/*******************************************************************************
    * Portions created by Sebastian Thomschke are copyright (c) 2005-2013 Sebastian
    * Thomschke.
    *
    * All Rights Reserved. This program and the accompanying materials
    * are made available under the terms of the Eclipse Public License v1.0
    * which accompanies this distribution, and is available at
    * http://www.eclipse.org/legal/epl-v10.html
    *
   * Contributors:
   *     Sebastian Thomschke - initial implementation.
   *******************************************************************************/
  package net.sf.oval.expression;
  
  import java.util.Map;
  
  import net.sf.oval.exception.ExpressionEvaluationException;
  import net.sf.oval.internal.Log;
  import net.sf.oval.internal.util.ObjectCache;
  
  import org.apache.commons.jexl2.Expression;
  import org.apache.commons.jexl2.JexlEngine;
  import org.apache.commons.jexl2.MapContext;
  
  /**
   * @author Sebastian Thomschke
   */
  public class ExpressionLanguageJEXLImpl implements ExpressionLanguage
  {
  	private static final Log LOG = Log.getLog(ExpressionLanguageJEXLImpl.class);
  
  	private static final JexlEngine jexl = new JexlEngine();
  
  	private final ObjectCache<String, Expression> expressionCache = new ObjectCache<String, Expression>();
  
  	/**
  	 * {@inheritDoc}
  	 */
  	@SuppressWarnings("unchecked")
  	public Object evaluate(final String expression, final Map<String, ? > values) throws ExpressionEvaluationException
  	{
  		LOG.debug("Evaluating JEXL expression: {1}", expression);
  		try
  		{
  			Expression expr = expressionCache.get(expression);
  			if (expr == null)
  			{
  				expr = jexl.createExpression(expression);
  				expressionCache.put(expression, expr);
  			}
  			return expr.evaluate(new MapContext((Map<String, Object>) values));
  		}
  		catch (final Exception ex)
  		{
  			throw new ExpressionEvaluationException("Evaluating JEXL expression failed: " + expression, ex);
  		}
  	}
  
  	/**
  	 * {@inheritDoc}
  	 */
  	public boolean evaluateAsBoolean(final String expression, final Map<String, ? > values) throws ExpressionEvaluationException
  	{
  		final Object result = evaluate(expression, values);
  		if (!(result instanceof Boolean)) throw new ExpressionEvaluationException("The script must return a boolean value.");
  		return (Boolean) result;
  	}
  }