/* 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.behavior;

import java.util.List;

import org.activiti.engine.impl.context.Context;
import org.activiti.engine.impl.persistence.entity.ExecutionEntity;
import org.activiti.engine.impl.pvm.PvmActivity;
import org.activiti.engine.impl.pvm.PvmTransition;
import org.activiti.engine.impl.pvm.delegate.ActivityExecution;
import org.flowable.engine.delegate.DelegateExecution;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Implementation of the Parallel Gateway/AND gateway as defined in the BPMN 2.0 specification.
 * 
 * The Parallel Gateway can be used for splitting a path of execution into multiple paths of executions (AND-split/fork behavior), one for every outgoing sequence flow.
 * 
 * The Parallel Gateway can also be used for merging or joining paths of execution (AND-join). In this case, on every incoming sequence flow an execution needs to arrive, before leaving the Parallel
 * Gateway (and potentially then doing the fork behavior in case of multiple outgoing sequence flow).
 * 
 * Note that there is a slight difference to spec (p. 436): "The parallel gateway is activated if there is at least one Token on each incoming sequence flow." We only check the number of incoming
 * tokens to the number of sequenceflow. So if two tokens would arrive through the same sequence flow, our implementation would activate the gateway.
 * 
 * Note that a Parallel Gateway having one incoming and multiple outgoing sequence flow, is the same as having multiple outgoing sequence flow on a given activity. However, a parallel gateway does NOT
 * check conditions on the outgoing sequence flow.
 * 
 * @author Joram Barrez
 * @author Tom Baeyens
 */
public class ParallelGatewayActivityBehavior extends GatewayActivityBehavior {

    private static final long serialVersionUID = 1L;

    private static final Logger LOGGER = LoggerFactory.getLogger(ParallelGatewayActivityBehavior.class);

    @Override
    public void execute(DelegateExecution execution) {
        ActivityExecution activityExecution = (ActivityExecution) execution;
        // Join
        PvmActivity activity = activityExecution.getActivity();
        List<PvmTransition> outgoingTransitions = activityExecution.getActivity().getOutgoingTransitions();
        execution.inactivate();
        lockConcurrentRoot(activityExecution);

        List<ActivityExecution> joinedExecutions = activityExecution.findInactiveConcurrentExecutions(activity);
        int nbrOfExecutionsToJoin = activityExecution.getActivity().getIncomingTransitions().size();
        int nbrOfExecutionsJoined = joinedExecutions.size();
        Context.getCommandContext().getHistoryManager().recordActivityEnd((ExecutionEntity) execution);
        if (nbrOfExecutionsJoined == nbrOfExecutionsToJoin) {

            // Fork
            if (LOGGER.isDebugEnabled()) {
                LOGGER.debug("parallel gateway '{}' activates: {} of {} joined", activity.getId(), nbrOfExecutionsJoined, nbrOfExecutionsToJoin);
            }
            activityExecution.takeAll(outgoingTransitions, joinedExecutions);

        } else if (LOGGER.isDebugEnabled()) {
            LOGGER.debug("parallel gateway '{}' does not activate: {} of {} joined", activity.getId(), nbrOfExecutionsJoined, nbrOfExecutionsToJoin);
        }
    }

}
