// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
//
// 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 google.registry.export;

import static google.registry.model.ofy.ObjectifyService.ofy;
import static google.registry.request.Action.Method.POST;
import static google.registry.util.CollectionUtils.nullToEmpty;
import static google.registry.util.RegistrarUtils.normalizeClientId;
import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
import static javax.servlet.http.HttpServletResponse.SC_OK;

import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Sets;
import com.googlecode.objectify.VoidWork;
import google.registry.config.ConfigModule.Config;
import google.registry.groups.GroupsConnection;
import google.registry.groups.GroupsConnection.Role;
import google.registry.model.registrar.Registrar;
import google.registry.model.registrar.RegistrarContact;
import google.registry.request.Action;
import google.registry.request.Response;
import google.registry.util.Concurrent;
import google.registry.util.FormattingLogger;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import javax.annotation.Nullable;
import javax.inject.Inject;

/**
 * Action that syncs changes to {@link RegistrarContact} entities with Google Groups.
 *
 * <p>This uses the <a href="https://developers.google.com/admin-sdk/directory/">Directory API</a>.
 */
@Action(path = "/_dr/task/syncGroupMembers", method = POST)
public final class SyncGroupMembersAction implements Runnable {

  /**
   * The number of threads to run simultaneously (one per registrar) while processing group syncs.
   * This number is purposefully low because App Engine will complain about a large number of
   * requests per second, so it's better to spread the work out (as we are only running this servlet
   * once per hour anyway).
   */
  private static final int NUM_WORK_THREADS = 2;

  private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();


  private enum Result {
    OK(SC_OK, "Group memberships successfully updated."),
    NOT_MODIFIED(SC_OK, "No registrar contacts have been updated since the last time servlet ran."),
    FAILED(SC_INTERNAL_SERVER_ERROR, "Error occurred while updating registrar contacts.") {
      @Override
      protected void log(Throwable cause) {
        logger.severefmt(cause, "%s", message);
      }};

    final int statusCode;
    final String message;

    private Result(int statusCode, String message) {
      this.statusCode = statusCode;
      this.message = message;
    }

    /** Log an error message. Results that use log levels other than info should override this. */
    void log(@Nullable Throwable cause) {
      logger.infofmt(cause, "%s", message);
    }
  }

  @Inject GroupsConnection groupsConnection;
  @Inject Response response;
  @Inject @Config("publicDomainName") String publicDomainName;
  @Inject SyncGroupMembersAction() {}

  private void sendResponse(Result result, @Nullable List<Throwable> causes) {
    for (Throwable cause : nullToEmpty(causes)) {
      result.log(cause);
    }
    response.setStatus(result.statusCode);
    response.setPayload(String.format("%s %s\n", result.name(), result.message));
  }

  /**
   * Returns the Google Groups email address for the given registrar clientId and
   * RegistrarContact.Type
   */
  public static String getGroupEmailAddressForContactType(
      String clientId,
      RegistrarContact.Type type,
      String publicDomainName) {
    // Take the registrar's clientId, make it lowercase, and remove all characters that aren't
    // alphanumeric, hyphens, or underscores.
    return String.format(
        "%s-%s-contacts@%s", normalizeClientId(clientId), type.getDisplayName(), publicDomainName);
  }

  /**
   * Loads all Registrars, and for each one that is marked dirty, grabs the existing group
   * memberships and updates them to reflect the current state of the RegistrarContacts.
   */
  @Override
  public void run() {
    List<Registrar> dirtyRegistrars = Registrar
        .loadAllActive()
        .filter(new Predicate<Registrar>() {
          @Override
          public boolean apply(Registrar registrar) {
            // Only grab registrars that require syncing and are of the correct type.
            return registrar.getContactsRequireSyncing()
                && registrar.getType() == Registrar.Type.REAL;
          }})
        .toList();
    if (dirtyRegistrars.isEmpty()) {
      sendResponse(Result.NOT_MODIFIED, null);
      return;
    }

