// Copyright (C) 2012 The Android Open Source Project
//
// 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 com.google.gerrit.server.plugins;

import com.google.common.base.CharMatcher;
import com.google.common.base.Joiner;
import com.google.common.base.MoreObjects;
import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.collect.LinkedHashMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.collect.Queues;
import com.google.common.collect.Sets;
import com.google.gerrit.extensions.annotations.PluginName;
import com.google.gerrit.extensions.events.LifecycleListener;
import com.google.gerrit.extensions.systemstatus.ServerInformation;
import com.google.gerrit.extensions.webui.JavaScriptPlugin;
import com.google.gerrit.server.PluginUser;
import com.google.gerrit.server.cache.PersistentCacheFactory;
import com.google.gerrit.server.config.CanonicalWebUrl;
import com.google.gerrit.server.config.ConfigUtil;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.gerrit.server.config.SitePaths;
import com.google.gerrit.server.plugins.ServerPluginProvider.PluginDescription;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.Singleton;

import org.eclipse.jgit.internal.storage.file.FileSnapshot;
import org.eclipse.jgit.lib.Config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileFilter;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Queue;
import java.util.Set;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;

@Singleton
public class PluginLoader implements LifecycleListener {
  static final String PLUGIN_TMP_PREFIX = "plugin_";
  static final Logger log = LoggerFactory.getLogger(PluginLoader.class);

  public String getPluginName(File srcFile) {
    return MoreObjects.firstNonNull(getGerritPluginName(srcFile),
        nameOf(srcFile));
  }

  private final File pluginsDir;
  private final File dataDir;
  private final PluginGuiceEnvironment env;
  private final ServerInformationImpl srvInfoImpl;
  private final PluginUser.Factory pluginUserFactory;
  private final ConcurrentMap<String, Plugin> running;
  private final ConcurrentMap<String, Plugin> disabled;
  private final Map<String, FileSnapshot> broken;
  private final Map<Plugin, CleanupHandle> cleanupHandles;
  private final Queue<Plugin> toCleanup;
  private final Provider<PluginCleanerTask> cleaner;
  private final PluginScannerThread scanner;
  private final Provider<String> urlProvider;
  private final PersistentCacheFactory persistentCacheFactory;
  private final boolean remoteAdmin;
  private final UniversalServerPluginProvider serverPluginFactory;

  @Inject
  public PluginLoader(SitePaths sitePaths,
      PluginGuiceEnvironment pe,
      ServerInformationImpl sii,
      PluginUser.Factory puf,
      Provider<PluginCleanerTask> pct,
      @GerritServerConfig Config cfg,
      @CanonicalWebUrl Provider<String> provider,
      PersistentCacheFactory cacheFactory,
      UniversalServerPluginProvider pluginFactory) {
    pluginsDir = sitePaths.plugins_dir;
    dataDir = sitePaths.data_dir;
    env = pe;
    srvInfoImpl = sii;
    pluginUserFactory = puf;
    running = Maps.newConcurrentMap();
    disabled = Maps.newConcurrentMap();
    broken = Maps.newHashMap();
    toCleanup = Queues.newArrayDeque();
    cleanupHandles = Maps.newConcurrentMap();
    cleaner = pct;
    urlProvider = provider;
    persistentCacheFactory = cacheFactory;
    serverPluginFactory = pluginFactory;

    remoteAdmin =
        cfg.getBoolean("plugins", null, "allowRemoteAdmin", false);

    long checkFrequency = ConfigUtil.getTimeUnit(cfg,
        "plugins", null, "checkFrequency",
        TimeUnit.MINUTES.toMillis(1), TimeUnit.MILLISECONDS);
    if (checkFrequency > 0) {
      scanner = new PluginScannerThread(this, checkFrequency);
    } else {
      scanner = null;
    }
  }

  public boolean isRemoteAdminEnabled() {
    return remoteAdmin;
  }

  public Plugin get(String name) {
    Plugin p = running.get(name);
    if (p != null) {
      return p;
    }
    return disabled.get(name);
  }

  public Iterable<Plugin> getPlugins(boolean all) {
    if (!all) {
      return running.values();
    } else {
      List<Plugin> plugins = new ArrayList<>(running.values());
      plugins.addAll(disabled.values());
      return plugins;
    }
  }

  public void installPluginFromStream(String originalName, InputStream in)
      throws IOException, PluginInstallException {
    checkRemoteInstall();

