );
+                String dest = getString( args, 1 );
                 try {
                     m_fileSystem.move( path, dest );
                     return null;
@@ -221,12 +187,8 @@ public class FSAPI implements ILuaAPI
             case 9:
             {
                 // copy
-                if( args.length != 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof String) )
-                {
-                    throw new LuaException( "Expected string, string" );
-                }
-                String path = (String)args[0];
-                String dest = (String)args[1];
+                String path = getString( args, 0 );
+                String dest = getString( args, 1 );
                 try {
                     m_fileSystem.copy( path, dest );
                     return null;
@@ -237,11 +199,7 @@ public class FSAPI implements ILuaAPI
             case 10:
             {
                 // delete
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     m_fileSystem.delete( path );
                     return null;
@@ -252,12 +210,8 @@ public class FSAPI implements ILuaAPI
             case 11:
             {
                 // open
-                if( args.length < 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof String) )
-                {
-                    throw new LuaException( "Expected string, string" );
-                }
-                String path = (String)args[0];
-                String mode = (String)args[1];
+                String path = getString( args, 0 );
+                String mode = getString( args, 1 );
                 try {
                     if( mode.equals( "r" ) ) {
                         // Open the file for reading, then create a wrapper around the reader
@@ -300,11 +254,7 @@ public class FSAPI implements ILuaAPI
             case 12:
             {
                 // getDrive
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     if( !m_fileSystem.exists( path ) )
                     {
@@ -318,11 +268,7 @@ public class FSAPI implements ILuaAPI
             case 13:
             {
                 // getFreeSpace
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     long freeSpace = m_fileSystem.getFreeSpace( path );
                     if( freeSpace >= 0 )
@@ -337,11 +283,7 @@ public class FSAPI implements ILuaAPI
             case 14:
             {
                 // find
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 try {
                     String[] results = m_fileSystem.find( path );
                     Map<Object,Object> table = new HashMap<Object,Object>();
@@ -356,11 +298,7 @@ public class FSAPI implements ILuaAPI
             case 15:
             {
                 // getDir
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String path = (String)args[0];
+                String path = getString( args, 0 );
                 return new Object[]{ FileSystem.getDirectory( path ) };
             }
             default:

src/main/java/dan200/computercraft/core/apis/HTTPAPI.java

@@ -7,24 +7,26 @@
 package dan200.computercraft.core.apis;
 
 import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.api.lua.LuaException;
-import dan200.computercraft.core.apis.handles.BinaryInputHandle;
-import dan200.computercraft.core.apis.handles.EncodedInputHandle;
+import dan200.computercraft.core.apis.http.HTTPCheck;
+import dan200.computercraft.core.apis.http.HTTPRequest;
+import dan200.computercraft.core.apis.http.HTTPTask;
 
 import javax.annotation.Nonnull;
-import java.io.InputStream;
+import java.net.URL;
 import java.util.*;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.*;
+
 public class HTTPAPI implements ILuaAPI
 {
     private final IAPIEnvironment m_apiEnvironment;
-    private final List<HTTPRequest> m_httpRequests;
+    private final List<HTTPTask> m_httpTasks;
     
     public HTTPAPI( IAPIEnvironment environment )
     {
         m_apiEnvironment = environment;
-        m_httpRequests = new ArrayList<HTTPRequest>();
+        m_httpTasks = new ArrayList<HTTPTask>();
     }
     
     @Override
@@ -44,95 +46,31 @@ public class HTTPAPI implements ILuaAPI
     public void advance( double _dt )
     {
         // Wait for all of our http requests 
-        synchronized( m_httpRequests )
+        synchronized( m_httpTasks )
         {
-            Iterator<HTTPRequest> it = m_httpRequests.iterator();
-            while( it.hasNext() ) {
-                final HTTPRequest h = it.next();
-                if( h.isComplete() ) {
-                    final String url = h.getURL();
-                    if( h.wasSuccessful() ) {
-                        // Queue the "http_success" event
-                        InputStream contents = h.getContents();
-                        Object result = wrapStream(
-                            h.isBinary() ? new BinaryInputHandle( contents ) : new EncodedInputHandle( contents, h.getEncoding() ),
-                            h.getResponseCode(), h.getResponseHeaders()
-                        );
-                        m_apiEnvironment.queueEvent( "http_success", new Object[] { url, result } );
-                    } else {
-                        // Queue the "http_failure" event
-                        InputStream contents = h.getContents();
-                        Object result = null;
-                        if( contents != null ) {
-                            result = wrapStream(
-                                h.isBinary() ? new BinaryInputHandle( contents ) : new EncodedInputHandle( contents, h.getEncoding() ),
-                                h.getResponseCode(), h.getResponseHeaders()
-                            );
-                        }
-                        m_apiEnvironment.queueEvent( "http_failure", new Object[]{ url, "Could not connect", result } );
-                    }
+            Iterator<HTTPTask> it = m_httpTasks.iterator();
+            while( it.hasNext() )
+            {
+                final HTTPTask h = it.next();
+                if( h.isFinished() )
+                {
+                    h.whenFinished( m_apiEnvironment );
                     it.remove();
                 }
             }
         }
     }
-
-    private static ILuaObject wrapStream( final ILuaObject reader, final int responseCode, final Map<String, String> responseHeaders )
-    {
-        String[] oldMethods = reader.getMethodNames();
-        final int methodOffset = oldMethods.length;
-
-        final String[] newMethods = Arrays.copyOf( oldMethods, oldMethods.length + 2 );
-        newMethods[ methodOffset + 0 ] = "getResponseCode";
-        newMethods[ methodOffset + 1 ] = "getResponseHeaders";
-
-        return new ILuaObject()
-        {
-            @Nonnull
-            @Override
-            public String[] getMethodNames()
-            {
-                return newMethods;
-            }
-
-            @Override
-            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
-            {
-                if( method < methodOffset )
-                {
-                    return reader.callMethod( context, method, args );
-                }
-                switch( method - methodOffset )
-                {
-                    case 0:
-                    {
-                        // getResponseCode
-                        return new Object[] { responseCode };
-                    }
-                    case 1:
-                    {
-                        // getResponseHeaders
-                        return new Object[] { responseHeaders };
-                    }
-                    default:
-                    {
-                        return null;
-                    }
-                }
-            }
-        };
-    }
     
     @Override
     public void shutdown( )
     {
-        synchronized( m_httpRequests )
+        synchronized( m_httpTasks )
         {
-            for( HTTPRequest r : m_httpRequests )
+            for( HTTPTask r : m_httpTasks )
             {
                 r.cancel();
             }
-            m_httpRequests.clear();
+            m_httpTasks.clear();
         }
     }
 
@@ -155,24 +93,16 @@ public class HTTPAPI implements ILuaAPI
             {
                 // request
                 // Get URL
-                if( args.length < 1 || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String urlString = args[0].toString();
+                String urlString = getString( args, 0 );
 
                 // Get POST
-                String postString = null;
-                if( args.length >= 2 && args[1] instanceof String )
-                {
-                    postString = args[1].toString();
-                }
+                String postString = optString( args, 1, null );
 
                 // Get Headers
                 Map<String, String> headers = null;
-                if( args.length >= 3 && args[2] instanceof Map )
+                Map<Object, Object> table = optTable( args, 2, null );
+                if( table != null )
                 {
-                    Map<?, ?> table = (Map<?, ?>)args[2];
                     headers = new HashMap<String, String>( table.size() );
                     for( Object key : table.keySet() )
                     {
@@ -194,10 +124,11 @@ public class HTTPAPI implements ILuaAPI
                 // Make the request
                 try
                 {
-                    HTTPRequest request = new HTTPRequest( urlString, postString, headers, binary );
-                    synchronized( m_httpRequests )
+                    URL url = HTTPRequest.checkURL( urlString );
+                    HTTPRequest request = new HTTPRequest( urlString, url, postString, headers, binary );
+                    synchronized( m_httpTasks )
                     {
-                        m_httpRequests.add( request );
+                        m_httpTasks.add( HTTPTask.submit( request ) );
                     }
                     return new Object[] { true };
                 }
@@ -210,16 +141,16 @@ public class HTTPAPI implements ILuaAPI
             {
                 // checkURL
                 // Get URL
-                if( args.length < 1 || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                String urlString = args[0].toString();
+                String urlString = getString( args, 0 );
 
                 // Check URL
                 try
                 {
-                    HTTPRequest.checkURL( urlString );
+                    URL url = HTTPRequest.checkURL( urlString );
+                    HTTPCheck check = new HTTPCheck( urlString, url );
+                    synchronized( m_httpTasks ) {
+                        m_httpTasks.add( HTTPTask.submit( check ) );
+                    }
                     return new Object[] { true };
                 }
                 catch( HTTPRequestException e )

src/main/java/dan200/computercraft/core/apis/HTTPRequest.java

@@ -1,261 +0,0 @@
-/*
- * This file is part of ComputerCraft - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2017. Do not distribute without permission.
- * Send enquiries to dratcliffe@gmail.com
- */
-
-package dan200.computercraft.core.apis;
-
-import com.google.common.base.Joiner;
-import com.google.common.io.ByteStreams;
-import dan200.computercraft.ComputerCraft;
-
-import java.io.*;
-import java.net.HttpURLConnection;
-import java.net.MalformedURLException;
-import java.net.URL;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.regex.Pattern;
-
-public class HTTPRequest
-{
-    public static URL checkURL( String urlString ) throws HTTPRequestException
-    {
-        URL url;
-        try
-        {
-            url = new URL( urlString );
-        }
-        catch( MalformedURLException e )
-        {
-            throw new HTTPRequestException( "URL malformed" );
-        }
-
-        // Validate the URL
-        String protocol = url.getProtocol().toLowerCase();
-        if( !protocol.equals("http") && !protocol.equals("https") )
-        {
-            throw new HTTPRequestException( "URL not http" );
-        }
-
-        // Compare the URL to the whitelist
-        boolean allowed = false;
-        String whitelistString = ComputerCraft.http_whitelist;
-        String[] allowedURLs = whitelistString.split( ";" );
-        for( String allowedURL : allowedURLs )
-        {
-            Pattern allowedURLPattern = Pattern.compile( "^\\Q" + allowedURL.replaceAll( "\\*", "\\\\E.*\\\\Q" ) + "\\E$" );
-            if( allowedURLPattern.matcher( url.getHost() ).matches() )
-            {
-                allowed = true;
-                break;
-            }
-        }
-        if( !allowed )
-        {
-            throw new HTTPRequestException( "Domain not permitted" );
-        }
-
-        return url;
-    }
-
-    public HTTPRequest( String url, final String postText, final Map<String, String> headers, boolean binary ) throws HTTPRequestException
-    {
-        // Parse the URL
-        m_urlString = url;
-        m_url = checkURL( m_urlString );
-        m_binary = binary;
-
-        // Start the thread
-        m_cancelled = false;
-        m_complete = false;
-        m_success = false;
-        m_result = null;
-        m_responseCode = -1;
-
-        Thread thread = new Thread( new Runnable() {
-            @Override
-            public void run()
-            {
-                try
-                {
-                    // Connect to the URL
-                    HttpURLConnection connection = (HttpURLConnection)m_url.openConnection();
-
-                    if( postText != null )
-                    {
-                        connection.setRequestMethod( "POST" );
-                        connection.setDoOutput( true );
-                    }
-                    else
-                    {
-                        connection.setRequestMethod( "GET" );
-                    }
-
-                    // Set headers
-                    connection.setRequestProperty( "accept-charset", "UTF-8" );
-                    if( postText != null )
-                    {
-                        connection.setRequestProperty( "content-type", "application/x-www-form-urlencoded; charset=utf-8" );
-                        connection.setRequestProperty( "content-encoding", "UTF-8" );
-                    }
-                    if( headers != null )
-                    {
-                        for( Map.Entry<String, String> header : headers.entrySet() )
-                        {
-                            connection.setRequestProperty( header.getKey(), header.getValue() );
-                        }
-                    }
-
-                    // Send POST text
-                    if( postText != null )
-                    {
-                        OutputStream os = connection.getOutputStream();
-                        OutputStreamWriter osw;
-                        try
-                        {
-                            osw = new OutputStreamWriter( os, "UTF-8" );
-                        }
-                        catch( UnsupportedEncodingException e )
-                        {
-                            osw = new OutputStreamWriter( os );
-                        }
-                        BufferedWriter writer = new BufferedWriter( osw );
-                        writer.write( postText, 0, postText.length() );
-                        writer.close();
-                    }
-
-                    // Read response
-                    InputStream is;
-                    int code = connection.getResponseCode();
-                    boolean responseSuccess;
-                    if (code >= 200 && code < 400) {
-                        is = connection.getInputStream();
-                        responseSuccess = true;
-                    } else {
-                        is = connection.getErrorStream();
-                        responseSuccess = false;
-                    }
-                    
-                    byte[] result = ByteStreams.toByteArray( is );
-                    is.close();
-                    
-                    synchronized( m_lock )
-                    {
-                        if( m_cancelled )
-                        {
-                            // We cancelled
-                            m_complete = true;
-                            m_success = false;
-                            m_result = null;
-                        }
-                        else
-                        {
-                            // We completed
-                            m_complete = true;
-                            m_success = responseSuccess;
-                            m_result = result;
-                            m_responseCode = connection.getResponseCode();
-                            m_encoding = connection.getContentEncoding();
-
-                            Joiner joiner = Joiner.on( ',' );
-                            Map<String, String> headers = m_responseHeaders = new HashMap<String, String>();
-                            for (Map.Entry<String, List<String>> header : connection.getHeaderFields().entrySet()) {
-                                headers.put(header.getKey(), joiner.join( header.getValue() ));
-                            }
-                        }
-                    }
-
-                    connection.disconnect(); // disconnect
-
-                }
-                catch( IOException e )
-                {
-                    synchronized( m_lock )
-                    {
-                        // There was an error
-                        m_complete = true;
-                        m_success = false;
-                        m_result = null;
-                    }
-                }
-            }
-        } );
-        thread.setDaemon(true);
-        thread.start();
-    }
-    
-    public String getURL() {
-        return m_urlString;
-    }
-    
-    public void cancel()
-    {
-        synchronized(m_lock) {
-            m_cancelled = true;
-        }
-    }
-    
-    public boolean isComplete()
-    {
-        synchronized(m_lock) {
-            return m_complete;
-        }
-    }
-
-    public int getResponseCode() {
-        synchronized(m_lock) {
-            return m_responseCode;
-        }
-    }
-
-    public Map<String, String> getResponseHeaders() {
-        synchronized (m_lock) {
-            return m_responseHeaders;
-        }
-    }
-
-    public boolean wasSuccessful()
-    {
-        synchronized(m_lock) {
-            return m_success;
-        }
-    }
-
-    public boolean isBinary()
-    {
-        return m_binary;
-    }
-    
-    public InputStream getContents()
-    {
-        byte[] result;
-        synchronized(m_lock) {
-            result = m_result;
-        }
-        
-        if( result != null ) {
-            return new ByteArrayInputStream( result );
-        }
-        return null;
-    }
-    
-    public String getEncoding() {
-        return m_encoding;
-    }
-    
-    private final Object m_lock = new Object();
-    private final URL m_url;
-    private final String m_urlString;
-    
-    private boolean m_complete;
-    private boolean m_cancelled;
-    private boolean m_success;
-    private String m_encoding;
-    private byte[] m_result;
-    private boolean m_binary;
-    private int m_responseCode;
-    private Map<String, String> m_responseHeaders;
-}

src/main/java/dan200/computercraft/core/apis/OSAPI.java

@@ -13,6 +13,8 @@ import dan200.computercraft.shared.util.StringUtil;
 import javax.annotation.Nonnull;
 import java.util.*;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.*;
+
 public class OSAPI implements ILuaAPI
 {
     private IAPIEnvironment m_apiEnvironment;
@@ -225,21 +227,13 @@ public class OSAPI implements ILuaAPI
             case 0:
             {
                 // queueEvent
-                if( args.length == 0 || args[0] == null || !(args[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                queueLuaEvent( (String)args[0], trimArray( args, 1 ) );
+                queueLuaEvent( getString( args, 0 ), trimArray( args, 1 ) );
                 return null;
             }
             case 1:
             {
                 // startTimer
-                if( args.length < 1 || args[0] == null || !(args[0] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number" );
-                }
-                double timer = ((Number)args[0]).doubleValue();
+                double timer = getReal( args, 0 );
                 synchronized( m_timers )
                 {
                     m_timers.put( m_nextTimerToken, new Timer( (int)Math.round( timer / 0.05 ) ) );
@@ -249,11 +243,7 @@ public class OSAPI implements ILuaAPI
             case 2:
             {
                 // setAlarm
-                if( args.length < 1 || args[0] == null || !(args[0] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number" );
-                }
-                double time = ((Number)args[0]).doubleValue();
+                double time = getReal( args, 0 );
                 if( time < 0.0 || time >= 24.0 )
                 {
                     throw new LuaException( "Number out of range" );
@@ -286,16 +276,8 @@ public class OSAPI implements ILuaAPI
             case 7:
             {
                 // setComputerLabel
-                String label = null;
-                if( args.length > 0 && args[0] != null )
-                {
-                    if(!(args[0] instanceof String))
-                    {
-                        throw new LuaException( "Expected string or nil" );
-                    }
-                    label = StringUtil.normaliseLabel( (String) args[0] );
-                }
-                m_apiEnvironment.setLabel( label );
+                String label = optString( args, 0, null );
+                m_apiEnvironment.setLabel( StringUtil.normaliseLabel( label ) );
                 return null;
             }
             case 8:
@@ -320,13 +302,7 @@ public class OSAPI implements ILuaAPI
             case 11:
             {
                 // time
-                String param = "ingame";
-                if (args.length > 0 && args[0] != null) {
-                    if (!(args[0] instanceof String)) {
-                        throw new LuaException("Expected string");
-                    }
-                    param = (String)args[0];
-                }
+                String param = optString( args, 0, "ingame" );
 
