/*
 * This file is part of the public ComputerCraft API - http://www.computercraft.info
 * Copyright Daniel Ratcliffe, 2011-2021. This API may be redistributed unmodified and in full only.
 * For help using the API, and posting your mods, visit the forums at computercraft.info.
 */

package dan200.computercraft.api.lua;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.nio.ByteBuffer;
import java.util.Map;

/**
 * Various utility functions for operating with Lua values.
 *
 * @see IArguments
 */
public final class LuaValues
{
    private LuaValues()
    {
    }

    /**
     * Encode a Lua string into a read-only {@link ByteBuffer}.
     *
     * @param string The string to encode.
     * @return The encoded string.
     */
    @Nonnull
    public static ByteBuffer encode( @Nonnull String string )
    {
        byte[] chars = new byte[string.length()];
        for( int i = 0; i < chars.length; i++ )
        {
            char c = string.charAt( i );
            chars[i] = c < 256 ? (byte) c : 63;
        }

        return ByteBuffer.wrap( chars )
            .asReadOnlyBuffer();
    }

    /**
     * Construct a "bad argument" exception, from an expected type and the actual value provided.
     *
     * @param index    The argument number, starting from 0.
     * @param expected The expected type for this argument.
     * @param actual   The actual value provided for this argument.
     * @return The constructed exception, which should be thrown immediately.
     */
    @Nonnull
    public static LuaException badArgumentOf( int index, @Nonnull String expected, @Nullable Object actual )
    {
        return badArgument( index, expected, getType( actual ) );
    }

    /**
     * Construct a "bad argument" exception, from an expected and actual type.
     *
     * @param index    The argument number, starting from 0.
     * @param expected The expected type for this argument.
     * @param actual   The provided type for this argument.
     * @return The constructed exception, which should be thrown immediately.
     */
    @Nonnull
    public static LuaException badArgument( int index, @Nonnull String expected, @Nonnull String actual )
    {
        return new LuaException( "bad argument #" + (index + 1) + " (" + expected + " expected, got " + actual + ")" );
    }

    /**
     * Get a string representation of the given value's type.
     *
     * @param value The value whose type we are trying to compute.
     * @return A string representation of the given value's type, in a similar format to that provided by Lua's {@code type} function.
     */
    @Nonnull
    public static String getType( @Nullable Object value )
    {
        if( value == null )
        {
            return "nil";
        }
        if( value instanceof String )
        {
            return "string";
        }
        if( value instanceof Boolean )
        {
            return "boolean";
        }
        if( value instanceof Number )
        {
            return "number";
        }
        if( value instanceof Map )
        {
            return "table";
        }
        return "userdata";
    }

    /**
     * Ensure a numeric argument is finite (i.e. not infinite or {@link Double#NaN}.
     *
     * @param index The argument index to check.
     * @param value The value to check.
     * @return The input {@code value}.
     * @throws LuaException If this is not a finite number.
     */
    public static Number checkFiniteNum( int index, Number value ) throws LuaException
    {
        checkFinite( index, value.doubleValue() );
        return value;
    }

    /**
     * Ensure a numeric argument is finite (i.e. not infinite or {@link Double#NaN}.
     *
     * @param index The argument index to check.
     * @param value The value to check.
     * @return The input {@code value}.
     * @throws LuaException If this is not a finite number.
     */
    public static double checkFinite( int index, double value ) throws LuaException
    {
        if( !Double.isFinite( value ) )
        {
            throw badArgument( index, "number", getNumericType( value ) );
        }
        return value;
    }

    /**
     * Returns a more detailed representation of this number's type. If this is finite, it will just return "number", otherwise it returns whether it is
     * infinite or NaN.
     *
     * @param value The value to extract the type for.
     * @return This value's numeric type.
     */
    @Nonnull
    public static String getNumericType( double value )
    {
        if( Double.isNaN( value ) )
        {
            return "nan";
        }
        if( value == Double.POSITIVE_INFINITY )
        {
            return "inf";
        }
        if( value == Double.NEGATIVE_INFINITY )
        {
            return "-inf";
        }
        return "number";
    }

    /**
     * Ensure a string is a valid enum value.
     *
     * @param index The argument index to check.
     * @param klass The class of the enum instance.
     * @param value The value to extract.
     * @param <T>   The type of enum we are extracting.
     * @return The parsed enum value.
     * @throws LuaException If this is not a known enum value.
     */
    public static <T extends Enum<T>> T checkEnum( int index, Class<T> klass, String value ) throws LuaException
    {
        for( T possibility : klass.getEnumConstants() )
        {
            if( possibility.name()
                .equalsIgnoreCase( value ) )
            {
                return possibility;
            }
        }

        throw new LuaException( "bad argument #" + (index + 1) + " (unknown option " + value + ")" );
    }
}