feat(ground-suite): redesign observability console

ground-suite/lib/features/observability/presentation/observability_controller.dart

@@ -20,6 +20,7 @@ final observabilityControllerProvider =
 
 class ObservabilityController extends Notifier<ObservabilityState> {
   static const _criticalAnnouncementWindow = Duration(seconds: 2);
+  static const _timelineCapacity = 500;
 
   StreamSubscription<VehicleDataUpdate>? _subscription;
   DateTime? _lastCriticalAnnouncementAt;
@@ -75,10 +76,22 @@ class ObservabilityController extends Notifier<ObservabilityState> {
 
   void _record(ObservedEvent event) {
     final announcement = _announcementFor(event);
+    final retention = _isTimelineEvent(event)
+        ? _retainTimelineEvent(state.events, event)
+        : _TimelineRetention(state.events);
+    final heartbeat = event is HeartbeatEvent ? event : state.lastHeartbeat;
+    final observedStreams = switch (event) {
+      TelemetryEvent(:final kind) => {...state.observedTelemetryKinds, kind},
+      _ => state.observedTelemetryKinds,
+    };
     state = state.copyWith(
       status: ObservationStatus.receiving,
       lastFrameAt: event.receivedAt,
-      events: [...state.events, event],
+      events: retention.events,
+      lastHeartbeat: heartbeat,
+      observedTelemetryKinds: Set.unmodifiable(observedStreams),
+      localTimelineEvictionCount:
+          state.localTimelineEvictionCount + retention.evictionCount,
       accessibilityAnnouncement: announcement.message,
       replaceAccessibilityAnnouncement: true,
       coalescedAlertCount:
@@ -110,6 +123,45 @@ class ObservabilityController extends Notifier<ObservabilityState> {
   void _cancelSubscription() {
     _subscription?.cancel();
   }
+
+  _TimelineRetention _retainTimelineEvent(
+    List<ObservedEvent> current,
+    ObservedEvent incoming,
+  ) {
+    if (current.length < _timelineCapacity) {
+      return _TimelineRetention([...current, incoming]);
+    }
+
+    final retained = List<ObservedEvent>.of(current);
+    final optionalIndex = retained.indexWhere((event) => !_isCritical(event));
+    if (optionalIndex >= 0) {
+      retained.removeAt(optionalIndex);
+      retained.add(incoming);
+      return _TimelineRetention(retained, evictionCount: 1);
+    }
+
+    if (_isCritical(incoming)) {
+      retained.removeAt(0);
+      retained.add(incoming);
+      return _TimelineRetention(retained, evictionCount: 1);
+    }
+
+    return _TimelineRetention(retained, evictionCount: 1);
+  }
+}
+
+bool _isCritical(ObservedEvent event) =>
+    event is ErrorEvent || event is ShutdownEvent;
+
+bool _isTimelineEvent(ObservedEvent event) =>
+    event is LogEvent || _isCritical(event);
+
+class _TimelineRetention {
+  _TimelineRetention(Iterable<ObservedEvent> events, {this.evictionCount = 0})
+    : events = List.unmodifiable(events);
+
+  final List<ObservedEvent> events;
+  final int evictionCount;
 }
 
 enum ObservationStatus {
@@ -129,9 +181,12 @@ class ObservabilityState {
     required this.isReplay,
     required this.status,
     required this.events,
+    required this.lastHeartbeat,
+    required this.observedTelemetryKinds,
     required this.parserDropCount,
     required this.semanticDropCount,
     required this.coalescedAlertCount,
+    required this.localTimelineEvictionCount,
     this.lastFrameAt,
     this.accessibilityAnnouncement,
   });
@@ -142,9 +197,12 @@ class ObservabilityState {
       isReplay: source.isReplay,
       status: ObservationStatus.starting,
       events: const [],
+      lastHeartbeat: null,
+      observedTelemetryKinds: const {},
       parserDropCount: 0,
       semanticDropCount: 0,
       coalescedAlertCount: 0,
+      localTimelineEvictionCount: 0,
     );
   }
 
@@ -152,32 +210,24 @@ class ObservabilityState {
   final bool isReplay;
   final ObservationStatus status;
   final List<ObservedEvent> events;
+  final HeartbeatEvent? lastHeartbeat;
+  final Set<TelemetryKind> observedTelemetryKinds;
   final int parserDropCount;
   final int semanticDropCount;
   final int coalescedAlertCount;
+  final int localTimelineEvictionCount;
   final DateTime? lastFrameAt;
   final String? accessibilityAnnouncement;
 
-  HeartbeatEvent? get lastHeartbeat {
-    for (final event in events.reversed) {
-      if (event case HeartbeatEvent()) {
-        return event;
-      }
-    }
-    return null;
-  }
-
-  Set<TelemetryKind> get observedTelemetryKinds => {
-    for (final event in events)
-      if (event case TelemetryEvent(:final kind)) kind,
-  };
-
   ObservabilityState copyWith({
     ObservationStatus? status,
     List<ObservedEvent>? events,
+    HeartbeatEvent? lastHeartbeat,
+    Set<TelemetryKind>? observedTelemetryKinds,
     int? parserDropCount,
     int? semanticDropCount,
     int? coalescedAlertCount,
+    int? localTimelineEvictionCount,
     DateTime? lastFrameAt,
     String? accessibilityAnnouncement,
     bool replaceAccessibilityAnnouncement = false,
@@ -187,9 +237,14 @@ class ObservabilityState {
       isReplay: isReplay,
       status: status ?? this.status,
       events: events ?? this.events,
+      lastHeartbeat: lastHeartbeat ?? this.lastHeartbeat,
+      observedTelemetryKinds:
+          observedTelemetryKinds ?? this.observedTelemetryKinds,
       parserDropCount: parserDropCount ?? this.parserDropCount,
       semanticDropCount: semanticDropCount ?? this.semanticDropCount,
       coalescedAlertCount: coalescedAlertCount ?? this.coalescedAlertCount,
+      localTimelineEvictionCount:
+          localTimelineEvictionCount ?? this.localTimelineEvictionCount,
       lastFrameAt: lastFrameAt ?? this.lastFrameAt,
       accessibilityAnnouncement: replaceAccessibilityAnnouncement
           ? accessibilityAnnouncement