                 if (param.equals("utc")) {
                     // Get Hour of day (UTC)
@@ -351,13 +327,7 @@ public class OSAPI implements ILuaAPI
             case 12:
             {
                 // day
-                String param = "ingame";
-                if (args.length > 0 && args[0] != null) {
-                    if (!(args[0] instanceof String)) {
-                        throw new LuaException("Expected string");
-                    }
-                    param = (String)args[0];
-                }
+                String param = optString( args, 0, "ingame" );
                 if (param.equals("utc")) {
                     // Get numbers of days since 1970-01-01 (utc)
                     Calendar c = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
@@ -381,11 +351,7 @@ public class OSAPI implements ILuaAPI
             case 13:
             {
                 // cancelTimer
-                if( args.length < 1 || args[0] == null || !(args[0] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number" );
-                }
-                int token = ((Number)args[0]).intValue();
+                int token = getInt( args, 0 );
                 synchronized( m_timers )
                 {
                     if( m_timers.containsKey( token ) )
@@ -398,11 +364,7 @@ public class OSAPI implements ILuaAPI
             case 14:
             {
                 // cancelAlarm
-                if( args.length < 1 || args[0] == null || !(args[0] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number" );
-                }
-                int token = ((Number)args[0]).intValue();
+                int token = getInt( args, 0 );
                 synchronized( m_alarms )
                 {
                     if( m_alarms.containsKey( token ) )
@@ -415,13 +377,7 @@ public class OSAPI implements ILuaAPI
             case 15:
             {
                 // epoch
-                String param = "ingame";
-                if (args.length > 0 && args[0] != null) {
-                    if (!(args[0] instanceof String)) {
-                        throw new LuaException("Expected string");
-                    }
-                    param = (String)args[0];
-                }
+                String param = optString( args, 0, "ingame" );
                 if (param.equals("utc")) {
                     // Get utc epoch
                     Calendar c = Calendar.getInstance(TimeZone.getTimeZone("UTC"));

src/main/java/dan200/computercraft/core/apis/PeripheralAPI.java

@@ -21,6 +21,8 @@ import dan200.computercraft.core.filesystem.FileSystemException;
 import javax.annotation.Nonnull;
 import java.util.*;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getString;
+
 public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChangeListener
 {
     private class PeripheralWrapper implements IComputerAccess
@@ -460,14 +462,10 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             case 3:
             {
                 // call
-                if( args.length < 2 || args[1] == null || !(args[1] instanceof String) )
-                {
-                    throw new LuaException( "Expected string, string" );
-                }
-                String methodName = (String)args[1];
+                int side = parseSide( args );
+                String methodName = getString( args, 1 );
                 Object[] methodArgs = trimArray( args, 2 );
                 
-                int side = parseSide( args );
                 if( side >= 0 )
                 {
                     PeripheralWrapper p;
@@ -498,11 +496,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
 
     private int parseSide( Object[] args ) throws LuaException
     {
-        if( args.length < 1 || args[0] == null || !(args[0] instanceof String) )
-        {
-            throw new LuaException( "Expected string" );
-        }
-        String side = (String)args[0];
+        String side = getString( args, 0 );
         for( int n=0; n<Computer.s_sideNames.length; ++n )
         {
             if( side.equals( Computer.s_sideNames[n] ) )

src/main/java/dan200/computercraft/core/apis/RedstoneAPI.java

@@ -14,6 +14,8 @@ import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Map;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.*;
+
 public class RedstoneAPI implements ILuaAPI
 {
     private IAPIEnvironment m_environment;
@@ -86,12 +88,8 @@ public class RedstoneAPI implements ILuaAPI
             case 1:
             {
                 // setOutput
-                if( args.length < 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof Boolean) )
-                {
-                    throw new LuaException( "Expected string, boolean" );
-                }
                 int side = parseSide( args );
-                boolean output = (Boolean) args[ 1 ];
+                boolean output = getBoolean( args, 1 );
                 m_environment.setOutput( side, output ? 15 : 0 );
                 return null;
             }
@@ -110,12 +108,8 @@ public class RedstoneAPI implements ILuaAPI
             case 4:
             {
                 // setBundledOutput
-                if( args.length < 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof Double) )
-                {
-                    throw new LuaException( "Expected string, number" );
-                }
                 int side = parseSide( args );
-                int output = ((Double)args[1]).intValue();
+                int output = getInt( args, 1 );
                 m_environment.setBundledOutput( side, output );
                 return null;
             }
@@ -134,12 +128,8 @@ public class RedstoneAPI implements ILuaAPI
             case 7:
             {
                 // testBundledInput
-                if( args.length < 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof Double) )
-                {
-                    throw new LuaException( "Expected string, number" );
-                }
                 int side = parseSide( args );
-                int mask = ((Double)args[1]).intValue();
+                int mask = getInt( args, 1 );
                 int input = m_environment.getBundledInput( side );
                 return new Object[] { ((input & mask) == mask) };
             }
@@ -147,12 +137,8 @@ public class RedstoneAPI implements ILuaAPI
             case 9:
             {
                 // setAnalogOutput/setAnalogueOutput
-                if( args.length < 2 || args[0] == null || !(args[0] instanceof String) || args[1] == null || !(args[1] instanceof Double) )
-                {
-                    throw new LuaException( "Expected string, number" );
-                }
                 int side = parseSide( args );
-                int output = ((Double)args[1]).intValue();
+                int output = getInt( args, 1 );
                 if( output < 0 || output > 15 )
                 {
                     throw new LuaException( "Expected number in range 0-15" );
@@ -183,11 +169,7 @@ public class RedstoneAPI implements ILuaAPI
     
     private int parseSide( Object[] args ) throws LuaException
     {
-        if( args.length < 1 || args[0] == null || !(args[0] instanceof String) )
-        {
-            throw new LuaException( "Expected string" );
-        }
-        String side = (String)args[0];
+        String side = getString( args, 0 );
         for( int n=0; n<Computer.s_sideNames.length; ++n )
         {
             if( side.equals( Computer.s_sideNames[n] ) )

src/main/java/dan200/computercraft/core/apis/TermAPI.java

@@ -13,12 +13,10 @@ import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.shared.util.Palette;
 import org.apache.commons.lang3.ArrayUtils;
 
-import java.util.HashMap;
-import java.util.Map;
-import java.util.Set;
-
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.*;
+
 public class TermAPI implements ILuaAPI
 {
     private final Terminal m_terminal;
@@ -86,11 +84,7 @@ public class TermAPI implements ILuaAPI
     
     public static int parseColour( Object[] args ) throws LuaException
     {
-        if( args.length < 1 || args[0] == null || !(args[0] instanceof Double) )
-        {
-            throw new LuaException( "Expected number" );
-        }            
-        int colour = (int)((Double)args[0]).doubleValue();
+        int colour = getInt( args, 0 );
         if( colour <= 0 )
         {
             throw new LuaException( "Colour out of range" );
@@ -144,12 +138,7 @@ public class TermAPI implements ILuaAPI
             case 1:
             {
                 // scroll
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof Double) )
-                {
-                    throw new LuaException( "Expected number" );
-                }
-                
-                int y = (int)((Double)args[0]).doubleValue();
+                int y = getInt( args, 0 );
                 synchronized( m_terminal )
                 {
                     m_terminal.scroll(y);
@@ -159,12 +148,8 @@ public class TermAPI implements ILuaAPI
             case 2:
             {
                 // setCursorPos
-                if( args.length != 2 || args[0] == null || !(args[0] instanceof Double) || args[1] == null || !(args[1] instanceof Double) )
-                {
-                    throw new LuaException( "Expected number, number" );
-                }
-                int x = (int)((Double)args[0]).doubleValue() - 1;
-                int y = (int)((Double)args[1]).doubleValue() - 1;
+                int x = getInt( args, 0 ) - 1;
+                int y = getInt( args, 1 ) - 1;
                 synchronized( m_terminal )
                 {
                     m_terminal.setCursorPos( x, y );
@@ -174,11 +159,7 @@ public class TermAPI implements ILuaAPI
             case 3:
             {
                 // setCursorBlink
-                if( args.length != 1 || args[0] == null || !(args[0] instanceof Boolean) )
-                {
-                    throw new LuaException( "Expected boolean" );
-                }
-                boolean b = (Boolean) args[ 0 ];
+                boolean b = getBoolean( args, 0 );
                 synchronized( m_terminal )
                 {
                     m_terminal.setCursorBlink( b );
@@ -268,14 +249,9 @@ public class TermAPI implements ILuaAPI
             case 18:
             {
                 // blit
-                if( args.length < 3 || !(args[0] instanceof String) || !(args[1] instanceof String) || !(args[2] instanceof String) )
-                {
-                    throw new LuaException( "Expected string, string, string" );
-                }
-
-                String text = (String)args[0];
-                String textColour = (String)args[1];
-                String backgroundColour = (String)args[2];
+                String text = getString( args, 0 );
+                String textColour = getString( args, 1 );
+                String backgroundColour = getString( args, 2 );
                 if( textColour.length() != text.length() || backgroundColour.length() != text.length() )
                 {
                     throw new LuaException( "Arguments must be the same length" );
@@ -292,36 +268,26 @@ public class TermAPI implements ILuaAPI
             case 20:
             {
                 // setPaletteColour/setPaletteColor
-                if(args.length == 2 && args[0] instanceof Double && args[1] instanceof Double)
+                int colour = 15 - parseColour( args );
+                if( args.length == 2 )
                 {
-                    int colour = 15 - parseColour( args );
-                    int hex = ((Double)args[1]).intValue();
+                    int hex = getInt( args, 1 );
                     double[] rgb = Palette.decodeRGB8( hex );
-                    setColour( m_terminal, colour, rgb[0], rgb[1], rgb[2] );
-                    return null;
+                    setColour( m_terminal, colour, rgb[ 0 ], rgb[ 1 ], rgb[ 2 ] );
                 }
-
-                if(args.length >= 4 && args[0] instanceof Double && args[1] instanceof Double && args[2] instanceof Double && args[3] instanceof Double)
+                else
                 {
-                    int colour = 15 - parseColour( args );
-                    double r = (Double)args[1];
-                    double g = (Double)args[2];
-                    double b = (Double)args[3];
+                    double r = getReal( args, 1 );
+                    double g = getReal( args, 2 );
+                    double b = getReal( args, 3 );
                     setColour( m_terminal, colour, r, g, b );
-                    return null;
                 }
-
-                throw new LuaException( "Expected number, number or number, number, number, number" );
+                return null;
             }
             case 21:
             case 22:
             {
                 // getPaletteColour/getPaletteColor
-                if(args.length < 1 || !(args[0] instanceof Double))
-                {
-                    throw new LuaException( "Expected number" );
-                }
-
                 int colour = 15 - parseColour( args );
                 synchronized( m_terminal )
                 {

src/main/java/dan200/computercraft/core/apis/handles/BinaryInputHandle.java

@@ -9,6 +9,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
+
 public class BinaryInputHandle extends HandleGeneric
 {
     private final InputStream m_stream;
@@ -42,13 +44,7 @@ public class BinaryInputHandle extends HandleGeneric
                 {
                     if( args.length > 0 && args[ 0 ] != null )
                     {
-                        if( !(args[ 0 ] instanceof Number) )
-                        {
-                            throw new LuaException( "Expected number" );
-                        }
-
-                        int count = ((Number) args[ 0 ]).intValue();
-
+                        int count = getInt( args, 0 );
                         if( count <= 0 || count >= 1024 * 16 )
                         {
                             throw new LuaException( "Count out of range" );

src/main/java/dan200/computercraft/core/apis/handles/BinaryOutputHandle.java

@@ -2,6 +2,7 @@ package dan200.computercraft.core.apis.handles;
 
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.core.apis.ArgumentHelper;
 import dan200.computercraft.shared.util.StringUtil;
 
 import javax.annotation.Nonnull;
@@ -51,7 +52,7 @@ public class BinaryOutputHandle extends HandleGeneric
                     }
                     else
                     {
-                        throw new LuaException( "Expected number" );
+                        throw ArgumentHelper.badArgument( 0, "string or number", args.length > 0 ? args[ 0 ] : null );
                     }
                     return null;
                 }

src/main/java/dan200/computercraft/core/apis/http/HTTPCheck.java

@@ -0,0 +1,45 @@
+package dan200.computercraft.core.apis.http;
+
+import dan200.computercraft.core.apis.HTTPRequestException;
+import dan200.computercraft.core.apis.IAPIEnvironment;
+
+import java.net.URL;
+
+public class HTTPCheck implements HTTPTask.IHTTPTask
+{
+    private final String urlString;
+    private final URL url;
+    private String error;
+
+    public HTTPCheck( String urlString, URL url )
+    {
+        this.urlString = urlString;
+        this.url = url;
+    }
+
+    @Override
+    public void run()
+    {
+        try
+        {
+            HTTPRequest.checkHost( url );
+        }
+        catch( HTTPRequestException e )
+        {
+            error = e.getMessage();
+        }
+    }
+
+    @Override
+    public void whenFinished( IAPIEnvironment environment )
+    {
+        if( error == null )
+        {
+            environment.queueEvent( "http_check", new Object[] { urlString, true } );
+        }
+        else
+        {
+            environment.queueEvent( "http_check", new Object[] { urlString, false, error } );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/apis/http/HTTPRequest.java

