/*
 * libjingle
 * Copyright 2014 Google Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.appspot.apprtc;

import org.appspot.apprtc.AppRTCClient.SignalingParameters;
import org.appspot.apprtc.util.AsyncHttpURLConnection;
import org.appspot.apprtc.util.AsyncHttpURLConnection.AsyncHttpEvents;

import android.util.Log;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.webrtc.IceCandidate;
import org.webrtc.MediaConstraints;
import org.webrtc.PeerConnection;
import org.webrtc.SessionDescription;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.LinkedList;
import java.util.Scanner;

/**
 * AsyncTask that converts an AppRTC room URL into the set of signaling
 * parameters to use with that room.
 */
public class RoomParametersFetcher {
  private static final String TAG = "RoomRTCClient";
  private final RoomParametersFetcherEvents events;
  private final boolean loopback;
  private AsyncHttpURLConnection httpConnection;

  /**
   * Room parameters fetcher callbacks.
   */
  public static interface RoomParametersFetcherEvents {
    /**
     * Callback fired once the room's signaling parameters
     * SignalingParameters are extracted.
     */
    public void onSignalingParametersReady(final SignalingParameters params);

    /**
     * Callback for room parameters extraction error.
     */
    public void onSignalingParametersError(final String description);
  }

  public RoomParametersFetcher(boolean loopback, String registerUrl,
      final RoomParametersFetcherEvents events) {
    Log.d(TAG, "Connecting to room: " + registerUrl);
    this.loopback = loopback;
    this.events = events;

    httpConnection = new AsyncHttpURLConnection("POST", registerUrl, null,
        new AsyncHttpEvents() {
          @Override
          public void onHttpError(String errorMessage) {
            Log.e(TAG, "Room connection error: " + errorMessage);
            events.onSignalingParametersError(errorMessage);
          }

          @Override
          public void onHttpComplete(String response) {
            roomHttpResponseParse(response);
          }
        });
    httpConnection.send();
  }

  private void roomHttpResponseParse(String response) {
    Log.d(TAG, "Room response: " + response);
    try {
      LinkedList<IceCandidate> iceCandidates = null;
      SessionDescription offerSdp = null;
      JSONObject roomJson = new JSONObject(response);

      String result = roomJson.getString("result");
      if (!result.equals("SUCCESS")) {
        events.onSignalingParametersError("Room response error: " + result);
        return;
      }
      response = roomJson.getString("params");
      roomJson = new JSONObject(response);
      String roomId = roomJson.getString("room_id");
      String clientId = roomJson.getString("client_id");
      String wssUrl = roomJson.getString("wss_url");
      String wssPostUrl = roomJson.getString("wss_post_url");
      boolean initiator = (roomJson.getBoolean("is_initiator"));
      if (!initiator) {
        iceCandidates = new LinkedList<IceCandidate>();
        String messagesString = roomJson.getString("messages");
        JSONArray messages = new JSONArray(messagesString);
        for (int i = 0; i < messages.length(); ++i) {
          String messageString = messages.getString(i);
          JSONObject message = new JSONObject(messageString);
          String messageType = message.getString("type");
          Log.d(TAG, "GAE->C #" + i + " : " + messageString);
          if (messageType.equals("offer")) {
            offerSdp = new SessionDescription(
                SessionDescription.Type.fromCanonicalForm(messageType),
                message.getString("sdp"));
          } else if (messageType.equals("candidate")) {
            IceCandidate candidate = new IceCandidate(
                message.getString("id"),
                message.getInt("label"),
                message.getString("candidate"));
            iceCandidates.add(candidate);
          } else {
            Log.e(TAG, "Unknown message: " + messageString);
          }
        }
      }
      Log.d(TAG, "RoomId: " + roomId + ". ClientId: " + clientId);
      Log.d(TAG, "Initiator: " + initiator);
      Log.d(TAG, "WSS url: " + wssUrl);
      Log.d(TAG, "WSS POST url: " + wssPostUrl);

      LinkedList<PeerConnection.IceServer> iceServers =
          iceServersFromPCConfigJSON(roomJson.getString("pc_config"));
      boolean isTurnPresent = false;
      for (PeerConnection.IceServer server : iceServers) {
        Log.d(TAG, "IceServer: " + server);
        if (server.uri.startsWith("turn:")) {
          isTurnPresent = true;
          break;
        }
      }
      if (!isTurnPresent) {
        LinkedList<PeerConnection.IceServer> turnServers =
            requestTurnServers(roomJson.getString("turn_url"));
        for (PeerConnection.IceServer turnServer : turnServers) {
          Log.d(TAG, "TurnServer: " + turnServer);
          iceServers.add(turnServer);
        }
      }

      MediaConstraints pcConstraints = constraintsFromJSON(
          roomJson.getString("pc_constraints"));
      addDTLSConstraintIfMissing(pcConstraints, loopback);
      Log.d(TAG, "pcConstraints: " + pcConstraints);
      MediaConstraints videoConstraints = constraintsFromJSON(
          getAVConstraints("video",
              roomJson.getString("media_constraints")));
      Log.d(TAG, "videoConstraints: " + videoConstraints);
      MediaConstraints audioConstraints = constraintsFromJSON(
          getAVConstraints("audio",
              roomJson.getString("media_constraints")));
      Log.d(TAG, "audioConstraints: " + audioConstraints);

