/*
 *  Copyright 2014 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

package org.appspot.apprtc;

import org.appspot.apprtc.AppRTCClient.SignalingParameters;

import android.content.Context;
import android.os.Environment;
import android.os.ParcelFileDescriptor;
import android.util.Log;

import org.webrtc.AudioSource;
import org.webrtc.AudioTrack;
import org.webrtc.Camera1Enumerator;
import org.webrtc.Camera2Enumerator;
import org.webrtc.CameraEnumerationAndroid;
import org.webrtc.CameraEnumerator;
import org.webrtc.CameraVideoCapturer;
import org.webrtc.DataChannel;
import org.webrtc.EglBase;
import org.webrtc.IceCandidate;
import org.webrtc.Logging;
import org.webrtc.MediaCodecVideoEncoder;
import org.webrtc.MediaConstraints;
import org.webrtc.MediaConstraints.KeyValuePair;
import org.webrtc.MediaStream;
import org.webrtc.PeerConnection;
import org.webrtc.PeerConnection.IceConnectionState;
import org.webrtc.PeerConnectionFactory;
import org.webrtc.SdpObserver;
import org.webrtc.SessionDescription;
import org.webrtc.StatsObserver;
import org.webrtc.StatsReport;
import org.webrtc.VideoCapturer;
import org.webrtc.VideoRenderer;
import org.webrtc.VideoSource;
import org.webrtc.VideoTrack;
import org.webrtc.voiceengine.WebRtcAudioManager;
import org.webrtc.voiceengine.WebRtcAudioUtils;

import java.io.File;
import java.io.IOException;
import java.util.EnumSet;
import java.util.LinkedList;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Peer connection client implementation.
 *
 * <p>All public methods are routed to local looper thread.
 * All PeerConnectionEvents callbacks are invoked from the same looper thread.
 * This class is a singleton.
 */
public class PeerConnectionClient {
  public static final String VIDEO_TRACK_ID = "ARDAMSv0";
  public static final String AUDIO_TRACK_ID = "ARDAMSa0";
  private static final String TAG = "PCRTCClient";
  private static final String VIDEO_CODEC_VP8 = "VP8";
  private static final String VIDEO_CODEC_VP9 = "VP9";
  private static final String VIDEO_CODEC_H264 = "H264";
  private static final String AUDIO_CODEC_OPUS = "opus";
  private static final String AUDIO_CODEC_ISAC = "ISAC";
  private static final String VIDEO_CODEC_PARAM_START_BITRATE =
      "x-google-start-bitrate";
  private static final String AUDIO_CODEC_PARAM_BITRATE = "maxaveragebitrate";
  private static final String AUDIO_ECHO_CANCELLATION_CONSTRAINT = "googEchoCancellation";
  private static final String AUDIO_AUTO_GAIN_CONTROL_CONSTRAINT= "googAutoGainControl";
  private static final String AUDIO_HIGH_PASS_FILTER_CONSTRAINT  = "googHighpassFilter";
  private static final String AUDIO_NOISE_SUPPRESSION_CONSTRAINT = "googNoiseSuppression";
  private static final String MAX_VIDEO_WIDTH_CONSTRAINT = "maxWidth";
  private static final String MIN_VIDEO_WIDTH_CONSTRAINT = "minWidth";
  private static final String MAX_VIDEO_HEIGHT_CONSTRAINT = "maxHeight";
  private static final String MIN_VIDEO_HEIGHT_CONSTRAINT = "minHeight";
  private static final String MAX_VIDEO_FPS_CONSTRAINT = "maxFrameRate";
  private static final String MIN_VIDEO_FPS_CONSTRAINT = "minFrameRate";
  private static final String DTLS_SRTP_KEY_AGREEMENT_CONSTRAINT = "DtlsSrtpKeyAgreement";
  private static final int HD_VIDEO_WIDTH = 1280;
  private static final int HD_VIDEO_HEIGHT = 720;
  private static final int MAX_VIDEO_WIDTH = 1280;
  private static final int MAX_VIDEO_HEIGHT = 1280;
  private static final int MAX_VIDEO_FPS = 30;

  private static final PeerConnectionClient instance = new PeerConnectionClient();
  private final PCObserver pcObserver = new PCObserver();
  private final SDPObserver sdpObserver = new SDPObserver();
  private final ScheduledExecutorService executor;