@@ -0,0 +1,290 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.apis.http;
+
+import com.google.common.base.Joiner;
+import com.google.common.io.ByteStreams;
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ILuaObject;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.core.apis.HTTPRequestException;
+import dan200.computercraft.core.apis.IAPIEnvironment;
+import dan200.computercraft.core.apis.handles.BinaryInputHandle;
+import dan200.computercraft.core.apis.handles.EncodedInputHandle;
+
+import javax.annotation.Nonnull;
+import java.io.*;
+import java.net.*;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class HTTPRequest implements HTTPTask.IHTTPTask
+{
+    public static URL checkURL( String urlString ) throws HTTPRequestException
+    {
+        URL url;
+        try
+        {
+            url = new URL( urlString );
+        }
+        catch( MalformedURLException e )
+        {
+            throw new HTTPRequestException( "URL malformed" );
+        }
+
+        // Validate the URL
+        String protocol = url.getProtocol().toLowerCase();
+        if( !protocol.equals( "http" ) && !protocol.equals( "https" ) )
+        {
+            throw new HTTPRequestException( "URL not http" );
+        }
+
+        // Compare the URL to the whitelist
+        if( !ComputerCraft.http_whitelist.matches( url.getHost() ) || ComputerCraft.http_blacklist.matches( url.getHost() ) )
+        {
+            throw new HTTPRequestException( "Domain not permitted" );
+        }
+
+        return url;
+    }
+
+    public static InetAddress checkHost( URL url ) throws HTTPRequestException
+    {
+        try
+        {
+            InetAddress resolved = InetAddress.getByName( url.getHost() );
+            if( !ComputerCraft.http_whitelist.matches( resolved ) || ComputerCraft.http_blacklist.matches( resolved ) )
+            {
+                throw new HTTPRequestException( "Domain not permitted" );
+            }
+
+            return resolved;
+        }
+        catch( UnknownHostException e )
+        {
+            throw new HTTPRequestException( "Unknown host" );
+        }
+    }
+
+    private final URL m_url;
+    private final String m_urlString;
+    private final String m_postText;
+    private final Map<String, String> m_headers;
+
+    private boolean m_success = false;
+    private String m_encoding;
+    private byte[] m_result;
+    private boolean m_binary;
+    private int m_responseCode = -1;
+    private Map<String, String> m_responseHeaders;
+    private String m_errorMessage;
+
+    public HTTPRequest( String urlString, URL url, final String postText, final Map<String, String> headers, boolean binary ) throws HTTPRequestException
+    {
+        // Parse the URL
+        m_urlString = urlString;
+        m_url = url;
+        m_binary = binary;
+        m_postText = postText;
+        m_headers = headers;
+    }
+
+    public InputStream getContents()
+    {
+        byte[] result = m_result;
+        if( result != null )
+        {
+            return new ByteArrayInputStream( result );
+        }
+        return null;
+    }
+
+    @Override
+    public void run()
+    {
+        // First verify the address is allowed.
+        try
+        {
+            checkHost( m_url );
+        }
+        catch( HTTPRequestException e )
+        {
+            m_success = false;
+            m_errorMessage = e.getMessage();
+            return;
+        }
+
+        try
+        {
+            // Connect to the URL
+            HttpURLConnection connection = (HttpURLConnection) m_url.openConnection();
+
+            if( m_postText != null )
+            {
+                connection.setRequestMethod( "POST" );
+                connection.setDoOutput( true );
+            }
+            else
+            {
+                connection.setRequestMethod( "GET" );
+            }
+
+            // Set headers
+            connection.setRequestProperty( "accept-charset", "UTF-8" );
+            if( m_postText != null )
+            {
+                connection.setRequestProperty( "content-type", "application/x-www-form-urlencoded; charset=utf-8" );
+                connection.setRequestProperty( "content-encoding", "UTF-8" );
+            }
+            if( m_postText != null )
+            {
+                for( Map.Entry<String, String> header : m_headers.entrySet() )
+                {
+                    connection.setRequestProperty( header.getKey(), header.getValue() );
+                }
+            }
+
+            // Send POST text
+            if( m_postText != null )
+            {
+                OutputStream os = connection.getOutputStream();
+                OutputStreamWriter osw;
+                try
+                {
+                    osw = new OutputStreamWriter( os, "UTF-8" );
+                }
+                catch( UnsupportedEncodingException e )
+                {
+                    osw = new OutputStreamWriter( os );
+                }
+                BufferedWriter writer = new BufferedWriter( osw );
+                writer.write( m_postText, 0, m_postText.length() );
+                writer.close();
+            }
+
+            // Read response
+            InputStream is;
+            int code = connection.getResponseCode();
+            boolean responseSuccess;
+            if( code >= 200 && code < 400 )
+            {
+                is = connection.getInputStream();
+                responseSuccess = true;
+            }
+            else
+            {
+                is = connection.getErrorStream();
+                responseSuccess = false;
+            }
+
+            byte[] result = ByteStreams.toByteArray( is );
+            is.close();
+
+            // We completed
+            m_success = responseSuccess;
+            m_result = result;
+            m_responseCode = connection.getResponseCode();
+            m_encoding = connection.getContentEncoding();
+
+            Joiner joiner = Joiner.on( ',' );
+            Map<String, String> headers = m_responseHeaders = new HashMap<String, String>();
+            for( Map.Entry<String, List<String>> header : connection.getHeaderFields().entrySet() )
+            {
+                headers.put( header.getKey(), joiner.join( header.getValue() ) );
+            }
+
+            connection.disconnect(); // disconnect
+        }
+        catch( IOException e )
+        {
+            // There was an error
+            m_success = false;
+        }
+    }
+
+    @Override
+    public void whenFinished( IAPIEnvironment environment )
+    {
+        final String url = m_urlString;
+        if( m_success )
+        {
+            // Queue the "http_success" event
+            InputStream contents = getContents();
+            Object result = wrapStream(
+                m_binary ? new BinaryInputHandle( contents ) : new EncodedInputHandle( contents, m_encoding ),
+                m_responseCode, m_responseHeaders
+            );
+            environment.queueEvent( "http_success", new Object[] { url, result } );
+        }
+        else
+        {
+            // Queue the "http_failure" event
+            String error = "Could not connect";
+            if( m_errorMessage != null ) error = m_errorMessage;
+
+            InputStream contents = getContents();
+            Object result = null;
+            if( contents != null )
+            {
+                result = wrapStream(
+                    m_binary ? new BinaryInputHandle( contents ) : new EncodedInputHandle( contents, m_encoding ),
+                    m_responseCode, m_responseHeaders
+                );
+            }
+            environment.queueEvent( "http_failure", new Object[] { url, error, result } );
+        }
+    }
+
+    private static ILuaObject wrapStream( final ILuaObject reader, final int responseCode, final Map<String, String> responseHeaders )
+    {
+        String[] oldMethods = reader.getMethodNames();
+        final int methodOffset = oldMethods.length;
+
+        final String[] newMethods = Arrays.copyOf( oldMethods, oldMethods.length + 2 );
+        newMethods[ methodOffset + 0 ] = "getResponseCode";
+        newMethods[ methodOffset + 1 ] = "getResponseHeaders";
+
+        return new ILuaObject()
+        {
+            @Nonnull
+            @Override
+            public String[] getMethodNames()
+            {
+                return newMethods;
+            }
+
+            @Override
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
+            {
+                if( method < methodOffset )
+                {
+                    return reader.callMethod( context, method, args );
+                }
+                switch( method - methodOffset )
+                {
+                    case 0:
+                    {
+                        // getResponseCode
+                        return new Object[] { responseCode };
+                    }
+                    case 1:
+                    {
+                        // getResponseHeaders
+                        return new Object[] { responseHeaders };
+                    }
+                    default:
+                    {
+                        return null;
+                    }
+                }
+            }
+        };
+    }
+}

src/main/java/dan200/computercraft/core/apis/http/HTTPTask.java

@@ -0,0 +1,61 @@
+package dan200.computercraft.core.apis.http;
+
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import dan200.computercraft.core.apis.IAPIEnvironment;
+
+import java.util.concurrent.*;
+
+/**
+ * A task which executes asynchronously on a new thread.
+ *
+ * This functions very similarly to a {@link Future}, but with an additional
+ * method which is called on the main thread when the task is completed.
+ */
+public class HTTPTask
+{
+    public interface IHTTPTask extends Runnable
+    {
+        void whenFinished( IAPIEnvironment environment );
+    }
+
+    private static final ExecutorService httpThreads = new ThreadPoolExecutor(
+        4, Integer.MAX_VALUE,
+        60L, TimeUnit.SECONDS,
+        new SynchronousQueue<Runnable>(),
+        new ThreadFactoryBuilder()
+            .setDaemon( true )
+            .setPriority( Thread.MIN_PRIORITY + (Thread.NORM_PRIORITY - Thread.MIN_PRIORITY) / 2 )
+            .setNameFormat( "ComputerCraft-HTTP-%d" )
+            .build()
+    );
+
+    private final Future<?> future;
+    private final IHTTPTask task;
+
+    private HTTPTask( Future<?> future, IHTTPTask task )
+    {
+        this.future = future;
+        this.task = task;
+    }
+
+    public static HTTPTask submit( IHTTPTask task )
+    {
+        Future<?> future = httpThreads.submit( task );
+        return new HTTPTask( future, task );
+    }
+
+    public void cancel()
+    {
+        future.cancel( false );
+    }
+
+    public boolean isFinished()
+    {
+        return future.isDone();
+    }
+
+    public void whenFinished( IAPIEnvironment environment )
+    {
+        task.whenFinished( environment );
+    }
+}

src/main/java/dan200/computercraft/core/filesystem/FileSystem.java

@@ -172,7 +172,7 @@ public class FileSystem
         {
             if( m_writableMount == null )
             {
-                throw new FileSystemException( "Access Denied" );
+                throw new FileSystemException( "Access denied" );
             }
             try
             {
@@ -199,7 +199,7 @@ public class FileSystem
         {
             if( m_writableMount == null )
             {
-                throw new FileSystemException( "Access Denied" );
+                throw new FileSystemException( "Access denied" );
             }
             try
             {
@@ -219,7 +219,7 @@ public class FileSystem
         {
             if( m_writableMount == null )
             {
-                throw new FileSystemException( "Access Denied" );
+                throw new FileSystemException( "Access denied" );
             }
             try
             {
@@ -251,7 +251,7 @@ public class FileSystem
         {
             if( m_writableMount == null )
             {
-                throw new FileSystemException( "Access Denied" );
+                throw new FileSystemException( "Access denied" );
             }
             try
             {

src/main/java/dan200/computercraft/shared/computer/apis/CommandAPI.java

@@ -28,6 +28,9 @@ import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Map;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
+import static dan200.computercraft.core.apis.ArgumentHelper.getString;
+
 public class CommandAPI implements ILuaAPI
 {
     private TileCommandComputer m_computer;
@@ -151,11 +154,7 @@ public class CommandAPI implements ILuaAPI
             case 0:
             {
                 // exec
-                if( arguments.length < 1 || !(arguments[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                final String command = (String)arguments[0];
+                final String command = getString( arguments, 0 );
                 return context.executeMainThreadTask( new ILuaTask()
                 {
                     @Override
@@ -168,11 +167,7 @@ public class CommandAPI implements ILuaAPI
             case 1:
             {
                 // execAsync
-                if( arguments.length < 1 || !(arguments[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-                final String command = (String)arguments[0];
+                final String command = getString( arguments, 0 );
                 long taskID = context.issueMainThreadTask( new ILuaTask()
                 {
                     @Override
@@ -234,22 +229,12 @@ public class CommandAPI implements ILuaAPI
             case 4:
             {
                 // getBlockInfos
-                if( arguments.length < 6 ||
-                    !(arguments[0] instanceof Number) ||
-                    !(arguments[1] instanceof Number) ||
-                    !(arguments[2] instanceof Number) ||
-                    !(arguments[3] instanceof Number) ||
-                    !(arguments[4] instanceof Number) ||
-                    !(arguments[5] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number, number, number, number, number, number" );
-                }
-                final int minx = ((Number)arguments[0]).intValue();
-                final int miny = ((Number)arguments[1]).intValue();
-                final int minz = ((Number)arguments[2]).intValue();
-                final int maxx = ((Number)arguments[3]).intValue();
-                final int maxy = ((Number)arguments[4]).intValue();
-                final int maxz = ((Number)arguments[5]).intValue();
+                final int minx = getInt( arguments, 0 );
+                final int miny = getInt( arguments, 1 );
+                final int minz = getInt( arguments, 2 );
+                final int maxx = getInt( arguments, 3 );
+                final int maxy = getInt( arguments, 4 );
+                final int maxz = getInt( arguments, 5 );
                 return context.executeMainThreadTask( new ILuaTask()
                 {
                     @Override
@@ -295,16 +280,9 @@ public class CommandAPI implements ILuaAPI
             case 5:
             {
                 // getBlockInfo
-                if( arguments.length < 3 ||
-                        !(arguments[0] instanceof Number) ||
-                        !(arguments[1] instanceof Number) ||
-                        !(arguments[2] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number, number, number" );
-                }
-                final int x = ((Number)arguments[0]).intValue();
-                final int y = ((Number)arguments[1]).intValue();
-                final int z = ((Number)arguments[2]).intValue();
+                final int x = getInt( arguments, 0 );
+                final int y = getInt( arguments, 1 );
+                final int z = getInt( arguments, 2 );
                 return context.executeMainThreadTask( new ILuaTask()
                 {
                     @Override

src/main/java/dan200/computercraft/shared/peripheral/commandblock/CommandBlockPeripheral.java

@@ -16,6 +16,8 @@ import net.minecraft.util.math.BlockPos;
 
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getString;
+
 public class CommandBlockPeripheral implements IPeripheral
 {
     private final TileEntityCommandBlock m_commandBlock;
@@ -67,12 +69,7 @@ public class CommandBlockPeripheral implements IPeripheral
             case 1:
             {
                 // setCommand
-                if( arguments.length < 1 || !(arguments[0] instanceof String) )
-                {
-                    throw new LuaException( "Expected string" );
-                }
-
-                final String command = (String) arguments[ 0 ];
+                final String command = getString( arguments, 0 );
                 context.issueMainThreadTask( new ILuaTask()
                 {
                     @Override

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/DiskDrivePeripheral.java

@@ -18,6 +18,8 @@ import net.minecraft.item.ItemStack;
 
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.optString;
+
 public class DiskDrivePeripheral implements IPeripheral
 {
     private final TileDiskDrive m_diskDrive;
@@ -78,15 +80,7 @@ public class DiskDrivePeripheral implements IPeripheral
             case 2:
             {
                 // setDiskLabel
-                String label = null;
-                if( arguments.length > 0 )
-                {
-                    if( arguments[0] != null && !(arguments[0] instanceof String) )
-                    {
-                        throw new LuaException( "Expected string" );
-                    }
-                    label = (String)arguments[0];
-                }
+                String label = optString( arguments, 0, null );
 
                 IMedia media = m_diskDrive.getDiskMedia();
                 if( media != null )

src/main/java/dan200/computercraft/shared/peripheral/modem/ModemPeripheral.java

@@ -21,6 +21,8 @@ import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
+
 public abstract class ModemPeripheral
     implements IPeripheral, IPacketSender, IPacketReceiver
 {
@@ -147,11 +149,7 @@ public abstract class ModemPeripheral
     
     private static int parseChannel( Object[] arguments, int index ) throws LuaException
     {
-        if( arguments.length <= index || !(arguments[index] instanceof Double) )
-        {
-            throw new LuaException( "Expected number" );
-        }
-        int channel = (int)((Double)arguments[index]).doubleValue();
+        int channel = getInt( arguments, index );
         if( channel < 0 || channel > 65535 )
         {
             throw new LuaException( "Expected number in range 0-65535" );

src/main/java/dan200/computercraft/shared/peripheral/modem/TileCable.java

@@ -40,6 +40,8 @@ import javax.annotation.Nonnull;
 import java.io.File;
 import java.util.*;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getString;
+
 public class TileCable extends TileModemBase
     implements IPacketNetwork
 {
@@ -116,15 +118,6 @@ public class TileCable extends TileModemBase
             return newMethods;
         }
 
-        private String parseString( Object[] arguments, int index ) throws LuaException
-        {
-            if( arguments.length < (index + 1) || !(arguments[index] instanceof String) )
-            {
-                throw new LuaException( "Expected string" );
-            }
-            return (String)arguments[index];
-        }
-
         @Override
         public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
         {
@@ -148,13 +141,13 @@ public class TileCable extends TileModemBase
                 case 1:
                 {
                     // isPresentRemote
-                    String type = m_entity.getTypeRemote( parseString( arguments, 0 ) );
+                    String type = m_entity.getTypeRemote( getString( arguments, 0 ) );
                     return new Object[] { type != null };
                 }
                 case 2:
                 {
                     // getTypeRemote
-                    String type = m_entity.getTypeRemote( parseString( arguments, 0 ) );
+                    String type = m_entity.getTypeRemote( getString( arguments, 0 ) );
                     if( type != null )
                     {
                         return new Object[] { type };
@@ -164,7 +157,7 @@ public class TileCable extends TileModemBase
                 case 3:
                 {
                     // getMethodsRemote
-                    String[] methodNames = m_entity.getMethodNamesRemote( parseString( arguments, 0 ) );
+                    String[] methodNames = m_entity.getMethodNamesRemote( getString( arguments, 0 ) );
                     if( methodNames != null )
                     {
                         Map<Object,Object> table = new HashMap<Object,Object>();
@@ -178,8 +171,8 @@ public class TileCable extends TileModemBase
                 case 4:
                 {
                     // callRemote
-                    String remoteName = parseString( arguments, 0 );
-                    String methodName = parseString( arguments, 1 );
+                    String remoteName = getString( arguments, 0 );
+                    String methodName = getString( arguments, 1 );
                     Object[] methodArgs = new Object[ arguments.length - 2 ];
                     System.arraycopy( arguments, 2, methodArgs, 0, arguments.length - 2 );
                     return m_entity.callMethodRemote( remoteName, context, methodName, methodArgs );

src/main/java/dan200/computercraft/shared/peripheral/monitor/MonitorPeripheral.java

@@ -10,14 +10,15 @@ import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.core.apis.TermAPI;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.shared.util.Palette;
 import org.apache.commons.lang3.ArrayUtils;
 
