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/* 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.engine.impl.bpmn.helper;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;

import org.activiti.bpmn.model.MapExceptionEntry;
import org.activiti.engine.ActivitiException;
import org.activiti.engine.ActivitiIllegalArgumentException;
import org.activiti.engine.DynamicBpmnConstants;
import org.activiti.engine.delegate.BpmnError;
import org.activiti.engine.delegate.DelegateExecution;
import org.activiti.engine.delegate.DelegateTask;
import org.activiti.engine.delegate.ExecutionListener;
import org.activiti.engine.delegate.Expression;
import org.activiti.engine.delegate.JavaDelegate;
import org.activiti.engine.delegate.TaskListener;
import org.activiti.engine.impl.bpmn.behavior.AbstractBpmnActivityBehavior;
import org.activiti.engine.impl.bpmn.behavior.ServiceTaskJavaDelegateActivityBehavior;
import org.activiti.engine.impl.bpmn.parser.FieldDeclaration;
import org.activiti.engine.impl.context.Context;
import org.activiti.engine.impl.delegate.ActivityBehavior;
import org.activiti.engine.impl.delegate.SubProcessActivityBehavior;
import org.activiti.engine.impl.delegate.TriggerableActivityBehavior;
import org.activiti.engine.impl.delegate.invocation.ExecutionListenerInvocation;
import org.activiti.engine.impl.delegate.invocation.TaskListenerInvocation;
import org.activiti.engine.impl.persistence.entity.ExecutionEntity;
import org.activiti.engine.impl.util.ReflectUtil;
import org.apache.commons.lang3.StringUtils;

import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * Helper class for bpmn constructs that allow class delegation.
 * 
 * This class will lazily instantiate the referenced classes when needed at runtime.
 * 
 * @author Joram Barrez
 * @author Falko Menge
 * @author Saeid Mirzaei
 */
public class ClassDelegate extends AbstractBpmnActivityBehavior implements TaskListener, ExecutionListener, SubProcessActivityBehavior {

  private static final long serialVersionUID = 1L;
  
  protected String serviceTaskId;
  protected String className;
  protected List fieldDeclarations;
  protected ExecutionListener executionListenerInstance;
  protected TaskListener taskListenerInstance;
  protected ActivityBehavior activityBehaviorInstance;
  protected Expression skipExpression;
  protected List mapExceptions;

  public ClassDelegate(String className, List fieldDeclarations, Expression skipExpression) {
    this.className = className;
    this.fieldDeclarations = fieldDeclarations;
    this.skipExpression = skipExpression;

  }

  public ClassDelegate(String id, String className, List fieldDeclarations, Expression skipExpression, List mapExceptions) {
    this(className, fieldDeclarations, skipExpression);
    this.serviceTaskId = id;
    this.mapExceptions = mapExceptions;
  }

  public ClassDelegate(String className, List fieldDeclarations) {
    this(className, fieldDeclarations, null);
  }

  public ClassDelegate(Class clazz, List fieldDeclarations) {
    this(clazz.getName(), fieldDeclarations, null);
  }

  public ClassDelegate(Class clazz, List fieldDeclarations, Expression skipExpression) {
    this(clazz.getName(), fieldDeclarations, skipExpression);
  }

  // Execution listener
  public void notify(DelegateExecution execution) {
    if (executionListenerInstance == null) {
      executionListenerInstance = getExecutionListenerInstance();
    }
    Context.getProcessEngineConfiguration().getDelegateInterceptor().handleInvocation(new ExecutionListenerInvocation(executionListenerInstance, execution));
  }

  protected ExecutionListener getExecutionListenerInstance() {
    Object delegateInstance = instantiateDelegate(className, fieldDeclarations);
    if (delegateInstance instanceof ExecutionListener) {
      return (ExecutionListener) delegateInstance;
    } else if (delegateInstance instanceof JavaDelegate) {
      return new ServiceTaskJavaDelegateActivityBehavior((JavaDelegate) delegateInstance);
    } else {
      throw new ActivitiIllegalArgumentException(delegateInstance.getClass().getName() + " doesn't implement " + ExecutionListener.class + " nor " + JavaDelegate.class);
    }
  }

