// 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.ComparisonChain;
import com.google.common.collect.ImmutableList;
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.common.io.ByteStreams;
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.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.AbstractMap;
import java.util.ArrayList;
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(Path srcPath) {
    return MoreObjects.firstNonNull(getGerritPluginName(srcPath),
        nameOf(srcPath));
  }

  private final Path pluginsDir;
  private final Path 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;
    Path 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);
    Path dst = pluginsDir.resolve(name + fileExtension);
    synchronized (this) {
      Plugin active = running.get(name);
      if (active != null) {
        fileName = active.getSrcFile().getFileName().toString();
        log.info(String.format("Replacing plugin %s", active.getName()));
        Path old = pluginsDir.resolve(".last_" + fileName);
        Files.deleteIfExists(old);
        Files.move(active.getSrcFile(), old);
      }

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

      cleanInBackground();
    }
  }

  static Path asTemp(InputStream in, String prefix, String suffix, Path dir)
      throws IOException {
    Path tmp = Files.createTempFile(dir, prefix, suffix);
    boolean keep = false;
    try (OutputStream out = Files.newOutputStream(tmp)) {
      ByteStreams.copy(in, out);
      keep = true;
      return tmp;
    } finally {
      if (!keep) {
        Files.delete(tmp);
      }
    }
  }

  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()));
        Path off = active.getSrcFile().resolveSibling(
            active.getSrcFile().getFileName() + ".disabled");
        try {
          Files.move(active.getSrcFile(), off);
        } catch (IOException e) {
          log.error("Failed to disable plugin", e);
          // In theory we could still unload the plugin even if the rename
          // failed. However, it would be reloaded on the next server startup,
          // which is probably not what the user expects.
          continue;
        }

        unloadPlugin(active);
        try {
          FileSnapshot snapshot = FileSnapshot.save(off.toFile());
          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().toFile().getName();
        if (n.endsWith(".disabled")) {
          n = n.substring(0, n.lastIndexOf('.'));
        }
        Path on = pluginsDir.resolve(n);
        try {
          Files.move(off.getSrcFile(), on);
        } catch (IOException e) {
          log.error("Failed to move plugin " + name + " into place", e);
          continue;
        }
        disabled.remove(name);
        runPlugin(name, on, null);
      }
      cleanInBackground();
    }
  }

  @Override
  public synchronized void start() {
    log.info("Loading plugins from " + pluginsDir.toAbsolutePath());
    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, Path> pluginsFiles = prunePlugins(pluginsDir);
    if (pluginsFiles.isEmpty()) {
      return;
    }

    syncDisabledPlugins(pluginsFiles);

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

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

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

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

      try {
        Plugin loadedPlugin = runPlugin(name, path, 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, Path> from,
      TreeSet<Entry<String, Path>> to) {
    Iterator<Entry<String, Path>> it = from.entrySet().iterator();
    while (it.hasNext()) {
      Entry<String,Path> entry = it.next();
      to.add(new AbstractMap.SimpleImmutableEntry<>(
          entry.getKey(), entry.getValue()));
    }
  }

  private TreeSet<Entry<String, Path>> jarsFirstSortedPluginsSet(
      Map<String, Path> activePlugins) {
    TreeSet<Entry<String, Path>> sortedPlugins =
        Sets.newTreeSet(new Comparator<Entry<String, Path>>() {
          @Override
          public int compare(Entry<String, Path> e1, Entry<String, Path> e2) {
            Path n1 = e1.getValue().getFileName();
            Path n2 = e2.getValue().getFileName();
            return ComparisonChain.start()
                .compareTrueFirst(n1.endsWith(".jar"), n2.endsWith(".jar"))
                .compare(n1, n2)
                .result();
          }
        });

    addAllEntries(activePlugins, sortedPlugins);
    return sortedPlugins;
  }

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

  private Plugin runPlugin(String name, Path plugin, Plugin oldPlugin)
      throws PluginInstallException {
    FileSnapshot snapshot = FileSnapshot.save(plugin.toFile());
    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, Path> jars) {
    Set<String> unload = Sets.newHashSet(running.keySet());
    for (Map.Entry<String, Collection<Path>> entry : jars.asMap().entrySet()) {
      for (Path path : entry.getValue()) {
        if (!path.getFileName().toString().endsWith(".disabled")) {
          unload.remove(entry.getKey());
        }
      }
    }
    for (String name : unload) {
      unloadPlugin(running.get(name));
    }
  }

  private void dropRemovedDisabledPlugins(Multimap<String, Path> jars) {
    Set<String> unload = Sets.newHashSet(disabled.keySet());
    for (Map.Entry<String, Collection<Path>> entry : jars.asMap().entrySet()) {
      for (Path path : entry.getValue()) {
        if (path.getFileName().toString().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(Path plugin) {
    return nameOf(plugin.getFileName().toString());
  }