    String fileName = originalName;
    File tmp = asTemp(in, ".next_" + fileName + "_", ".tmp", pluginsDir);
    String name = MoreObjects.firstNonNull(getGerritPluginName(tmp),
        nameOf(fileName));
    if (!originalName.equals(name)) {
      log.warn(String.format("Plugin provides its own name: <%s>,"
          + " use it instead of the input name: <%s>",
          name, originalName));
    }

    String fileExtension = getExtension(fileName);
    File dst = new File(pluginsDir, name + fileExtension);
    synchronized (this) {
      Plugin active = running.get(name);
      if (active != null) {
        fileName = active.getSrcFile().getName();
        log.info(String.format("Replacing plugin %s", active.getName()));
        File old = new File(pluginsDir, ".last_" + fileName);
        old.delete();
        active.getSrcFile().renameTo(old);
      }

      new File(pluginsDir, fileName + ".disabled").delete();
      tmp.renameTo(dst);
      try {
        Plugin plugin = runPlugin(name, dst, active);
        if (active == null) {
          log.info(String.format("Installed plugin %s", plugin.getName()));
        }
      } catch (PluginInstallException e) {
        dst.delete();
        throw e;
      }

      cleanInBackground();
    }
  }

  static File asTemp(InputStream in, String prefix, String suffix, File dir)
      throws IOException {
    File tmp = File.createTempFile(prefix, suffix, dir);
    boolean keep = false;
    try (FileOutputStream out = new FileOutputStream(tmp)) {
      byte[] data = new byte[8192];
      int n;
      while ((n = in.read(data)) > 0) {
        out.write(data, 0, n);
      }
      keep = true;
      return tmp;
    } finally {
      if (!keep) {
        tmp.delete();
      }
    }
  }

  private synchronized void unloadPlugin(Plugin plugin) {
    persistentCacheFactory.onStop(plugin);
    String name = plugin.getName();
    log.info(String.format("Unloading plugin %s", name));
    plugin.stop(env);
    env.onStopPlugin(plugin);
    running.remove(name);
    disabled.remove(name);
    toCleanup.add(plugin);
  }

  public void disablePlugins(Set<String> names) {
    if (!isRemoteAdminEnabled()) {
      log.warn("Remote plugin administration is disabled,"
          + " ignoring disablePlugins(" + names + ")");
      return;
    }

    synchronized (this) {
      for (String name : names) {
        Plugin active = running.get(name);
        if (active == null) {
          continue;
        }

        log.info(String.format("Disabling plugin %s", active.getName()));
        File off = new File(active.getSrcFile() + ".disabled");
        active.getSrcFile().renameTo(off);

        unloadPlugin(active);
        try {
          FileSnapshot snapshot = FileSnapshot.save(off);
          Plugin offPlugin = loadPlugin(name, off, snapshot);
          disabled.put(name, offPlugin);
        } catch (Throwable e) {
          // This shouldn't happen, as the plugin was loaded earlier.
          log.warn(String.format(
              "Cannot load disabled plugin %s", active.getName()),
              e.getCause());
        }
      }
      cleanInBackground();
    }
  }

  public void enablePlugins(Set<String> names) throws PluginInstallException {
    if (!isRemoteAdminEnabled()) {
      log.warn("Remote plugin administration is disabled,"
          + " ignoring enablePlugins(" + names + ")");
      return;
    }

    synchronized (this) {
      for (String name : names) {
        Plugin off = disabled.get(name);
        if (off == null) {
          continue;
        }

        log.info(String.format("Enabling plugin %s", name));
        String n = off.getSrcFile().getName();
        if (n.endsWith(".disabled")) {
          n = n.substring(0, n.lastIndexOf('.'));
        }
        File on = new File(pluginsDir, n);
        off.getSrcFile().renameTo(on);

        disabled.remove(name);
        runPlugin(name, on, null);
      }
      cleanInBackground();
    }
  }

  @Override
  public synchronized void start() {
    log.info("Loading plugins from " + pluginsDir.getAbsolutePath());
    srvInfoImpl.state = ServerInformation.State.STARTUP;
    rescan();
    srvInfoImpl.state = ServerInformation.State.RUNNING;
    if (scanner != null) {
      scanner.start();
    }
  }

