// Copyright (C) 2020 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.replication.pull;

import com.google.auto.value.AutoValue;
import com.google.common.collect.Queues;
import com.google.gerrit.entities.Project;
import com.google.gerrit.extensions.events.GitReferenceUpdatedListener;
import com.google.gerrit.extensions.events.LifecycleListener;
import com.google.gerrit.extensions.registration.DynamicItem;
import com.google.gerrit.server.events.EventDispatcher;
import com.google.gerrit.server.git.WorkQueue;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.googlesource.gerrit.plugins.replication.ObservableQueue;
import com.googlesource.gerrit.plugins.replication.pull.FetchResultProcessing.GitUpdateProcessing;
import com.googlesource.gerrit.plugins.replication.pull.client.FetchRestApiClient;
import com.googlesource.gerrit.plugins.replication.pull.client.HttpResult;
import java.net.URISyntaxException;
import java.util.HashSet;
import java.util.Queue;
import java.util.Set;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.transport.URIish;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ReplicationQueue
    implements ObservableQueue, LifecycleListener, GitReferenceUpdatedListener {

  static final String PULL_REPLICATION_LOG_NAME = "pull_replication_log";
  static final Logger repLog = LoggerFactory.getLogger(PULL_REPLICATION_LOG_NAME);

  private final ReplicationStateListener stateLog;

  private final WorkQueue workQueue;
  private final DynamicItem<EventDispatcher> dispatcher;
  private final Provider<SourcesCollection> sources; // For Guice circular dependency
  private volatile boolean running;
  private volatile boolean replaying;
  private final Queue<ReferenceUpdatedEvent> beforeStartupEventsQueue;
  private FetchRestApiClient.Factory fetchClientFactory;

  @Inject
  ReplicationQueue(
      WorkQueue wq,
      Provider<SourcesCollection> rd,
      DynamicItem<EventDispatcher> dis,
      ReplicationStateListeners sl,
      FetchRestApiClient.Factory fetchClientFactory) {
    workQueue = wq;
    dispatcher = dis;
    sources = rd;
    stateLog = sl;
    beforeStartupEventsQueue = Queues.newConcurrentLinkedQueue();
    this.fetchClientFactory = fetchClientFactory;
  }

  @Override
  public void start() {
    if (!running) {
      sources.get().startup(workQueue);
      running = true;
      fireBeforeStartupEvents();
    }
  }

  @Override
  public void stop() {
    running = false;
    int discarded = sources.get().shutdown();
    if (discarded > 0) {
      repLog.warn("Canceled {} replication events during shutdown", discarded);
    }
  }

  @Override
  public boolean isRunning() {
    return running;
  }

  @Override
  public boolean isReplaying() {
    return replaying;
  }

  @Override
  public void onGitReferenceUpdated(GitReferenceUpdatedListener.Event event) {
    fire(event.getProjectName(), ObjectId.fromString(event.getNewObjectId()), event.getRefName());
  }

  private void fire(String projectName, ObjectId objectId, String refName) {
    ReplicationState state = new ReplicationState(new GitUpdateProcessing(dispatcher.get()));
    fire(Project.nameKey(projectName), objectId, refName, state);
    state.markAllFetchTasksScheduled();
  }

  private void fire(
      Project.NameKey project, ObjectId objectId, String refName, ReplicationState state) {
    if (!running) {
      stateLog.warn(
          "Replication plugin did not finish startup before event, event replication is postponed",
          state);
      beforeStartupEventsQueue.add(ReferenceUpdatedEvent.create(project.get(), refName, objectId));
      return;
    }

    for (Source cfg : sources.get().getAll()) {
      if (cfg.wouldFetchProject(project) && cfg.wouldFetchRef(refName)) {
        for (String apiUrl : cfg.getApis()) {
          try {
            URIish uri = new URIish(apiUrl);
            FetchRestApiClient fetchClient = fetchClientFactory.create(cfg);

            HttpResult result = fetchClient.callFetch(project, refName, uri);

            if (!result.isSuccessful()) {
              stateLog.warn(
                  String.format(
                      "Pull replication rest api fetch call failed. Endpoint url: %s, reason:%s",
                      apiUrl, result.getMessage().orElse("unknown")),
                  state);
            }
          } catch (URISyntaxException e) {
            stateLog.warn(String.format("Cannot parse pull replication api url:%s", apiUrl), state);
          } catch (Exception e) {
            stateLog.error(
                String.format(
                    "Exception during the pull replication fetch rest api call. Endpoint url:%s, message:%s",
                    apiUrl, e.getMessage()),
                e,
                state);
          }
        }
      }
    }
  }

  public boolean retry(int attempt, int maxRetries) {
    return maxRetries == 0 || attempt < maxRetries;
  }

  private void fireBeforeStartupEvents() {
    Set<String> eventsReplayed = new HashSet<>();
    for (ReferenceUpdatedEvent event : beforeStartupEventsQueue) {
      String eventKey = String.format("%s:%s", event.projectName(), event.refName());
      if (!eventsReplayed.contains(eventKey)) {
        repLog.info("Firing pending task {}", event);
        fire(event.projectName(), event.objectId(), event.refName());
        eventsReplayed.add(eventKey);
      }
    }
  }

  @AutoValue
  abstract static class ReferenceUpdatedEvent {

    static ReferenceUpdatedEvent create(String projectName, String refName, ObjectId objectId) {
      return new AutoValue_ReplicationQueue_ReferenceUpdatedEvent(projectName, refName, objectId);
    }

    public abstract String projectName();

    public abstract String refName();

    public abstract ObjectId objectId();
  }
}