-import java.util.HashMap;
-
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.*;
+
 public class MonitorPeripheral implements IPeripheral
 {
     private final TileMonitor m_monitor;
@@ -90,23 +91,16 @@ public class MonitorPeripheral implements IPeripheral
             case 1:
             {
                 // scroll
-                if( args.length < 1 || !(args[0] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number" );
-                }
+                int value = getInt( args, 0 );
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
-                terminal.scroll( ((Number)(args[0])).intValue() );
+                terminal.scroll( value );
                 return null;
             }
             case 2:
             {
                 // setCursorPos
-                if( args.length < 2 || !(args[0] instanceof Number) || !(args[1] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number, number" );
-                }
-                int x = ((Number)args[0]).intValue() - 1;
-                int y = ((Number)args[1]).intValue() - 1;
+                int x = getInt( args, 0 ) - 1;
+                int y = getInt( args, 1 ) - 1;
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
                 terminal.setCursorPos( x, y );
                 return null;
@@ -114,12 +108,9 @@ public class MonitorPeripheral implements IPeripheral
             case 3:
             {
                 // setCursorBlink
-                if( args.length < 1 || !(args[0] instanceof Boolean) )
-                {
-                    throw new LuaException( "Expected boolean" );
-                }
+                boolean blink = getBoolean( args, 0 );
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
-                terminal.setCursorBlink( (Boolean) args[ 0 ] );
+                terminal.setCursorBlink( blink );
                 return null;
             }
             case 4:
@@ -157,11 +148,7 @@ public class MonitorPeripheral implements IPeripheral
             case 8:
             {
                 // setTextScale
-                if( args.length < 1 || !(args[0] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number" );
-                }
-                int scale = (int)(((Number)args[0]).doubleValue() * 2.0);
+                int scale = (int) (getReal( args, 0 ) * 2.0);
                 if( scale < 1 || scale > 10 )
                 {
                     throw new LuaException( "Expected number in range 0.5-5" );
@@ -173,7 +160,7 @@ public class MonitorPeripheral implements IPeripheral
             case 10:
             {
                 // setTextColour/setTextColor
-                int colour = dan200.computercraft.core.apis.TermAPI.parseColour( args );
+                int colour = TermAPI.parseColour( args );
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
                 terminal.setTextColour( colour );
                 return null;
@@ -182,7 +169,7 @@ public class MonitorPeripheral implements IPeripheral
             case 12:
             {
                 // setBackgroundColour/setBackgroundColor
-                int colour = dan200.computercraft.core.apis.TermAPI.parseColour( args );
+                int colour = TermAPI.parseColour( args );
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
                 terminal.setBackgroundColour( colour );
                 return null;
@@ -200,26 +187,21 @@ public class MonitorPeripheral implements IPeripheral
             {
                 // getTextColour/getTextColor
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
-                return dan200.computercraft.core.apis.TermAPI.encodeColour( terminal.getTextColour() );
+                return TermAPI.encodeColour( terminal.getTextColour() );
             }
             case 17:
             case 18:
             {
                 // getBackgroundColour/getBackgroundColor
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
-                return dan200.computercraft.core.apis.TermAPI.encodeColour( terminal.getBackgroundColour() );
+                return TermAPI.encodeColour( terminal.getBackgroundColour() );
             }
             case 19:
             {
                 // blit
-                if( args.length < 3 || !(args[0] instanceof String) || !(args[1] instanceof String) || !(args[2] instanceof String) )
-                {
-                    throw new LuaException( "Expected string, string, string" );
-                }
-
-                String text = (String)args[0];
-                String textColour = (String)args[1];
-                String backgroundColour = (String)args[2];
+                String text = getString( args, 0 );
+                String textColour = getString( args, 1 );
+                String backgroundColour = getString( args, 2 );
                 if( textColour.length() != text.length() || backgroundColour.length() != text.length() )
                 {
                     throw new LuaException( "Arguments must be the same length" );
@@ -236,26 +218,21 @@ public class MonitorPeripheral implements IPeripheral
                 // setPaletteColour/setPaletteColor
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
 
-                if(args.length == 2 && args[0] instanceof Double && args[1] instanceof Double)
+                int colour = 15 - TermAPI.parseColour( args );
+                if( args.length == 2 )
                 {
-                    int colour = 15 - dan200.computercraft.core.apis.TermAPI.parseColour( args );
-                    int hex = ((Double)args[1]).intValue();
+                    int hex = getInt( args, 1 );
                     double[] rgb = Palette.decodeRGB8( hex );
-                    dan200.computercraft.core.apis.TermAPI.setColour( terminal, colour, rgb[0], rgb[1], rgb[2] );
-                    return null;
+                    TermAPI.setColour( terminal, colour, rgb[ 0 ], rgb[ 1 ], rgb[ 2 ] );
                 }
-
-                if (args.length >= 4 && args[0] instanceof Double && args[1] instanceof Double && args[2] instanceof Double && args[3] instanceof Double)
+                else
                 {
-                    int colour = 15 - dan200.computercraft.core.apis.TermAPI.parseColour( args );
-                    double r = (Double)args[1];
-                    double g = (Double)args[2];
-                    double b = (Double)args[3];
-                    dan200.computercraft.core.apis.TermAPI.setColour( terminal, colour, r, g, b );
-                    return null;
+                    double r = getReal( args, 1 );
+                    double g = getReal( args, 2 );
+                    double b = getReal( args, 3 );
+                    TermAPI.setColour( terminal, colour, r, g, b );
                 }
-
-                throw new LuaException( "Expected number, number, number, number" );
+                return null;
             }
             case 22:
             case 23:
@@ -264,7 +241,7 @@ public class MonitorPeripheral implements IPeripheral
                 Terminal terminal = m_monitor.getTerminal().getTerminal();
                 Palette palette = terminal.getPalette();
 
-                int colour = 15 - dan200.computercraft.core.apis.TermAPI.parseColour( args );
+                int colour = 15 - TermAPI.parseColour( args );
 
                 if( palette != null )
                 {

src/main/java/dan200/computercraft/shared/peripheral/printer/PrinterPeripheral.java

@@ -14,6 +14,9 @@ import dan200.computercraft.core.terminal.Terminal;
 
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
+import static dan200.computercraft.core.apis.ArgumentHelper.optString;
+
 public class PrinterPeripheral implements IPeripheral
 {
     private final TilePrinter m_printer;
@@ -70,13 +73,8 @@ public class PrinterPeripheral implements IPeripheral
             case 1:
             {
                 // setCursorPos
-                if( args.length != 2 || args[0] == null || !(args[0] instanceof Number) || args[1] == null || !(args[1] instanceof Number) )
-                {
-                    throw new LuaException( "Expected number, number" );
-                }
-
-                int x = ((Number)args[0]).intValue() - 1;
-                int y = ((Number)args[1]).intValue() - 1;
+                int x = getInt( args, 0 ) - 1;
+                int y = getInt( args, 1 ) - 1;
                 Terminal page = getCurrentPage();
                 page.setCursorPos( x, y );
                 return null;
@@ -116,16 +114,7 @@ public class PrinterPeripheral implements IPeripheral
             case 7:
             {
                 // setPageTitle
-                String title = "";
-                if( args.length > 0 && args[0] != null )
-                {
-                    if( !(args[0] instanceof String) )
-                    {
-                        throw new LuaException( "Expected string" );
-                    }
-                    title = (String)args[0];
-                }
-
+                String title = optString( args, 0, "" );
                 getCurrentPage();
                 m_printer.setPageTitle( title );
                 return null;

src/main/java/dan200/computercraft/shared/peripheral/speaker/SpeakerPeripheral.java

@@ -17,9 +17,13 @@ import net.minecraft.util.SoundCategory;
 import net.minecraft.util.SoundEvent;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
+
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.getString;
+import static dan200.computercraft.core.apis.ArgumentHelper.optReal;
+
 public class SpeakerPeripheral implements IPeripheral {
     private TileSpeaker m_speaker;
     private long m_clock;
@@ -127,47 +131,20 @@ public class SpeakerPeripheral implements IPeripheral {
     @Nonnull
     private synchronized Object[] playNote( Object[] arguments, ILuaContext context ) throws LuaException
     {
-        float volume = 1.0f;
-        float pitch = 1.0f;
+        String name = getString(arguments, 0);
+        float volume = (float) optReal( arguments, 1, 1.0 );
+        float pitch = (float) optReal( arguments, 2, 1.0 );
 
-        // Check if arguments are correct
-        if( arguments.length == 0 ) // Too few args
-        {
-            throw new LuaException( "Expected string, number (optional), number (optional)" );
-        }
-
-        if( !(arguments[0] instanceof String) ) // Arg wrong type
-        {
-            throw new LuaException("Expected string, number (optional), number (optional)");
-        }
-
-        if ( !SoundEvent.REGISTRY.containsKey( new ResourceLocation( "block.note." + arguments[0] ) ) )
+        // Check if sound exists
+        if ( !SoundEvent.REGISTRY.containsKey( new ResourceLocation( "block.note." + name ) ) )
         {
             throw new LuaException("Invalid instrument, \"" + arguments[0] + "\"!");
         }
 
-        if ( arguments.length > 1 )
-        {
-            if ( arguments[1] != null && !(arguments[1] instanceof Double) )   // Arg wrong type
-            {
-                throw new LuaException( "Expected string, number (optional), number (optional)" );
-            }
-            volume = arguments[1] != null ? ((Double) arguments[1]).floatValue() : 1f;
-        }
-
-        if( arguments.length > 2 )
-        {
-            if( arguments[2] != null && !(arguments[2] instanceof Double) )  // Arg wrong type
-            {
-                throw new LuaException("Expected string, number (optional), number (optional)");
-            }
-            pitch = arguments[2] != null ? ((Double) arguments[2]).floatValue() : 1f;
-        }
-
         // If the resource location for note block notes changes, this method call will need to be updated
         Object[] returnValue = playSound(
             new Object[] {
-                "block.note." + arguments[0],
+                "block.note." + name,
                 (double)Math.min( volume, 3f ),
                 Math.pow( 2.0f, ( pitch - 12.0f ) / 12.0f)
             }, context, true
@@ -184,42 +161,11 @@ public class SpeakerPeripheral implements IPeripheral {
     @Nonnull
     private synchronized Object[] playSound( Object[] arguments, ILuaContext context, boolean isNote ) throws LuaException
     {
+        String name = getString(arguments, 0);
+        float volume = (float) optReal( arguments, 1, 1.0 );
+        float pitch = (float) optReal( arguments, 2, 1.0 );
 
-        float volume = 1.0f;
-        float pitch = 1.0f;
-
-        // Check if arguments are correct
-        if( arguments.length == 0 ) // Too few args
-        {
-            throw new LuaException( "Expected string, number (optional), number (optional)" );
-        }
-
-        if( !(arguments[0] instanceof String) ) // Arg wrong type
-        {
-            throw new LuaException( "Expected string, number (optional), number (optional)" );
-        }
-
-        if( arguments.length > 1 )
-        {
-            if( arguments[1] != null && !(arguments[1] instanceof Double) )  // Arg wrong type
-            {
-                throw new LuaException( "Expected string, number (optional), number (optional)" );
-            }
-
-            volume = arguments[1] != null ? ((Double) arguments[1]).floatValue() : 1f;
-
-        }
-
-        if( arguments.length > 2 )
-        {
-            if( arguments[2] != null && !(arguments[2] instanceof Double) )  // Arg wrong type
-            {
-                throw new LuaException( "Expected string, number (optional), number (optional)" );
-            }
-            pitch = arguments[2] != null ? ((Double) arguments[2]).floatValue() : 1f;
-        }
-
-        ResourceLocation resourceName = new ResourceLocation( (String) arguments[0] );
+        ResourceLocation resourceName = new ResourceLocation( name );
 
         if( m_clock - m_lastPlayTime >= TileSpeaker.MIN_TICKS_BETWEEN_SOUNDS || ( ( m_clock - m_lastPlayTime == 0 ) && ( m_notesThisTick < ComputerCraft.maxNotesPerTick ) && isNote ) )
         {

src/main/java/dan200/computercraft/shared/turtle/apis/TurtleAPI.java

@@ -22,6 +22,8 @@ import javax.annotation.Nonnull;
 import java.util.HashMap;
 import java.util.Map;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.*;
+
 public class TurtleAPI implements ILuaAPI
 {
     private IAPIEnvironment m_environment;
@@ -115,38 +117,23 @@ public class TurtleAPI implements ILuaAPI
 
     private int parseSlotNumber( Object[] arguments, int index ) throws LuaException
     {
-        int slot = parseOptionalSlotNumber( arguments, index, 99 );
-        if( slot == 99 )
-        {
-            throw new LuaException( "Expected number" );
-        }
-        return slot;
+        int slot = getInt( arguments, index );
+        if( slot < 1 || slot > 16 ) throw new LuaException( "Slot number " + slot + " out of range" );
+        return slot - 1;
     }
 
     private int parseOptionalSlotNumber( Object[] arguments, int index, int fallback ) throws LuaException
     {
-        if( arguments.length <= index || !(arguments[index] instanceof Number) )
-        {
-            return fallback;
-        }
-        int slot = ((Number)arguments[index]).intValue();
-        if( slot >= 1 && slot <= 16 )
-        {
-            return slot - 1;
-        }
-        else
-        {
-            throw new LuaException( "Slot number " + slot + " out of range" );
-        }
+        if( index >= arguments.length || arguments[ index ] == null ) return fallback;
+
+        int slot = getInt( arguments, index );
+        if( slot < 1 || slot > 16 ) throw new LuaException( "Slot number " + slot + " out of range" );
+        return slot - 1;
     }
     
     private int parseCount( Object[] arguments, int index ) throws LuaException
     {
-        if( arguments.length <= index || !(arguments[index] instanceof Number) )
-        {
-            throw new LuaException( "Expected number" );
-        }
-        int count = ((Number)arguments[index]).intValue();
+        int count = optInt( arguments, index, 64 );
         if( count >= 0 && count <= 64 )
         {
             return count;
@@ -159,19 +146,16 @@ public class TurtleAPI implements ILuaAPI
 
     private Optional<TurtleSide> parseSide( Object[] arguments, int index ) throws LuaException
     {
-        if( arguments.length <= index || arguments[index] == null )
+        String side = optString( arguments, index, null );
+        if( side == null )
         {
             return Optional.absent();
         }
-        if( !(arguments[ index ] instanceof String) )
-        {
-            throw new LuaException( "Expected string" );
-        }
-        if( arguments[ index ].equals( "left" ) )
+        else if( side.equalsIgnoreCase( "left" ) )
         {
             return Optional.of( TurtleSide.Left );
         }
-        else if( arguments[ index ].equals( "right" ) )
+        else if( side.equalsIgnoreCase( "right" ) )
         {
             return Optional.of( TurtleSide.Right );
         }
@@ -252,11 +236,7 @@ public class TurtleAPI implements ILuaAPI
             case 12:
             {
                 // drop
-                int count = 64;
-                if( args.length > 0 )
-                {
-                    count = parseCount( args, 0 );
-                }
+                int count = parseCount( args, 0 );
                 return tryCommand( context, new TurtleDropCommand( InteractDirection.Forward, count ) );
             }
             case 13:
@@ -343,51 +323,31 @@ public class TurtleAPI implements ILuaAPI
             case 25:
             {
                 // dropUp
-                int count = 64;
-                if( args.length > 0 )
-                {
-                    count = parseCount( args, 0 );
-                }
+                int count = parseCount( args, 0 );
                 return tryCommand( context, new TurtleDropCommand( InteractDirection.Up, count ) );
             }
             case 26:
             {
                 // dropDown
-                int count = 64;
-                if( args.length > 0 )
-                {
-                    count = parseCount( args, 0 );
-                }
+                int count = parseCount( args, 0 );
                 return tryCommand( context, new TurtleDropCommand( InteractDirection.Down, count ) );
             }
             case 27:
             {
                 // suck
-                int count = 64;
-                if( args.length > 0 )
-                {
-                    count = parseCount( args, 0 );
-                }
+                int count = parseCount( args, 0 );
                 return tryCommand( context, new TurtleSuckCommand( InteractDirection.Forward, count ) );
             }
             case 28:
             {
                 // suckUp
-                int count = 64;
-                if( args.length > 0 )
-                {
-                    count = parseCount( args, 0 );
-                }
+                int count = parseCount( args, 0 );
                 return tryCommand( context, new TurtleSuckCommand( InteractDirection.Up, count ) );
             }
             case 29:
             {
                 // suckDown
-                int count = 64;
-                if( args.length > 0 )
-                {
-                    count = parseCount( args, 0 );
-                }
+                int count = parseCount( args, 0 );
                 return tryCommand( context, new TurtleSuckCommand( InteractDirection.Down, count ) );
             }
             case 30:
@@ -405,11 +365,7 @@ public class TurtleAPI implements ILuaAPI
             case 31:
             {
                 // refuel
-                int count = 64;
-                if( args.length > 0 )
-                {
-                    count = parseCount( args, 0 );
-                }
+                int count = parseCount( args, 0 );
                 return tryCommand( context, new TurtleRefuelCommand( count ) );
             }
             case 32:
@@ -422,11 +378,7 @@ public class TurtleAPI implements ILuaAPI
             {
                 // transferTo
                 int slot = parseSlotNumber( args, 0 );
-                int count = 64;
-                if( args.length > 1 )
-                {
-                    count = parseCount( args, 1 );
-                }
+                int count = parseCount( args, 1 );
                 return tryCommand( context, new TurtleTransferToCommand( slot, count ) );
             }
             case 34:

src/main/java/dan200/computercraft/shared/turtle/core/TurtlePlaceCommand.java

@@ -24,13 +24,16 @@ import net.minecraft.tileentity.TileEntity;
 import net.minecraft.tileentity.TileEntitySign;
 import net.minecraft.util.ActionResult;
 import net.minecraft.util.EnumActionResult;
+import net.minecraft.util.EnumFacing;
 import net.minecraft.util.EnumHand;
 import net.minecraft.util.math.BlockPos;
-import net.minecraft.util.text.TextComponentString;
-import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.Vec3d;
+import net.minecraft.util.text.TextComponentString;
 import net.minecraft.world.World;
 import net.minecraft.world.WorldServer;
+import net.minecraftforge.common.ForgeHooks;
+import net.minecraftforge.event.entity.player.PlayerInteractEvent;
+import net.minecraftforge.fml.common.eventhandler.Event;
 import org.apache.commons.lang3.tuple.Pair;
 
 import javax.annotation.Nonnull;
@@ -215,7 +218,6 @@ public class TurtlePlaceCommand implements ITurtleCommand
         }
 
