/*--
 * Copyright 2012 René M. de Bloois
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package solidstack.script.expressions;

import solidstack.io.SourceLocation;
import solidstack.script.ThreadContext;
import solidstack.script.ThrowException;
import solidstack.script.UndefinedPropertyException;



public class Defined extends LocalizedExpression
{
	private Expression expression;

	public Defined( SourceLocation location, Expression expression )
	{
		super( location );
		this.expression = expression;
	}

	@Override
	public Expression compile()
	{
		this.expression = this.expression.compile();
		return this;
	}

	@Override
	public Object evaluate( ThreadContext thread )
	{
		try
		{
			if( this.expression == null ) // TODO This could be moved to compile()
				throw new ThrowException( "defined() expects a parameter", thread.cloneStack( getLocation() ) );
			this.expression.evaluate( thread );
			return true;
		}
		catch( UndefinedPropertyException e )
		{
			return false;
		}
	}

	@Override
	public void writeTo( StringBuilder out )
	{
		out.append( "defined(" );
		this.expression.writeTo( out );
		out.append( ')' );
	}
}