  // Task listener
  public void notify(DelegateTask delegateTask) {
    if (taskListenerInstance == null) {
      taskListenerInstance = getTaskListenerInstance();
    }
    try {
      Context.getProcessEngineConfiguration().getDelegateInterceptor().handleInvocation(new TaskListenerInvocation(taskListenerInstance, delegateTask));
    } catch (Exception e) {
      throw new ActivitiException("Exception while invoking TaskListener: " + e.getMessage(), e);
    }
  }

  protected TaskListener getTaskListenerInstance() {
    Object delegateInstance = instantiateDelegate(className, fieldDeclarations);
    if (delegateInstance instanceof TaskListener) {
      return (TaskListener) delegateInstance;
    } else {
      throw new ActivitiIllegalArgumentException(delegateInstance.getClass().getName() + " doesn't implement " + TaskListener.class);
    }
  }

  // Activity Behavior
  public void execute(DelegateExecution execution) {
    boolean isSkipExpressionEnabled = SkipExpressionUtil.isSkipExpressionEnabled(execution, skipExpression);
    if (!isSkipExpressionEnabled || (isSkipExpressionEnabled && !SkipExpressionUtil.shouldSkipFlowElement(execution, skipExpression))) {

      if (Context.getProcessEngineConfiguration().isEnableProcessDefinitionInfoCache()) {
        ObjectNode taskElementProperties = Context.getBpmnOverrideElementProperties(serviceTaskId, execution.getProcessDefinitionId());
        if (taskElementProperties != null && taskElementProperties.has(DynamicBpmnConstants.SERVICE_TASK_CLASS_NAME)) {
          String overrideClassName = taskElementProperties.get(DynamicBpmnConstants.SERVICE_TASK_CLASS_NAME).asText();
          if (StringUtils.isNotEmpty(overrideClassName) && overrideClassName.equals(className) == false) {
            className = overrideClassName;
            activityBehaviorInstance = null;
          }
        }
      }
      
      if (activityBehaviorInstance == null) {
        activityBehaviorInstance = getActivityBehaviorInstance(execution);
      }

      try {
        activityBehaviorInstance.execute(execution);
      } catch (BpmnError error) {
        ErrorPropagation.propagateError(error, execution);
      } catch (RuntimeException e) {
        if (!ErrorPropagation.mapException(e, (ExecutionEntity) execution, mapExceptions))
          throw e;
      }
    }
  }

  // Signallable activity behavior
  public void trigger(DelegateExecution execution, String signalName, Object signalData) {
    if (activityBehaviorInstance == null) {
      activityBehaviorInstance = getActivityBehaviorInstance(execution);
    }

    if (activityBehaviorInstance instanceof TriggerableActivityBehavior) {
      ((TriggerableActivityBehavior) activityBehaviorInstance).trigger(execution, signalName, signalData);
    } else {
      throw new ActivitiException("signal() can only be called on a " + TriggerableActivityBehavior.class.getName() + " instance");
    }
  }

  // Subprocess activityBehaviour

  @Override
  public void completing(DelegateExecution execution, DelegateExecution subProcessInstance) throws Exception {
    if (activityBehaviorInstance == null) {
      activityBehaviorInstance = getActivityBehaviorInstance(execution);
    }

    if (activityBehaviorInstance instanceof SubProcessActivityBehavior) {
      ((SubProcessActivityBehavior) activityBehaviorInstance).completing(execution, subProcessInstance);
    } else {
      throw new ActivitiException("completing() can only be called on a " + SubProcessActivityBehavior.class.getName() + " instance");
    }
  }

