Add a timeout to websocket.receive

- Move timer handling to IAPIEnvironment, rather than OSAPI. This means
   the environment is reset on startup/shutdown, much like normal APIs.
 - Websocket.receive now accepts an optional timetout (much like
   rednet.receive). This starts a timer, and waits for it to complete.

Closes #201

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

@@ -18,6 +18,8 @@ import javax.annotation.Nullable;
 
 public interface IAPIEnvironment
 {
+    String TIMER_EVENT = "timer";
+
     @FunctionalInterface
     interface IPeripheralChangeListener
     {
@@ -64,6 +66,10 @@ public interface IAPIEnvironment
 
     void setLabel( @Nullable String label );
 
+    int startTimer( long ticks );
+
+    void cancelTimer( int id );
+
     void addTrackingChange( @Nonnull TrackingField field, long change );
 
     default void addTrackingChange( @Nonnull TrackingField field )

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

@@ -9,6 +9,8 @@ import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.shared.util.StringUtil;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 
 import javax.annotation.Nonnull;
 import java.time.Instant;
@@ -24,24 +26,12 @@ public class OSAPI implements ILuaAPI
 {
     private IAPIEnvironment m_apiEnvironment;
 
-    private final Map<Integer, Timer> m_timers;
+    private final Int2ObjectMap<Alarm> m_alarms = new Int2ObjectOpenHashMap<>();
-    private final Map<Integer, Alarm> m_alarms;
     private int m_clock;
     private double m_time;
     private int m_day;
 
-    private int m_nextTimerToken;
+    private int m_nextAlarmToken = 0;
-    private int m_nextAlarmToken;
-
-    private static class Timer
-    {
-        int m_ticksLeft;
-
-        Timer( int ticksLeft )
-        {
-            m_ticksLeft = ticksLeft;
-        }
-    }
 
     private static class Alarm implements Comparable<Alarm>
     {
@@ -66,10 +56,6 @@ public class OSAPI implements ILuaAPI
     public OSAPI( IAPIEnvironment environment )
     {
         m_apiEnvironment = environment;
-        m_nextTimerToken = 0;
-        m_nextAlarmToken = 0;
-        m_timers = new HashMap<>();
-        m_alarms = new HashMap<>();
     }
 
     // ILuaAPI implementation
@@ -87,11 +73,6 @@ public class OSAPI implements ILuaAPI
         m_day = m_apiEnvironment.getComputerEnvironment().getDay();
         m_clock = 0;
 
-        synchronized( m_timers )
-        {
-            m_timers.clear();
-        }
-
         synchronized( m_alarms )
         {
             m_alarms.clear();
@@ -101,26 +82,7 @@ public class OSAPI implements ILuaAPI
     @Override
     public void update()
     {
-        synchronized( m_timers )
+        m_clock++;
-        {
-            // Update the clock
-            m_clock++;
-
-            // Countdown all of our active timers
-            Iterator<Map.Entry<Integer, Timer>> it = m_timers.entrySet().iterator();
-            while( it.hasNext() )
-            {
-                Map.Entry<Integer, Timer> entry = it.next();
-                Timer timer = entry.getValue();
-                timer.m_ticksLeft--;
-                if( timer.m_ticksLeft <= 0 )
-                {
-                    // Queue the "timer" event
-                    queueLuaEvent( "timer", new Object[] { entry.getKey() } );
-                    it.remove();
-                }
-            }
-        }
 
         // Wait for all of our alarms
         synchronized( m_alarms )
@@ -155,11 +117,6 @@ public class OSAPI implements ILuaAPI
     @Override
     public void shutdown()
     {
-        synchronized( m_timers )
-        {
-            m_timers.clear();
-        }
-
         synchronized( m_alarms )
         {
             m_alarms.clear();
@@ -229,11 +186,8 @@ public class OSAPI implements ILuaAPI
             {
                 // startTimer
                 double timer = getFiniteDouble( args, 0 );
-                synchronized( m_timers )
+                int id = m_apiEnvironment.startTimer( Math.round( timer / 0.05 ) );
-                {
+                return new Object[] { id };
-                    m_timers.put( m_nextTimerToken, new Timer( (int) Math.round( timer / 0.05 ) ) );
-                    return new Object[] { m_nextTimerToken++ };
-                }
             }
             case 2:
             {
@@ -278,10 +232,7 @@ public class OSAPI implements ILuaAPI
                 return null;
             }
             case 10: // clock
-                synchronized( m_timers )
+                return new Object[] { m_clock * 0.05 };
-                {
-                    return new Object[] { m_clock * 0.05 };
-                }
             case 11:
             {
                 // time
@@ -345,10 +296,7 @@ public class OSAPI implements ILuaAPI
             {
                 // cancelTimer
                 int token = getInt( args, 0 );
-                synchronized( m_timers )
+                m_apiEnvironment.cancelTimer( token );
-                {
-                    m_timers.remove( token );
-                }
                 return null;
             }
             case 14:

src/main/java/dan200/computercraft/core/apis/http/websocket/WebsocketHandle.java

@@ -7,6 +7,7 @@ package dan200.computercraft.core.apis.http.websocket;
 
 import com.google.common.base.Objects;
 import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.ArgumentHelper;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.api.lua.LuaException;
@@ -23,6 +24,7 @@ import java.io.Closeable;
 import java.util.Arrays;
 
 import static dan200.computercraft.api.lua.ArgumentHelper.optBoolean;
+import static dan200.computercraft.core.apis.IAPIEnvironment.TIMER_EVENT;
 import static dan200.computercraft.core.apis.http.websocket.Websocket.CLOSE_EVENT;
 import static dan200.computercraft.core.apis.http.websocket.Websocket.MESSAGE_EVENT;
 