  @Override
  public void stop() {
    if (scanner != null) {
      scanner.end();
    }
    srvInfoImpl.state = ServerInformation.State.SHUTDOWN;
    synchronized (this) {
      for (Plugin p : running.values()) {
        unloadPlugin(p);
      }
      running.clear();
      disabled.clear();
      broken.clear();
      if (!toCleanup.isEmpty()) {
        System.gc();
        processPendingCleanups();
      }
    }
  }

  public void reload(List<String> names)
      throws InvalidPluginException, PluginInstallException {
    synchronized (this) {
      List<Plugin> reload = Lists.newArrayListWithCapacity(names.size());
      List<String> bad = Lists.newArrayListWithExpectedSize(4);
      for (String name : names) {
        Plugin active = running.get(name);
        if (active != null) {
          reload.add(active);
        } else {
          bad.add(name);
        }
      }
      if (!bad.isEmpty()) {
        throw new InvalidPluginException(String.format(
            "Plugin(s) \"%s\" not running",
            Joiner.on("\", \"").join(bad)));
      }

      for (Plugin active : reload) {
        String name = active.getName();
        try {
          log.info(String.format("Reloading plugin %s", name));
          runPlugin(name, active.getSrcFile(), active);
        } catch (PluginInstallException e) {
          log.warn(String.format("Cannot reload plugin %s", name), e.getCause());
          throw e;
        }
      }

      cleanInBackground();
    }
  }

  public synchronized void rescan() {
    Multimap<String, File> pluginsFiles = prunePlugins(pluginsDir);
    if (pluginsFiles.isEmpty()) {
      return;
    }

    syncDisabledPlugins(pluginsFiles);

    Map<String, File> activePlugins = filterDisabled(pluginsFiles);
    for (Map.Entry<String, File> entry : jarsFirstSortedPluginsSet(activePlugins)) {
      String name = entry.getKey();
      File file = entry.getValue();
      String fileName = file.getName();
      if (!isJsPlugin(fileName) && !serverPluginFactory.handles(file)) {
        log.warn("No Plugin provider was found that handles this file format: {}", fileName);
        continue;
      }

      FileSnapshot brokenTime = broken.get(name);
      if (brokenTime != null && !brokenTime.isModified(file)) {
        continue;
      }

      Plugin active = running.get(name);
      if (active != null && !active.isModified(file)) {
        continue;
      }

      if (active != null) {
        log.info(String.format("Reloading plugin %s, version %s",
            active.getName(), active.getVersion()));
      }

      try {
        Plugin loadedPlugin = runPlugin(name, file, active);
        if (active == null && !loadedPlugin.isDisabled()) {
          log.info(String.format("Loaded plugin %s, version %s",
              loadedPlugin.getName(), loadedPlugin.getVersion()));
        }
      } catch (PluginInstallException e) {
        log.warn(String.format("Cannot load plugin %s", name), e.getCause());
      }
    }

    cleanInBackground();
  }

  private void addAllEntries(Map<String, File> from,
      TreeSet<Entry<String, File>> to) {
    Iterator<Entry<String, File>> it = from.entrySet().iterator();
    while (it.hasNext()) {
      Entry<String,File> entry = it.next();
      to.add(new AbstractMap.SimpleImmutableEntry<>(
          entry.getKey(), entry.getValue()));
    }
  }

  private TreeSet<Entry<String, File>> jarsFirstSortedPluginsSet(
      Map<String, File> activePlugins) {
    TreeSet<Entry<String, File>> sortedPlugins =
        Sets.newTreeSet(new Comparator<Entry<String, File>>() {
          @Override
          public int compare(Entry<String, File> entry1,
              Entry<String, File> entry2) {
            String file1 = entry1.getValue().getName();
            String file2 = entry2.getValue().getName();
            int cmp = file1.compareTo(file2);
            if (file1.endsWith(".jar")) {
              return (file2.endsWith(".jar") ? cmp : -1);
            } else {
              return (file2.endsWith(".jar") ? +1 : cmp);
            }
          }
        });

    addAllEntries(activePlugins, sortedPlugins);
    return sortedPlugins;
  }

  private void syncDisabledPlugins(Multimap<String, File> jars) {
    stopRemovedPlugins(jars);
    dropRemovedDisabledPlugins(jars);
  }

  private Plugin runPlugin(String name, File plugin, Plugin oldPlugin)
      throws PluginInstallException {
    FileSnapshot snapshot = FileSnapshot.save(plugin);
    try {
      Plugin newPlugin = loadPlugin(name, plugin, snapshot);
      if (newPlugin.getCleanupHandle() != null) {
        cleanupHandles.put(newPlugin, newPlugin.getCleanupHandle());
      }
      /*
       * Pluggable plugin provider may have assigned a plugin name that could be
       * actually different from the initial one assigned during scan. It is
       * safer then to reassign it.
       */
      name = newPlugin.getName();
      boolean reload = oldPlugin != null
          && oldPlugin.canReload()
          && newPlugin.canReload();
      if (!reload && oldPlugin != null) {
        unloadPlugin(oldPlugin);
      }
      if (!newPlugin.isDisabled()) {
        newPlugin.start(env);
      }
      if (reload) {
        env.onReloadPlugin(oldPlugin, newPlugin);
        unloadPlugin(oldPlugin);
      } else if (!newPlugin.isDisabled()) {
        env.onStartPlugin(newPlugin);
      }
      if (!newPlugin.isDisabled()) {
        running.put(name, newPlugin);
      } else {
        disabled.put(name, newPlugin);
      }
      broken.remove(name);
      return newPlugin;
    } catch (Throwable err) {
      broken.put(name, snapshot);
      throw new PluginInstallException(err);
    }
  }

