fix: continue replay when historical rts data is missing

lib/core/network/api_client.dart

@@ -188,9 +188,15 @@ class ApiClient {
         _health?.success(tier, hosts[i], path);
         return response;
       } on DioException catch (e) {
-        _health?.failure(tier, hosts[i], path);
+        final retryable = _isRetryable(e);
+        // Only what the *host* is answerable for, which is what [_isRetryable]
+        // already separates. A 404 says the route or the resource is wrong, not
+        // that the region is sick: replaying an event older than the RTS
+        // retention 404s once a second, and charging those to the host parked
+        // `api-1` at `down` on the status screen for the rest of the session.
+        if (retryable) _health?.failure(tier, hosts[i], path);
         final isLastHost = i == hosts.length - 1;
-        if (isLastHost || !_isRetryable(e)) rethrow;
+        if (isLastHost || !retryable) rethrow;
         Log.warning(
           'ApiClient: ${tier.name} ${hosts[i]} failed (${_describe(e)}); '
           'failing over to ${hosts[i + 1]}',
@@ -239,9 +245,12 @@ class ApiClient {
         _health?.success(tier, hosts[i], path);
         return StreamedResponse(response.data!.stream, cancelToken.cancel);
       } on DioException catch (e) {
-        _health?.failure(tier, hosts[i], path);
+        // Same split as [request]: a host is only charged for what it is
+        // answerable for.
+        final retryable = _isRetryable(e);
+        if (retryable) _health?.failure(tier, hosts[i], path);
         final isLastHost = i == hosts.length - 1;
-        if (isLastHost || !_isRetryable(e)) rethrow;
+        if (isLastHost || !retryable) rethrow;
         Log.warning(
           'ApiClient: ${tier.name} stream ${hosts[i]} failed (${_describe(e)}); '
           'failing over to ${hosts[i + 1]}',

lib/core/network/api_exception.dart

@@ -10,15 +10,28 @@ import 'package:dpip/core/logging/log.dart';
 /// every repository method is a one-liner and none can accidentally forget the
 /// `try` or return `Ok` on failure — which for a safety feed would turn a dead
 /// source into a false all-clear.
-Future<Result<T>> guardResult<T>(Future<T> Function() body) async {
+///
+/// [shouldLog] is the narrow exception to the logging below, for a caller whose
+/// failure is an expected shape rather than a fault — a replay polling past the
+/// end of a feed's retention, say, where the 404 arrives once a second for the
+/// whole session. It drops the log line only; the [Err] is returned either way,
+/// so no caller can mistake a suppressed log for a success.
+Future<Result<T>> guardResult<T>(
+  Future<T> Function() body, {
+  bool Function(Failure failure)? shouldLog,
+}) async {
   try {
     return Ok(await body());
   } catch (error, stackTrace) {
     // Silent failures are the worst kind: the UI shows its error state and
     // nothing else records WHY. One line per failure, here at the single
-    // choke point every repository passes through.
-    Log.handle(error, stackTrace, 'repository fetch/decode');
-    return Err(mapException(error));
+    // choke point every repository passes through — unless the caller has
+    // said this particular failure is expected (see [shouldLog]).
+    final failure = mapException(error);
+    if (shouldLog?.call(failure) ?? true) {
+      Log.handle(error, stackTrace, 'repository fetch/decode');
+    }
+    return Err(failure);
   }
 }
 

