/**
 * Copyright 2011 Google Inc.
 *
 * 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 org.waveprotocol.box.server.rpc;

import com.google.common.base.Joiner;
import com.google.common.collect.Lists;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.google.inject.name.Named;
import com.google.protobuf.MessageLite;
import com.google.wave.api.FetchProfilesRequest;
import com.google.wave.api.FetchProfilesResult;
import com.google.wave.api.JsonRpcConstant.ParamsProperty;
import com.google.wave.api.JsonRpcResponse;
import com.google.wave.api.OperationQueue;
import com.google.wave.api.OperationRequest;
import com.google.wave.api.ParticipantProfile;
import com.google.wave.api.ProtocolVersion;
import com.google.wave.api.data.converter.EventDataConverterManager;

import org.waveprotocol.box.profile.ProfilesProto.ProfileRequest;
import org.waveprotocol.box.profile.ProfilesProto.ProfileResponse;
import org.waveprotocol.box.server.authentication.SessionManager;
import org.waveprotocol.box.server.robots.OperationContextImpl;
import org.waveprotocol.box.server.robots.OperationServiceRegistry;
import org.waveprotocol.box.server.robots.util.ConversationUtil;
import org.waveprotocol.box.server.robots.util.OperationUtil;
import org.waveprotocol.box.server.rpc.ProtoSerializer.SerializationException;
import org.waveprotocol.box.server.waveserver.WaveletProvider;
import org.waveprotocol.wave.model.wave.ParticipantId;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * A servlet that enables the client side to fetch user profiles using Data API.
 * Typically will be hosted on /profile.
 * 
 * Valid request is: GET
 * /profile/?addresses=user1@example.com,user2@example.com - in URL encoded
 * format. The format of the returned information is the protobuf-JSON format
 * used by the websocket interface.
 * 
 * @author yurize@apache.org (Yuri Zelikov)
 */
@SuppressWarnings("serial")
@Singleton
public final class FetchProfilesServlet extends HttpServlet {

  private static final Logger LOG = Logger.getLogger(FetchProfilesServlet.class.getCanonicalName());

  private final ConversationUtil conversationUtil;
  private final EventDataConverterManager converterManager;
  private final WaveletProvider waveletProvider;
  private final SessionManager sessionManager;
  private final OperationServiceRegistry operationRegistry;
  private final ProtoSerializer serializer;
  
  /**
   * Extracts profile query params from request.
   * 
   * @param req the request.
   * @param response the response.
   * @return the ProfileRequest with query data.
   * @throws UnsupportedEncodingException if the request parameters encoding is invalid.
   */
  private static ProfileRequest parseProfileRequest(HttpServletRequest req,
      HttpServletResponse response) throws UnsupportedEncodingException {
    String[] addresses = URLDecoder.decode(req.getParameter("addresses"), "UTF-8").split(",");
    ProfileRequest profileRequest =
        ProfileRequest.newBuilder().addAllAddresses(Lists.newArrayList(addresses)).build();
    return profileRequest;
  }

  /**
   * Constructs ProfileResponse which is a protobuf generated class from the
   * output of Data API profile service. ProfileResponse contains the same
   * information as profileResult.
   * 
   * @param profileResult the profile results with digests.
   * @return ProfileResponse
   */
  private static ProfileResponse serializeProfileResult(FetchProfilesResult profileResult) {
    ProfileResponse.Builder builder = ProfileResponse.newBuilder();
    for (ParticipantProfile participantProfile : profileResult.getProfiles()) {
      ProfileResponse.FetchedProfile fetchedProfile =
          ProfileResponse.FetchedProfile.newBuilder().setAddress(participantProfile.getAddress())
              .setImageUrl(participantProfile.getImageUrl())
              .setName(participantProfile.getName())
              .setProfileUrl(participantProfile.getProfileUrl()).build();
      builder.addProfiles(fetchedProfile);
    }
    return builder.build();
  }

  @Inject
  public FetchProfilesServlet(SessionManager sessionManager,
      EventDataConverterManager converterManager,
      @Named("DataApiRegistry") OperationServiceRegistry operationRegistry,
      WaveletProvider waveletProvider, ConversationUtil conversationUtil,
      ProtoSerializer serializer) {
    this.converterManager = converterManager;
    this.waveletProvider = waveletProvider;
    this.conversationUtil = conversationUtil;
    this.sessionManager = sessionManager;
    this.operationRegistry = operationRegistry;
    this.serializer = serializer;
  }

  /**
   * Creates HTTP response to the profile query. Main entrypoint for this class.
   */
  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse response) throws IOException {
    ParticipantId user = sessionManager.getLoggedInUser(req.getSession(false));
    if (user == null) {
      response.setStatus(HttpServletResponse.SC_FORBIDDEN);
      return;
    }
    ProfileRequest profileRequest = parseProfileRequest(req, response);
    ProfileResponse profileResponse = fetchProfiles(profileRequest, user);
    serializeObjectToServlet(profileResponse, response);
  }

  /**
   * Fetches profile using Data API.
   */
  private ProfileResponse fetchProfiles(ProfileRequest profileRequest, ParticipantId user) {
    if (LOG.isLoggable(Level.FINE)) {
      LOG.fine("Fetching profiles: " + Joiner.on(",").join(profileRequest.getAddressesList()));
    }
    FetchProfilesResult profileResult =
        fetchProfilesFromService(user, profileRequest.getAddressesList());
    LOG.fine("Fetched profiles: " + profileResult.getProfiles().size());
    return serializeProfileResult(profileResult);
  }

  /**
   * Fetches multiple profiles using Data API.
   */
  private FetchProfilesResult fetchProfilesFromService(ParticipantId user,
      List<String> addresses) {
    OperationQueue opQueue = new OperationQueue();
    FetchProfilesRequest request = new FetchProfilesRequest(addresses);
    opQueue.fetchProfiles(request);
    OperationContextImpl context =
        new OperationContextImpl(waveletProvider,
            converterManager.getEventDataConverter(ProtocolVersion.DEFAULT), conversationUtil);
    OperationRequest operationRequest = opQueue.getPendingOperations().get(0);
    String opId = operationRequest.getId();
    OperationUtil.executeOperation(operationRequest, operationRegistry, context, user);
    JsonRpcResponse jsonRpcResponse = context.getResponses().get(opId);
    FetchProfilesResult profileResults =
        (FetchProfilesResult) jsonRpcResponse.getData().get(ParamsProperty.FETCH_PROFILES_RESULT);
    return profileResults;
  }

  /**
   * Writes the json with profile results to Response.
   */
  private void serializeObjectToServlet(MessageLite message, HttpServletResponse resp)
      throws IOException {
    if (message == null) {
      resp.setStatus(HttpServletResponse.SC_FORBIDDEN);
    } else {
      resp.setStatus(HttpServletResponse.SC_OK);
      resp.setContentType("application/json");
      try {
        resp.getWriter().append(serializer.toJson(message).toString());
      } catch (SerializationException e) {
        throw new IOException(e);
      }
    }
  }
}