// Copyright (C) 2013 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.googlesource.gerrit.plugins.reviewers;

import java.io.IOException;
import java.util.Collections;
import java.util.Set;

import org.eclipse.jgit.errors.RepositoryNotFoundException;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevWalk;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;
import com.google.gerrit.common.ChangeListener;
import com.google.gerrit.extensions.annotations.PluginName;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.account.AccountByEmailCache;
import com.google.gerrit.server.account.AccountResolver;
import com.google.gerrit.server.account.GroupMembers;
import com.google.gerrit.server.config.PluginConfigFactory;
import com.google.gerrit.server.events.ChangeEvent;
import com.google.gerrit.server.events.PatchSetCreatedEvent;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.git.WorkQueue;
import com.google.gerrit.server.group.GroupsCollection;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.gerrit.server.util.RequestContext;
import com.google.gerrit.server.util.ThreadLocalRequestContext;
import com.google.gwtorm.server.OrmException;
import com.google.gwtorm.server.SchemaFactory;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.ProvisionException;

class ChangeEventListener implements ChangeListener {

  private static final Logger log = LoggerFactory
      .getLogger(ChangeEventListener.class);

  private final AccountResolver accountResolver;
  private final AccountByEmailCache byEmailCache;
  private final Provider<GroupsCollection> groupsCollection;
  private final GroupMembers.Factory groupMembersFactory;
  private final DefaultReviewers.Factory reviewersFactory;
  private final GitRepositoryManager repoManager;
  private final WorkQueue workQueue;
  private final IdentifiedUser.GenericFactory identifiedUserFactory;
  private final ThreadLocalRequestContext tl;
  private final SchemaFactory<ReviewDb> schemaFactory;
  private final PluginConfigFactory cfg;
  private final String pluginName;
  private ReviewDb db;

  @Inject
  ChangeEventListener(
      final AccountResolver accountResolver,
      final AccountByEmailCache byEmailCache,
      final Provider<GroupsCollection> groupsCollection,
      final GroupMembers.Factory groupMembersFactory,
      final DefaultReviewers.Factory reviewersFactory,
      final GitRepositoryManager repoManager,
      final WorkQueue workQueue,
      final IdentifiedUser.GenericFactory identifiedUserFactory,
      final ThreadLocalRequestContext tl,
      final SchemaFactory<ReviewDb> schemaFactory,
      final PluginConfigFactory cfg,
      final @PluginName String pluginName) {
    this.accountResolver = accountResolver;
    this.byEmailCache = byEmailCache;
    this.groupsCollection = groupsCollection;
    this.groupMembersFactory = groupMembersFactory;
    this.reviewersFactory = reviewersFactory;
    this.repoManager = repoManager;
    this.workQueue = workQueue;
    this.identifiedUserFactory = identifiedUserFactory;
    this.tl = tl;
    this.schemaFactory = schemaFactory;
    this.cfg = cfg;
    this.pluginName = pluginName;
  }

  @Override
  public void onChangeEvent(ChangeEvent event) {
    if (!(event instanceof PatchSetCreatedEvent)) {
      return;
    }
    PatchSetCreatedEvent e = (PatchSetCreatedEvent) event;
    Project.NameKey projectName = new Project.NameKey(e.change.project);
    Set<Account> reviewers;
    try {
      reviewers = reviewers(cfg
          .getFromProjectConfigWithInheritance(projectName, pluginName)
          .getStringList("reviewer"), projectName, e.uploader.email);
    } catch (NoSuchProjectException x) {
      log.error(x.getMessage(), x);
      return;
    }

    if (reviewers.isEmpty()) {
      return;
    }

    Repository git;
    try {
      git = repoManager.openRepository(projectName);
    } catch (RepositoryNotFoundException x) {
      log.error(x.getMessage(), x);
      return;
    } catch (IOException x) {
      log.error(x.getMessage(), x);
      return;
    }

    final ReviewDb reviewDb;
    final RevWalk rw = new RevWalk(git);

    try {
      reviewDb = schemaFactory.open();
      try {
        Change.Id changeId = new Change.Id(Integer.parseInt(e.change.number));
        PatchSet.Id psId = new PatchSet.Id(changeId,
            Integer.parseInt(e.patchSet.number));
        PatchSet ps = reviewDb.patchSets().get(psId);
        if (ps == null) {
          log.warn("Patch set " + psId.get() + " not found.");
          return;
        }

        final Change change = reviewDb.changes().get(psId.getParentKey());
        if (change == null) {
          log.warn("Change " + changeId.get() + " not found.");
          return;
        }

        final Runnable task = reviewersFactory.create(change, reviewers);

        workQueue.getDefaultQueue().submit(new Runnable() {
          public void run() {
            RequestContext old = tl.setContext(new RequestContext() {

              @Override
              public CurrentUser getCurrentUser() {
                return identifiedUserFactory.create(change.getOwner());
              }

              @Override
              public Provider<ReviewDb> getReviewDbProvider() {
                return new Provider<ReviewDb>() {
                  @Override
                  public ReviewDb get() {
                    if (db == null) {
                      try {
                        db = schemaFactory.open();
                      } catch (OrmException e) {
                        throw new ProvisionException("Cannot open ReviewDb", e);
                      }
                    }
                    return db;
                  }
                };
              }
            });
            try {
              task.run();
            } finally {
              tl.setContext(old);
              if (db != null) {
                db.close();
                db = null;
              }
            }
          }
        });
      } catch (OrmException x) {
        log.error(x.getMessage(), x);
      } finally {
        reviewDb.close();
      }
    } catch (OrmException x) {
      log.error(x.getMessage(), x);
    } finally {
      rw.release();
      git.close();
    }
  }

  private Set<Account> reviewers(String[] list, Project.NameKey p,
      String uploaderEMail) {
    if (list == null || list.length == 0) {
      return Collections.emptySet();
    }
    Set<Account> reviewers = Sets.newHashSetWithExpectedSize(list.length);
    GroupMembers groupMembers = null;
    for (String r : list) {
      try {
        Account account = accountResolver.find(r);
        if (account != null) {
          reviewers.add(account);
          continue;
        }
        if (groupMembers == null) {
          groupMembers =
              groupMembersFactory.create(identifiedUserFactory.create(Iterables
                  .getOnlyElement(byEmailCache.get(uploaderEMail))));
        }
        reviewers.addAll(groupMembers.listAccounts(groupsCollection.get()
            .parseInternal(r).getGroupUUID(), p));
      } catch (Exception e) {
        log.warn("Cannot resolve reviewer: " + r, e);
      }
    }
    return reviewers;
  }
}