lib/core/realtime/realtime_channel.dart

@@ -224,6 +224,10 @@ class RealtimeChannel<T> implements RealtimeChannelBase {
           final status = _classify();
           final changed =
               status != _current.status ||
+              // A recovery is always worth telling: the state being replaced
+              // carries the reason the feed was empty, which the replay page
+              // shows even while the status word itself hasn't moved.
+              _current.lastFailure != null ||
               !_source.sameData(value, _current.data);
           _current = RealtimeState<T>(
             status: status,
@@ -234,17 +238,38 @@ class RealtimeChannel<T> implements RealtimeChannelBase {
           );
           if (changed) _publish();
         case Err(:final failure):
+          // "There is no data for that instant" is an answer, not a fault. It
+          // is still *recorded* — a replay page reads it to say "重播中" rather
+          // than "連線中斷" — but it is not counted and not logged: the poll
+          // runs at 1 Hz, so an old replay would otherwise file one crash
+          // report a second for its whole length.
+          //
+          // Freshness is untouched either way. The tick that preceded this
+          // fetch already aged the status (see [_onTick]), so an ignored
+          // failure still reaches stale and then offline on schedule — nothing
+          // here can hold a feed that is receiving nothing at `live`.
+          final ignorable = _source.isIgnorableFailure(failure);
           final status = _classify();
-          final changed = status != _current.status;
+          // A change of failure *kind* is published even when the status word
+          // hasn't moved, because that is what the replay page switches on.
+          // Repeats of one kind are not: at 1 Hz that would be a rebuild a
+          // second for the length of an outage.
+          final changed =
+              status != _current.status ||
+              _current.lastFailure.runtimeType != failure.runtimeType;
           _current = _current.copyWith(
             status: status,
             lastFailure: failure,
-            consecutiveFailures: _current.consecutiveFailures + 1,
-          );
-          Log.warning(
-            '[$_label] poll failed '
-            '(${_current.consecutiveFailures}×): ${failure.message}',
+            consecutiveFailures: ignorable
+                ? _current.consecutiveFailures
+                : _current.consecutiveFailures + 1,
           );
+          if (!ignorable) {
+            Log.warning(
+              '[$_label] poll failed '
+              '(${_current.consecutiveFailures}×): ${failure.message}',
+            );
+          }
           if (changed) _publish();
       }
     } catch (error, stackTrace) {

lib/core/realtime/realtime_source.dart

@@ -1,3 +1,4 @@
+import 'package:dpip/core/error/failure.dart';
 import 'package:dpip/core/error/result.dart';
 
 /// The transport + freshness-reference seam a [RealtimeChannel] polls.
@@ -23,6 +24,22 @@ abstract class RealtimeSource<T> {
   /// whose default `==` is identity (e.g. `List`).
   bool sameData(T? a, T? b) => identical(a, b) || a == b;
 
+  /// Whether a fetch failure means there is simply no data for the requested
+  /// point in time, rather than a fault worth counting. The channel still
+  /// records it as `lastFailure` — that is what a replay page reads to say the
+  /// instant has no snapshot instead of calling itself disconnected — but does
+  /// not count it toward `consecutiveFailures` and does not log it.
+  ///
+  /// **A noise switch, not a liveness one.** Freshness is unaffected either
+  /// way: the channel ages its status from elapsed time alone, so a source that
+  /// ignores every failure still goes stale and then offline on schedule and
+  /// nothing here can present a dead feed as current.
+  ///
+  /// Only a replay source has cause to override it — it polls a fixed instant
+  /// in the past, where "this far back is no longer retained" is an answer, not
+  /// a fault. For a live feed every failure is a real one; leave this alone.
+  bool isIgnorableFailure(Failure failure) => false;
+
   /// Drops any transport the source is holding open while the app is in the
   /// background, where nothing is watching the feed.
   ///

lib/features/earthquake/data/rts_replay_source.dart

@@ -1,3 +1,4 @@
+import 'package:dpip/core/error/failure.dart';
 import 'package:dpip/core/error/result.dart';
 import 'package:dpip/core/network/api_exception.dart';
 import 'package:dpip/core/realtime/realtime_source.dart';
@@ -25,7 +26,16 @@ class RtsReplaySource extends RealtimeSource<Rts> {
     final seconds = clock.now().millisecondsSinceEpoch ~/ 1000;
     final json = await _api.getRtsAt(seconds);
     return Rts.fromJson(json as Map<String, dynamic>);
-  });
+  }, shouldLog: (failure) => !isIgnorableFailure(failure));
+
+  /// A 404 is the ordinary shape of an old replay, not a fault: RTS snapshots
+  /// are retained for far less time than the EEW history, so an event old
+  /// enough (0403, say) still has alerts to replay and no shaking left to draw.
+  /// Counted as a failure it would be one crash report and one log line **per
+  /// second** for the whole session — the poll runs at 1 Hz, which never trips
+  /// `Log`'s repeat suppression (8 within 5s).
+  @override
+  bool isIgnorableFailure(Failure failure) => failure is NotFoundFailure;
 
   /// Null: freshness is "did the last poll succeed", not payload age — the
   /// payload's own [Rts.time] is *intentionally* historical, so keying off it

lib/features/earthquake/presentation/pages/report_replay_page.dart

@@ -1342,12 +1342,18 @@ class _ReplayStatusBar extends StatelessWidget {
     final taipeiTime = AppTime.taipei(clock.now());
     final timeText = _clockFormat.format(taipeiTime);
 