         // Load up the turtle's inventory
-        Item item = stack.getItem();
         ItemStack stackCopy = stack.copy();
         turtlePlayer.loadInventory( stackCopy );
 
@@ -237,21 +239,26 @@ public class TurtlePlaceCommand implements ITurtleCommand
 
         // Place on the entity
         boolean placed = false;
-        if( hitEntity.applyPlayerInteraction( turtlePlayer, hitPos, stackCopy, EnumHand.MAIN_HAND ) == EnumActionResult.SUCCESS )
+        if( !ForgeHooks.onInteractEntityAt( turtlePlayer, hitEntity, hitPos, stack, EnumHand.MAIN_HAND ) &&
+            hitEntity.applyPlayerInteraction( turtlePlayer, hitPos, stackCopy, EnumHand.MAIN_HAND ) == EnumActionResult.SUCCESS )
         {
             placed = true;
             turtlePlayer.loadInventory( stackCopy );
         }
-        else if( hitEntity.processInitialInteract( turtlePlayer, stackCopy, EnumHand.MAIN_HAND ) )
+        else if( !ForgeHooks.onInteractEntity( turtlePlayer, hitEntity, stack, EnumHand.MAIN_HAND ) )
         {
-            placed = true;
-        }
-        else if( hitEntity instanceof EntityLivingBase )
-        {
-            placed = item.itemInteractionForEntity( stackCopy, turtlePlayer, (EntityLivingBase)hitEntity, EnumHand.MAIN_HAND );
-            if( placed )
+            // See EntityPlayer.interact
+            if( hitEntity.processInitialInteract( turtlePlayer, stackCopy, EnumHand.MAIN_HAND ) )
             {
-                turtlePlayer.loadInventory( stackCopy );
+                placed = true;
+            }
+            else if( hitEntity instanceof EntityLivingBase )
+            {
+                placed = stackCopy.interactWithEntity( turtlePlayer, (EntityLivingBase) hitEntity, EnumHand.MAIN_HAND );
+                if( placed )
+                {
+                    turtlePlayer.loadInventory( stackCopy );
+                }
             }
         }
 
@@ -352,19 +359,29 @@ public class TurtlePlaceCommand implements ITurtleCommand
 
         // Do the deploying (put everything in the players inventory)
         boolean placed = false;
-        if( item.onItemUseFirst( stackCopy, turtlePlayer, turtle.getWorld(), position, side, hitX, hitY, hitZ, EnumHand.MAIN_HAND ) == EnumActionResult.SUCCESS )
+
+
+        // See PlayerInteractionManager.processRightClickBlock
+        PlayerInteractEvent.RightClickBlock event = ForgeHooks.onRightClickBlock( turtlePlayer, EnumHand.MAIN_HAND, stackCopy, position, side, new Vec3d( hitX, hitY, hitZ ) );
+        if( !event.isCanceled() )
         {
-            placed = true;
-            turtlePlayer.loadInventory( stackCopy );
+            if( item.onItemUseFirst( stackCopy, turtlePlayer, turtle.getWorld(), position, side, hitX, hitY, hitZ, EnumHand.MAIN_HAND ) == EnumActionResult.SUCCESS )
+            {
+                placed = true;
+                turtlePlayer.loadInventory( stackCopy );
+            }
+            else if( event.getUseItem() != Event.Result.DENY &&
+                stackCopy.onItemUse( turtlePlayer, turtle.getWorld(), position, EnumHand.MAIN_HAND, side, hitX, hitY, hitZ ) == EnumActionResult.SUCCESS )
+            {
+                placed = true;
+                turtlePlayer.loadInventory( stackCopy );
+            }
         }
-        else if( item.onItemUse( stackCopy, turtlePlayer, turtle.getWorld(), position, EnumHand.MAIN_HAND, side, hitX, hitY, hitZ ) == EnumActionResult.SUCCESS )
+
+        if( !placed && (item instanceof ItemBucket || item instanceof ItemBoat || item instanceof ItemLilyPad || item instanceof ItemGlassBottle)
+            && ForgeHooks.onItemRightClick( turtlePlayer, EnumHand.MAIN_HAND, stackCopy ) )
         {
-            placed = true;
-            turtlePlayer.loadInventory( stackCopy );
-        }
-        else if( item instanceof ItemBucket || item instanceof ItemBoat || item instanceof ItemLilyPad || item instanceof ItemGlassBottle )
-        {
-            ActionResult<ItemStack> result = item.onItemRightClick( stackCopy, turtle.getWorld(), turtlePlayer, EnumHand.MAIN_HAND );
+            ActionResult<ItemStack> result = stackCopy.useItemRightClick( turtle.getWorld(), turtlePlayer, EnumHand.MAIN_HAND );
             if( result.getType() == EnumActionResult.SUCCESS && !ItemStack.areItemStacksEqual( stack, result.getResult() ) )
             {
                 placed = true;

src/main/java/dan200/computercraft/shared/turtle/upgrades/CraftingTablePeripheral.java

@@ -15,6 +15,8 @@ import dan200.computercraft.shared.turtle.core.TurtleCraftCommand;
 
 import javax.annotation.Nonnull;
 
+import static dan200.computercraft.core.apis.ArgumentHelper.optInt;
+
 public class CraftingTablePeripheral
     implements IPeripheral
 {
@@ -45,16 +47,7 @@ public class CraftingTablePeripheral
         
     private int parseCount( Object[] arguments ) throws LuaException
     {
-        if( arguments.length < 1 )
-        {
-            return 64;
-        }
-        
-        if( !(arguments[0] instanceof Number) )
-        {
-            throw new LuaException( "Expected number" );
-        }
-        int count = ((Number)arguments[0]).intValue();
+        int count = optInt( arguments, 0, 64 );
         if( count < 0 || count > 64 )
         {
             throw new LuaException( "Crafting count " + count + " out of range" );

src/main/java/dan200/computercraft/shared/turtle/upgrades/TurtleTool.java

@@ -22,14 +22,22 @@ import net.minecraft.client.renderer.block.model.IBakedModel;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.SharedMonsterAttributes;
 import net.minecraft.entity.item.EntityArmorStand;
+import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.init.Blocks;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
-import net.minecraft.util.*;
-import net.minecraft.util.math.*;
+import net.minecraft.util.DamageSource;
+import net.minecraft.util.EnumFacing;
+import net.minecraft.util.ResourceLocation;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
 import net.minecraft.world.WorldServer;
 import net.minecraftforge.common.ForgeHooks;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.event.ForgeEventFactory;
+import net.minecraftforge.event.entity.player.AttackEntityEvent;
+import net.minecraftforge.event.world.BlockEvent;
 import net.minecraftforge.fml.relauncher.Side;
 import net.minecraftforge.fml.relauncher.SideOnly;
 import org.apache.commons.lang3.tuple.Pair;
@@ -189,9 +197,10 @@ public class TurtleTool implements ITurtleUpgrade
                 }
             } );
 
-            // Place on the entity
-            boolean placed = false;
-            if( hitEntity.canBeAttackedWithItem() && !hitEntity.hitByEntity( turtlePlayer ) )
+            // Attack the entity
+            boolean attacked = false;
+            if( hitEntity.canBeAttackedWithItem() && !hitEntity.hitByEntity( turtlePlayer )
+                && !MinecraftForge.EVENT_BUS.post( new AttackEntityEvent( turtlePlayer, hitEntity ) ) )
             {
                 float damage = (float)turtlePlayer.getEntityAttribute( SharedMonsterAttributes.ATTACK_DAMAGE ).getAttributeValue();
                 damage *= getDamageMultiplier();
@@ -206,13 +215,13 @@ public class TurtleTool implements ITurtleUpgrade
                         {
                             hitEntity.attackEntityFrom( source, damage );
                         }
-                        placed = true;
+                        attacked = true;
                     }
                     else
                     {
                         if( hitEntity.attackEntityFrom( source, damage ) )
                         {
-                            placed = true;
+                            attacked = true;
                         }
                     }
                 }
@@ -222,7 +231,7 @@ public class TurtleTool implements ITurtleUpgrade
             ComputerCraft.clearEntityDropConsumer( hitEntity );
 
             // Put everything we collected into the turtles inventory, then return
-            if( placed )
+            if( attacked )
             {
                 turtlePlayer.unloadInventory( turtle );
                 return TurtleCommandResult.success();
@@ -243,10 +252,16 @@ public class TurtleTool implements ITurtleUpgrade
             !world.isAirBlock( newPosition ) &&
             !WorldUtil.isLiquidBlock( world, newPosition ) )
         {
+            TurtlePlayer turtlePlayer = TurtlePlaceCommand.createPlayer( turtle, position, direction );
             if( ComputerCraft.turtlesObeyBlockProtection )
             {
                 // Check spawn protection
-                TurtlePlayer turtlePlayer = TurtlePlaceCommand.createPlayer( turtle, position, direction );
+
+                if( MinecraftForge.EVENT_BUS.post( new BlockEvent.BreakEvent( world, newPosition, world.getBlockState( newPosition ), turtlePlayer ) ) )
+                {
+                    return TurtleCommandResult.failure( "Cannot break protected block" );
+                }
+                
                 if( !ComputerCraft.isBlockEditable( world, newPosition, turtlePlayer ) )
                 {
                     return TurtleCommandResult.failure( "Cannot break protected block" );
@@ -262,7 +277,7 @@ public class TurtleTool implements ITurtleUpgrade
             // Consume the items the block drops
             if( canHarvestBlock( world, newPosition ) )
             {
-                List<ItemStack> items = getBlockDropped( world, newPosition );
+                List<ItemStack> items = getBlockDropped( world, newPosition, turtlePlayer );
                 if( items != null && items.size() > 0 )
                 {
                     for( ItemStack stack : items )
@@ -279,7 +294,7 @@ public class TurtleTool implements ITurtleUpgrade
 
             // Destroy the block
             IBlockState previousState = world.getBlockState( newPosition );
-			world.playEvent(2001, newPosition, Block.getStateId(previousState));
+            world.playEvent(2001, newPosition, Block.getStateId(previousState));
             world.setBlockToAir( newPosition );
 
             // Remember the previous block
@@ -295,9 +310,20 @@ public class TurtleTool implements ITurtleUpgrade
         return TurtleCommandResult.failure( "Nothing to dig here" );
     }
 
-    private java.util.List<ItemStack> getBlockDropped( World world, BlockPos pos )
+    private List<ItemStack> getBlockDropped( World world, BlockPos pos, EntityPlayer player )
     {
-        Block block = world.getBlockState( pos ).getBlock();
-        return block.getDrops( world, pos, world.getBlockState( pos ), 0 );
+        IBlockState state = world.getBlockState( pos );
+        Block block = state.getBlock();
+        List<ItemStack> drops = block.getDrops( world, pos, world.getBlockState( pos ), 0 );
+        double chance = ForgeEventFactory.fireBlockHarvesting( drops, world, pos, state, 0, 1, false, player );
+
+        for( int i = drops.size() - 1; i >= 0; i-- )
+        {
+            if( world.rand.nextFloat() > chance )
+            {
+                drops.remove( i );
+            }
+        }
+        return drops;
     }
 }

src/main/java/dan200/computercraft/shared/util/InventoryUtil.java

@@ -163,13 +163,13 @@ public class InventoryUtil
         }
 
         // Inspect the slots in order and try to find empty or stackable slots
-        ItemStack remainder = stack;
+        ItemStack remainder = stack.copy();
         for( int slot : slots )
         {
             if( remainder == null ) break;
             remainder = inventory.insertItem( slot, remainder, false );
         }
-        return remainder;
+        return areItemsEqual( stack, remainder ) ? stack : remainder;
     }
 
     private static ItemStack takeItems( int count, IItemHandler inventory, int[] slots )

src/main/resources/assets/computercraft/lang/en_US.lang

@@ -44,6 +44,7 @@ gui.computercraft:wired_modem.peripheral_disconnected=Peripheral "%s" disconnect
 
 gui.computercraft:config.http_enable=Enable HTTP API
 gui.computercraft:config.http_whitelist=HTTP whitelist
+gui.computercraft:config.http_blacklist=HTTP blacklist
 gui.computercraft:config.disable_lua51_features=Disable Lua 5.1 features
 gui.computercraft:config.default_computer_settings=Default Computer settings
 gui.computercraft:config.log_peripheral_errors=Log peripheral errors

src/main/resources/assets/computercraft/lua/bios.lua

@@ -184,6 +184,9 @@ end
 
 -- Install globals
 function sleep( nTime )
+    if nTime ~= nil and type( nTime ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( nTime ) .. ")", 2 ) 
+    end
     local timer = os.startTimer( nTime or 0 )
     repeat
         local sEvent, param = os.pullEvent( "timer" )
@@ -191,6 +194,10 @@ function sleep( nTime )
 end
 
 function write( sText )
+    if sText ~= nil and type( sText ) ~= "string" and type( sText ) ~= "number" then
+        error( "bad argument #1 (expected string, got " .. type( sText ) .. ")", 2 ) 
+    end
+
     local w,h = term.getSize()        
     local x,y = term.getCursorPos()
     
@@ -276,12 +283,29 @@ function printError( ... )
     end
 end
 
-function read( _sReplaceChar, _tHistory, _fnComplete )
+function read( _sReplaceChar, _tHistory, _fnComplete, _sDefault )
+    if _sReplaceChar ~= nil and type( _sReplaceChar ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sReplaceChar ) .. ")", 2 ) 
+    end
+    if _tHistory ~= nil and type( _tHistory ) ~= "table" then
+        error( "bad argument #2 (expected table, got " .. type( _tHistory ) .. ")", 2 ) 
+    end
+    if _fnComplete ~= nil and type( _fnComplete ) ~= "function" then
+        error( "bad argument #3 (expected function, got " .. type( _fnComplete ) .. ")", 2 ) 
+    end
+    if _sDefault ~= nil and type( _sDefault ) ~= "string" then
+        error( "bad argument #4 (expected string, got " .. type( _sDefault ) .. ")", 2 ) 
+    end
     term.setCursorBlink( true )
 
-    local sLine = ""
+    local sLine
+    if type( _sDefault ) == "string" then
+        sLine = _sDefault
+    else
+        sLine = ""
+    end
     local nHistoryPos
-    local nPos = 0
+    local nPos = #sLine
     if _sReplaceChar then
         _sReplaceChar = string.sub( _sReplaceChar, 1, 1 )
     end
@@ -530,6 +554,12 @@ function read( _sReplaceChar, _tHistory, _fnComplete )
 end
 
 loadfile = function( _sFile, _tEnv )
+    if type( _sFile ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sFile ) .. ")", 2 ) 
+    end
+    if _tEnv ~= nil and type( _tEnv ) ~= "table" then
+        error( "bad argument #2 (expected table, got " .. type( _tEnv ) .. ")", 2 ) 
+    end
     local file = fs.open( _sFile, "r" )
     if file then
         local func, err = load( file.readAll(), fs.getName( _sFile ), "t", _tEnv )
@@ -540,6 +570,9 @@ loadfile = function( _sFile, _tEnv )
 end
 
 dofile = function( _sFile )
+    if type( _sFile ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sFile ) .. ")", 2 ) 
+    end
     local fnFile, e = loadfile( _sFile, _G )
     if fnFile then
         return fnFile()
@@ -550,6 +583,12 @@ end
 
