/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you 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.elasticsearch.tasks;

import org.elasticsearch.common.Nullable;

import java.util.concurrent.atomic.AtomicReference;

/**
 * A task that can be canceled
 */
public abstract class CancellableTask extends Task {

    private final AtomicReference<String> reason = new AtomicReference<>();

    public CancellableTask(long id, String type, String action, String description, TaskId parentTaskId) {
        super(id, type, action, description, parentTaskId);
    }

    /**
     * This method is called by the task manager when this task is cancelled.
     */
    final void cancel(String reason) {
        assert reason != null;
        this.reason.compareAndSet(null, reason);
        onCancelled();
    }

    /**
     * Returns true if this task should be automatically cancelled if the coordinating node that
     * requested this task left the cluster.
     */
    public boolean cancelOnParentLeaving() {
        return true;
    }

    /**
     * Returns true if this task should can potentially have children that needs to be cancelled when the parent is cancelled.
     */
    public abstract boolean shouldCancelChildrenOnCancellation();

    public boolean isCancelled() {
        return reason.get() != null;
    }

    /**
     * The reason the task was cancelled or null if it hasn't been cancelled.
     */
    @Nullable
    public String getReasonCancelled() {
        return reason.get();
    }

    /**
     * Called after the task is cancelled so that it can take any actions that it has to take.
     */
    protected void onCancelled() {
    }
}