net.kuujo.vertigo.util.IncrementalCompletionHandler.java Source code

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Here is the source code for net.kuujo.vertigo.util.IncrementalCompletionHandler.java

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/*
 * Copyright 2014 the original author or authors.
 *
 * 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 net.kuujo.vertigo.util;

import io.vertx.core.AsyncResult;
import io.vertx.core.Future;
import io.vertx.core.Handler;

/**
 * An incremental version of the counting completion handler.
 *
 * @author <a href="http://github.com/ef-labs">Magnus Koch</a>
 */
public class IncrementalCompletionHandler<T> {
    private int count;
    private int required;
    private Handler<AsyncResult<T>> doneHandler;
    private Throwable cause;
    private boolean failed;
    private boolean complete;

    public IncrementalCompletionHandler() {
    }

    /**
     * Increases the required operation count and returns a completion handler for that operation.
     */
    public Handler<AsyncResult<T>> increment() {
        if (complete) {
            throw new IllegalStateException("Cannot increment after completed() has been called.");
        }
        required++;
        return event -> {
            if (event.succeeded()) {
                count++;
                checkDone();
            } else {
                fail(event.cause());
            }
        };
    }

    /**
     * Signals that all operations are registered
     *
     * @param handler
     */
    public void completed(Handler<AsyncResult<T>> handler) {
        setHandler(handler);
        this.complete = true;
        checkDone();
    }

    /**
     * Indicates that a call failed. This will immediately fail the handler.
     *
     * @param t The cause of the failure.
     */
    protected void fail(Throwable t) {
        if (!failed) {
            failed = true;
            cause = t;
            checkDone();
        }
    }

    /**
     * Sets the completion handler.
     *
     * @param doneHandler An asynchronous handler to be called once all calls have completed.
     */
    protected IncrementalCompletionHandler setHandler(Handler<AsyncResult<T>> doneHandler) {
        this.doneHandler = doneHandler;
        checkDone();
        return this;
    }

    /**
     * Checks whether the handler should be called.
     */
    protected void checkDone() {
        if (failed && doneHandler != null) {
            doneHandler.handle(Future.failedFuture(cause));
            doneHandler = null;
        } else if (complete && count == required) {
            doneHandler.handle(Future.succeededFuture());
            doneHandler = null;
        }
    }

}