  private Context context;
  private PeerConnectionFactory factory;
  private PeerConnection peerConnection;
  PeerConnectionFactory.Options options = null;
  private AudioSource audioSource;
  private VideoSource videoSource;
  private boolean videoCallEnabled;
  private boolean preferIsac;
  private String preferredVideoCodec;
  private boolean videoCapturerStopped;
  private boolean isError;
  private Timer statsTimer;
  private VideoRenderer.Callbacks localRender;
  private VideoRenderer.Callbacks remoteRender;
  private SignalingParameters signalingParameters;
  private MediaConstraints pcConstraints;
  private int videoWidth;
  private int videoHeight;
  private int videoFps;
  private MediaConstraints audioConstraints;
  private ParcelFileDescriptor aecDumpFileDescriptor;
  private MediaConstraints sdpMediaConstraints;
  private PeerConnectionParameters peerConnectionParameters;
  // Queued remote ICE candidates are consumed only after both local and
  // remote descriptions are set. Similarly local ICE candidates are sent to
  // remote peer after both local and remote description are set.
  private LinkedList<IceCandidate> queuedRemoteCandidates;
  private PeerConnectionEvents events;
  private boolean isInitiator;
  private SessionDescription localSdp; // either offer or answer SDP
  private MediaStream mediaStream;
  private int numberOfCameras;
  private CameraVideoCapturer videoCapturer;
  // enableVideo is set to true if video should be rendered and sent.
  private boolean renderVideo;
  private VideoTrack localVideoTrack;
  private VideoTrack remoteVideoTrack;
  // enableAudio is set to true if audio should be sent.
  private boolean enableAudio;
  private AudioTrack localAudioTrack;

  /**
   * Peer connection parameters.
   */
  public static class PeerConnectionParameters {
    public final boolean videoCallEnabled;
    public final boolean loopback;
    public final boolean tracing;
    public final boolean useCamera2;
    public final int videoWidth;
    public final int videoHeight;
    public final int videoFps;
    public final int videoStartBitrate;
    public final String videoCodec;
    public final boolean videoCodecHwAcceleration;
    public final boolean captureToTexture;
    public final int audioStartBitrate;
    public final String audioCodec;
    public final boolean noAudioProcessing;
    public final boolean aecDump;
    public final boolean useOpenSLES;
    public final boolean disableBuiltInAEC;

    public PeerConnectionParameters(
        boolean videoCallEnabled, boolean loopback, boolean tracing, boolean useCamera2,
        int videoWidth, int videoHeight, int videoFps,
        int videoStartBitrate, String videoCodec, boolean videoCodecHwAcceleration,
        boolean captureToTexture, int audioStartBitrate, String audioCodec,
        boolean noAudioProcessing, boolean aecDump, boolean useOpenSLES,
        boolean disableBuiltInAEC) {
      this.videoCallEnabled = videoCallEnabled;
      this.useCamera2 = useCamera2;
      this.loopback = loopback;
      this.tracing = tracing;
      this.videoWidth = videoWidth;
      this.videoHeight = videoHeight;
      this.videoFps = videoFps;
      this.videoStartBitrate = videoStartBitrate;
      this.videoCodec = videoCodec;
      this.videoCodecHwAcceleration = videoCodecHwAcceleration;
      this.captureToTexture = captureToTexture;
      this.audioStartBitrate = audioStartBitrate;
      this.audioCodec = audioCodec;
      this.noAudioProcessing = noAudioProcessing;
      this.aecDump = aecDump;
      this.useOpenSLES = useOpenSLES;
      this.disableBuiltInAEC = disableBuiltInAEC;
    }
  }

  /**
   * Peer connection events.
   */
  public interface PeerConnectionEvents {
    /**
     * Callback fired once local SDP is created and set.
     */
    void onLocalDescription(final SessionDescription sdp);

    /**
     * Callback fired once local Ice candidate is generated.
     */
    void onIceCandidate(final IceCandidate candidate);

    /**
     * Callback fired once local ICE candidates are removed.
     */
    void onIceCandidatesRemoved(final IceCandidate[] candidates);

    /**
     * Callback fired once connection is established (IceConnectionState is
     * CONNECTED).
     */
    void onIceConnected();

    /**
     * Callback fired once connection is closed (IceConnectionState is
     * DISCONNECTED).
     */
    void onIceDisconnected();

    /**
     * Callback fired once peer connection is closed.
     */
    void onPeerConnectionClosed();

    /**
     * Callback fired once peer connection statistics is ready.
     */
    void onPeerConnectionStatsReady(final StatsReport[] reports);

    /**
     * Callback fired once peer connection error happened.
     */
    void onPeerConnectionError(final String description);
  }

  private PeerConnectionClient() {
    // Executor thread is started once in private ctor and is used for all
    // peer connection API calls to ensure new peer connection factory is
    // created on the same thread as previously destroyed factory.
    executor = Executors.newSingleThreadScheduledExecutor();
  }

  public static PeerConnectionClient getInstance() {
    return instance;
  }

  public void setPeerConnectionFactoryOptions(PeerConnectionFactory.Options options) {
    this.options = options;
  }

  public void createPeerConnectionFactory(
      final Context context,
      final PeerConnectionParameters peerConnectionParameters,
      final PeerConnectionEvents events) {
    this.peerConnectionParameters = peerConnectionParameters;
    this.events = events;
    videoCallEnabled = peerConnectionParameters.videoCallEnabled;
    // Reset variables to initial states.
    this.context = null;
    factory = null;
    peerConnection = null;
    preferIsac = false;
    videoCapturerStopped = false;
    isError = false;
    queuedRemoteCandidates = null;
    localSdp = null; // either offer or answer SDP
    mediaStream = null;
    videoCapturer = null;
    renderVideo = true;
    localVideoTrack = null;
    remoteVideoTrack = null;
    enableAudio = true;
    localAudioTrack = null;
    statsTimer = new Timer();

