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* Copyright (c) 2009-2011 Luaj.org. All rights reserved.
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* of this software and associated documentation files (the "Software"), to deal
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* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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package org.luaj.vm2.libs.jse;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import org.luaj.vm2.LuaDouble;
import org.luaj.vm2.LuaInteger;
import org.luaj.vm2.LuaString;
import org.luaj.vm2.LuaUserdata;
import org.luaj.vm2.LuaValue;

/**
 * Helper class to coerce values from Java to lua within the luajava library. 
 * <p>
 * This class is primarily used by the {@link LuajavaLib},
 * but can also be used directly when working with Java/lua bindings. 
 * <p>
 * To coerce scalar types, the various, generally the {@code valueOf(type)} methods 
 * on {@link LuaValue} may be used:
 * <ul>
 * <li>{@link LuaValue#valueOf(boolean)}</li>
 * <li>{@link LuaValue#valueOf(byte[])}</li>
 * <li>{@link LuaValue#valueOf(double)}</li>
 * <li>{@link LuaValue#valueOf(int)}</li>
 * <li>{@link LuaValue#valueOf(String)}</li>
 * </ul>
 * <p>
 * To coerce arrays of objects and lists, the {@code listOf(..)} and {@code tableOf(...)} methods 
 * on {@link LuaValue} may be used:
 * <ul>
 * <li>{@link LuaValue#listOf(LuaValue[])}</li>
 * <li>{@link LuaValue#listOf(LuaValue[], org.luaj.vm2.Varargs)}</li>
 * <li>{@link LuaValue#tableOf(LuaValue[])}</li>
 * <li>{@link LuaValue#tableOf(LuaValue[], LuaValue[], org.luaj.vm2.Varargs)}</li>
 * </ul>
 * The method {@link CoerceJavaToLua#coerce(Object)} looks as the type and dimesioning 
 * of the argument and tries to guess the best fit for corrsponding lua scalar, 
 * table, or table of tables. 
 * 
 * @see CoerceJavaToLua#coerce(Object)
 * @see LuajavaLib
 */
public class CoerceJavaToLua {

	static interface Coercion { 
		public LuaValue coerce( Object javaValue );
	};
	
	private static final class BoolCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			Boolean b = (Boolean) javaValue;
			return b.booleanValue()? LuaValue.TRUE: LuaValue.FALSE;
		}
	}
	
	private static final class IntCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			Number n = (Number) javaValue;
			return LuaInteger.valueOf( n.longValue() );
		}
	}

	private static final class CharCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			Character c = (Character) javaValue;
			return LuaInteger.valueOf( c.charValue() );
		}
	}

	private static final class DoubleCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			Number n = (Number) javaValue;
			return LuaDouble.valueOf( n.doubleValue() );
		}
	}

	private static final class StringCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			return LuaString.valueOf( javaValue.toString() );
		}
	}

	private static final class BytesCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			return LuaValue.valueOf((byte[]) javaValue);
		}
	}

	private static final class ClassCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			return JavaClass.forClass((Class) javaValue);
		}
	}

	private static final class InstanceCoercion implements Coercion {
		public LuaValue coerce(Object javaValue) {
			return new JavaInstance(javaValue);
		}
	}

	private static final class ArrayCoercion implements Coercion {
		public LuaValue coerce(Object javaValue) {
			// should be userdata? 
			return new JavaArray(javaValue);
		}
	}

	private static final class LuaCoercion implements Coercion {
		public LuaValue coerce( Object javaValue ) {
			return (LuaValue) javaValue;
		}
	}


	static final Map COERCIONS = Collections.synchronizedMap(new HashMap());
	
	static {
		Coercion boolCoercion = new BoolCoercion() ;
		Coercion intCoercion = new IntCoercion() ;
		Coercion charCoercion = new CharCoercion() ;
		Coercion doubleCoercion = new DoubleCoercion() ;
		Coercion stringCoercion = new StringCoercion() ;
		Coercion bytesCoercion = new BytesCoercion() ;
		Coercion classCoercion = new ClassCoercion() ;
		COERCIONS.put( Boolean.class, boolCoercion );
		COERCIONS.put( Byte.class, intCoercion );
		COERCIONS.put( Character.class, charCoercion );
		COERCIONS.put( Short.class, intCoercion );
		COERCIONS.put( Integer.class, intCoercion );
		COERCIONS.put( Long.class, intCoercion );
		COERCIONS.put( Float.class, doubleCoercion );
		COERCIONS.put( Double.class, doubleCoercion );
		COERCIONS.put( String.class, stringCoercion );
		COERCIONS.put( byte[].class, bytesCoercion );
		COERCIONS.put( Class.class, classCoercion );
	}

	/**
	 * Coerse a Java object to a corresponding lua value. 
	 * <p>
	 * Integral types {@code boolean}, {@code byte},  {@code char}, {@code int}, and {@code long} 
	 * will become {@link LuaInteger};
	 * {@code float} and {@code double} will become {@link LuaDouble};
	 * {@code String} and {@code byte[]} will become {@link LuaString}; 
	 * types inheriting from {@link LuaValue} will be returned without coercion;
	 * other types will become {@link LuaUserdata}.
	 * @param o Java object needing conversion
	 * @return {@link LuaValue} corresponding to the supplied Java value. 
	 * @see LuaValue
	 * @see LuaInteger
	 * @see LuaDouble
	 * @see LuaString
	 * @see LuaUserdata
	 */
	public static LuaValue coerce(Object o) {
		if ( o == null )
			return LuaValue.NIL;
		Class clazz = o.getClass();
		Coercion c = (Coercion) COERCIONS.get( clazz );
		if ( c == null ) {
			c = clazz.isArray()? arrayCoercion:
				o instanceof LuaValue ? luaCoercion:
					instanceCoercion;
			COERCIONS.put( clazz, c );
		}
		return c.coerce(o);
	}

	static final Coercion instanceCoercion = new InstanceCoercion();
	
	static final Coercion arrayCoercion = new ArrayCoercion();	

	static final Coercion luaCoercion = new LuaCoercion() ;
}