-    final (Color dot, String? statusWord) = switch (rts.status) {
-      RealtimeStatus.live => (Colors.green, null),
-      RealtimeStatus.stale => (Colors.amber, l10n.feedStale),
-      RealtimeStatus.offline => (Colors.red, l10n.feedOffline),
-      RealtimeStatus.connecting => (Colors.grey, l10n.feedConnecting),
-    };
+    // RTS snapshots age out of the server long before the EEW history does, so
+    // an old enough event replays as alerts over a map with no shaking on it.
+    // That feed is not broken and saying "連線中斷" reads as a broken app —
+    // the replay is running, there is just nothing recorded that far back.
+    final (Color dot, String? statusWord) = rts.isMissingHistory
+        ? (Colors.orange, l10n.feedReplaying)
+        : switch (rts.status) {
+            RealtimeStatus.live => (Colors.green, null),
+            RealtimeStatus.stale => (Colors.amber, l10n.feedStale),
+            RealtimeStatus.offline => (Colors.red, l10n.feedOffline),
+            RealtimeStatus.connecting => (Colors.grey, l10n.feedConnecting),
+          };
 
     final alertCount = eew.alerts.length;
     final hasActiveEew = alertCount > 0;

lib/features/earthquake/presentation/rts_realtime_controller.dart

@@ -1,3 +1,4 @@
+import 'package:dpip/core/error/failure.dart';
 import 'package:dpip/core/realtime/realtime_notifier.dart';
 import 'package:dpip/core/realtime/realtime_state.dart';
 import 'package:dpip/features/earthquake/domain/rts.dart';
@@ -29,4 +30,12 @@ class RtsRealtimeController extends RealtimeNotifier<Rts> {
 
   /// Whether the feed has aged past the freshness threshold.
   bool get isStale => status == RealtimeStatus.stale;
+
+  /// Whether the last poll found no snapshot for the instant it asked for.
+  ///
+  /// Only a replay reaches this: RTS snapshots are retained for far less time
+  /// than the EEW history, so an old enough event still has alerts to replay
+  /// and no shaking left to draw. The feed is not broken, so a UI must not call
+  /// it disconnected — there is simply nothing recorded that far back.
+  bool get isMissingHistory => state.lastFailure is NotFoundFailure;
 }

lib/l10n/app_en.arb

@@ -831,6 +831,7 @@
   },
   "moreSectionLinks": "Links",
   "feedOffline": "Connection lost",
+  "feedReplaying": "Replaying",
   "mapLayerStyleBd": "Dvorak BD",
   "@mapLayerSatelliteB09": {
     "description": "Himawari mid-level water-vapour channel (B09, 6.9 µm) layer name"
@@ -1136,6 +1137,9 @@
   "@feedOffline": {
     "description": "Banner/headline when a realtime feed has gone offline"
   },
+  "@feedReplaying": {
+    "description": "Status word on the replay page when the replayed instant is older than the RTS retention window: the replay is running, the server just has no shaking snapshot that far back. Never 'offline' — the feed is not broken"
+  },
   "reportFilterIntensityInfoModernTitle": "Current (from 2020)",
   "@mapAppGoogleMaps": {
     "description": "External map app choice: Google Maps"

lib/l10n/app_fil.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "Kahapon",
   "moreSectionLinks": "Mga Link",
   "feedOffline": "Nawala ang koneksyon",
+  "feedReplaying": "Nire-replay",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "Display",
   "rainInterval3d": "3 araw",

lib/l10n/app_id.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "Kemarin",
   "moreSectionLinks": "Tautan",
   "feedOffline": "Koneksi terputus",
+  "feedReplaying": "Memutar ulang",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "Tampilan",
   "rainInterval3d": "3 hr",

lib/l10n/app_ja.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "昨日",
   "moreSectionLinks": "関連リンク",
   "feedOffline": "接続が切断されました",
+  "feedReplaying": "再生中",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "表示",
   "rainInterval3d": "3日",

lib/l10n/app_ko.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "어제",
   "moreSectionLinks": "링크",
   "feedOffline": "연결이 끊어졌습니다",
+  "feedReplaying": "재생 중",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "표시",
   "rainInterval3d": "3일",

lib/l10n/app_th.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "เมื่อวาน",
   "moreSectionLinks": "ลิงก์ที่เกี่ยวข้อง",
   "feedOffline": "การเชื่อมต่อขาดหาย",
+  "feedReplaying": "กำลังเล่นซ้ำ",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "การแสดงผล",
   "rainInterval3d": "3 วัน",

