major refactor

lib/services/data_service/data_service_trips.dart

@@ -0,0 +1,87 @@
+part of 'data_service.dart';
+
+extension DataServiceTrips on DataService {
+  Future<void> fetchTripDetails() async {
+    _isTripDetailsLoading = true;
+    try {
+      final json = await api.get('/trips/legs-and-stats');
+      if (json is List) {
+        final tripMap = json.map((e) => TripDetail.fromJson(e)).toList();
+        _tripDetails = [...tripMap]..sort((a, b) => b.id.compareTo(a.id));
+      } else {
+        _tripDetails = [];
+      }
+    } catch (e) {
+      debugPrint('Failed to fetch trip_map: $e');
+      _tripDetails = [];
+    } finally {
+      _isTripDetailsLoading = false;
+      _notifyAsync();
+    }
+  }
+
+  Future<List<TripLocoStat>> fetchTripLocoStats(int tripId) async {
+    try {
+      final json = await api.get('/trips/stats/$tripId');
+      return _parseTripLocoStats(json);
+    } catch (e) {
+      debugPrint('Failed to fetch trip loco stats: $e');
+      return [];
+    }
+  }
+
+  List<TripLocoStat> _parseTripLocoStats(dynamic json) {
+    List<dynamic>? list;
+    if (json is List) {
+      list = json.expand((e) => e is List ? e : [e]).toList();
+    } else if (json is Map) {
+      for (final key in ['locos', 'stats', 'data', 'trip_locos']) {
+        final candidate = json[key];
+        if (candidate is List) {
+          list = candidate.expand((e) => e is List ? e : [e]).toList();
+          break;
+        }
+      }
+    }
+    if (list == null) return [];
+    return list
+        .whereType<Map<String, dynamic>>()
+        .map((e) => TripLocoStat.fromJson(e))
+        .toList();
+  }
+
+  Future<void> fetchTrips() async {
+    try {
+      final json = await api.get('/trips/mileage');
+      Iterable<dynamic>? raw;
+      if (json is List) {
+        raw = json;
+      } else if (json is Map) {
+        for (final key in ['trips', 'trip_data', 'data']) {
+          final value = json[key];
+          if (value is List) {
+            raw = value;
+            break;
+          }
+        }
+      }
+      if (raw != null) {
+        final tripMap = raw
+            .whereType<Map<String, dynamic>>()
+            .map((e) => TripSummary.fromJson(e))
+            .toList();
+
+        _tripList = [...tripMap]..sort((a, b) => b.tripId.compareTo(a.tripId));
+      } else {
+        debugPrint('Unexpected trip list response: $json');
+        _tripList = [];
+      }
+    } catch (e) {
+      debugPrint('Failed to fetch trip list: $e');
+      _tripList = [];
+    } finally {
+      _notifyAsync();
+    }
+  }
+}
+