feat(study): add review streak tracking and home indicator

lib/features/decks/presentation/screens/deck_list_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 import 'package:lapse/core/routing/routes.dart';
+import 'package:lapse/core/theme/app_colors.dart';
 import 'package:lapse/core/theme/spacing.dart';
 import 'package:lapse/core/widgets/app_snack_bar.dart';
 import 'package:lapse/core/widgets/confirm_dialog.dart';
@@ -16,6 +17,7 @@ import 'package:lapse/features/decks/domain/deck_with_counts.dart';
 import 'package:lapse/features/decks/presentation/providers/deck_list_provider.dart';
 import 'package:lapse/features/decks/presentation/widgets/deck_card.dart';
 import 'package:lapse/features/decks/presentation/widgets/empty_deck_state.dart';
+import 'package:lapse/features/study/presentation/providers/review_streak_provider.dart';
 
 class DeckListScreen extends ConsumerWidget {
   const DeckListScreen({super.key});
@@ -34,6 +36,7 @@ class DeckListScreen extends ConsumerWidget {
         ),
         title: const Text('Decks'),
         actions: [
+          const _StreakAppBarAction(),
           IconButton(
             icon: const Icon(Icons.view_list),
             tooltip: 'View all cards',
@@ -65,6 +68,122 @@ class DeckListScreen extends ConsumerWidget {
   }
 }
 
+class _StreakAppBarAction extends ConsumerWidget {
+  const _StreakAppBarAction();
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final streakAsync = ref.watch(reviewStreakProvider);
+
+    return streakAsync.when(
+      data: (streak) {
+        if (streak.currentStreak <= 0) {
+          return const SizedBox.shrink();
+        }
+
+        return Padding(
+          padding: const EdgeInsets.symmetric(vertical: Spacing.sm),
+          child: Container(
+            margin: const EdgeInsets.only(right: Spacing.xs),
+            padding: const EdgeInsets.symmetric(
+              horizontal: Spacing.sm,
+              vertical: Spacing.xs,
+            ),
+            decoration: BoxDecoration(
+              color: AppColors.surfaceElevated,
+              borderRadius: BorderRadius.circular(Spacing.radiusMd),
+              border: Border.all(color: AppColors.outline),
+            ),
+            child: Row(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                const _AnimatedFlameIcon(),
+                const SizedBox(width: Spacing.xs),
+                Text(
+                  '${streak.currentStreak}',
+                  style: Theme.of(context).textTheme.labelLarge?.copyWith(
+                    color: AppColors.textPrimary,
+                    fontWeight: FontWeight.w700,
+                  ),
+                ),
+              ],
+            ),
+          ),
+        );
+      },
+      loading: () => const SizedBox.shrink(),
+      error: (_, _) => const SizedBox.shrink(),
+    );
+  }
+}
+
+class _AnimatedFlameIcon extends StatefulWidget {
+  const _AnimatedFlameIcon();
+
+  @override
+  State<_AnimatedFlameIcon> createState() => _AnimatedFlameIconState();
+}
+
+class _AnimatedFlameIconState extends State<_AnimatedFlameIcon>
+    with SingleTickerProviderStateMixin {
+  late final AnimationController _controller;
+  late final Animation<double> _scale;
+  late final Animation<double> _glow;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = AnimationController(
+      vsync: this,
+      duration: const Duration(milliseconds: 900),
+    )..repeat(reverse: true);
+
+    final curve = CurvedAnimation(parent: _controller, curve: Curves.easeInOut);
+    _scale = Tween<double>(begin: 0.92, end: 1.10).animate(curve);
+    _glow = Tween<double>(begin: 0.15, end: 0.55).animate(curve);
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedBuilder(
+      animation: _controller,
+      builder: (context, child) {
+        return Transform.scale(
+          scale: _scale.value,
+          child: DecoratedBox(
+            decoration: BoxDecoration(
+              shape: BoxShape.circle,
+              boxShadow: [
+                BoxShadow(
+                  color: Color.lerp(
+                    Colors.transparent,
+                    AppColors.warning,
+                    _glow.value,
+                  )!,
+                  blurRadius: 8,
+                  spreadRadius: 0.5,
+                ),
+              ],
+            ),
+            child: child,
+          ),
+        );
+      },
+      child: const Icon(
+        Icons.local_fire_department_rounded,
+        size: 16,
+        color: AppColors.warning,
+      ),
+    );
+  }
+}
+
 class _DeckList extends ConsumerWidget {
   final List<DeckWithCounts> decks;
 