    executor.execute(new Runnable() {
      @Override
      public void run() {
        createPeerConnectionFactoryInternal(context);
      }
    });
  }

  public void createPeerConnection(
      final EglBase.Context renderEGLContext,
      final VideoRenderer.Callbacks localRender,
      final VideoRenderer.Callbacks remoteRender,
      final SignalingParameters signalingParameters) {
    if (peerConnectionParameters == null) {
      Log.e(TAG, "Creating peer connection without initializing factory.");
      return;
    }
    this.localRender = localRender;
    this.remoteRender = remoteRender;
    this.signalingParameters = signalingParameters;
    executor.execute(new Runnable() {
      @Override
      public void run() {
        try {
          createMediaConstraintsInternal();
          createPeerConnectionInternal(renderEGLContext);
        } catch (Exception e) {
          reportError("Failed to create peer connection: " + e.getMessage());
          throw e;
        }
      }
    });
  }

  public void close() {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        closeInternal();
      }
    });
  }

  public boolean isVideoCallEnabled() {
    return videoCallEnabled;
  }

  private void createPeerConnectionFactoryInternal(Context context) {
      PeerConnectionFactory.initializeInternalTracer();
      if (peerConnectionParameters.tracing) {
          PeerConnectionFactory.startInternalTracingCapture(
                  Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator
                  + "webrtc-trace.txt");
      }
    Log.d(TAG, "Create peer connection factory. Use video: " +
        peerConnectionParameters.videoCallEnabled);
    isError = false;

    // Initialize field trials.
    PeerConnectionFactory.initializeFieldTrials("");

    // Check preferred video codec.
    preferredVideoCodec = VIDEO_CODEC_VP8;
    if (videoCallEnabled && peerConnectionParameters.videoCodec != null) {
      if (peerConnectionParameters.videoCodec.equals(VIDEO_CODEC_VP9)) {
        preferredVideoCodec = VIDEO_CODEC_VP9;
      } else if (peerConnectionParameters.videoCodec.equals(VIDEO_CODEC_H264)) {
        preferredVideoCodec = VIDEO_CODEC_H264;
      }
    }
    Log.d(TAG, "Pereferred video codec: " + preferredVideoCodec);

    // Check if ISAC is used by default.
    preferIsac = peerConnectionParameters.audioCodec != null
        && peerConnectionParameters.audioCodec.equals(AUDIO_CODEC_ISAC);

    // Enable/disable OpenSL ES playback.
    if (!peerConnectionParameters.useOpenSLES) {
      Log.d(TAG, "Disable OpenSL ES audio even if device supports it");
      WebRtcAudioManager.setBlacklistDeviceForOpenSLESUsage(true /* enable */);
    } else {
      Log.d(TAG, "Allow OpenSL ES audio if device supports it");
      WebRtcAudioManager.setBlacklistDeviceForOpenSLESUsage(false);
    }

    if (peerConnectionParameters.disableBuiltInAEC) {
      Log.d(TAG, "Disable built-in AEC even if device supports it");
      WebRtcAudioUtils.setWebRtcBasedAcousticEchoCanceler(true);
    } else {
      Log.d(TAG, "Enable built-in AEC if device supports it");
      WebRtcAudioUtils.setWebRtcBasedAcousticEchoCanceler(false);
    }

    // Create peer connection factory.
    if (!PeerConnectionFactory.initializeAndroidGlobals(context, true, true,
        peerConnectionParameters.videoCodecHwAcceleration)) {
      events.onPeerConnectionError("Failed to initializeAndroidGlobals");
    }
    if (options != null) {
      Log.d(TAG, "Factory networkIgnoreMask option: " + options.networkIgnoreMask);
    }
    this.context = context;
    factory = new PeerConnectionFactory(options);
    Log.d(TAG, "Peer connection factory created.");
  }

  private void createMediaConstraintsInternal() {
    // Create peer connection constraints.
    pcConstraints = new MediaConstraints();
    // Enable DTLS for normal calls and disable for loopback calls.
    if (peerConnectionParameters.loopback) {
      pcConstraints.optional.add(
          new MediaConstraints.KeyValuePair(DTLS_SRTP_KEY_AGREEMENT_CONSTRAINT, "false"));
    } else {
      pcConstraints.optional.add(
          new MediaConstraints.KeyValuePair(DTLS_SRTP_KEY_AGREEMENT_CONSTRAINT, "true"));
    }

    // Check if there is a camera on device and disable video call if not.
    numberOfCameras = CameraEnumerationAndroid.getDeviceCount();
    if (numberOfCameras == 0) {
      Log.w(TAG, "No camera on device. Switch to audio only call.");
      videoCallEnabled = false;
    }
    // Create video constraints if video call is enabled.
    if (videoCallEnabled) {
      videoWidth = peerConnectionParameters.videoWidth;
      videoHeight = peerConnectionParameters.videoHeight;
      videoFps = peerConnectionParameters.videoFps;

