/*
 * Licensed to Crate under one or more contributor license agreements.
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.  Crate 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.
 *
 * However, if you have executed another commercial license agreement
 * with Crate these terms will supersede the license and you may use the
 * software solely pursuant to the terms of the relevant commercial
 * agreement.
 */

package io.crate.executor.transport.executionphases;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Triggers {@link #future} after {@code numServer} calls to either
 * {@link #jobInitialized()} or {@link #jobInitializationFailed(Throwable)}
 * <p>
 *     If {@link #jobInitializationFailed(Throwable)}} has been called at least once
 *     the future will emit a failure.
 * </p>
 */
class InitializationTracker {

    final CompletableFuture<Void> future = new CompletableFuture<>();
    private final AtomicInteger serverToInitialize;
    private volatile Throwable failure;

    InitializationTracker(int numServer) {
        if (numServer == 0) {
            future.complete(null);
        }
        serverToInitialize = new AtomicInteger(numServer);
    }

    void jobInitialized() {
        if (serverToInitialize.decrementAndGet() <= 0) {
            // no need to synchronize here, since there cannot be a failure after all servers have finished
            if (failure == null) {
                future.complete(null);
            } else {
                future.completeExceptionally(failure);
            }
        }
    }

    /**
     * Indicates that a jobInitialization failed
     *
     * @param t The cause of the initialization failure.
     *          If no failure has been set so far or if it was an InterruptedException it is overwritten.
     */
    void jobInitializationFailed(Throwable t) {
        synchronized (this) {
            if (failure == null || failure instanceof InterruptedException) {
                failure = t;
            }
        }
        jobInitialized();
    }
}