/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.logging.log4j.core.util;

import java.io.File;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.AbstractLifeCycle;
import org.apache.logging.log4j.core.config.ConfigurationFileWatcher;
import org.apache.logging.log4j.core.config.ConfigurationScheduler;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.LoaderUtil;

Manages FileWatchers. 
See Also:
FileWatcher
ConfigurationScheduler/**
 * Manages {@link FileWatcher}s.
 *
 * @see FileWatcher
 * @see ConfigurationScheduler
 */
public class WatchManager extends AbstractLifeCycle {

    private static Logger logger = StatusLogger.getLogger();
    private final ConcurrentMap<Source, ConfigurationMonitor> watchers = new ConcurrentHashMap<>();
    private int intervalSeconds = 0;
    private ScheduledFuture<?> future;
    private final ConfigurationScheduler scheduler;
    private final List<WatchEventService> eventServiceList;
    private final UUID id = UuidUtil.getTimeBasedUuid();

    public WatchManager(final ConfigurationScheduler scheduler) {
        this.scheduler = scheduler;
        eventServiceList = getEventServices();
    }

    public UUID getId() {
        return this.id;
    }

    public boolean hasEventListeners() {
        return eventServiceList.size() > 0;
    }

    
Resets all file monitors to their current last modified time. If this manager does not watch any file, nothing
happens.

This allows you to start, stop, reset and start again a manager, without triggering file modified events if the a
watched file has changed during the period of time when the manager was stopped.

Since:
2.11.0/**
     * Resets all file monitors to their current last modified time. If this manager does not watch any file, nothing
     * happens.
     * <p>
     * This allows you to start, stop, reset and start again a manager, without triggering file modified events if the a
     * watched file has changed during the period of time when the manager was stopped.
     * </p>
     *
     * @since 2.11.0
     */
    public void reset() {
        logger.debug("Resetting {}", this);
        for (final Source source : watchers.keySet()) {
            reset(source);
        }
    }

    
Resets the file monitor for the given file being watched to its current last modified time. If this manager does
not watch the given file, nothing happens.

This allows you to start, stop, reset and start again a manager, without triggering file modified events if the
given watched file has changed during the period of time when the manager was stopped.

Params:
file – the file for the monitor to reset.
Since:
2.11.0/**
     * Resets the file monitor for the given file being watched to its current last modified time. If this manager does
     * not watch the given file, nothing happens.
     * <p>
     * This allows you to start, stop, reset and start again a manager, without triggering file modified events if the
     * given watched file has changed during the period of time when the manager was stopped.
     * </p>
     *
     * @param file the file for the monitor to reset.
     * @since 2.11.0
     */
    public void reset(final File file) {
        if (file == null) {
            return;
        }
        Source source = new Source(file);
        reset(source);
    }

    
Resets the configuration monitor for the given file being watched to its current last modified time. If this
manager does not watch the given configuration, nothing happens.

This allows you to start, stop, reset and start again a manager, without triggering file modified events if the
given watched configuration has changed during the period of time when the manager was stopped.

Params:
source – the Source for the monitor to reset.
Since:
2.12.0/**
     * Resets the configuration monitor for the given file being watched to its current last modified time. If this
     * manager does not watch the given configuration, nothing happens.
     * <p>
     * This allows you to start, stop, reset and start again a manager, without triggering file modified events if the
     * given watched configuration has changed during the period of time when the manager was stopped.
     * </p>
     *
     * @param source the Source for the monitor to reset.
     * @since 2.12.0
     */
    public void reset(final Source source) {
        if (source == null) {
            return;
        }
        final ConfigurationMonitor monitor = watchers.get(source);
        if (monitor != null) {
            Watcher watcher = monitor.getWatcher();
            if (watcher.isModified()) {
                final long lastModifiedMillis = watcher.getLastModified();
                if (logger.isDebugEnabled()) {
                    logger.debug("Resetting file monitor for '{}' from {} ({}) to {} ({})", source.getLocation(),
                        millisToString(monitor.lastModifiedMillis), monitor.lastModifiedMillis,
                        millisToString(lastModifiedMillis), lastModifiedMillis);
                }
                monitor.setLastModifiedMillis(lastModifiedMillis);
            }
        }
    }