      // If video resolution is not specified, default to HD.
      if (videoWidth == 0 || videoHeight == 0) {
        videoWidth = HD_VIDEO_WIDTH;
        videoHeight = HD_VIDEO_HEIGHT;
      }

      // If fps is not specified, default to 30.
      if (videoFps == 0) {
        videoFps = 30;
      }

      videoWidth = Math.min(videoWidth, MAX_VIDEO_WIDTH);
      videoHeight = Math.min(videoHeight, MAX_VIDEO_HEIGHT);
      videoFps = Math.min(videoFps, MAX_VIDEO_FPS);
    }

    // Create audio constraints.
    audioConstraints = new MediaConstraints();
    // added for audio performance measurements
    if (peerConnectionParameters.noAudioProcessing) {
      Log.d(TAG, "Disabling audio processing");
      audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
            AUDIO_ECHO_CANCELLATION_CONSTRAINT, "false"));
      audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
            AUDIO_AUTO_GAIN_CONTROL_CONSTRAINT, "false"));
      audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
            AUDIO_HIGH_PASS_FILTER_CONSTRAINT, "false"));
      audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
           AUDIO_NOISE_SUPPRESSION_CONSTRAINT , "false"));
    }
    // Create SDP constraints.
    sdpMediaConstraints = new MediaConstraints();
    sdpMediaConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
        "OfferToReceiveAudio", "true"));
    if (videoCallEnabled || peerConnectionParameters.loopback) {
      sdpMediaConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
          "OfferToReceiveVideo", "true"));
    } else {
      sdpMediaConstraints.mandatory.add(new MediaConstraints.KeyValuePair(
          "OfferToReceiveVideo", "false"));
    }
  }

  private void createCapturer(CameraEnumerator enumerator) {
    final String[] deviceNames = enumerator.getDeviceNames();

    // First, try to find front facing camera
    Logging.d(TAG, "Looking for front facing cameras.");
    for (String deviceName : deviceNames) {
      if (enumerator.isFrontFacing(deviceName)) {
        Logging.d(TAG, "Creating front facing camera capturer.");
        videoCapturer = enumerator.createCapturer(deviceName, null);

        if (videoCapturer != null) {
          return;
        }
      }
    }

    // Front facing camera not found, try something else
    Logging.d(TAG, "Looking for other cameras.");
    for (String deviceName : deviceNames) {
      if (!enumerator.isFrontFacing(deviceName)) {
        Logging.d(TAG, "Creating other camera capturer.");
        videoCapturer = enumerator.createCapturer(deviceName, null);

        if (videoCapturer != null) {
          return;
        }
      }
    }
  }

  private void createPeerConnectionInternal(EglBase.Context renderEGLContext) {
    if (factory == null || isError) {
      Log.e(TAG, "Peerconnection factory is not created");
      return;
    }
    Log.d(TAG, "Create peer connection.");

    Log.d(TAG, "PCConstraints: " + pcConstraints.toString());
    queuedRemoteCandidates = new LinkedList<IceCandidate>();

    if (videoCallEnabled) {
      Log.d(TAG, "EGLContext: " + renderEGLContext);
      factory.setVideoHwAccelerationOptions(renderEGLContext, renderEGLContext);
    }

    PeerConnection.RTCConfiguration rtcConfig =
        new PeerConnection.RTCConfiguration(signalingParameters.iceServers);
    // TCP candidates are only useful when connecting to a server that supports
    // ICE-TCP.
    rtcConfig.tcpCandidatePolicy = PeerConnection.TcpCandidatePolicy.DISABLED;
    rtcConfig.bundlePolicy = PeerConnection.BundlePolicy.MAXBUNDLE;
    rtcConfig.rtcpMuxPolicy = PeerConnection.RtcpMuxPolicy.REQUIRE;
    rtcConfig.continualGatheringPolicy = PeerConnection.ContinualGatheringPolicy.GATHER_CONTINUALLY;
    // Use ECDSA encryption.
    rtcConfig.keyType = PeerConnection.KeyType.ECDSA;

    peerConnection = factory.createPeerConnection(
        rtcConfig, pcConstraints, pcObserver);
    isInitiator = false;

    // Set default WebRTC tracing and INFO libjingle logging.
    // NOTE: this _must_ happen while |factory| is alive!
    Logging.enableTracing(
        "logcat:",
        EnumSet.of(Logging.TraceLevel.TRACE_DEFAULT));
    Logging.enableLogToDebugOutput(Logging.Severity.LS_INFO);

    mediaStream = factory.createLocalMediaStream("ARDAMS");
    if (videoCallEnabled) {
      if (peerConnectionParameters.useCamera2) {
        if (!peerConnectionParameters.captureToTexture) {
          reportError(context.getString(R.string.camera2_texture_only_error));
          return;
        }