lib/l10n/app_vi.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "Hôm qua",
   "moreSectionLinks": "Liên kết",
   "feedOffline": "Mất kết nối",
+  "feedReplaying": "Đang phát lại",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "Hiển thị",
   "rainInterval3d": "3 ngày",

lib/l10n/app_yue.arb

@@ -286,6 +286,7 @@
   "reportListYesterday": "昨天",
   "moreSectionLinks": "相關連結",
   "feedOffline": "連接中斷",
+  "feedReplaying": "重播緊",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "顯示",
   "rainInterval3d": "3 日",

lib/l10n/app_zh.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "昨天",
   "moreSectionLinks": "相關連結",
   "feedOffline": "連線中斷",
+  "feedReplaying": "重播中",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "顯示",
   "rainInterval3d": "3 日",

lib/l10n/app_zh_Hans.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "昨天",
   "moreSectionLinks": "相关链接",
   "feedOffline": "连接中断",
+  "feedReplaying": "重播中",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "显示",
   "rainInterval3d": "3 日",

lib/l10n/app_zh_Hant_HK.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "昨天",
   "moreSectionLinks": "相關連結",
   "feedOffline": "連接中斷",
+  "feedReplaying": "重播中",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "顯示",
   "rainInterval3d": "3 日",

lib/l10n/app_zh_TW.arb

@@ -284,6 +284,7 @@
   "reportListYesterday": "昨天",
   "moreSectionLinks": "相關連結",
   "feedOffline": "連線中斷",
+  "feedReplaying": "重播中",
   "mapLayerStyleBd": "Dvorak BD",
   "moreSectionDisplay": "顯示",
   "rainInterval3d": "3 日",

lib/l10n/gen/app_localizations.dart

@@ -1265,6 +1265,12 @@ abstract class AppLocalizations {
   /// **'Connection lost'**
   String get feedOffline;
 
+  /// Status word on the replay page when the replayed instant is older than the RTS retention window: the replay is running, the server just has no shaking snapshot that far back. Never 'offline' — the feed is not broken
+  ///
+  /// In en, this message translates to:
+  /// **'Replaying'**
+  String get feedReplaying;
+
   /// Colour-style option: Dvorak BD curve stepped grayscale
   ///
   /// In en, this message translates to:

lib/l10n/gen/app_localizations_en.dart

@@ -631,6 +631,9 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get feedOffline => 'Connection lost';
 
+  @override
+  String get feedReplaying => 'Replaying';
+
   @override
   String get mapLayerStyleBd => 'Dvorak BD';
 

lib/l10n/gen/app_localizations_fil.dart

@@ -634,6 +634,9 @@ class AppLocalizationsFil extends AppLocalizations {
   @override
   String get feedOffline => 'Nawala ang koneksyon';
 
+  @override
+  String get feedReplaying => 'Nire-replay';
+
   @override
   String get mapLayerStyleBd => 'Dvorak BD';
 

lib/l10n/gen/app_localizations_id.dart

@@ -632,6 +632,9 @@ class AppLocalizationsId extends AppLocalizations {
   @override
   String get feedOffline => 'Koneksi terputus';
 
+  @override
+  String get feedReplaying => 'Memutar ulang';
+
   @override
   String get mapLayerStyleBd => 'Dvorak BD';
 

lib/l10n/gen/app_localizations_ja.dart

@@ -623,6 +623,9 @@ class AppLocalizationsJa extends AppLocalizations {
   @override
   String get feedOffline => '接続が切断されました';
 
+  @override
+  String get feedReplaying => '再生中';
+
   @override
   String get mapLayerStyleBd => 'Dvorak BD';
 

lib/l10n/gen/app_localizations_ko.dart

@@ -622,6 +622,9 @@ class AppLocalizationsKo extends AppLocalizations {
   @override
   String get feedOffline => '연결이 끊어졌습니다';
 
+  @override
+  String get feedReplaying => '재생 중';
+
   @override
   String get mapLayerStyleBd => 'Dvorak BD';
 

lib/l10n/gen/app_localizations_th.dart

@@ -629,6 +629,9 @@ class AppLocalizationsTh extends AppLocalizations {
   @override
   String get feedOffline => 'การเชื่อมต่อขาดหาย';
 
+  @override
+  String get feedReplaying => 'กำลังเล่นซ้ำ';
+
   @override
   String get mapLayerStyleBd => 'Dvorak BD';