 -- Install the rest of the OS api
 function os.run( _tEnv, _sPath, ... )
+    if type( _tEnv ) ~= "table" then
+        error( "bad argument #1 (expected table, got " .. type( _tEnv ) .. ")", 2 ) 
+    end
+    if type( _sPath ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( _sPath ) .. ")", 2 ) 
+    end
     local tArgs = table.pack( ... )
     local tEnv = _tEnv
     setmetatable( tEnv, { __index = _G } )
@@ -574,6 +613,9 @@ end
 
 local tAPIsLoading = {}
 function os.loadAPI( _sPath )
+    if type( _sPath ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sPath ) .. ")", 2 ) 
+    end
     local sName = fs.getName( _sPath )
     if sName:sub(-4) == ".lua" then
         sName = sName:sub(1,-5)
@@ -613,6 +655,9 @@ function os.loadAPI( _sPath )
 end
 
 function os.unloadAPI( _sName )
+    if type( _sName ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sName ) .. ")", 2 ) 
+    end
     if _sName ~= "_G" and type(_G[_sName]) == "table" then
         _G[_sName] = nil
     end
@@ -658,25 +703,73 @@ if http then
     end
     
     http.get = function( _url, _headers, _binary)
+        if type( _url ) ~= "string" then
+            error( "bad argument #1 (expected string, got " .. type( _url ) .. ")", 2 ) 
+        end
+        if _headers ~= nil and type( _headers ) ~= "table" then
+            error( "bad argument #2 (expected table, got " .. type( _headers ) .. ")", 2 ) 
+        end
         return wrapRequest( _url, nil, _headers, _binary)
     end
 
     http.post = function( _url, _post, _headers, _binary)
+        if type( _url ) ~= "string" then
+            error( "bad argument #1 (expected string, got " .. type( _url ) .. ")", 2 ) 
+        end
+        if type( _post ) ~= "string" then
+            error( "bad argument #2 (expected string, got " .. type( _post ) .. ")", 2 ) 
+        end
+        if _headers ~= nil and type( _headers ) ~= "table" then
+            error( "bad argument #3 (expected table, got " .. type( _headers ) .. ")", 2 ) 
+        end
         return wrapRequest( _url, _post or "", _headers, _binary)
     end
 
     http.request = function( _url, _post, _headers, _binary )
+        if type( _url ) ~= "string" then
+            error( "bad argument #1 (expected string, got " .. type( _url ) .. ")", 2 ) 
+        end
+        if _post ~= nil and type( _post ) ~= "string" then
+            error( "bad argument #2 (expected string, got " .. type( _post ) .. ")", 2 ) 
+        end
+        if _headers ~= nil and type( _headers ) ~= "table" then
+            error( "bad argument #3 (expected table, got " .. type( _headers ) .. ")", 2 ) 
+        end
         local ok, err = nativeHTTPRequest( _url, _post, _headers, _binary )
         if not ok then
             os.queueEvent( "http_failure", _url, err )
         end
         return ok, err
     end
+    
+    local nativeCheckURL = http.checkURL
+    http.checkURLAsync = nativeCheckURL
+    http.checkURL = function( _url )
+        local ok, err = nativeCheckURL( _url )
+        if not ok then return ok, err end
+    
+        while true do
+            local event, url, ok, err = os.pullEvent( "http_check" )
+            if url == _url then return ok, err end
+        end
+    end
 end
 
 -- Install the lua part of the FS api
 local tEmpty = {}
 function fs.complete( sPath, sLocation, bIncludeFiles, bIncludeDirs )
+    if type( sPath ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sPath ) .. ")", 2 ) 
+    end
+    if type( sLocation ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( sLocation ) .. ")", 2 ) 
+    end
+    if bIncludeFiles ~= nil and type( bIncludeFiles ) ~= "boolean" then
+        error( "bad argument #3 (expected boolean, got " .. type( bIncludeFiles ) .. ")", 2 ) 
+    end
+    if bIncludeDirs ~= nil and type( bIncludeDirs ) ~= "boolean" then
+        error( "bad argument #4 (expected boolean, got " .. type( bIncludeDirs ) .. ")", 2 ) 
+    end
     bIncludeFiles = (bIncludeFiles ~= false)
     bIncludeDirs = (bIncludeDirs ~= false)
     local sDir = sLocation
@@ -747,7 +840,7 @@ for n,sFile in ipairs( tApis ) do
     end
 end
 
-if turtle then
+if turtle and fs.isDir( "rom/apis/turtle" ) then
     -- Load turtle APIs
     local tApis = fs.list( "rom/apis/turtle" )
     for n,sFile in ipairs( tApis ) do

src/main/resources/assets/computercraft/lua/rom/apis/colors.lua

@@ -19,32 +19,51 @@ black = 32768
 function combine( ... )
     local r = 0
     for n,c in ipairs( { ... } ) do
+        if type( c ) ~= "number" then
+            error( "bad argument #"..n.." (expected number, got " .. type( c ) .. ")", 2 )
+        end
         r = bit32.bor(r,c)
     end
     return r
 end
 
 function subtract( colors, ... )
+    if type( colors ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( colors ) .. ")", 2 )
+    end
     local r = colors
     for n,c in ipairs( { ... } ) do
+        if type( c ) ~= "number" then
+            error( "bad argument #"..tostring( n+1 ).." (expected number, got " .. type( c ) .. ")", 2 )
+        end
         r = bit32.band(r, bit32.bnot(c))
     end
     return r
 end
 
 function test( colors, color )
+    if type( colors ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( colors ) .. ")", 2 )
+    end
+    if type( color ) ~= "number" then
+        error( "bad argument #2 (expected number, got " .. type( color ) .. ")", 2 )
+    end
     return ((bit32.band(colors, color)) == color)
 end
 
 function rgb8( r, g, b )
-    if type(r) == "number" and g == nil and b == nil then
+    if type( r ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( r ) .. ")", 2 )
+    elseif type(r) == "number" and g == nil and b == nil then
         return bit32.band( bit32.rshift( r, 16 ), 0xFF ) / 255, bit32.band( bit32.rshift( r, 8 ), 0xFF ) / 255, bit32.band( r, 0xFF ) / 255
     elseif type(r) == "number" and type(g) == "number" and type(b) == "number" then
         return 
             bit32.lshift( bit32.band(r * 255, 0xFF), 16 ) +
             bit32.lshift( bit32.band(g * 255, 0xFF), 8 ) +
             bit32.band(b * 255, 0xFF)
-    else
-        error( "Expected 1 or 3 numbers" )
+    elseif type( g ) ~= "number" then
+        error( "bad argument #2 (expected number, got " .. type( g ) .. ")", 2 )
+    elseif type( b ) ~= "number" then
+        error( "bad argument #3 (expected number, got " .. type( b ) .. ")", 2 )
     end
 end

src/main/resources/assets/computercraft/lua/rom/apis/disk.lua

@@ -1,5 +1,8 @@
 
 local function isDrive( name )
+    if type( name ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( name ) .. ")", 3 ) 
+    end
 	return peripheral.getType( name ) == "drive"
 end
 

src/main/resources/assets/computercraft/lua/rom/apis/gps.lua

@@ -56,6 +56,12 @@ local function narrow( p1, p2, fix )
 end
 
 function locate( _nTimeout, _bDebug )
+    if _nTimeout ~= nil and type( _nTimeout ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( _nTimeout ) .. ")", 2 ) 
+    end
+    if _bDebug ~= nil and type( _bDebug ) ~= "boolean" then
+        error( "bad argument #2 (expected boolean, got " .. type( _bDebug) .. ")", 2 ) 
+    end
     -- Let command computers use their magic fourth-wall-breaking special abilities
     if commands then
         return commands.getBlockPosition()

src/main/resources/assets/computercraft/lua/rom/apis/help.lua

@@ -6,10 +6,16 @@ function path()
 end
 
 function setPath( _sPath )
+    if type( _sPath ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sPath ) .. ")", 2 ) 
+    end
 	sPath = _sPath
 end
 
 function lookup( _sTopic )
+    if type( _sTopic ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sTopic ) .. ")", 2 ) 
+    end
  	-- Look on the path variable
     for sPath in string.gmatch(sPath, "[^:]+") do
     	sPath = fs.combine( sPath, _sTopic )
@@ -57,6 +63,9 @@ function topics()
 end
 
 function completeTopic( sText )
+    if type( sText ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sText ) .. ")", 2 ) 
+    end
     local tTopics = topics()
     local tResults = {}
     for n=1,#tTopics do

src/main/resources/assets/computercraft/lua/rom/apis/keys.lua

@@ -55,5 +55,8 @@ end
 keys["return"] = keys.enter
 
 function getName( _nKey )
+    if type( _nKey ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( _nKey ) .. ")", 2 ) 
+    end
 	return tKeys[ _nKey ]
 end

src/main/resources/assets/computercraft/lua/rom/apis/paintutils.lua

@@ -11,7 +11,7 @@ end
 
 function loadImage( sPath )
     if type( sPath ) ~= "string" then
-        error( "Expected path", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sPath ) .. ")", 2 )
     end
 
     local tImage = {}
@@ -33,9 +33,9 @@ function loadImage( sPath )
 end
 
 function drawPixel( xPos, yPos, nColour )
-    if type( xPos ) ~= "number" or type( yPos ) ~= "number" or (nColour ~= nil and type( nColour ) ~= "number") then
-        error( "Expected x, y, colour", 2 )
-    end
+    if type( xPos ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( xPos ) .. ")", 2 ) end
+    if type( yPos ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( yPos ) .. ")", 2 ) end
+    if nColour ~= nil and type( nColour ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( nColour ) .. ")", 2 ) end
     if nColour then
         term.setBackgroundColor( nColour )
     end
@@ -43,11 +43,11 @@ function drawPixel( xPos, yPos, nColour )
 end
 
 function drawLine( startX, startY, endX, endY, nColour )
-    if type( startX ) ~= "number" or type( startX ) ~= "number" or
-       type( endX ) ~= "number" or type( endY ) ~= "number" or
-       (nColour ~= nil and type( nColour ) ~= "number") then
-        error( "Expected startX, startY, endX, endY, colour", 2 )
-    end
+    if type( startX ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( startX ) .. ")", 2 ) end
+    if type( startY ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( startY ) .. ")", 2 ) end
+    if type( endX ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( endX ) .. ")", 2 ) end
+    if type( endY ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( endY ) .. ")", 2 ) end
+    if nColour ~= nil and type( nColour ) ~= "number" then error( "bad argument #5 (expected number, got " .. type( nColour ) .. ")", 2 ) end
     
     startX = math.floor(startX)
     startY = math.floor(startY)
@@ -103,11 +103,11 @@ function drawLine( startX, startY, endX, endY, nColour )
 end
 
 function drawBox( startX, startY, endX, endY, nColour )
-    if type( startX ) ~= "number" or type( startX ) ~= "number" or
-       type( endX ) ~= "number" or type( endY ) ~= "number" or
-       (nColour ~= nil and type( nColour ) ~= "number") then
-        error( "Expected startX, startY, endX, endY, colour", 2 )
-    end
+    if type( startX ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( startX ) .. ")", 2 ) end
+    if type( startY ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( startY ) .. ")", 2 ) end
+    if type( endX ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( endX ) .. ")", 2 ) end
+    if type( endY ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( endY ) .. ")", 2 ) end
+    if nColour ~= nil and type( nColour ) ~= "number" then error( "bad argument #5 (expected number, got " .. type( nColour ) .. ")", 2 ) end
 
     startX = math.floor(startX)
     startY = math.floor(startY)
@@ -147,11 +147,11 @@ function drawBox( startX, startY, endX, endY, nColour )
 end
 
 function drawFilledBox( startX, startY, endX, endY, nColour )
-    if type( startX ) ~= "number" or type( startX ) ~= "number" or
-       type( endX ) ~= "number" or type( endY ) ~= "number" or
-       (nColour ~= nil and type( nColour ) ~= "number") then
-        error( "Expected startX, startY, endX, endY, colour", 2 )
-    end
+    if type( startX ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( startX ) .. ")", 2 ) end
+    if type( startY ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( startY ) .. ")", 2 ) end
+    if type( endX ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( endX ) .. ")", 2 ) end
+    if type( endY ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( endY ) .. ")", 2 ) end
+    if nColour ~= nil and type( nColour ) ~= "number" then error( "bad argument #5 (expected number, got " .. type( nColour ) .. ")", 2 ) end
 
     startX = math.floor(startX)
     startY = math.floor(startY)
@@ -185,9 +185,9 @@ function drawFilledBox( startX, startY, endX, endY, nColour )
 end
 
 function drawImage( tImage, xPos, yPos )
-    if type( tImage ) ~= "table" or type( xPos ) ~= "number" or type( yPos ) ~= "number" then
-        error( "Expected image, x, y", 2 )
-    end
+    if type( tImage ) ~= "table" then error( "bad argument #1 (expected table, got " .. type( tImage ) .. ")", 2 ) end
+    if type( xPos ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( xPos ) .. ")", 2 ) end
+    if type( yPos ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( yPos ) .. ")", 2 ) end
     for y=1,#tImage do
         local tLine = tImage[y]
         for x=1,#tLine do

src/main/resources/assets/computercraft/lua/rom/apis/parallel.lua

@@ -1,12 +1,17 @@
 
-local function create( first, ... )
-	if first ~= nil then
-	    if type( first ) ~= "function" then
-    		error( "Expected function, got "..type( first ), 3 )
-    	end
- 		return coroutine.create(first), create( ... )
+local function create( ... )
+    local tFns = table.pack(...)
+    local tCos = {}
+    for i = 1, tFns.n, 1 do
+        local fn = tFns[i]
+        if type( fn ) ~= "function" then 
+            error( "bad argument #" .. i .. " (expected function, got " .. type( fn ) .. ")", 3 ) 
+        end
+        
+        tCos[i] = coroutine.create(fn)
     end
-    return nil
+    
+    return tCos
 end
 
 local function runUntilLimit( _routines, _limit )
@@ -51,11 +56,11 @@ local function runUntilLimit( _routines, _limit )
 end
 
 function waitForAny( ... )
-    local routines = { create( ... ) }
+    local routines = create( ... )
     return runUntilLimit( routines, #routines - 1 )
 end
 
 function waitForAll( ... )
-    local routines = { create( ... ) }
+    local routines = create( ... )
 	runUntilLimit( routines, 0 )
 end

src/main/resources/assets/computercraft/lua/rom/apis/peripheral.lua

@@ -18,7 +18,7 @@ end
 
 function isPresent( _sSide )
     if type( _sSide ) ~= "string" then
-        error( "Expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( _sSide ) .. ")", 2 ) 
     end
 	if native.isPresent( _sSide ) then
 		return true
@@ -35,7 +35,7 @@ end
 
 function getType( _sSide )
     if type( _sSide ) ~= "string" then
-        error( "Expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( _sSide ) .. ")", 2 )
     end
 	if native.isPresent( _sSide ) then
 		return native.getType( _sSide )
@@ -52,7 +52,7 @@ end
 
 function getMethods( _sSide )
     if type( _sSide ) ~= "string" then
-        error( "Expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( _sSide ) .. ")", 2 )
     end
 	if native.isPresent( _sSide ) then
 		return native.getMethods( _sSide )
@@ -68,8 +68,11 @@ function getMethods( _sSide )
 end
 
 function call( _sSide, _sMethod, ... )
-    if type( _sSide ) ~= "string" or type( _sMethod ) ~= "string" then
-        error( "Expected string, string", 2 )
+    if type( _sSide ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sSide ) .. ")", 2 )
+    end
+    if type( _sSide ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( _sMethod ) .. ")", 2 )
     end
 	if native.isPresent( _sSide ) then
 		return native.call( _sSide, _sMethod, ... )
@@ -85,8 +88,8 @@ function call( _sSide, _sMethod, ... )
 end
 
 function wrap( _sSide )
-    if type( _sSide ) ~= "string"  then
-        error( "Expected string", 2 )
+    if type( _sSide ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sSide ) .. ")", 2 )
     end
 	if peripheral.isPresent( _sSide ) then
 		local tMethods = peripheral.getMethods( _sSide )
@@ -102,8 +105,11 @@ function wrap( _sSide )
 end
 
 function find( sType, fnFilter )
-    if type( sType ) ~= "string" or (fnFilter ~= nil and type( fnFilter ) ~= "function") then
-        error( "Expected string, [function]", 2 )
+    if type( sType ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sType ) .. ")", 2 )
+    end
+    if fnFilter ~= nil and type( fnFilter ) ~= "function" then
+        error( "bad argument #2 (expected function, got " .. type( fnFilter ) .. ")", 2 )
     end
 	local tResults = {}
 	for n,sName in ipairs( peripheral.getNames() ) do

src/main/resources/assets/computercraft/lua/rom/apis/rednet.lua

@@ -7,14 +7,14 @@ local tReceivedMessageTimeouts = {}
 local tHostnames = {}
 
 function open( sModem )
-	if type( sModem ) ~= "string" then
-		error( "expected string", 2 )
-	end
-	if peripheral.getType( sModem ) ~= "modem" then	
-		error( "No such modem: "..sModem, 2 )
-	end
-	peripheral.call( sModem, "open", os.getComputerID() )
-	peripheral.call( sModem, "open", CHANNEL_BROADCAST )
+    if type( sModem ) ~= "string" then
+        error( "expected string", 2 )
+    end
+    if peripheral.getType( sModem ) ~= "modem" then 
+        error( "No such modem: "..sModem, 2 )
+    end
+    peripheral.call( sModem, "open", os.getComputerID() )
+    peripheral.call( sModem, "open", CHANNEL_BROADCAST )
 end
 
 function close( sModem )
@@ -55,7 +55,7 @@ function isOpen( sModem )
             end
         end
     end
-	return false
+    return false
 end
 
 function send( nRecipient, message, sProtocol )
@@ -93,7 +93,7 @@ function send( nRecipient, message, sProtocol )
 end
 
 function broadcast( message, sProtocol )
-	send( CHANNEL_BROADCAST, message, sProtocol )
+    send( CHANNEL_BROADCAST, message, sProtocol )
 end
 
 function receive( sProtocolFilter, nTimeout )
@@ -103,31 +103,31 @@ function receive( sProtocolFilter, nTimeout )
     end
 