        Logging.d(TAG, "Creating capturer using camera2 API.");
        createCapturer(new Camera2Enumerator(context));
      } else {
        Logging.d(TAG, "Creating capturer using camera1 API.");
        createCapturer(new Camera1Enumerator(peerConnectionParameters.captureToTexture));
      }

      if (videoCapturer == null) {
        reportError("Failed to open camera");
        return;
      }
      mediaStream.addTrack(createVideoTrack(videoCapturer));
    }

    mediaStream.addTrack(createAudioTrack());
    peerConnection.addStream(mediaStream);

    if (peerConnectionParameters.aecDump) {
      try {
        aecDumpFileDescriptor = ParcelFileDescriptor.open(
            new File(Environment.getExternalStorageDirectory().getPath()
                + File.separator
                + "Download/audio.aecdump"),
                ParcelFileDescriptor.MODE_READ_WRITE |
                ParcelFileDescriptor.MODE_CREATE |
                ParcelFileDescriptor.MODE_TRUNCATE);
        factory.startAecDump(aecDumpFileDescriptor.getFd(), -1);
      } catch(IOException e) {
        Log.e(TAG, "Can not open aecdump file", e);
      }
    }

    Log.d(TAG, "Peer connection created.");
  }

  private void closeInternal() {
    if (factory != null && peerConnectionParameters.aecDump) {
      factory.stopAecDump();
    }
    Log.d(TAG, "Closing peer connection.");
    statsTimer.cancel();
    if (peerConnection != null) {
      peerConnection.dispose();
      peerConnection = null;
    }
    Log.d(TAG, "Closing audio source.");
    if (audioSource != null) {
      audioSource.dispose();
      audioSource = null;
    }
    Log.d(TAG, "Stopping capture.");
    if (videoCapturer != null) {
      try {
        videoCapturer.stopCapture();
      } catch(InterruptedException e) {
        throw new RuntimeException(e);
      }
      videoCapturer.dispose();
      videoCapturer = null;
    }
    Log.d(TAG, "Closing video source.");
    if (videoSource != null) {
      videoSource.dispose();
      videoSource = null;
    }
    Log.d(TAG, "Closing peer connection factory.");
    if (factory != null) {
      factory.dispose();
      factory = null;
    }
    options = null;
    Log.d(TAG, "Closing peer connection done.");
    events.onPeerConnectionClosed();
    PeerConnectionFactory.stopInternalTracingCapture();
    PeerConnectionFactory.shutdownInternalTracer();
  }

  public boolean isHDVideo() {
    if (!videoCallEnabled) {
      return false;
    }

    return videoWidth * videoHeight >= 1280 * 720;
  }

  private void getStats() {
    if (peerConnection == null || isError) {
      return;
    }
    boolean success = peerConnection.getStats(new StatsObserver() {
      @Override
      public void onComplete(final StatsReport[] reports) {
        events.onPeerConnectionStatsReady(reports);
      }
    }, null);
    if (!success) {
      Log.e(TAG, "getStats() returns false!");
    }
  }

  public void enableStatsEvents(boolean enable, int periodMs) {
    if (enable) {
      try {
        statsTimer.schedule(new TimerTask() {
          @Override
          public void run() {
            executor.execute(new Runnable() {
              @Override
              public void run() {
                getStats();
              }
            });
          }
        }, 0, periodMs);
      } catch (Exception e) {
        Log.e(TAG, "Can not schedule statistics timer", e);
      }
    } else {
      statsTimer.cancel();
    }
  }

  public void setAudioEnabled(final boolean enable) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        enableAudio = enable;
        if (localAudioTrack != null) {
          localAudioTrack.setEnabled(enableAudio);
        }
      }
    });
  }

  public void setVideoEnabled(final boolean enable) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        renderVideo = enable;
        if (localVideoTrack != null) {
          localVideoTrack.setEnabled(renderVideo);
        }
        if (remoteVideoTrack != null) {
          remoteVideoTrack.setEnabled(renderVideo);
        }
      }
    });
  }

  public void createOffer() {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (peerConnection != null && !isError) {
          Log.d(TAG, "PC Create OFFER");
          isInitiator = true;
          peerConnection.createOffer(sdpObserver, sdpMediaConstraints);
        }
      }
    });
  }

  public void createAnswer() {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (peerConnection != null && !isError) {
          Log.d(TAG, "PC create ANSWER");
          isInitiator = false;
          peerConnection.createAnswer(sdpObserver, sdpMediaConstraints);
        }
      }
    });
  }

  public void addRemoteIceCandidate(final IceCandidate candidate) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (peerConnection != null && !isError) {
          if (queuedRemoteCandidates != null) {
            queuedRemoteCandidates.add(candidate);
          } else {
            peerConnection.addIceCandidate(candidate);
          }
        }
      }
    });
  }

  public void removeRemoteIceCandidates(final IceCandidate[] candidates) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (peerConnection == null || isError) {
          return;
        }
        // Drain the queued remote candidates if there is any so that
        // they are processed in the proper order.
        drainCandidates();
        peerConnection.removeIceCandidates(candidates);
      }
    });
  }

