/* 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 org.activiti.crystalball.simulator;

import org.activiti.engine.delegate.VariableScope;
import org.activiti.engine.impl.el.ExpressionManager;
import org.activiti.engine.impl.javax.el.CompositeELResolver;
import org.activiti.engine.impl.javax.el.ELContext;
import org.activiti.engine.impl.javax.el.ELResolver;
import org.activiti.engine.impl.javax.el.PropertyNotWritableException;

import java.beans.FeatureDescriptor;
import java.util.Iterator;
import java.util.Map;


/**
 * {@link org.activiti.engine.impl.el.ExpressionManager} that exposes the simulation event in expressions
 *
 * @author martin.grofcik
 */
public class SimulationExpressionManager extends ExpressionManager {

  /**
   */
  public SimulationExpressionManager(Map<Object, Object> beans) {
    super(beans);
  }

  @Override
  protected ELResolver createElResolver(VariableScope variableScope) {
    CompositeELResolver compositeElResolver = new CompositeELResolver();
    compositeElResolver.add(new SimulationScopeElResolver(variableScope));
    compositeElResolver.add(super.createElResolver(variableScope));
    return compositeElResolver;
  }


  private class SimulationScopeElResolver extends ELResolver {

    public static final String EVENT_CALENDAR_KEY= "eventCalendar";

    protected VariableScope variableScope;

    public SimulationScopeElResolver(VariableScope variableScope) {
      this.variableScope = variableScope;
    }


    @Override
    public Object getValue(ELContext context, Object base, Object property) {
      if (base == null) {
        if (EVENT_CALENDAR_KEY.equals(property)) {
          context.setPropertyResolved(true);
          return SimulationRunContext.getEventCalendar();
        }
      }
      return null;
    }

    @Override
    public boolean isReadOnly(ELContext context, Object base, Object property) {
      return true;
    }

    @Override
    public void setValue(ELContext context, Object base, Object property, Object value) {
      throw new PropertyNotWritableException(
        "Variable '" + property + "' is not writable");
    }

    @Override
    public Class<?> getCommonPropertyType(ELContext arg0, Object arg1) {
      return Object.class;
    }

    @Override
    public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext arg0, Object arg1) {
      return null;
    }

    @Override
    public Class<?> getType(ELContext arg0, Object arg1, Object arg2) {
      return Object.class;
    }
  }
}