/**
 * AmbientTalk/2 Project
 * AGCase.java created on Jul 6, 2008 at 12:31:50 PM
 * (c) Programming Technology Lab, 2006 - 2007
 * Authors: Tom Van Cutsem & Stijn Mostinckx
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or
 * sell 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
package edu.vub.at.objects.natives;

import edu.vub.at.exceptions.InterpreterException;
import edu.vub.at.exceptions.XArityMismatch;
import edu.vub.at.exceptions.XIllegalArgument;
import edu.vub.at.objects.ATAbstractGrammar;
import edu.vub.at.objects.ATBoolean;
import edu.vub.at.objects.ATContext;
import edu.vub.at.objects.ATObject;
import edu.vub.at.objects.ATTable;
import edu.vub.at.objects.ATTypeTag;
import edu.vub.at.objects.grammar.ATApplication;
import edu.vub.at.objects.grammar.ATAssignVariable;
import edu.vub.at.objects.grammar.ATClosureLiteral;
import edu.vub.at.objects.grammar.ATSymbol;
import edu.vub.at.objects.natives.grammar.NATAbstractGrammar;

/**
 * @author smostinc
 *
 */
public class AGCase extends NATAbstractGrammar {

	private ATSymbol		bindingForm_	= null;
	private ATSymbol		typeName_		= null;
	private ATTable			arguments_		= NATTable.EMPTY;
	
	private ATAbstractGrammar	pattern_;
	private ATClosureLiteral	consequence_;
	
	public AGCase(ATAbstractGrammar pattern, ATClosureLiteral consequence) throws InterpreterException {
		if (pattern instanceof ATAssignVariable) {
			ATAssignVariable assignment	= (ATAssignVariable) pattern;
			bindingForm_ 				= assignment.base_name();
			pattern						= assignment.base_valueExpression();
		}
		
		if(pattern instanceof ATSymbol) {
			typeName_	= pattern.asSymbol();
			
		} else if(pattern instanceof ATApplication) {
			ATApplication application	= (ATApplication) pattern;

			typeName_	= application.base_function().asSymbol();
			arguments_	= application.base_arguments();
		}

		pattern_		= pattern;
		consequence_	= consequence;
	}
	
	public NATText meta_print() throws InterpreterException {
		return NATText.atValue(
			"case " + (bindingForm_==null?"":(bindingForm_.toString() + " := ")) +
			pattern_.meta_print().javaValue + " => " + consequence_.meta_print().javaValue);
	}
	
	public ATBoolean base_isApplicable(ATContext theContext, ATObject theObjectToBeMatched) throws InterpreterException {
		ATTypeTag theTypeTag = theContext.base_lexicalScope().impl_callField(typeName_).asTypeTag();
		
		return theObjectToBeMatched.meta_isTaggedAs(theTypeTag);
	}
	
	public ATObject base_attemptToExecute(ATObject theObjectToBeMatched, ATContext theContext) throws InterpreterException {
		ATTypeTag theTypeTag = theContext.base_lexicalScope().impl_callField(typeName_).asTypeTag();

		ATTable theArguments = NATTable.EMPTY;
		
		NATCallframe bindings = new NATCallframe(theContext.base_lexicalScope());

		if(bindingForm_ != null)
			bindings.meta_defineField(bindingForm_, theObjectToBeMatched);
		
		if(theTypeTag instanceof NATPatternType) {
			NATPatternType thePattern = (NATPatternType) theTypeTag;
			
			theArguments = thePattern.base_unapply(theObjectToBeMatched).asTable();
		}
		
		ATObject[] parameters = arguments_.asNativeTable().elements_;
		ATObject[] arguments  = theArguments.asNativeTable().elements_;
		
		if(parameters.length != arguments.length)
			throw new XArityMismatch(theTypeTag.base_typeName().toString(), parameters.length, arguments.length);
		
		for (int i = 0; i < parameters.length; i++) {
			ATObject parameter = parameters[i];
			ATObject argument  = arguments[i];
			
			if(parameter instanceof ATSymbol) {
				ATSymbol theVariableName = parameter.asSymbol();
				
				if(! bindings.hasLocalField(theVariableName)) {
					bindings.meta_defineField((ATSymbol)parameter, argument);
					continue;
				} else {
					parameter = bindings.getLocalField(theVariableName);
				}
			}
			
			if(/* parameter != argument */
			   !parameter.base__opeql__opeql_(argument).asNativeBoolean().javaValue) {
				throw new XIllegalArgument("No valid match since " + parameter + " != " + argument);
			}
		}
		
		
		
		NATContext theExtendedContext = new NATContext(bindings, theContext.base_receiver());
		
		return consequence_.meta_eval(theExtendedContext).asClosure().base_apply(NATTable.EMPTY);
	}

}