/*******************************************************************************
    * Portions created by Sebastian Thomschke are copyright (c) 2005-2012 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 groovy.lang.Binding;
  import groovy.lang.GroovyShell;
  import groovy.lang.Script;
  
  import java.util.Map;
  import java.util.Map.Entry;
  
  import net.sf.oval.exception.ExpressionEvaluationException;
  import net.sf.oval.internal.Log;
  import net.sf.oval.internal.util.ObjectCache;
  import net.sf.oval.internal.util.ThreadLocalObjectCache;
  
  /**
   * @author Sebastian Thomschke
   */
  public class ExpressionLanguageGroovyImpl implements ExpressionLanguage
  {
  	private static final Log LOG = Log.getLog(ExpressionLanguageGroovyImpl.class);
  
  	private static final GroovyShell GROOVY_SHELL = new GroovyShell();
  
  	private final ThreadLocalObjectCache<String, Script> threadScriptCache = new ThreadLocalObjectCache<String, Script>();
  
  	/**
  	 * {@inheritDoc}
  	 */
  	public Object evaluate(final String expression, final Map<String, ? > values) throws ExpressionEvaluationException
  	{
  		LOG.debug("Evaluating Groovy expression: {1}", expression);
  		try
  		{
  			final ObjectCache<String, Script> scriptCache = threadScriptCache.get();
  			Script script = scriptCache.get(expression);
  			if (script == null)
  			{
  				script = GROOVY_SHELL.parse(expression);
  				scriptCache.put(expression, script);
  			}
  
  			final Binding binding = new Binding();
  			for (final Entry<String, ? > entry : values.entrySet())
  				binding.setVariable(entry.getKey(), entry.getValue());
  			script.setBinding(binding);
  			return script.run();
  		}
  		catch (final Exception ex)
  		{
  			throw new ExpressionEvaluationException("Evaluating script with Groovy failed.", 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;
  	}
  }