    // Run multiple threads to communicate with Google Groups simultaneously.
    ImmutableList<Optional<Throwable>> results = Concurrent.transform(
        dirtyRegistrars,
        NUM_WORK_THREADS,
        new Function<Registrar, Optional<Throwable>>() {
          @Override
          public Optional<Throwable> apply(final Registrar registrar) {
            try {
              syncRegistrarContacts(registrar);
              return Optional.<Throwable> absent();
            } catch (Throwable e) {
              logger.severe(e, e.getMessage());
              return Optional.of(e);
            }
          }});

    List<Throwable> errors = getErrorsAndUpdateFlagsForSuccesses(dirtyRegistrars, results);
    // If there were no errors, return success; otherwise return a failed status and log the errors.
    if (errors.isEmpty()) {
      sendResponse(Result.OK, null);
    } else {
      sendResponse(Result.FAILED, errors);
    }
  }

  /**
   * Parses the results from Google Groups for each registrar, setting the dirty flag to false in
   * Datastore for the calls that succeeded and accumulating the errors for the calls that failed.
   */
  private List<Throwable> getErrorsAndUpdateFlagsForSuccesses(
      List<Registrar> registrars,
      List<Optional<Throwable>> results) {
    final ImmutableList.Builder<Registrar> registrarsToSave = new ImmutableList.Builder<>();
    List<Throwable> errors = new ArrayList<>();
    for (int i = 0; i < results.size(); i++) {
      Optional<Throwable> opt = results.get(i);
      if (opt.isPresent()) {
        errors.add(opt.get());
      } else {
        registrarsToSave.add(
            registrars.get(i).asBuilder().setContactsRequireSyncing(false).build());
      }
    }
    ofy().transactNew(new VoidWork() {
      @Override
      public void vrun() {
          ofy().save().entities(registrarsToSave.build());
      }});
    return errors;
  }

  /** Syncs the contacts for an individual registrar to Google Groups. */
  private void syncRegistrarContacts(Registrar registrar) {
    String groupKey = "";
    try {
      Set<RegistrarContact> registrarContacts = registrar.getContacts();
      long totalAdded = 0;
      long totalRemoved = 0;
      for (final RegistrarContact.Type type : RegistrarContact.Type.values()) {
        groupKey = getGroupEmailAddressForContactType(
            registrar.getClientIdentifier(), type, publicDomainName);
        Set<String> currentMembers = groupsConnection.getMembersOfGroup(groupKey);
        Set<String> desiredMembers = FluentIterable.from(registrarContacts)
            .filter(new Predicate<RegistrarContact>() {
              @Override
              public boolean apply(RegistrarContact contact) {
                return contact.getTypes().contains(type);
              }})
            .transform(new Function<RegistrarContact, String>() {
              @Override
              public String apply(RegistrarContact contact) {
                return contact.getEmailAddress();
              }})
            .toSet();
        for (String email : Sets.difference(desiredMembers, currentMembers)) {
          groupsConnection.addMemberToGroup(groupKey, email, Role.MEMBER);
          totalAdded++;
        }
        for (String email : Sets.difference(currentMembers, desiredMembers)) {
          groupsConnection.removeMemberFromGroup(groupKey, email);
          totalRemoved++;
        }
      }
      logger.infofmt("Successfully synced contacts for registrar %s: added %d and removed %d",
          registrar.getClientIdentifier(),
          totalAdded,
          totalRemoved);
    } catch (IOException e) {
      // Bail out of the current sync job if an error occurs. This is OK because (a) errors usually
      // indicate that retrying won't succeed at all, or at least not immediately, and (b) the sync
      // job will run within an hour anyway and effectively resume where it left off if this was a
      // transient error.
      String msg = String.format("Couldn't sync contacts for registrar %s to group %s",
          registrar.getClientIdentifier(), groupKey);
      throw new RuntimeException(msg, e);
    }
  }
}