  private void stopRemovedPlugins(Multimap<String, File> jars) {
    Set<String> unload = Sets.newHashSet(running.keySet());
    for (Map.Entry<String, Collection<File>> entry : jars.asMap().entrySet()) {
      for (File file : entry.getValue()) {
        if (!file.getName().endsWith(".disabled")) {
          unload.remove(entry.getKey());
        }
      }
    }
    for (String name : unload) {
      unloadPlugin(running.get(name));
    }
  }

  private void dropRemovedDisabledPlugins(Multimap<String, File> jars) {
    Set<String> unload = Sets.newHashSet(disabled.keySet());
    for (Map.Entry<String, Collection<File>> entry : jars.asMap().entrySet()) {
      for (File file : entry.getValue()) {
        if (file.getName().endsWith(".disabled")) {
          unload.remove(entry.getKey());
        }
      }
    }
    for (String name : unload) {
      disabled.remove(name);
    }
  }

  synchronized int processPendingCleanups() {
    Iterator<Plugin> iterator = toCleanup.iterator();
    while (iterator.hasNext()) {
      Plugin plugin = iterator.next();
      iterator.remove();

      CleanupHandle cleanupHandle = cleanupHandles.remove(plugin);
      if (cleanupHandle != null) {
        cleanupHandle.cleanup();
      }
    }
    return toCleanup.size();
  }

  private void cleanInBackground() {
    int cnt = toCleanup.size();
    if (0 < cnt) {
      cleaner.get().clean(cnt);
    }
  }

  public static String nameOf(File plugin) {
    return nameOf(plugin.getName());
  }

  private static String nameOf(String name) {
    if (name.endsWith(".disabled")) {
      name = name.substring(0, name.lastIndexOf('.'));
    }
    int ext = name.lastIndexOf('.');
    return 0 < ext ? name.substring(0, ext) : name;
  }

  private static String getExtension(String name) {
    int ext = name.lastIndexOf('.');
    return 0 < ext ? name.substring(ext) : "";
  }

  private Plugin loadPlugin(String name, File srcPlugin, FileSnapshot snapshot)
      throws InvalidPluginException {
    String pluginName = srcPlugin.getName();
    if (isJsPlugin(pluginName)) {
      return loadJsPlugin(name, srcPlugin, snapshot);
    } else if (serverPluginFactory.handles(srcPlugin)) {
      return loadServerPlugin(srcPlugin, snapshot);
    } else {
      throw new InvalidPluginException(String.format(
          "Unsupported plugin type: %s", srcPlugin.getName()));
    }
  }

  private File getPluginDataDir(String name) {
    return new File(dataDir, name);
  }

  private String getPluginCanonicalWebUrl(String name) {
    String url = String.format("%s/plugins/%s/",
        CharMatcher.is('/').trimTrailingFrom(urlProvider.get()),
        name);
    return url;
  }

  private Plugin loadJsPlugin(String name, File srcJar, FileSnapshot snapshot) {
    return new JsPlugin(name, srcJar, pluginUserFactory.create(name), snapshot);
  }

  private ServerPlugin loadServerPlugin(File scriptFile,
      FileSnapshot snapshot) throws InvalidPluginException {
    String name = serverPluginFactory.getPluginName(scriptFile);
    return serverPluginFactory.get(scriptFile, snapshot, new PluginDescription(
        pluginUserFactory.create(name), getPluginCanonicalWebUrl(name),
        getPluginDataDir(name)));
  }

  static ClassLoader parentFor(Plugin.ApiType type)
      throws InvalidPluginException {
    switch (type) {
      case EXTENSION:
        return PluginName.class.getClassLoader();
      case PLUGIN:
        return PluginLoader.class.getClassLoader();
      case JS:
        return JavaScriptPlugin.class.getClassLoader();
      default:
        throw new InvalidPluginException("Unsupported ApiType " + type);
    }
  }