  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, Path srcPlugin, FileSnapshot snapshot)
      throws InvalidPluginException {
    String pluginName = srcPlugin.getFileName().toString();
    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.getFileName()));
    }
  }

  private Path getPluginDataDir(String name) {
    return dataDir.resolve(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, Path srcJar, FileSnapshot snapshot) {
    return new JsPlugin(name, srcJar, pluginUserFactory.create(name), snapshot);
  }

  private ServerPlugin loadServerPlugin(Path 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, Path> filterDisabled(
      Multimap<String, Path> pluginPaths) {
    Map<String, Path> activePlugins = Maps.newHashMapWithExpectedSize(
        pluginPaths.keys().size());
    for (String name : pluginPaths.keys()) {
      for (Path pluginPath : pluginPaths.asMap().get(name)) {
        if (!pluginPath.getFileName().toString().endsWith(".disabled")) {
          assert(!activePlugins.containsKey(name));
          activePlugins.put(name, pluginPath);
        }
      }
    }
    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, Path> prunePlugins(Path pluginsDir) {
    List<Path> pluginPaths = scanPathsInPluginsDirectory(pluginsDir);
    Multimap<String, Path> map;
    map = asMultimap(pluginPaths);
    for (String plugin : map.keySet()) {
      Collection<Path> files = map.asMap().get(plugin);
      if (files.size() == 1) {
        continue;
      }
      // retrieve enabled plugins
      Iterable<Path> enabled = filterDisabledPlugins(files);
      // If we have only one (the winner) plugin, nothing to do
      if (!Iterables.skip(enabled, 1).iterator().hasNext()) {
        continue;
      }
      Path 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<Path> elementsToRemove = Lists.newArrayList();
      Collection<Path> elementsToAdd = Lists.newArrayList();
      for (Path 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));
        Path disabledPlugin = Paths.get(loser + ".disabled");
        elementsToAdd.add(disabledPlugin);
        elementsToRemove.add(loser);
        try {
          Files.move(loser, disabledPlugin);
        } catch (IOException e) {
          log.warn("Failed to fully disable plugin " + loser, e);
        }
      }
      Iterables.removeAll(files, elementsToRemove);
      Iterables.addAll(files, elementsToAdd);
    }
    return map;
  }

  private List<Path> scanPathsInPluginsDirectory(Path pluginsDir) {
    if (pluginsDir == null || !Files.exists(pluginsDir)) {
      return Collections.emptyList();
    }
    DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
      @Override
      public boolean accept(Path entry) throws IOException {
        String n = entry.getFileName().toString();
        return !n.startsWith(".last_")
            && !n.startsWith(".next_");
      }
    };
    try (DirectoryStream<Path> files
        = Files.newDirectoryStream(pluginsDir, filter)) {
      return ImmutableList.copyOf(files);
    } catch (IOException e) {
      log.error("Cannot list " + pluginsDir.toAbsolutePath(), e);
      return ImmutableList.of();
    }
  }

  private static Iterable<Path> filterDisabledPlugins(
      Collection<Path> paths) {
    return Iterables.filter(paths, new Predicate<Path>() {
      @Override
      public boolean apply(Path p) {
        return !p.getFileName().toString().endsWith(".disabled");
      }
    });
  }

  public String getGerritPluginName(Path srcPath) {
    String fileName = srcPath.getFileName().toString();
    if (isJsPlugin(fileName)) {
      return fileName.substring(0, fileName.length() - 3);
    }
    if (serverPluginFactory.handles(srcPath)) {
      return serverPluginFactory.getPluginName(srcPath);
    }
    return null;
  }

  private Multimap<String, Path> asMultimap(List<Path> plugins) {
    Multimap<String, Path> map = LinkedHashMultimap.create();
    for (Path srcPath : plugins) {
      map.put(getPluginName(srcPath), srcPath);
    }
    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");
    }
  }
}