checkpoint - participant & tracks initial stubs

lib/src/participant/local_participant.dart

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+import 'participant.dart';
+
+class LocalParticipant extends Participant {
+
+}

lib/src/participant/participant.dart

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+import '../proto/livekit_models.pb.dart';
+import '../track/track_publication.dart';
+
+mixin ParticipantDelegate {
+  void onMetadataChanged(Participant participant);
+  void onSpeakingChanged(Participant participant, bool speaking);
+}
+
+class Participant {
+  Map<String, TrackPublication> audioTracks = {};
+  Map<String, TrackPublication> videoTracks = {};
+
+  /// map of track sid => published track
+  Map<String, TrackPublication> tracks = {};
+
+  /// audio level between 0-1, 1 being the loudest
+  double audioLevel = 0;
+
+  /// server assigned unique id
+  String sid;
+
+  /// user-assigned identity
+  String identity;
+
+  /// client-assigned metadata, opaque to livekit
+  String? metadata;
+
+  /// when the participant had last spoken
+  DateTime? lastSpokeAt;
+
+  Participant(this.sid, this.identity);
+
+  ParticipantDelegate? _roomDelegate;
+  ParticipantDelegate? delegate;
+
+  ParticipantInfo? _participantInfo;
+  bool _isSpeaking = false;
+
+  DateTime get joinedAt {
+    var pi = _participantInfo;
+    if (pi != null) {
+      return DateTime.fromMillisecondsSinceEpoch((pi.joinedAt as int) * 1000,
+          isUtc: true);
+    }
+    return DateTime.now();
+  }
+
+  /// if participant is currently speaking
+  bool get isSpeaking => _isSpeaking;
+
+  set isSpeaking(bool speaking) {
+    if (_isSpeaking != speaking) {
+      return;
+    }
+    _isSpeaking = speaking;
+    if (speaking) {
+      lastSpokeAt = DateTime.now();
+    }
+    delegate?.onSpeakingChanged(this, speaking);
+    _roomDelegate?.onSpeakingChanged(this, speaking);
+  }
+
+  _setMetadata(String md) {
+    var changed = this._participantInfo?.metadata != md;
+    this.metadata = md;
+    if (changed) {
+      delegate?.onMetadataChanged(this);
+      _roomDelegate?.onMetadataChanged(this);
+    }
+  }
+
+  _updateInfo(ParticipantInfo info) {
+    this.identity = info.identity;
+    this.sid = info.sid;
+    if (info.metadata.isNotEmpty) {
+      _setMetadata(info.metadata);
+    }
+    this._participantInfo = info;
+  }
+
+  _addTrackPublication(TrackPublication pub) {
+    pub.track?.sid = pub.sid;
+    tracks[pub.sid] = pub;
+    switch (pub.kind) {
+      case TrackType.AUDIO:
+        audioTracks[pub.sid] = pub;
+        break;
+      case TrackType.VIDEO:
+        videoTracks[pub.sid] = pub;
+        break;
+      default:
+        // nothing
+    }
+  }
+}

lib/src/participant/remote_participant.dart

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+import 'participant.dart';
+
+class RemoteParticipant extends Participant {}