     -- Start the timer
-	local timer = nil
-	local sFilter = nil
-	if nTimeout then
-		timer = os.startTimer( nTimeout )
-		sFilter = nil
-	else
-		sFilter = "rednet_message"
-	end
+    local timer = nil
+    local sFilter = nil
+    if nTimeout then
+        timer = os.startTimer( nTimeout )
+        sFilter = nil
+    else
+        sFilter = "rednet_message"
+    end
 
-	-- Wait for events
-	while true do
-		local sEvent, p1, p2, p3 = os.pullEvent( sFilter )
-		if sEvent == "rednet_message" then
-		    -- Return the first matching rednet_message
-			local nSenderID, message, sProtocol = p1, p2, p3
-			if sProtocolFilter == nil or sProtocol == sProtocolFilter then
-    			return nSenderID, message, sProtocol
-    	    end
-		elseif sEvent == "timer" then
-		    -- Return nil if we timeout
-		    if p1 == timer then
-    			return nil
-    		end
-		end
-	end
+    -- Wait for events
+    while true do
+        local sEvent, p1, p2, p3 = os.pullEvent( sFilter )
+        if sEvent == "rednet_message" then
+            -- Return the first matching rednet_message
+            local nSenderID, message, sProtocol = p1, p2, p3
+            if sProtocolFilter == nil or sProtocol == sProtocolFilter then
+                return nSenderID, message, sProtocol
+            end
+        elseif sEvent == "timer" then
+            -- Return nil if we timeout
+            if p1 == timer then
+                return nil
+            end
+        end
+    end
 end
 
 function host( sProtocol, sHostname )
@@ -219,41 +219,41 @@ end
 
 local bRunning = false
 function run()
-	if bRunning then
-		error( "rednet is already running", 2 )
-	end
-	bRunning = true
-	
-	while bRunning do
-		local sEvent, p1, p2, p3, p4 = os.pullEventRaw()
-		if sEvent == "modem_message" then
-			-- Got a modem message, process it and add it to the rednet event queue
-    		local sModem, nChannel, nReplyChannel, tMessage = p1, p2, p3, p4
-		    if isOpen( sModem ) and ( nChannel == os.getComputerID() or nChannel == CHANNEL_BROADCAST ) then
-    			if type( tMessage ) == "table" and tMessage.nMessageID then
-	    			if not tReceivedMessages[ tMessage.nMessageID ] then
-		    			tReceivedMessages[ tMessage.nMessageID ] = true
-                        tReceivedMessageTimeouts[ os.startTimer( 30 ) ] = nMessageID
-			    		os.queueEvent( "rednet_message", nReplyChannel, tMessage.message, tMessage.sProtocol )
-				    end
-			    end
-			end
+    if bRunning then
+        error( "rednet is already running", 2 )
+    end
+    bRunning = true
+    
+    while bRunning do
+        local sEvent, p1, p2, p3, p4 = os.pullEventRaw()
+        if sEvent == "modem_message" then
+            -- Got a modem message, process it and add it to the rednet event queue
+            local sModem, nChannel, nReplyChannel, tMessage = p1, p2, p3, p4
+            if isOpen( sModem ) and ( nChannel == os.getComputerID() or nChannel == CHANNEL_BROADCAST ) then
+                if type( tMessage ) == "table" and tMessage.nMessageID then
+                    if not tReceivedMessages[ tMessage.nMessageID ] then
+                        tReceivedMessages[ tMessage.nMessageID ] = true
+                        tReceivedMessageTimeouts[ os.startTimer( 30 ) ] = tMessage.nMessageID
+                        os.queueEvent( "rednet_message", nReplyChannel, tMessage.message, tMessage.sProtocol )
+                    end
+                end
+            end
 
-		elseif sEvent == "rednet_message" then
-		    -- Got a rednet message (queued from above), respond to dns lookup
-		    local nSenderID, tMessage, sProtocol = p1, p2, p3
-		    if sProtocol == "dns" and type(tMessage) == "table" and tMessage.sType == "lookup" then
-		        local sHostname = tHostnames[ tMessage.sProtocol ]
-		        if sHostname ~= nil and (tMessage.sHostname == nil or tMessage.sHostname == sHostname) then
-		            rednet.send( nSenderID, {
-		                sType = "lookup response",
-		                sHostname = sHostname,
-		                sProtocol = tMessage.sProtocol,
-		            }, "dns" )
-		        end
-		    end
+        elseif sEvent == "rednet_message" then
+            -- Got a rednet message (queued from above), respond to dns lookup
+            local nSenderID, tMessage, sProtocol = p1, p2, p3
+            if sProtocol == "dns" and type(tMessage) == "table" and tMessage.sType == "lookup" then
+                local sHostname = tHostnames[ tMessage.sProtocol ]
+                if sHostname ~= nil and (tMessage.sHostname == nil or tMessage.sHostname == sHostname) then
+                    rednet.send( nSenderID, {
+                        sType = "lookup response",
+                        sHostname = sHostname,
+                        sProtocol = tMessage.sProtocol,
+                    }, "dns" )
+                end
+            end
 
-		elseif sEvent == "timer" then
+        elseif sEvent == "timer" then
             -- Got a timer event, use it to clear the event queue
             local nTimer = p1
             local nMessage = tReceivedMessageTimeouts[ nTimer ]
@@ -261,6 +261,6 @@ function run()
                 tReceivedMessageTimeouts[ nTimer ] = nil
                 tReceivedMessages[ nMessage ] = nil
             end
-		end
-	end
+        end
+    end
 end

src/main/resources/assets/computercraft/lua/rom/apis/settings.lua

@@ -2,11 +2,13 @@
 local tSettings = {}
 
 function set( sName, value )
-    if type(sName) ~= "string" or
-       (type(value) ~= "string" and type(value) ~= "number" and type(value) ~= "boolean" and type(value) ~= "table") then
-        error( "Expected string, value", 2 )
+    if type( sName ) ~= "string" then error( "bad argument #1 (expected string, got " .. type( sName ) .. ")", 2 ) end
+    
+    local sValueTy = type(value)
+    if sValueTy ~= "number" and sValueTy ~= "string" and sValueTy ~= "boolean" and sValueTy ~= "table" then 
+        error( "bad argument #2 (expected value, got " .. sValueTy .. ")", 2 ) 
     end
-    if type(value) == "table" then
+    if sValueTy == "table" then
         -- Ensure value is serializeable
         value = textutils.unserialize( textutils.serialize(value) )
     end
@@ -28,7 +30,7 @@ end
 
 function get( sName, default )
     if type(sName) ~= "string" then
-        error( "Expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sName ) .. ")", 2 ) 
     end
     local result = tSettings[ sName ]
     if result ~= nil then
@@ -40,7 +42,7 @@ end
 
 function unset( sName )
     if type(sName) ~= "string" then
-        error( "Expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sName ) .. ")", 2 ) 
     end
     tSettings[ sName ] = nil
 end
@@ -54,12 +56,13 @@ function getNames()
     for k,v in pairs( tSettings ) do
         result[ #result + 1 ] = k
     end
+    table.sort(result)
     return result
 end
 
 function load( sPath )
     if type(sPath) ~= "string" then
-        error( "Expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sPath ) .. ")", 2 ) 
     end
     local file = fs.open( sPath, "r" )
     if not file then
@@ -86,7 +89,7 @@ end
 
 function save( sPath )
     if type(sPath) ~= "string" then
-        error( "Expected string", 2 )
+        error( "bad argument #1 (expected string, got " .. type( sPath ) .. ")", 2 ) 
     end
     local file = fs.open( sPath, "w" )
     if not file then

src/main/resources/assets/computercraft/lua/rom/apis/textutils.lua

@@ -7,7 +7,7 @@ function slowWrite( sText, nRate )
     local nSleep = 1 / nRate
         
     sText = tostring( sText )
-    local x,y = term.getCursorPos(x,y)
+    local x,y = term.getCursorPos()
     local len = string.len( sText )
     
     for n=1,len do
@@ -25,6 +25,12 @@ function slowPrint( sText, nRate )
 end
 
 function formatTime( nTime, bTwentyFourHour )
+    if type( nTime ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( nTime ) .. ")", 2 )
+    end
+    if bTwentyFourHour ~= nil and type( bTwentyFourHour ) ~= "boolean" then
+        error( "bad argument #2 (expected boolean, got " .. type( bTwentyFourHour ) .. ")", 2 ) 
+    end
     local sTOD = nil
     if not bTwentyFourHour then
         if nTime >= 12 then
@@ -68,6 +74,9 @@ local function makePagedScroll( _term, _nFreeLines )
 end
 
 function pagedPrint( _sText, _nFreeLines )
+    if _nFreeLines ~= nil and type( _nFreeLines ) ~= "number" then
+        error( "bad argument #2 (expected number, got " .. type( _nFreeLines ) .. ")", 2 ) 
+    end
     -- Setup a redirector
     local oldTerm = term.current()
     local newTerm = {}
@@ -99,6 +108,11 @@ end
 
 local function tabulateCommon( bPaged, ... )
     local tAll = { ... }
+    for k,v in ipairs( tAll ) do
+        if type( v ) ~= "number" and type( v ) ~= "table" then
+            error( "bad argument #"..k.." (expected number/table, got " .. type( v ) .. ")", 3 ) 
+        end
+    end
     
     local w,h = term.getSize()
     local nMaxLen = w / 8
@@ -301,6 +315,9 @@ function serialize( t )
 end
 
 function unserialize( s )
+    if type( s ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( s ) .. ")", 2 )
+    end
     local func = load( "return "..s, "unserialize", "t", {} )
     if func then
         local ok, result = pcall( func )
@@ -312,11 +329,20 @@ function unserialize( s )
 end
 
 function serializeJSON( t, bNBTStyle )
+    if type( t ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( t ) .. ")", 2 )
+    end
+    if bNBTStyle ~= nil and type( bNBTStyle ) ~= "boolean" then
+        error( "bad argument #2 (expected boolean, got " .. type( bNBTStyle ) .. ")", 2 ) 
+    end
     local tTracking = {}
     return serializeJSONImpl( t, tTracking, bNBTStyle or false )
 end
 
 function urlEncode( str )
+    if type( str ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( str ) .. ")", 2 )
+    end
     if str then
         str = string.gsub(str, "\n", "\r\n")
         str = string.gsub(str, "([^A-Za-z0-9 %-%_%.])", function(c)
@@ -338,6 +364,14 @@ end
 
 local tEmpty = {}
 function complete( sSearchText, tSearchTable )
+    if type( sSearchText ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sSearchText ) .. ")", 2 )
+    end
+    if type( tSearchTable ) ~= "table" then
+        error( "bad argument #2 (expected table, got " .. type( tSearchTable ) .. ")", 2 )
+    end
+
+    if g_tLuaKeywords[sSearchText] then return tEmpty end
     local nStart = 1
     local nDot = string.find( sSearchText, ".", nStart, true )
     local tTable = tSearchTable or _ENV
@@ -352,8 +386,19 @@ function complete( sSearchText, tSearchTable )
             return tEmpty
         end
     end
-
-    local sPart = string.sub( sSearchText, nStart, nDot )
+    local nColon = string.find( sSearchText, ":", nStart, true )
+    if nColon then
+        local sPart = string.sub( sSearchText, nStart, nColon - 1 )
+        local value = tTable[ sPart ]
+        if type( value ) == "table" then
+            tTable = value
+            nStart = nColon + 1
+        else
+            return tEmpty
+        end
+    end
+    
+    local sPart = string.sub( sSearchText, nStart )
     local nPartLength = string.len( sPart )
 
     local tResults = {}

src/main/resources/assets/computercraft/lua/rom/apis/window.lua

@@ -18,20 +18,18 @@ local tHex = {
     [ colors.black ] = "f",
 }
 
+local type = type
 local string_rep = string.rep
 local string_sub = string.sub
 local table_unpack = table.unpack
 
 function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
-
-    if type( parent ) ~= "table" or
-       type( nX ) ~= "number" or
-       type( nY ) ~= "number" or
-       type( nWidth ) ~= "number" or
-       type( nHeight ) ~= "number" or
-       (bStartVisible ~= nil and type( bStartVisible ) ~= "boolean") then
-        error( "Expected object, number, number, number, number, [boolean]", 2 )
-    end
+    if type( parent ) ~= "table" then error( "bad argument #1 (expected table, got " .. type( parent ) .. ")", 2 ) end
+    if type( nX ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( nX ) .. ")", 2 ) end
+    if type( nY ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( nY ) .. ")", 2 ) end
+    if type( nWidth ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( nWidth ) .. ")", 2 ) end
+    if type( nHeight ) ~= "number" then error( "bad argument #5 (expected number, got " .. type( nHeight ) .. ")", 2 ) end
+    if bStartVisible ~= nil and type( bStartVisible ) ~= "boolean" then error( "bad argument #6 (expected boolean, got " .. type( bStartVisible ) .. ")", 2 ) end
 
     if parent == term then
         error( "term is not a recommended window parent, try term.current() instead", 2 )
@@ -193,9 +191,9 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
     end
 
     function window.blit( sText, sTextColor, sBackgroundColor )
-        if type(sText) ~= "string" or type(sTextColor) ~= "string" or type(sBackgroundColor) ~= "string" then
-            error( "Expected string, string, string", 2 )
-        end
+        if type( sText ) ~= "string" then error( "bad argument #1 (expected string, got " .. type( sText ) .. ")", 2 ) end
+        if type( sTextColor ) ~= "string" then error( "bad argument #2 (expected string, got " .. type( sTextColor ) .. ")", 2 ) end
+        if type( sBackgroundColor ) ~= "string" then error( "bad argument #3 (expected string, got " .. type( sBackgroundColor ) .. ")", 2 ) end
         if #sTextColor ~= #sText or #sBackgroundColor ~= #sText then
             error( "Arguments must be the same length", 2 )
         end
@@ -243,9 +241,8 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
     end
 
     function window.setCursorPos( x, y )
-        if type( x ) ~= "number" or type( y ) ~= "number" then
-            error( "Expected number, number", 2 )
-        end
+        if type( x ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( x ) .. ")", 2 ) end
+        if type( y ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( y ) .. ")", 2 ) end
         nCursorX = math.floor( x )
         nCursorY = math.floor( y )
         if bVisible then
@@ -254,9 +251,7 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
     end
 
     function window.setCursorBlink( blink )
-        if type( blink ) ~= "boolean" then
-            error( "Expected boolean", 2 )
-        end
+        if type( blink ) ~= "boolean" then error( "bad argument #1 (expected boolean, got " .. type( blink ) .. ")", 2 ) end
         bCursorBlink = blink
         if bVisible then
             updateCursorBlink()
@@ -276,10 +271,10 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
     end
 
     local function setTextColor( color )
-        if type(color) ~= "number" then
-            error( "Expected number", 3 )
+        if type( color ) ~= "number" then 
+            error( "bad argument #1 (expected number, got " .. type( color ) .. ")", 2 )
         elseif tHex[color] == nil then
-            error( "Invalid color", 3 )
+            error( "Invalid color", 2 )
         end
         nTextColor = color
         if bVisible then
@@ -287,26 +282,25 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
         end
     end
 