  public void setRemoteDescription(final SessionDescription sdp) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (peerConnection == null || isError) {
          return;
        }
        String sdpDescription = sdp.description;
        if (preferIsac) {
          sdpDescription = preferCodec(sdpDescription, AUDIO_CODEC_ISAC, true);
        }
        if (videoCallEnabled) {
          sdpDescription = preferCodec(sdpDescription, preferredVideoCodec, false);
        }
        if (videoCallEnabled && peerConnectionParameters.videoStartBitrate > 0) {
          sdpDescription = setStartBitrate(VIDEO_CODEC_VP8, true,
              sdpDescription, peerConnectionParameters.videoStartBitrate);
          sdpDescription = setStartBitrate(VIDEO_CODEC_VP9, true,
              sdpDescription, peerConnectionParameters.videoStartBitrate);
          sdpDescription = setStartBitrate(VIDEO_CODEC_H264, true,
              sdpDescription, peerConnectionParameters.videoStartBitrate);
        }
        if (peerConnectionParameters.audioStartBitrate > 0) {
          sdpDescription = setStartBitrate(AUDIO_CODEC_OPUS, false,
              sdpDescription, peerConnectionParameters.audioStartBitrate);
        }
        Log.d(TAG, "Set remote SDP.");
        SessionDescription sdpRemote = new SessionDescription(
            sdp.type, sdpDescription);
        peerConnection.setRemoteDescription(sdpObserver, sdpRemote);
      }
    });
  }

  public void stopVideoSource() {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (videoCapturer != null && !videoCapturerStopped) {
          Log.d(TAG, "Stop video source.");
          try {
            videoCapturer.stopCapture();
          } catch (InterruptedException e) {}
          videoCapturerStopped = true;
        }
      }
    });
  }

  public void startVideoSource() {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (videoCapturer != null && videoCapturerStopped) {
          Log.d(TAG, "Restart video source.");
          videoCapturer.startCapture(videoWidth, videoHeight, videoFps);
          videoCapturerStopped = false;
        }
      }
    });
  }

  private void reportError(final String errorMessage) {
    Log.e(TAG, "Peerconnection error: " + errorMessage);
    executor.execute(new Runnable() {
      @Override
      public void run() {
        if (!isError) {
          events.onPeerConnectionError(errorMessage);
          isError = true;
        }
      }
    });
  }

  private AudioTrack createAudioTrack() {
    audioSource = factory.createAudioSource(audioConstraints);
    localAudioTrack = factory.createAudioTrack(AUDIO_TRACK_ID, audioSource);
    localAudioTrack.setEnabled(enableAudio);
    return localAudioTrack;
  }

  private VideoTrack createVideoTrack(VideoCapturer capturer) {
    videoSource = factory.createVideoSource(capturer);
    capturer.startCapture(videoWidth, videoHeight, videoFps);

    localVideoTrack = factory.createVideoTrack(VIDEO_TRACK_ID, videoSource);
    localVideoTrack.setEnabled(renderVideo);
    localVideoTrack.addRenderer(new VideoRenderer(localRender));
    return localVideoTrack;
  }

  private static String setStartBitrate(String codec, boolean isVideoCodec,
      String sdpDescription, int bitrateKbps) {
    String[] lines = sdpDescription.split("\r\n");
    int rtpmapLineIndex = -1;
    boolean sdpFormatUpdated = false;
    String codecRtpMap = null;
    // Search for codec rtpmap in format
    // a=rtpmap:<payload type> <encoding name>/<clock rate> [/<encoding parameters>]
    String regex = "^a=rtpmap:(\\d+) " + codec + "(/\\d+)+[\r]?$";
    Pattern codecPattern = Pattern.compile(regex);
    for (int i = 0; i < lines.length; i++) {
      Matcher codecMatcher = codecPattern.matcher(lines[i]);
      if (codecMatcher.matches()) {
        codecRtpMap = codecMatcher.group(1);
        rtpmapLineIndex = i;
        break;
      }
    }
    if (codecRtpMap == null) {
      Log.w(TAG, "No rtpmap for " + codec + " codec");
      return sdpDescription;
    }
    Log.d(TAG, "Found " +  codec + " rtpmap " + codecRtpMap
        + " at " + lines[rtpmapLineIndex]);

    // Check if a=fmtp string already exist in remote SDP for this codec and
    // update it with new bitrate parameter.
    regex = "^a=fmtp:" + codecRtpMap + " \\w+=\\d+.*[\r]?$";
    codecPattern = Pattern.compile(regex);
    for (int i = 0; i < lines.length; i++) {
      Matcher codecMatcher = codecPattern.matcher(lines[i]);
      if (codecMatcher.matches()) {
        Log.d(TAG, "Found " +  codec + " " + lines[i]);
        if (isVideoCodec) {
          lines[i] += "; " + VIDEO_CODEC_PARAM_START_BITRATE
              + "=" + bitrateKbps;
        } else {
          lines[i] += "; " + AUDIO_CODEC_PARAM_BITRATE
              + "=" + (bitrateKbps * 1000);
        }
        Log.d(TAG, "Update remote SDP line: " + lines[i]);
        sdpFormatUpdated = true;
        break;
      }
    }