    public void setIntervalSeconds(final int intervalSeconds) {
        if (!isStarted()) {
            if (this.intervalSeconds > 0 && intervalSeconds == 0) {
                scheduler.decrementScheduledItems();
            } else {
                if (this.intervalSeconds == 0 && intervalSeconds > 0) {
                    scheduler.incrementScheduledItems();
                }
            }
            this.intervalSeconds = intervalSeconds;
        }
    }

    
Gets how often this manager checks for file modifications.
Returns:
how often, in seconds, this manager checks for file modifications./**
     * Gets how often this manager checks for file modifications.
     *
     * @return how often, in seconds, this manager checks for file modifications.
     */
    public int getIntervalSeconds() {
        return this.intervalSeconds;
    }

    @Override
    public void start() {
        super.start();

        if (intervalSeconds > 0) {
            future = scheduler
                .scheduleWithFixedDelay(new WatchRunnable(), intervalSeconds, intervalSeconds, TimeUnit.SECONDS);
        }
        for (WatchEventService service : eventServiceList) {
            service.subscribe(this);
        }
    }

    @Override
    public boolean stop(final long timeout, final TimeUnit timeUnit) {
        setStopping();
        for (WatchEventService service : eventServiceList) {
            service.unsubscribe(this);
        }
        final boolean stopped = stop(future);
        setStopped();
        return stopped;
    }

    
Unwatches the given file.
Params:
file – the file to stop watching.
Since:
2.11.0/**
     * Unwatches the given file.
     *
     * @param file the file to stop watching.
     * @since 2.11.0
     */
    public void unwatchFile(final File file) {
        Source source = new Source(file);
        unwatch(source);
    }

    
Unwatches the given file.
Params:
source – the Source to stop watching.
              the file to stop watching.
Since:
2.12.0/**
     * Unwatches the given file.
     *
     * @param source the Source to stop watching.
     *               the file to stop watching.
     * @since 2.12.0
     */
    public void unwatch(final Source source) {
        logger.debug("Unwatching configuration {}", source);
        watchers.remove(source);
    }

    public void checkFiles() {
        new WatchRunnable().run();
    }

    
Watches the given file.
Params:
file –        the file to watch.
fileWatcher – the watcher to notify of file changes./**
     * Watches the given file.
     *
     * @param file        the file to watch.
     * @param fileWatcher the watcher to notify of file changes.
     */
    public void watchFile(final File file, final FileWatcher fileWatcher) {
        Watcher watcher;
        if (fileWatcher instanceof Watcher) {
            watcher = (Watcher) fileWatcher;
        } else {
            watcher = new WrappedFileWatcher(fileWatcher);
        }
        Source source = new Source(file);
        watch(source, watcher);
    }

    
Watches the given file.
Params:
source –  the source to watch.
watcher – the watcher to notify of file changes./**
     * Watches the given file.
     *
     * @param source  the source to watch.
     * @param watcher the watcher to notify of file changes.
     */
    public void watch(final Source source, final Watcher watcher) {
        watcher.watching(source);
        final long lastModified = watcher.getLastModified();
        if (logger.isDebugEnabled()) {
            logger.debug("Watching configuration '{}' for lastModified {} ({})", source, millisToString(lastModified),
                lastModified);
        }
        watchers.put(source, new ConfigurationMonitor(lastModified, watcher));
    }