      SignalingParameters params = new SignalingParameters(
          iceServers, initiator,
          pcConstraints, videoConstraints, audioConstraints,
          roomId, clientId,
          wssUrl, wssPostUrl,
          offerSdp, iceCandidates);
      events.onSignalingParametersReady(params);
    } catch (JSONException e) {
      events.onSignalingParametersError(
          "Room JSON parsing error: " + e.toString());
    } catch (IOException e) {
      events.onSignalingParametersError("Room IO error: " + e.toString());
    }
  }

  // Mimic Chrome and set DtlsSrtpKeyAgreement to true if not set to false by
  // the web-app.
  private void addDTLSConstraintIfMissing(
      MediaConstraints pcConstraints, boolean loopback) {
    for (MediaConstraints.KeyValuePair pair : pcConstraints.mandatory) {
      if (pair.getKey().equals("DtlsSrtpKeyAgreement")) {
        return;
      }
    }
    for (MediaConstraints.KeyValuePair pair : pcConstraints.optional) {
      if (pair.getKey().equals("DtlsSrtpKeyAgreement")) {
        return;
      }
    }
    // DTLS isn't being specified (e.g. for debug=loopback calls), so enable
    // it for normal calls and disable for loopback calls.
    if (loopback) {
      pcConstraints.optional.add(
          new MediaConstraints.KeyValuePair("DtlsSrtpKeyAgreement", "false"));
    } else {
      pcConstraints.optional.add(
          new MediaConstraints.KeyValuePair("DtlsSrtpKeyAgreement", "true"));
    }
  }

  // Return the constraints specified for |type| of "audio" or "video" in
  // |mediaConstraintsString|.
  private String getAVConstraints (
    String type, String mediaConstraintsString) throws JSONException {
    JSONObject json = new JSONObject(mediaConstraintsString);
    // Tricky handling of values that are allowed to be (boolean or
    // MediaTrackConstraints) by the getUserMedia() spec.  There are three
    // cases below.
    if (!json.has(type) || !json.optBoolean(type, true)) {
      // Case 1: "audio"/"video" is not present, or is an explicit "false"
      // boolean.
      return null;
    }
    if (json.optBoolean(type, false)) {
      // Case 2: "audio"/"video" is an explicit "true" boolean.
      return "{\"mandatory\": {}, \"optional\": []}";
    }
    // Case 3: "audio"/"video" is an object.
    return json.getJSONObject(type).toString();
  }

  private MediaConstraints constraintsFromJSON(String jsonString)
      throws JSONException {
    if (jsonString == null) {
      return null;
    }
    MediaConstraints constraints = new MediaConstraints();
    JSONObject json = new JSONObject(jsonString);
    JSONObject mandatoryJSON = json.optJSONObject("mandatory");
    if (mandatoryJSON != null) {
      JSONArray mandatoryKeys = mandatoryJSON.names();
      if (mandatoryKeys != null) {
        for (int i = 0; i < mandatoryKeys.length(); ++i) {
          String key = mandatoryKeys.getString(i);
          String value = mandatoryJSON.getString(key);
          constraints.mandatory.add(
              new MediaConstraints.KeyValuePair(key, value));
        }
      }
    }
    JSONArray optionalJSON = json.optJSONArray("optional");
    if (optionalJSON != null) {
      for (int i = 0; i < optionalJSON.length(); ++i) {
        JSONObject keyValueDict = optionalJSON.getJSONObject(i);
        String key = keyValueDict.names().getString(0);
        String value = keyValueDict.getString(key);
        constraints.optional.add(
            new MediaConstraints.KeyValuePair(key, value));
      }
    }
    return constraints;
  }

  // Requests & returns a TURN ICE Server based on a request URL.  Must be run
  // off the main thread!
  private LinkedList<PeerConnection.IceServer> requestTurnServers(String url)
      throws IOException, JSONException {
    LinkedList<PeerConnection.IceServer> turnServers =
        new LinkedList<PeerConnection.IceServer>();
    Log.d(TAG, "Request TURN from: " + url);
    URLConnection connection = (new URL(url)).openConnection();
    connection.addRequestProperty("user-agent", "Mozilla/5.0");
    connection.addRequestProperty("origin", "https://apprtc.appspot.com");
    String response = drainStream(connection.getInputStream());
    Log.d(TAG, "TURN response: " + response);
    JSONObject responseJSON = new JSONObject(response);
    String username = responseJSON.getString("username");
    String password = responseJSON.getString("password");
    JSONArray turnUris = responseJSON.getJSONArray("uris");
    for (int i = 0; i < turnUris.length(); i++) {
      String uri = turnUris.getString(i);
      turnServers.add(new PeerConnection.IceServer(uri, username, password));
    }
    return turnServers;
  }

  // Return the list of ICE servers described by a WebRTCPeerConnection
  // configuration string.
  private LinkedList<PeerConnection.IceServer> iceServersFromPCConfigJSON(
      String pcConfig) throws JSONException {
    JSONObject json = new JSONObject(pcConfig);
    JSONArray servers = json.getJSONArray("iceServers");
    LinkedList<PeerConnection.IceServer> ret =
        new LinkedList<PeerConnection.IceServer>();
    for (int i = 0; i < servers.length(); ++i) {
      JSONObject server = servers.getJSONObject(i);
      String url = server.getString("urls");
      String credential =
          server.has("credential") ? server.getString("credential") : "";
      ret.add(new PeerConnection.IceServer(url, "", credential));
    }
    return ret;
  }

  // Return the contents of an InputStream as a String.
  private String drainStream(InputStream in) {
    Scanner s = new Scanner(in).useDelimiter("\\A");
    return s.hasNext() ? s.next() : "";
  }

}