    StringBuilder newSdpDescription = new StringBuilder();
    for (int i = 0; i < lines.length; i++) {
      newSdpDescription.append(lines[i]).append("\r\n");
      // Append new a=fmtp line if no such line exist for a codec.
      if (!sdpFormatUpdated && i == rtpmapLineIndex) {
        String bitrateSet;
        if (isVideoCodec) {
          bitrateSet = "a=fmtp:" + codecRtpMap + " "
              + VIDEO_CODEC_PARAM_START_BITRATE + "=" + bitrateKbps;
        } else {
          bitrateSet = "a=fmtp:" + codecRtpMap + " "
              + AUDIO_CODEC_PARAM_BITRATE + "=" + (bitrateKbps * 1000);
        }
        Log.d(TAG, "Add remote SDP line: " + bitrateSet);
        newSdpDescription.append(bitrateSet).append("\r\n");
      }

    }
    return newSdpDescription.toString();
  }

  private static String preferCodec(
      String sdpDescription, String codec, boolean isAudio) {
    String[] lines = sdpDescription.split("\r\n");
    int mLineIndex = -1;
    String codecRtpMap = null;
    // a=rtpmap:<payload type> <encoding name>/<clock rate> [/<encoding parameters>]
    String regex = "^a=rtpmap:(\\d+) " + codec + "(/\\d+)+[\r]?$";
    Pattern codecPattern = Pattern.compile(regex);
    String mediaDescription = "m=video ";
    if (isAudio) {
      mediaDescription = "m=audio ";
    }
    for (int i = 0; (i < lines.length)
        && (mLineIndex == -1 || codecRtpMap == null); i++) {
      if (lines[i].startsWith(mediaDescription)) {
        mLineIndex = i;
        continue;
      }
      Matcher codecMatcher = codecPattern.matcher(lines[i]);
      if (codecMatcher.matches()) {
        codecRtpMap = codecMatcher.group(1);
      }
    }
    if (mLineIndex == -1) {
      Log.w(TAG, "No " + mediaDescription + " line, so can't prefer " + codec);
      return sdpDescription;
    }
    if (codecRtpMap == null) {
      Log.w(TAG, "No rtpmap for " + codec);
      return sdpDescription;
    }
    Log.d(TAG, "Found " +  codec + " rtpmap " + codecRtpMap + ", prefer at "
        + lines[mLineIndex]);
    String[] origMLineParts = lines[mLineIndex].split(" ");
    if (origMLineParts.length > 3) {
      StringBuilder newMLine = new StringBuilder();
      int origPartIndex = 0;
      // Format is: m=<media> <port> <proto> <fmt> ...
      newMLine.append(origMLineParts[origPartIndex++]).append(" ");
      newMLine.append(origMLineParts[origPartIndex++]).append(" ");
      newMLine.append(origMLineParts[origPartIndex++]).append(" ");
      newMLine.append(codecRtpMap);
      for (; origPartIndex < origMLineParts.length; origPartIndex++) {
        if (!origMLineParts[origPartIndex].equals(codecRtpMap)) {
          newMLine.append(" ").append(origMLineParts[origPartIndex]);
        }
      }
      lines[mLineIndex] = newMLine.toString();
      Log.d(TAG, "Change media description: " + lines[mLineIndex]);
    } else {
      Log.e(TAG, "Wrong SDP media description format: " + lines[mLineIndex]);
    }
    StringBuilder newSdpDescription = new StringBuilder();
    for (String line : lines) {
      newSdpDescription.append(line).append("\r\n");
    }
    return newSdpDescription.toString();
  }

  private void drainCandidates() {
    if (queuedRemoteCandidates != null) {
      Log.d(TAG, "Add " + queuedRemoteCandidates.size() + " remote candidates");
      for (IceCandidate candidate : queuedRemoteCandidates) {
        peerConnection.addIceCandidate(candidate);
      }
      queuedRemoteCandidates = null;
    }
  }

  private void switchCameraInternal() {
    if (!videoCallEnabled || numberOfCameras < 2 || isError || videoCapturer == null) {
      Log.e(TAG, "Failed to switch camera. Video: " + videoCallEnabled + ". Error : "
          + isError + ". Number of cameras: " + numberOfCameras);
      return;  // No video is sent or only one camera is available or error happened.
    }
    Log.d(TAG, "Switch camera");
    videoCapturer.switchCamera(null);
  }

  public void switchCamera() {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        switchCameraInternal();
      }
    });
  }

  public void changeCaptureFormat(final int width, final int height, final int framerate) {
    executor.execute(new Runnable() {
      @Override
      public void run() {
        changeCaptureFormatInternal(width, height, framerate);
      }
    });
  }

  private void changeCaptureFormatInternal(int width, int height, int framerate) {
    if (!videoCallEnabled || isError || videoCapturer == null) {
      Log.e(TAG, "Failed to change capture format. Video: " + videoCallEnabled + ". Error : "
          + isError);
      return;
    }
    Log.d(TAG, "changeCaptureFormat: " + width + "x" + height + "@" + framerate);
    videoCapturer.onOutputFormatRequest(width, height, framerate);
  }