  // Only one active plugin per plugin name can exist for each plugin name.
  // Filter out disabled plugins and transform the multimap to a map
  private static Map<String, File> filterDisabled(
      Multimap<String, File> pluginFiles) {
    Map<String, File> activePlugins = Maps.newHashMapWithExpectedSize(
        pluginFiles.keys().size());
    for (String name : pluginFiles.keys()) {
      for (File pluginFile : pluginFiles.asMap().get(name)) {
        if (!pluginFile.getName().endsWith(".disabled")) {
          assert(!activePlugins.containsKey(name));
          activePlugins.put(name, pluginFile);
        }
      }
    }
    return activePlugins;
  }

  // Scan the $site_path/plugins directory and fetch all files and directories.
  // The Key in returned multimap is the plugin name initially assigned from its filename.
  // Values are the files. Plugins can optionally provide their name in MANIFEST file.
  // If multiple plugin files provide the same plugin name, then only
  // the first plugin remains active and all other plugins with the same
  // name are disabled.
  //
  // NOTE: Bear in mind that the plugin name can be reassigned after load by the
  //       Server plugin provider.
  public Multimap<String, File> prunePlugins(File pluginsDir) {
    List<File> pluginFiles = scanFilesInPluginsDirectory(pluginsDir);
    Multimap<String, File> map;
    map = asMultimap(pluginFiles);
    for (String plugin : map.keySet()) {
      Collection<File> files = map.asMap().get(plugin);
      if (files.size() == 1) {
        continue;
      }
      // retrieve enabled plugins
      Iterable<File> enabled = filterDisabledPlugins(
          files);
      // If we have only one (the winner) plugin, nothing to do
      if (!Iterables.skip(enabled, 1).iterator().hasNext()) {
        continue;
      }
      File winner = Iterables.getFirst(enabled, null);
      assert(winner != null);
      // Disable all loser plugins by renaming their file names to
      // "file.disabled" and replace the disabled files in the multimap.
      Collection<File> elementsToRemove = Lists.newArrayList();
      Collection<File> elementsToAdd = Lists.newArrayList();
      for (File loser : Iterables.skip(enabled, 1)) {
        log.warn(String.format("Plugin <%s> was disabled, because"
             + " another plugin <%s>"
             + " with the same name <%s> already exists",
             loser, winner, plugin));
        File disabledPlugin = new File(loser + ".disabled");
        elementsToAdd.add(disabledPlugin);
        elementsToRemove.add(loser);
        loser.renameTo(disabledPlugin);
      }
      Iterables.removeAll(files, elementsToRemove);
      Iterables.addAll(files, elementsToAdd);
    }
    return map;
  }

  private List<File> scanFilesInPluginsDirectory(File pluginsDir) {
    if (pluginsDir == null || !pluginsDir.exists()) {
      return Collections.emptyList();
    }
    File[] matches = pluginsDir.listFiles(new FileFilter() {
      @Override
      public boolean accept(File pathname) {
        String n = pathname.getName();
        return !n.startsWith(".last_")
            && !n.startsWith(".next_");
      }
    });
    if (matches == null) {
      log.error("Cannot list " + pluginsDir.getAbsolutePath());
      return Collections.emptyList();
    }
    return Arrays.asList(matches);
  }

  private static Iterable<File> filterDisabledPlugins(
      Collection<File> files) {
    return Iterables.filter(files, new Predicate<File>() {
      @Override
      public boolean apply(File file) {
        return !file.getName().endsWith(".disabled");
      }
    });
  }

  public String getGerritPluginName(File srcFile) {
    String fileName = srcFile.getName();
    if (isJsPlugin(fileName)) {
      return fileName.substring(0, fileName.length() - 3);
    }
    if (serverPluginFactory.handles(srcFile)) {
      return serverPluginFactory.getPluginName(srcFile);
    }
    return null;
  }

  private Multimap<String, File> asMultimap(List<File> plugins) {
    Multimap<String, File> map = LinkedHashMultimap.create();
    for (File srcFile : plugins) {
      map.put(getPluginName(srcFile), srcFile);
    }
    return map;
  }

  private static boolean isJsPlugin(String name) {
    return isPlugin(name, "js");
  }

  private static boolean isPlugin(String fileName, String ext) {
    String fullExt = "." + ext;
    return fileName.endsWith(fullExt) || fileName.endsWith(fullExt + ".disabled");
  }

  private void checkRemoteInstall() throws PluginInstallException {
    if (!isRemoteAdminEnabled()) {
      throw new PluginInstallException("remote installation is disabled");
    }
  }
}