@@ -53,7 +55,21 @@ public class WebsocketHandle implements ILuaObject, Closeable
         switch( method )
         {
             case 0: // receive
+            {
                 checkOpen();
+                int timeoutId;
+                if( arguments.length <= 0 || arguments[0] == null )
+                {
+                    // We do this rather odd argument validation to ensure we can tell the difference between a
+                    // negative timeout and an absent one.
+                    timeoutId = -1;
+                }
+                else
+                {
+                    double timeout = ArgumentHelper.getFiniteDouble( arguments, 0 );
+                    timeoutId = websocket.environment().startTimer( Math.round( timeout / 0.05 ) );
+                }
+
                 while( true )
                 {
                     Object[] event = context.pullEvent( null );
@@ -63,9 +79,17 @@ public class WebsocketHandle implements ILuaObject, Closeable
                     }
                     else if( event.length >= 2 && Objects.equal( event[0], CLOSE_EVENT ) && Objects.equal( event[1], websocket.address() ) && closed )
                     {
+                        // If the socket is closed abort.
+                        return null;
+                    }
+                    else if( event.length >= 2 && timeoutId != -1 && Objects.equal( event[0], TIMER_EVENT )
+                        && event[1] instanceof Number && ((Number) event[1]).intValue() == timeoutId )
+                    {
+                        // If we received a matching timer event then abort.
                         return null;
                     }
                 }
+            }
 
             case 1: // send
             {

src/main/java/dan200/computercraft/core/computer/Computer.java

@@ -183,7 +183,7 @@ public class Computer
         executor.tick();
 
         // Update the environment's internal state.
-        internalEnvironment.update();
+        internalEnvironment.tick();
 
         // Propagate the environment's output to the world.
         if( internalEnvironment.updateOutput() ) externalOutputChanged.set( true );

src/main/java/dan200/computercraft/core/computer/ComputerExecutor.java

@@ -435,6 +435,7 @@ final class ComputerExecutor
             }
 
             // Init APIs
+            computer.getEnvironment().reset();
             for( ILuaAPI api : apis ) api.startup();
 
             // Init lua
@@ -478,6 +479,7 @@ final class ComputerExecutor
 
             // Shutdown our APIs
             for( ILuaAPI api : apis ) api.shutdown();
+            computer.getEnvironment().reset();
 
             // Unload filesystem
             if( fileSystem != null )

src/main/java/dan200/computercraft/core/computer/Environment.java

@@ -5,6 +5,7 @@
  */
 package dan200.computercraft.core.computer;
 
+import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.IWorkMonitor;
 import dan200.computercraft.core.apis.IAPIEnvironment;
@@ -12,9 +13,12 @@ import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.core.tracking.Tracking;
 import dan200.computercraft.core.tracking.TrackingField;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 
 import javax.annotation.Nonnull;
 import java.util.Arrays;
+import java.util.Iterator;
 
 /**
  * Represents the "environment" that a {@link Computer} exists in.
@@ -53,6 +57,9 @@ public final class Environment implements IAPIEnvironment
     private final IPeripheral[] peripherals = new IPeripheral[ComputerSide.COUNT];
     private IPeripheralChangeListener peripheralListener = null;
 
+    private final Int2ObjectMap<Timer> timers = new Int2ObjectOpenHashMap<>();
+    private int nextTimerToken = 0;
+
     Environment( Computer computer )
     {
         this.computer = computer;
@@ -198,17 +205,47 @@ public final class Environment implements IAPIEnvironment
     }
 
     /**
-     * Called on the main thread to update the internal state of the computer.
+     * Called when the computer starts up or shuts down, to reset any internal state.
      *
-     * This just queues a {@code redstone} event if the input has changed.
+     * @see ILuaAPI#startup()
+     * @see ILuaAPI#shutdown()
      */
-    void update()
+    void reset()
+    {
+        synchronized( timers )
+        {
+            timers.clear();
+        }
+    }
+
+    /**
+     * Called on the main thread to update the internal state of the computer.
+     */
+    void tick()
     {
         if( inputChanged )
         {
             inputChanged = false;
             queueEvent( "redstone", null );
         }
+
+        synchronized( timers )
+        {
+            // Countdown all of our active timers
+            Iterator<Int2ObjectMap.Entry<Timer>> it = timers.int2ObjectEntrySet().iterator();
+            while( it.hasNext() )
+            {
+                Int2ObjectMap.Entry<Timer> entry = it.next();
+                Timer timer = entry.getValue();
+                timer.ticksLeft--;
+                if( timer.ticksLeft <= 0 )
+                {
+                    // Queue the "timer" event
+                    queueEvent( TIMER_EVENT, new Object[] { entry.getIntKey() } );
+                    it.remove();
+                }
+            }
+        }
     }
 
     /**
@@ -303,9 +340,38 @@ public final class Environment implements IAPIEnvironment
         computer.setLabel( label );
     }
 
+    @Override
+    public int startTimer( long ticks )
+    {
+        synchronized( timers )
+        {
+            timers.put( nextTimerToken, new Timer( ticks ) );
+            return nextTimerToken++;
+        }
+    }
+
+    @Override
+    public void cancelTimer( int id )
+    {
+        synchronized( timers )
+        {
+            timers.remove( id );
+        }
+    }
+
     @Override
     public void addTrackingChange( @Nonnull TrackingField field, long change )
     {
         Tracking.addValue( computer, field, change );
     }
+
+    private static class Timer
+    {
+        long ticksLeft;
+
+        Timer( long ticksLeft )
+        {
+            this.ticksLeft = ticksLeft;
+        }
+    }
 }