  // Implementation detail: observe ICE & stream changes and react accordingly.
  private class PCObserver implements PeerConnection.Observer {
    @Override
    public void onIceCandidate(final IceCandidate candidate){
      executor.execute(new Runnable() {
        @Override
        public void run() {
          events.onIceCandidate(candidate);
        }
      });
    }

    @Override
    public void onIceCandidatesRemoved(final IceCandidate[] candidates) {
      executor.execute(new Runnable() {
        @Override
        public void run() {
          events.onIceCandidatesRemoved(candidates);
        }
      });
    }

    @Override
    public void onSignalingChange(
        PeerConnection.SignalingState newState) {
      Log.d(TAG, "SignalingState: " + newState);
    }

    @Override
    public void onIceConnectionChange(
        final PeerConnection.IceConnectionState newState) {
      executor.execute(new Runnable() {
        @Override
        public void run() {
          Log.d(TAG, "IceConnectionState: " + newState);
          if (newState == IceConnectionState.CONNECTED) {
            events.onIceConnected();
          } else if (newState == IceConnectionState.DISCONNECTED) {
            events.onIceDisconnected();
          } else if (newState == IceConnectionState.FAILED) {
            reportError("ICE connection failed.");
          }
        }
      });
    }

    @Override
    public void onIceGatheringChange(
      PeerConnection.IceGatheringState newState) {
      Log.d(TAG, "IceGatheringState: " + newState);
    }

    @Override
    public void onIceConnectionReceivingChange(boolean receiving) {
      Log.d(TAG, "IceConnectionReceiving changed to " + receiving);
    }

    @Override
    public void onAddStream(final MediaStream stream){
      executor.execute(new Runnable() {
        @Override
        public void run() {
          if (peerConnection == null || isError) {
            return;
          }
          if (stream.audioTracks.size() > 1 || stream.videoTracks.size() > 1) {
            reportError("Weird-looking stream: " + stream);
            return;
          }
          if (stream.videoTracks.size() == 1) {
            remoteVideoTrack = stream.videoTracks.get(0);
            remoteVideoTrack.setEnabled(renderVideo);
            remoteVideoTrack.addRenderer(new VideoRenderer(remoteRender));
          }
        }
      });
    }

    @Override
    public void onRemoveStream(final MediaStream stream){
      executor.execute(new Runnable() {
        @Override
        public void run() {
          remoteVideoTrack = null;
        }
      });
    }

    @Override
    public void onDataChannel(final DataChannel dc) {
      reportError("AppRTC doesn't use data channels, but got: " + dc.label()
          + " anyway!");
    }

    @Override
    public void onRenegotiationNeeded() {
      // No need to do anything; AppRTC follows a pre-agreed-upon
      // signaling/negotiation protocol.
    }
  }

  // Implementation detail: handle offer creation/signaling and answer setting,
  // as well as adding remote ICE candidates once the answer SDP is set.
  private class SDPObserver implements SdpObserver {
    @Override
    public void onCreateSuccess(final SessionDescription origSdp) {
      if (localSdp != null) {
        reportError("Multiple SDP create.");
        return;
      }
      String sdpDescription = origSdp.description;
      if (preferIsac) {
        sdpDescription = preferCodec(sdpDescription, AUDIO_CODEC_ISAC, true);
      }
      if (videoCallEnabled) {
        sdpDescription = preferCodec(sdpDescription, preferredVideoCodec, false);
      }
      final SessionDescription sdp = new SessionDescription(
          origSdp.type, sdpDescription);
      localSdp = sdp;
      executor.execute(new Runnable() {
        @Override
        public void run() {
          if (peerConnection != null && !isError) {
            Log.d(TAG, "Set local SDP from " + sdp.type);
            peerConnection.setLocalDescription(sdpObserver, sdp);
          }
        }
      });
    }

    @Override
    public void onSetSuccess() {
      executor.execute(new Runnable() {
        @Override
        public void run() {
          if (peerConnection == null || isError) {
            return;
          }
          if (isInitiator) {
            // For offering peer connection we first create offer and set
            // local SDP, then after receiving answer set remote SDP.
            if (peerConnection.getRemoteDescription() == null) {
              // We've just set our local SDP so time to send it.
              Log.d(TAG, "Local SDP set succesfully");
              events.onLocalDescription(localSdp);
            } else {
              // We've just set remote description, so drain remote
              // and send local ICE candidates.
              Log.d(TAG, "Remote SDP set succesfully");
              drainCandidates();
            }
          } else {
            // For answering peer connection we set remote SDP and then
            // create answer and set local SDP.
            if (peerConnection.getLocalDescription() != null) {
              // We've just set our local SDP so time to send it, drain
              // remote and send local ICE candidates.
              Log.d(TAG, "Local SDP set succesfully");
              events.onLocalDescription(localSdp);
              drainCandidates();
            } else {
              // We've just set remote SDP - do nothing for now -
              // answer will be created soon.
              Log.d(TAG, "Remote SDP set succesfully");
            }
          }
        }
      });
    }

    @Override
    public void onCreateFailure(final String error) {
      reportError("createSDP error: " + error);
    }

    @Override
    public void onSetFailure(final String error) {
      reportError("setSDP error: " + error);
    }
  }
}