  @Override
  public void completed(DelegateExecution execution) throws Exception {
    if (activityBehaviorInstance == null) {
      activityBehaviorInstance = getActivityBehaviorInstance(execution);
    }

    if (activityBehaviorInstance instanceof SubProcessActivityBehavior) {
      ((SubProcessActivityBehavior) activityBehaviorInstance).completed(execution);
    } else {
      throw new ActivitiException("completed() can only be called on a " + SubProcessActivityBehavior.class.getName() + " instance");
    }
  }

  protected ActivityBehavior getActivityBehaviorInstance(DelegateExecution execution) {
    Object delegateInstance = instantiateDelegate(className, fieldDeclarations);

    if (delegateInstance instanceof ActivityBehavior) {
      return determineBehaviour((ActivityBehavior) delegateInstance, execution);
    } else if (delegateInstance instanceof JavaDelegate) {
      return determineBehaviour(new ServiceTaskJavaDelegateActivityBehavior((JavaDelegate) delegateInstance), execution);
    } else {
      throw new ActivitiIllegalArgumentException(delegateInstance.getClass().getName() + " doesn't implement " + JavaDelegate.class.getName() + " nor " + ActivityBehavior.class.getName());
    }
  }

  // Adds properties to the given delegation instance (eg multi instance) if
  // needed
  protected ActivityBehavior determineBehaviour(ActivityBehavior delegateInstance, DelegateExecution execution) {
    if (hasMultiInstanceCharacteristics()) {
      multiInstanceActivityBehavior.setInnerActivityBehavior((AbstractBpmnActivityBehavior) delegateInstance);
      return multiInstanceActivityBehavior;
    }
    return delegateInstance;
  }

  protected Object instantiateDelegate(String className, List fieldDeclarations) {
    return ClassDelegate.defaultInstantiateDelegate(className, fieldDeclarations);
  }

  // --HELPER METHODS (also usable by external classes)
  // ----------------------------------------

  public static Object defaultInstantiateDelegate(Class clazz, List fieldDeclarations) {
    return defaultInstantiateDelegate(clazz.getName(), fieldDeclarations);
  }

  public static Object defaultInstantiateDelegate(String className, List fieldDeclarations) {
    Object object = ReflectUtil.instantiate(className);
    applyFieldDeclaration(fieldDeclarations, object);
    return object;
  }

  public static void applyFieldDeclaration(List fieldDeclarations, Object target) {
    if (fieldDeclarations != null) {
      for (FieldDeclaration declaration : fieldDeclarations) {
        applyFieldDeclaration(declaration, target);
      }
    }
  }

  public static void applyFieldDeclaration(FieldDeclaration declaration, Object target) {
    Method setterMethod = ReflectUtil.getSetter(declaration.getName(), target.getClass(), declaration.getValue().getClass());

    if (setterMethod != null) {
      try {
        setterMethod.invoke(target, declaration.getValue());
      } catch (IllegalArgumentException e) {
        throw new ActivitiException("Error while invoking '" + declaration.getName() + "' on class " + target.getClass().getName(), e);
      } catch (IllegalAccessException e) {
        throw new ActivitiException("Illegal access when calling '" + declaration.getName() + "' on class " + target.getClass().getName(), e);
      } catch (InvocationTargetException e) {
        throw new ActivitiException("Exception while invoking '" + declaration.getName() + "' on class " + target.getClass().getName(), e);
      }
    } else {
      Field field = ReflectUtil.getField(declaration.getName(), target);
      if (field == null) {
        throw new ActivitiIllegalArgumentException("Field definition uses non-existing field '" + declaration.getName() + "' on class " + target.getClass().getName());
      }
      // Check if the delegate field's type is correct
      if (!fieldTypeCompatible(declaration, field)) {
        throw new ActivitiIllegalArgumentException("Incompatible type set on field declaration '" + declaration.getName() + "' for class " + target.getClass().getName() + ". Declared value has type "
            + declaration.getValue().getClass().getName() + ", while expecting " + field.getType().getName());
      }
      ReflectUtil.setField(field, target, declaration.getValue());
    }
  }

  public static boolean fieldTypeCompatible(FieldDeclaration declaration, Field field) {
    if (declaration.getValue() != null) {
      return field.getType().isAssignableFrom(declaration.getValue().getClass());
    } else {
      // Null can be set any field type
      return true;
    }
  }

  /**
   * returns the class name this {@link ClassDelegate} is configured to. Comes in handy if you want to check which delegates you already have e.g. in a list of listeners
   */
  public String getClassName() {
    return className;
  }

}