/*
 * Copyright (c) 2006-2013 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Thierry Delprat
 *     Florent Guillaume
 */
package org.nuxeo.ecm.core.event.impl;

import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.FutureTask;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.nuxeo.ecm.core.event.EventBundle;
import org.nuxeo.ecm.core.event.EventStats;
import org.nuxeo.ecm.core.event.ReconnectedEventBundle;
import org.nuxeo.runtime.api.Framework;
import org.nuxeo.runtime.transaction.TransactionHelper;

/**
 * Executor that passes an event bundle to post-commit asynchronous listeners (in a separated thread in order to manage
 * transactions).
 * <p>
 * Allows a bulk mode where transaction management is not per-listener done once for the whole set of listeners.
 */
public class PostCommitEventExecutor {

    private static final Log log = LogFactory.getLog(PostCommitEventExecutor.class);

    public static final String TIMEOUT_MS_PROP = "org.nuxeo.ecm.core.event.tx.PostCommitExecutor.timeoutMs";

    public static final int DEFAULT_TIMEOUT_MS = 300; // 0.3s

    public static final int DEFAULT_TIMEOUT_TEST_MS = 60000; // 1 min

    private Integer defaultTimeoutMs;

    public static final String DEFAULT_BULK_TIMEOUT_S = "600"; // 10min

    public static final String BULK_TIMEOUT_PROP = "org.nuxeo.ecm.core.event.tx.BulkExecutor.timeout";

    private static final long KEEP_ALIVE_TIME_SECOND = 10;

    private static final int MAX_POOL_SIZE = 100;

    protected final ExecutorService executor;

    /**
     * Creates non-daemon threads at normal priority.
     */
    private static class NamedThreadFactory implements ThreadFactory {

        private final AtomicInteger threadNumber = new AtomicInteger();

        private final ThreadGroup group;

        private final String prefix;

        public NamedThreadFactory(String prefix) {
            SecurityManager sm = System.getSecurityManager();
            group = sm == null ? Thread.currentThread().getThreadGroup() : sm.getThreadGroup();
            this.prefix = prefix;
        }

        @Override
        public Thread newThread(Runnable r) {
            String name = prefix + threadNumber.incrementAndGet();
            Thread thread = new Thread(group, r, name);
            // do not set daemon
            thread.setPriority(Thread.NORM_PRIORITY);
            return thread;
        }
    }

    public PostCommitEventExecutor() {
        // use as much thread as needed up to MAX_POOL_SIZE
        // keep them alive a moment for reuse
        // have all threads torn down when there is no work to do
        ThreadFactory threadFactory = new NamedThreadFactory("Nuxeo-Event-PostCommit-");
        executor = new ThreadPoolExecutor(0, MAX_POOL_SIZE, KEEP_ALIVE_TIME_SECOND, TimeUnit.SECONDS,
                new SynchronousQueue<Runnable>(), threadFactory);
        ((ThreadPoolExecutor) executor).allowCoreThreadTimeOut(true);
    }

    protected int getDefaultTimeoutMs() {
        if (defaultTimeoutMs == null) {
            if (Framework.getProperty(TIMEOUT_MS_PROP) != null) {
                defaultTimeoutMs = Integer.parseInt(Framework.getProperty(TIMEOUT_MS_PROP));
            } else if (Framework.isTestModeSet()) {
                defaultTimeoutMs = DEFAULT_TIMEOUT_TEST_MS;
            } else {
                defaultTimeoutMs = DEFAULT_TIMEOUT_MS;
            }
        }
        return defaultTimeoutMs;
    }

    public void shutdown(long timeoutMillis) throws InterruptedException {
        executor.shutdown();
        executor.awaitTermination(timeoutMillis, TimeUnit.MILLISECONDS);
        if (!executor.isTerminated()) {
            executor.shutdownNow();
        }
    }

    public void run(List<EventListenerDescriptor> listeners, EventBundle event) {
        run(listeners, event, getDefaultTimeoutMs(), false);
    }

    public void runBulk(List<EventListenerDescriptor> listeners, EventBundle event) {
        String timeoutSeconds = Framework.getProperty(BULK_TIMEOUT_PROP, DEFAULT_BULK_TIMEOUT_S);
        run(listeners, event, Long.parseLong(timeoutSeconds) * 1000, true);
    }