-    function window.setTextColor( color )
-        setTextColor( color )
-    end
-
-    function window.setTextColour( color )
-        setTextColor( color )
-    end
+    window.setTextColor = setTextColor
+    window.setTextColour = setTextColor
 
     function window.setPaletteColour( colour, r, g, b )
+        if type( colour ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( colour ) .. ")", 2 ) end
+        
         local tCol
-        if type(colour) == "number" and type(r) == "number" and g == nil and b == nil then
+        if type(r) == "number" and g == nil and b == nil then
             tCol = { colours.rgb8( r ) }
             tPalette[ colour ] = tCol
-        elseif type(colour) == "number" and type(r) == "number" and type(g) == "number" and type(b) == "number" then
+        else
+            if type( r ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( r ) .. ")", 2 ) end
+            if type( g ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( g ) .. ")", 2 ) end
+            if type( b ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( b ) .. ")", 2 ) end
+            
             tCol = tPalette[ colour ]
             tCol[1] = r
             tCol[2] = g
             tCol[3] = b
-        else
-            error( "Expected number, number, number, number", 2 )
         end
 
         if bVisible then
@@ -324,30 +318,23 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
     window.getPaletteColor = window.getPaletteColour
 
     local function setBackgroundColor( color )
-        if type(color) ~= "number" then
-            error( "Expected number", 3 )
+        if type( color ) ~= "number" then
+            error( "bad argument #1 (expected number, got " .. type( color ) .. ")", 2 )
         elseif tHex[color] == nil then
             error( "Invalid color", 3 )
         end
         nBackgroundColor = color
     end
 
-    function window.setBackgroundColor( color )
-        setBackgroundColor( color )
-    end
-
-    function window.setBackgroundColour( color )
-        setBackgroundColor( color )
-    end
+    window.setBackgroundColor = setBackgroundColor
+    window.setBackgroundColour = setBackgroundColor
 
     function window.getSize()
         return nWidth, nHeight
     end
 
     function window.scroll( n )
-        if type( n ) ~= "number" then
-            error( "Expected number", 2 )
-        end
+        if type( n ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( n ) .. ")", 2 ) end
         if n ~= 0 then
             local tNewLines = {}
             local sEmptyText = sEmptySpaceLine
@@ -392,9 +379,7 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
 
     -- Other functions
     function window.setVisible( bVis )
-        if type( bVis) ~= "boolean" then
-            error( "Expected boolean", 2 )
-        end
+        if type( bVis ) ~= "boolean" then error( "bad argument #1 (expected boolean, got " .. type( bVis ) .. ")", 2 ) end
         if bVisible ~= bVis then
             bVisible = bVis
             if bVisible then
@@ -426,9 +411,11 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
     end
 
     function window.reposition( nNewX, nNewY, nNewWidth, nNewHeight )
-        if type( nNewX ) ~= "number" or type( nNewY ) ~= "number" or type( nNewWidth ) ~= "number" or type( nNewWidth ) ~= "number" then
-            error( "Expected number, number, number, number", 2 )
-        end
+        if type( nNewX ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( nNewX ) .. ")", 2 ) end
+        if type( nNewY ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( nNewY ) .. ")", 2 ) end
+        if type( nNewWidth ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( nNewWidth ) .. ")", 2 ) end
+        if type( nNewHeight ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( nNewHeight ) .. ")", 2 ) end
+
         nX = nNewX
         nY = nNewY
         if nNewWidth and nNewHeight then

src/main/resources/assets/computercraft/lua/rom/help/equip.txt

@@ -1,4 +1,5 @@
-equip is a program for Turtles. equip will equip an item from the Turtle's inventory for use as a tool of peripheral.
+equip is a program for Turtles and Pocket Computer. equip will equip an item from the Turtle's inventory for use as a tool of peripheral. On a Pocket Computer you don't need to write a side.
 
 ex:
 "equip 5 left" will equip the item from slot 5 of the turtle onto the left side of the turtle
+"equip" on a Pocket Computer will equip the first item from your inventory.

src/main/resources/assets/computercraft/lua/rom/help/http.txt

@@ -1,5 +1,6 @@
 Functions in the HTTP API:
 http.checkURL( url )
+http.checkURLAsync( url )
 http.request( url, [postData], [headers] )
 http.get( url, [headers] )
 http.post( url, postData, [headers] )

src/main/resources/assets/computercraft/lua/rom/help/unequip.txt

@@ -1,4 +1,5 @@
-unequip is a program for Turtles. unequip will remove tools of peripherals from the specified side of the turtle.
+unequip is a program for Turtles and Pocket Computers. unequip will remove tools of peripherals from the specified side of the turtle. On a Pocket Computer you don't need to write a side.
 
 ex:
 "unequip left" will remove the item on the left side of the turtle
+"unequip" on a Pocket Computer will remove the item from the Pocket Computer

src/main/resources/assets/computercraft/lua/rom/programs/advanced/multishell.lua

@@ -171,6 +171,9 @@ function multishell.getFocus()
 end
 
 function multishell.setFocus( n )
+    if type( n ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( n ) .. ")", 2 )
+    end
     if n >= 1 and n <= #tProcesses then
         selectProcess( n )
         redrawMenu()
@@ -180,6 +183,9 @@ function multishell.setFocus( n )
 end
 
 function multishell.getTitle( n )
+    if type( n ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( n ) .. ")", 2 )
+    end
     if n >= 1 and n <= #tProcesses then
         return tProcesses[n].sTitle
     end
@@ -187,6 +193,12 @@ function multishell.getTitle( n )
 end
 
 function multishell.setTitle( n, sTitle )
+    if type( n ) ~= "number" then
+        error( "bad argument #1 (expected number, got " .. type( n ) .. ")", 2 )
+    end
+    if type( sTitle ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( sTitle ) .. ")", 2 )
+    end
     if n >= 1 and n <= #tProcesses then
         setProcessTitle( n, sTitle )
         redrawMenu()
@@ -198,6 +210,12 @@ function multishell.getCurrent()
 end
 
 function multishell.launch( tProgramEnv, sProgramPath, ... )
+    if type( tProgramArgs ) ~= "table" then
+        error( "bad argument #1 (expected table, got " .. type( tProgramEnv ) .. ")", 2 )
+    end
+    if type( sProgramPath ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( sProgramPath ) .. ")", 2 )
+    end
     local previousTerm = term.current()
     setMenuVisible( (#tProcesses + 1) >= 2 )
     local nResult = launchProcess( tProgramEnv, sProgramPath, ... )

src/main/resources/assets/computercraft/lua/rom/programs/edit.lua

@@ -175,7 +175,7 @@ local nCompletion
 local tCompleteEnv = _ENV
 local function complete( sLine )
     if settings.get( "edit.autocomplete" ) then
-        local nStartPos = string.find( sLine, "[a-zA-Z0-9_%.]+$" )
+        local nStartPos = string.find( sLine, "[a-zA-Z0-9_%.:]+$" )
         if nStartPos then
             sLine = string.sub( sLine, nStartPos )
         end
@@ -709,7 +709,13 @@ while bRunning do
         end
 
     elseif sEvent == "paste" then
-        if not bMenu and not bReadOnly then
+        if not bReadOnly then
+            -- Close menu if open
+            if bMenu then
+                bMenu = false
+                term.setCursorBlink( true )
+                redrawMenu()
+            end
             -- Input text
             local sLine = tLines[y]
             tLines[y] = string.sub(sLine,1,x-1) .. param .. string.sub(sLine,x)

src/main/resources/assets/computercraft/lua/rom/programs/fun/advanced/paint.lua

@@ -310,7 +310,7 @@ local function accessMenu()
                 -- Select an option
                 if mChoices[selection]=="Save" then 
                     if bReadOnly then 
-                        fMessage = "Access Denied"
+                        fMessage = "Access denied"
                         return false
                     end
                     local success = save(sPath)

src/main/resources/assets/computercraft/lua/rom/programs/gps.lua

@@ -57,10 +57,6 @@ elseif sCommand == "host" then
         x,y,z = gps.locate( 2, true )
         if x == nil then
             print( "Run \"gps host <x> <y> <z>\" to set position manually" )
-            if bCloseChannel then
-                print( "Closing GPS channel" )
-                modem.close( gps.CHANNEL_GPS )
-            end
             return
         end
     end

src/main/resources/assets/computercraft/lua/rom/programs/lua.lua

@@ -34,7 +34,7 @@ while bRunning do
 
     local s = read( nil, tCommandHistory, function( sLine )
         if settings.get( "lua.autocomplete" ) then
-            local nStartPos = string.find( sLine, "[a-zA-Z0-9_%.]+$" )
+            local nStartPos = string.find( sLine, "[a-zA-Z0-9_%.:]+$" )
             if nStartPos then
                 sLine = string.sub( sLine, nStartPos )
             end
@@ -64,10 +64,10 @@ while bRunning do
     end
     
     if func then
-        local tResults = { pcall( func ) }
+        local tResults = table.pack( pcall( func ) )
         if tResults[1] then
             local n = 1
-            while (tResults[n + 1] ~= nil) or (n <= nForcePrint) do
+            while n < tResults.n or (n <= nForcePrint) do
                 local value = tResults[ n + 1 ]
                 if type( value ) == "table" then
                     local metatable = getmetatable( value )

src/main/resources/assets/computercraft/lua/rom/programs/pocket/equip.lua

@@ -0,0 +1,6 @@
+local ok, err = pcall( pocket.equipBack )
+if not ok then
+    printError( "Nothing to equip" )
+else
+    print( "Item equipped" )
+end

src/main/resources/assets/computercraft/lua/rom/programs/pocket/unequip.lua

@@ -0,0 +1,6 @@
+local ok, err = pcall( pocket.unequipBack )
+if not ok then
+    printError( "Nothing to unequip" )
+else
+    print( "Item unequipped" )
+end

src/main/resources/assets/computercraft/lua/rom/programs/rednet/chat.lua

@@ -310,14 +310,14 @@ elseif sCommand == "join" then
     function printMessage( sMessage )
         term.redirect( historyWindow )
         print()
-        if string.match( sMessage, "^\*" ) then
+        if string.match( sMessage, "^%*" ) then
             -- Information
             term.setTextColour( highlightColour )
             write( sMessage )
             term.setTextColour( textColour )
         else
             -- Chat
-            local sUsernameBit = string.match( sMessage, "^\<[^\>]*\>" )
+            local sUsernameBit = string.match( sMessage, "^<[^>]*>" )
             if sUsernameBit then
                 term.setTextColour( highlightColour )
                 write( sUsernameBit )

src/main/resources/assets/computercraft/lua/rom/programs/set.lua

@@ -2,9 +2,12 @@
 local tArgs = { ... }
 if #tArgs == 0 then
     -- "set"
+    local x,y = term.getCursorPos()
+    local tSettings = {}
     for n,sName in ipairs( settings.getNames() ) do
-        print( textutils.serialize(sName) .. " is " .. textutils.serialize(settings.get(sName)) )
+        tSettings[n] = textutils.serialize(sName) .. " is " .. textutils.serialize(settings.get(sName))
     end
+    textutils.pagedPrint(table.concat(tSettings,"\n"),y-3)
 
 elseif #tArgs == 1 then
     -- "set foo"

src/main/resources/assets/computercraft/lua/rom/programs/shell.lua

@@ -31,6 +31,7 @@ local function createShellEnv( sDir )
         table = table,
     }
     package.path = "?;?.lua;?/init.lua"
+    package.config = "/\n;\n?\n!\n-"
     package.preload = {}
     package.loaders = {
         function( name )
@@ -68,6 +69,9 @@ local function createShellEnv( sDir )
 
     local sentinel = {}
     local function require( name )
+        if type( name ) ~= "string" then
+            error( "bad argument #1 (expected string, got " .. type( name ) .. ")", 2 )
+        end
         if package.loaded[name] == sentinel then
             error("Loop detected requiring '" .. name .. "'", 0)
         end
@@ -181,6 +185,12 @@ function shell.dir()
 end
 
 function shell.setDir( _sDir )
+    if type( _sDir ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sDir ) .. ")", 2 )
+    end
+    if not fs.isDir( _sDir ) then
+        error( "Not a directory", 2 )
+    end
     sDir = _sDir
 end
 
@@ -189,10 +199,16 @@ function shell.path()
 end
 
 function shell.setPath( _sPath )
+    if type( _sPath ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sPath ) .. ")", 2 )
+    end
     sPath = _sPath
 end
 
 function shell.resolve( _sPath )
+    if type( _sPath ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sPath ) .. ")", 2 )
+    end
     local sStartChar = string.sub( _sPath, 1, 1 )
     if sStartChar == "/" or sStartChar == "\\" then
         return fs.combine( "", _sPath )
@@ -212,6 +228,9 @@ local function pathWithExtension( _sPath, _sExt )
 end
 
 function shell.resolveProgram( _sCommand )
+    if type( _sCommand ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sCommand ) .. ")", 2 )
+    end
     -- Substitute aliases firsts
     if tAliases[ _sCommand ] ~= nil then
         _sCommand = tAliases[ _sCommand ]
@@ -327,6 +346,9 @@ local function completeProgramArgument( sProgram, nArgument, sPart, tPreviousPar
 end
 
 function shell.complete( sLine )
+    if type( sLine ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sLine ) .. ")", 2 )
+    end
     if #sLine > 0 then
         local tWords = tokenise( sLine )
         local nIndex = #tWords
@@ -363,10 +385,19 @@ function shell.complete( sLine )
 end
 
 function shell.completeProgram( sProgram )
+    if type( sProgram ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sProgram ) .. ")", 2 )
+    end
     return completeProgram( sProgram )
 end
 
 function shell.setCompletionFunction( sProgram, fnComplete )
+    if type( sProgram ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( sProgram ) .. ")", 2 )
+    end
+    if type( fnComplete ) ~= "function" then
+        error( "bad argument #2 (expected function, got " .. type( fnComplete ) .. ")", 2 )
+    end
     tCompletionInfo[ sProgram ] = {
         fnComplete = fnComplete
     }
@@ -384,10 +415,19 @@ function shell.getRunningProgram()
 end
 
 function shell.setAlias( _sCommand, _sProgram )
+    if type( _sCommand ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sCommand ) .. ")", 2 )
+    end
+    if type( _sProgram ) ~= "string" then
+        error( "bad argument #2 (expected string, got " .. type( _sProgram ) .. ")", 2 )
+    end
     tAliases[ _sCommand ] = _sProgram
 end
 
 function shell.clearAlias( _sCommand )
+    if type( _sCommand ) ~= "string" then
+        error( "bad argument #1 (expected string, got " .. type( _sCommand ) .. ")", 2 )
+    end
     tAliases[ _sCommand ] = nil
 end
 
@@ -417,6 +457,9 @@ if multishell then
     end
 
     function shell.switchTab( nID )
+        if type( nID ) ~= "number" then
+            error( "bad argument #1 (expected number, got " .. type( nID ) .. ")", 2 )
+        end
         multishell.setFocus( nID )
     end
 end

src/main/resources/assets/computercraft/lua/rom/startup.lua

@@ -168,6 +168,15 @@ local function completeSet( shell, nIndex, sText, tPreviousText )
         return completeMultipleChoice( sText, settings.getNames(), true )
     end
 end
+local tCommands 
+if commands then
+    tCommands = commands.list()
+end
+local function completeExec( shell, nIndex, sText, tPreviousText )
+    if nIndex == 1 and commands then
+        return completeMultipleChoice( sText, tCommands, true )
+    end
+end
 shell.setCompletionFunction( "rom/programs/alias.lua", completeAlias )
 shell.setCompletionFunction( "rom/programs/cd.lua", completeDir )
 shell.setCompletionFunction( "rom/programs/copy.lua", completeEitherEither )
@@ -194,6 +203,36 @@ shell.setCompletionFunction( "rom/programs/fun/dj.lua", completeDJ )
 shell.setCompletionFunction( "rom/programs/fun/advanced/paint.lua", completeFile )
 shell.setCompletionFunction( "rom/programs/http/pastebin.lua", completePastebin )
 shell.setCompletionFunction( "rom/programs/rednet/chat.lua", completeChat )
+shell.setCompletionFunction( "rom/programs/command/exec.lua", completeExec )
+
+if turtle then
+    local tGoOptions = { "left", "right", "forward", "back", "down", "up" }
+    local function completeGo( shell, nIndex, sText )
+        return completeMultipleChoice(sText,tGoOptions)
+    end
+    local tTurnOptions = { "left", "right" }
+    local function completeTurn( shell, nIndex, sText )
+        if nIndex == 1 then
+            return completeMultipleChoice( sText, tTurnOptions )
+        end
+    end
+    local tEquipOptions = { "left", "right" }
+    local function completeEquip( shell, nIndex, sText )
+        if nIndex == 2 then
+            return completeMultipleChoice( sText, tEquipOptions )
+        end
+    end
+    local function completeUnequip( shell, nIndex, sText )
+        if nIndex == 1 then
+            return completeMultipleChoice( sText, tEquipOptions )
+        end
+    end
+    shell.setCompletionFunction( "rom/programs/turtle/go.lua", completeGo )
+    shell.setCompletionFunction( "rom/programs/turtle/turn.lua", completeTurn )
+    shell.setCompletionFunction( "rom/programs/turtle/equip.lua", completeEquip )
+    shell.setCompletionFunction( "rom/programs/turtle/unequip.lua", completeUnequip )
+end
+
 
 -- Run autorun files
 if fs.exists( "/rom/autorun" ) and fs.isDir( "/rom/autorun" ) then