    
Returns a Map of the file watchers.
Returns:
A Map of the file watchers.
Deprecated:
use getConfigurationWatchers./**
     * Returns a Map of the file watchers.
     *
     * @return A Map of the file watchers.
     * @deprecated use getConfigurationWatchers.
     */
    public Map<File, FileWatcher> getWatchers() {
        final Map<File, FileWatcher> map = new HashMap<>(watchers.size());
        for (Map.Entry<Source, ConfigurationMonitor> entry : watchers.entrySet()) {
            if (entry.getValue().getWatcher() instanceof ConfigurationFileWatcher) {
                map.put(entry.getKey().getFile(), (FileWatcher) entry.getValue().getWatcher());
            } else {
                map.put(entry.getKey().getFile(), new WrappedFileWatcher((FileWatcher) entry.getValue().getWatcher()));
            }
        }
        return map;
    }

    
Return the ConfigurationWaatchers.
Returns:
the ConfigurationWatchers.
Since:
2.11.2/**
     * Return the ConfigurationWaatchers.
     *
     * @return the ConfigurationWatchers.
     * @since 2.11.2
     */
    public Map<Source, Watcher> getConfigurationWatchers() {
        final Map<Source, Watcher> map = new HashMap<>(watchers.size());
        for (final Map.Entry<Source, ConfigurationMonitor> entry : watchers.entrySet()) {
            map.put(entry.getKey(), entry.getValue().getWatcher());
        }
        return map;
    }

    private String millisToString(final long millis) {
        return new Date(millis).toString();
    }

    private List<WatchEventService> getEventServices() {
        List<WatchEventService> list = new ArrayList<>();
        for (final ClassLoader classLoader : LoaderUtil.getClassLoaders()) {
            try {
                final ServiceLoader<WatchEventService> serviceLoader = ServiceLoader
                    .load(WatchEventService.class, classLoader);
                for (final WatchEventService service : serviceLoader) {
                    list.add(service);
                }
            } catch (final Throwable ex) {
                LOGGER.debug("Unable to retrieve WatchEventService from ClassLoader {}", classLoader, ex);
            }
        }
        return list;
    }

    private final class WatchRunnable implements Runnable {

        // Use a hard class reference here in case a refactoring changes the class name.
        private final String SIMPLE_NAME = WatchRunnable.class.getSimpleName();

        @Override
        public void run() {
            logger.trace("{} run triggered.", SIMPLE_NAME);
            for (final Map.Entry<Source, ConfigurationMonitor> entry : watchers.entrySet()) {
                final Source source = entry.getKey();
                final ConfigurationMonitor monitor = entry.getValue();
                if (monitor.getWatcher().isModified()) {
                    final long lastModified = monitor.getWatcher().getLastModified();
                    if (logger.isInfoEnabled()) {
                        logger.info("Source '{}' was modified on {} ({}), previous modification was on {} ({})", source,
                            millisToString(lastModified), lastModified, millisToString(monitor.lastModifiedMillis),
                            monitor.lastModifiedMillis);
                    }
                    monitor.lastModifiedMillis = lastModified;
                    monitor.getWatcher().modified();
                }
            }
            logger.trace("{} run ended.", SIMPLE_NAME);
        }
    }

    private final class ConfigurationMonitor {
        private final Watcher watcher;
        private volatile long lastModifiedMillis;

        public Watcher getWatcher() {
            return watcher;
        }

        public ConfigurationMonitor(final long lastModifiedMillis, final Watcher watcher) {
            this.watcher = watcher;
            this.lastModifiedMillis = lastModifiedMillis;
        }

        private void setLastModifiedMillis(final long lastModifiedMillis) {
            this.lastModifiedMillis = lastModifiedMillis;
        }

        @Override
        public String toString() {
            return "ConfigurationMonitor [watcher=" + watcher + ", lastModifiedMillis=" + lastModifiedMillis + "]";
        }

    }

    @Override
    public String toString() {
        return "WatchManager [intervalSeconds=" + intervalSeconds + ", watchers=" + watchers + ", scheduler="
            + scheduler + ", future=" + future + "]";
    }
}