    public void run(List<EventListenerDescriptor> listeners, EventBundle bundle, long timeoutMillis, boolean bulk) {
        // check that there's at list one listener interested
        boolean some = false;
        for (EventListenerDescriptor listener : listeners) {
            if (listener.acceptBundle(bundle)) {
                some = true;
                break;
            }
        }
        if (!some) {
            if (log.isDebugEnabled()) {
                log.debug("Events postcommit execution has nothing to do");
            }
            return;
        }

        if (log.isDebugEnabled()) {
            log.debug(String.format("Events postcommit execution starting with timeout %sms%s",
                    Long.valueOf(timeoutMillis), bulk ? " in bulk mode" : ""));
        }

        Callable<Boolean> callable = !bulk ? new EventBundleRunner(listeners, bundle) : new EventBundleBulkRunner(
                listeners, bundle);
        FutureTask<Boolean> futureTask = new FutureTask<Boolean>(callable);
        try {
            executor.execute(futureTask);
        } catch (RejectedExecutionException e) {
            log.error("Events postcommit execution rejected", e);
            return;
        }
        try {
            // wait for runner to be finished, with timeout
            Boolean ok = futureTask.get(timeoutMillis, TimeUnit.MILLISECONDS);
            if (Boolean.FALSE.equals(ok)) {
                log.error("Events postcommit bulk execution aborted due to previous error");
            }
        } catch (InterruptedException e) {
            // restore interrupted status
            Thread.currentThread().interrupt();
            // interrupt thread
            futureTask.cancel(true); // mayInterruptIfRunning=true
        } catch (TimeoutException e) {
            if (!bulk) {
                log.warn(String.format("Events postcommit execution exceeded timeout of %sms, leaving thread running",
                        Long.valueOf(timeoutMillis)));
                // don't cancel task, let it run
            } else {
                log.error(String.format(
                        "Events postcommit bulk execution exceeded timeout of %sms, interrupting thread",
                        Long.valueOf(timeoutMillis)));
                futureTask.cancel(true); // mayInterruptIfRunning=true
            }
        } catch (ExecutionException e) {
            log.error("Events postcommit execution encountered unexpected exception", e.getCause());
        }

        if (log.isDebugEnabled()) {
            log.debug("Events postcommit execution finished");
        }
    }

    /**
     * Lets the listeners process the event bundle.
     * <p>
     * For each listener, the event bundle is reconnected to a session and a transaction is started.
     * <p>
     * In case of exception in a listener, the transaction is rolled back for that listener but processing continues for
     * the other listeners.
     * <p>
     * In case of timeout, an error is logged but processing continues for the other listeners (the thread is left
     * running separately from the main thread that initiated post-commit processing).
     */
    protected static class EventBundleRunner implements Callable<Boolean> {

        protected final List<EventListenerDescriptor> listeners;

        protected final EventBundle bundle;

        public EventBundleRunner(List<EventListenerDescriptor> listeners, EventBundle bundle) {
            this.listeners = listeners;
            this.bundle = bundle;
        }

        @Override
        public Boolean call() {
            if (log.isDebugEnabled()) {
                log.debug("Events postcommit execution starting in thread: " + Thread.currentThread().getName());
            }
            long t0 = System.currentTimeMillis();
            EventStats stats = Framework.getLocalService(EventStats.class);

            for (EventListenerDescriptor listener : listeners) {
                EventBundle filtered = listener.filterBundle(bundle);
                if (filtered.isEmpty()) {
                    continue;
                }
                if (log.isDebugEnabled()) {
                    log.debug("Events postcommit execution start for listener: " + listener.getName());
                }
                long t1 = System.currentTimeMillis();

                boolean ok = false;
                ReconnectedEventBundle reconnected = null;
                // transaction timeout is managed by the FutureTask
                boolean tx = TransactionHelper.startTransaction();
                try {
                    reconnected = new ReconnectedEventBundleImpl(filtered, listeners.toString());

                    listener.asPostCommitListener().handleEvent(reconnected);

