/*******************************************************************************
    * 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.ArrayList;
  import java.util.Map;
  import java.util.Map.Entry;
  
  import net.sf.oval.exception.ExpressionEvaluationException;
  import net.sf.oval.internal.Log;
  
  import org.jruby.CompatVersion;
  import org.jruby.Ruby;
  import org.jruby.RubyInstanceConfig;
  import org.jruby.javasupport.JavaEmbedUtils;
  import org.jruby.runtime.builtin.IRubyObject;
  
  /**
   * @author Sebastian Thomschke
   *
   */
  public class ExpressionLanguageJRubyImpl implements ExpressionLanguage
  {
  	private static final Log LOG = Log.getLog(ExpressionLanguageJRubyImpl.class);
  
  	/**
  	 * {@inheritDoc}
  	 */
  	public Object evaluate(final String expression, final Map<String, ? > values) throws ExpressionEvaluationException
  	{
  		LOG.debug("Evaluating JRuby expression: {1}", expression);
  		try
  		{
  			final RubyInstanceConfig config = new RubyInstanceConfig();
  			config.setCompatVersion(CompatVersion.RUBY1_9);
  			final Ruby runtime = JavaEmbedUtils.initialize(new ArrayList<String>(), config);
  
  			final StringBuilder localVars = new StringBuilder();
  			for (final Entry<String, ? > entry : values.entrySet())
  			{
  				runtime.getGlobalVariables().set("$" + entry.getKey(), JavaEmbedUtils.javaToRuby(runtime, entry.getValue()));
  				localVars.append(entry.getKey()) //
  						.append("=$") //
  						.append(entry.getKey()) //
  						.append("\n");
  			}
  			final IRubyObject result = runtime.evalScriptlet(localVars + expression);
  			return JavaEmbedUtils.rubyToJava(runtime, result, Object.class);
  		}
  		catch (final RuntimeException ex)
  		{
  			throw new ExpressionEvaluationException("Evaluating JRuby 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;
  	}
  }