/**
 * Copyright (C) 2013 Open WhisperSystems
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.whispersystems.textsecuregcm.controllers;

import com.google.common.base.Optional;
import com.google.protobuf.ByteString;
import com.yammer.dropwizard.auth.Auth;
import com.yammer.metrics.annotation.Timed;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.whispersystems.textsecuregcm.entities.IncomingMessage;
import org.whispersystems.textsecuregcm.entities.IncomingMessageList;
import org.whispersystems.textsecuregcm.entities.MessageProtos.OutgoingMessageSignal;
import org.whispersystems.textsecuregcm.entities.MessageResponse;
import org.whispersystems.textsecuregcm.entities.MissingDevices;
import org.whispersystems.textsecuregcm.federation.FederatedClient;
import org.whispersystems.textsecuregcm.federation.FederatedClientManager;
import org.whispersystems.textsecuregcm.federation.NoSuchPeerException;
import org.whispersystems.textsecuregcm.limits.RateLimiters;
import org.whispersystems.textsecuregcm.push.NotPushRegisteredException;
import org.whispersystems.textsecuregcm.push.PushSender;
import org.whispersystems.textsecuregcm.push.TransientPushFailureException;
import org.whispersystems.textsecuregcm.storage.Account;
import org.whispersystems.textsecuregcm.storage.AccountsManager;
import org.whispersystems.textsecuregcm.storage.Device;
import org.whispersystems.textsecuregcm.util.Base64;

import javax.validation.Valid;
import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import java.io.IOException;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

@Path("/v1/messages")
public class MessageController {

  private final Logger logger = LoggerFactory.getLogger(MessageController.class);

  private final RateLimiters           rateLimiters;
  private final PushSender             pushSender;
  private final FederatedClientManager federatedClientManager;
  private final AccountsManager        accountsManager;

  public MessageController(RateLimiters rateLimiters,
                           PushSender pushSender,
                           AccountsManager accountsManager,
                           FederatedClientManager federatedClientManager)
  {
    this.rateLimiters           = rateLimiters;
    this.pushSender             = pushSender;
    this.accountsManager        = accountsManager;
    this.federatedClientManager = federatedClientManager;
  }

  @Timed
  @Path("/{destination}")
  @PUT
  @Consumes(MediaType.APPLICATION_JSON)
  public void sendMessage(@Auth                     Account source,
                          @PathParam("destination") String destinationName,
                          @Valid                    IncomingMessageList messages)
      throws IOException, RateLimitExceededException
  {
    rateLimiters.getMessagesLimiter().validate(source.getNumber());

    try {
      if (messages.getRelay() != null) sendLocalMessage(source, destinationName, messages);
      else                             sendRelayMessage(source, destinationName, messages);
    } catch (NoSuchUserException e) {
      throw new WebApplicationException(Response.status(404).build());
    } catch (MissingDevicesException e) {
      throw new WebApplicationException(Response.status(409)
                                                .entity(new MissingDevices(e.getMissingDevices()))
                                                .build());
    }
  }

  @Timed
  @Path("/")
  @POST
  @Consumes(MediaType.APPLICATION_JSON)
  @Produces(MediaType.APPLICATION_JSON)
  public MessageResponse sendMessageLegacy(@Auth Account source, @Valid IncomingMessageList messages)
      throws IOException, RateLimitExceededException
  {
    try {
      List<IncomingMessage> incomingMessages = messages.getMessages();
      validateLegacyDestinations(incomingMessages);

      messages.setRelay(incomingMessages.get(0).getRelay());
      sendMessage(source, incomingMessages.get(0).getDestination(), messages);

      return new MessageResponse(new LinkedList<String>(), new LinkedList<String>());
    } catch (ValidationException e) {
      throw new WebApplicationException(Response.status(422).build());
    }
  }

  private void sendLocalMessage(Account source,
                                String destinationName,
                                IncomingMessageList messages)
      throws NoSuchUserException, MissingDevicesException, IOException
  {
    Account destination = getDestinationAccount(destinationName);

    validateCompleteDeviceList(destination, messages.getMessages());

    for (IncomingMessage incomingMessage : messages.getMessages()) {
      Optional<Device> destinationDevice = destination.getDevice(incomingMessage.getDestinationDeviceId());

      if (destinationDevice.isPresent()) {
        sendLocalMessage(source, destination, destinationDevice.get(), incomingMessage);
      }
    }
  }

  private void sendLocalMessage(Account source,
                                Account destinationAccount,
                                Device destinationDevice,
                                IncomingMessage incomingMessage)
      throws NoSuchUserException, IOException
  {
    try {
      Optional<byte[]>              messageBody    = getMessageBody(incomingMessage);
      OutgoingMessageSignal.Builder messageBuilder = OutgoingMessageSignal.newBuilder();

      messageBuilder.setType(incomingMessage.getType())
                    .setSource(source.getNumber())
                    .setTimestamp(System.currentTimeMillis());

      if (messageBody.isPresent()) {
        messageBuilder.setMessage(ByteString.copyFrom(messageBody.get()));
      }

      if (source.getRelay().isPresent()) {
        messageBuilder.setRelay(source.getRelay().get());
      }

      pushSender.sendMessage(destinationAccount, destinationDevice, messageBuilder.build());
    } catch (NotPushRegisteredException e) {
      if (destinationDevice.isMaster()) throw new NoSuchUserException(e);
      else                              logger.debug("Not registered", e);
    } catch (TransientPushFailureException e) {
      if (destinationDevice.isMaster()) throw new IOException(e);
      else                              logger.debug("Transient failure", e);
    }
  }

  private void sendRelayMessage(Account source,
                                String destinationName,
                                IncomingMessageList messages)
      throws IOException, NoSuchUserException
  {
    try {
      FederatedClient client = federatedClientManager.getClient(messages.getRelay());
      client.sendMessages(source.getNumber(), destinationName, messages);
    } catch (NoSuchPeerException e) {
      throw new NoSuchUserException(e);
    }
  }

  private Account getDestinationAccount(String destination)
      throws NoSuchUserException
  {
    Optional<Account> account = accountsManager.get(destination);

    if (!account.isPresent() || !account.get().isActive()) {
      throw new NoSuchUserException(destination);
    }

    return account.get();
  }

  private void validateCompleteDeviceList(Account account, List<IncomingMessage> messages)
      throws MissingDevicesException
  {
    Set<Long> destinationDeviceIds = new HashSet<>();
    List<Long> missingDeviceIds    = new LinkedList<>();

    for (IncomingMessage message : messages) {
      destinationDeviceIds.add(message.getDestinationDeviceId());
    }

    for (Device device : account.getDevices()) {
      if (!destinationDeviceIds.contains(device.getId())) {
        missingDeviceIds.add(device.getId());
      }
    }

    if (!missingDeviceIds.isEmpty()) {
      throw new MissingDevicesException(missingDeviceIds);
    }
  }

  private void validateLegacyDestinations(List<IncomingMessage> messages)
      throws ValidationException
  {
    String destination = null;

    for (IncomingMessage message : messages) {
      if (destination != null && !destination.equals(message.getDestination())) {
        throw new ValidationException("Multiple account destinations!");
      }

      destination = message.getDestination();
    }
  }

  private Optional<byte[]> getMessageBody(IncomingMessage message) {
    try {
      return Optional.of(Base64.decode(message.getBody()));
    } catch (IOException ioe) {
      logger.debug("Bad B64", ioe);
      return Optional.absent();
    }
  }
}