                    if (Thread.currentThread().isInterrupted()) {
                        log.error("Events postcommit execution interrupted for listener: " + listener.getName());
                        ok = false;
                    } else {
                        ok = true;
                    }
                } catch (RuntimeException e) {
                    log.error("Events postcommit execution encountered exception for listener: " + listener.getName(),
                            e);
                    // don't rethrow, but rollback (ok=false) and continue loop
                } finally {
                    try {
                        if (reconnected != null) {
                            reconnected.disconnect();
                        }
                    } finally {
                        if (tx) {
                            if (!ok) {
                                TransactionHelper.setTransactionRollbackOnly();
                                log.error("Rolling back transaction");
                            }
                            TransactionHelper.commitOrRollbackTransaction();
                        }
                        if (stats != null) {
                            stats.logAsyncExec(listener, System.currentTimeMillis() - t1);
                        }
                        if (log.isDebugEnabled()) {
                            log.debug("Events postcommit execution end for listener: " + listener.getName() + " in "
                                    + (System.currentTimeMillis() - t1) + "ms");
                        }
                    }
                }
                // even if interrupted due to timeout, we continue the loop
            }
            if (log.isDebugEnabled()) {
                log.debug("Events postcommit execution finished in " + (System.currentTimeMillis() - t0) + "ms");
            }
            return Boolean.TRUE; // no error to report
        }
    }

    /**
     * Lets the listeners process the event bundle in bulk mode.
     * <p>
     * The event bundle is reconnected to a single session and a single transaction is started for all the listeners.
     * <p>
     * In case of exception in a listener, the transaction is rolled back and processing stops.
     * <p>
     * In case of timeout, the transaction is rolled back and processing stops.
     */
    protected static class EventBundleBulkRunner implements Callable<Boolean> {

        protected final List<EventListenerDescriptor> listeners;

        protected final EventBundle bundle;

        public EventBundleBulkRunner(List<EventListenerDescriptor> listeners, EventBundle bundle) {
            this.listeners = listeners;
            this.bundle = bundle;
        }

        @Override
        public Boolean call() {
            if (log.isDebugEnabled()) {
                log.debug("Events postcommit bulk execution starting in thread: " + Thread.currentThread().getName());
            }
            long t0 = System.currentTimeMillis();

            boolean ok = false;
            boolean interrupt = false;
            ReconnectedEventBundle reconnected = null;
            // transaction timeout is managed by the FutureTask
            boolean tx = TransactionHelper.startTransaction();
            try {
                reconnected = new ReconnectedEventBundleImpl(bundle, listeners.toString());
                for (EventListenerDescriptor listener : listeners) {
                    EventBundle filtered = listener.filterBundle(reconnected);
                    if (filtered.isEmpty()) {
                        continue;
                    }
                    if (log.isDebugEnabled()) {
                        log.debug("Events postcommit bulk execution start for listener: " + listener.getName());
                    }
                    long t1 = System.currentTimeMillis();
                    try {

                        listener.asPostCommitListener().handleEvent(filtered);

                        if (Thread.currentThread().isInterrupted()) {
                            log.error("Events postcommit bulk execution interrupted for listener: "
                                    + listener.getName() + ", will rollback and abort bulk processing");
                            interrupt = true;
                        }
                    } catch (RuntimeException e) {
                        log.error(
                                "Events postcommit bulk execution encountered exception for listener: "
                                        + listener.getName(), e);
                        return Boolean.FALSE; // report error
                    } finally {
                        if (log.isDebugEnabled()) {
                            log.debug("Events postcommit bulk execution end for listener: " + listener.getName()
                                    + " in " + (System.currentTimeMillis() - t1) + "ms");
                        }
                    }
                    if (interrupt) {
                        break;
                    }
                }
                ok = !interrupt;
            } finally {
                try {
                    if (reconnected != null) {
                        reconnected.disconnect();
                    }
                } finally {
                    if (tx) {
                        if (!ok) {
                            TransactionHelper.setTransactionRollbackOnly();
                            log.error("Rolling back transaction");
                        }
                        TransactionHelper.commitOrRollbackTransaction();
                    }
                }
                if (log.isDebugEnabled()) {
                    log.debug("Events postcommit bulk execution finished in " + (System.currentTimeMillis() - t0)
                            + "ms");
                }
            }
            return Boolean.TRUE; // no error to report
        }
    }
}