@@ -82,10 +201,7 @@ class _DeckList extends ConsumerWidget {
     }
 
     return ListView.builder(
-      padding: const EdgeInsets.only(
-        top: Spacing.sm,
-        bottom: Spacing.sm + 80,
-      ),
+      padding: const EdgeInsets.only(top: Spacing.sm, bottom: Spacing.sm + 80),
       itemCount: decks.length,
       itemBuilder: (context, index) {
         final item = decks[index];
@@ -135,8 +251,9 @@ class _DeckList extends ConsumerWidget {
         case ContextMenuAction.move:
           final deckRepo = ref.read(deckRepositoryProvider);
           final allDecks = await deckRepo.getAll();
-          final excludeIds =
-              (await deckRepo.getDescendantIds(deck.deckId)).toSet();
+          final excludeIds = (await deckRepo.getDescendantIds(
+            deck.deckId,
+          )).toSet();
 
           if (!context.mounted) return;
           final targetId = await DeckPickerDialog.show(
@@ -164,8 +281,9 @@ class _DeckList extends ConsumerWidget {
             return;
           }
 
-          final deckToMove =
-              deck.copyWith(parentId: Optional.value(newParentId));
+          final deckToMove = deck.copyWith(
+            parentId: Optional.value(newParentId),
+          );
           await deckRepo.update(deckToMove);
           ref.invalidate(deckListProvider);
           ref.read(syncServiceProvider.notifier).schedulePush();
@@ -175,8 +293,7 @@ class _DeckList extends ConsumerWidget {
       }
     } catch (e) {
       if (context.mounted) {
-        AppSnackBar.show(context, 'Action failed: $e',
-);
+        AppSnackBar.show(context, 'Action failed: $e');
       }
     }
   }

lib/features/study/data/review_session_summary_repository.dart

@@ -1,6 +1,7 @@
 import 'package:lapse/core/database/database_helper.dart';
 import 'package:lapse/core/database/database_constants.dart';
 import 'package:lapse/core/domain/sync_status.dart';
+import 'package:lapse/features/study/domain/review_streak.dart';
 import 'package:lapse/features/study/domain/review_session_summary.dart';
 
 class ReviewSessionSummaryRepository {
@@ -115,4 +116,96 @@ class ReviewSessionSummaryRepository {
       [startDate, endDate],
     );
   }
+
+  /// Returns streak stats derived from completed review sessions.
+  ///
+  /// Rules:
+  /// - A day counts only if at least one session that day has total_reviews > 0.
+  /// - Current streak is consecutive days ending at:
+  ///   - today, if completed today
+  ///   - yesterday, if not completed today but yesterday is completed
+  ///   - otherwise 0
+  /// - Longest streak is the max consecutive run across all completed days.
+  Future<ReviewStreak> getStreak({DateTime? asOf}) async {
+    final db = await _dbHelper.database;
+    final rows = await db.rawQuery('''
+      SELECT DISTINCT ${DatabaseConstants.colDate} AS ${DatabaseConstants.colDate}
+      FROM ${DatabaseConstants.tableReviewSessionSummary}
+      WHERE ${DatabaseConstants.colTotalReviews} > 0
+      ORDER BY ${DatabaseConstants.colDate} ASC
+      ''');
+
+    if (rows.isEmpty) return const ReviewStreak.empty();
+
+    final days =
+        rows
+            .map(
+              (row) => _parseDateOnly(row[DatabaseConstants.colDate] as String),
+            )
+            .toList()
+          ..sort();
+
+    final longest = _computeLongest(days);
+    final today = _dateOnly(asOf ?? DateTime.now());
+    final yesterday = today.subtract(const Duration(days: 1));
+    final daySet = days.toSet();
+
+    int current = 0;
+    if (daySet.contains(today)) {
+      current = _countBackwardsFrom(daySet, today);
+    } else if (daySet.contains(yesterday)) {
+      current = _countBackwardsFrom(daySet, yesterday);
+    }
+
+    final lastCompleted = _formatDateOnly(days.last);
+
+    return ReviewStreak(
+      currentStreak: current,
+      longestStreak: longest,
+      lastCompletedDate: lastCompleted,
+    );
+  }
+
+  static DateTime _dateOnly(DateTime d) => DateTime(d.year, d.month, d.day);
+
+  static DateTime _parseDateOnly(String date) {
+    final parsed = DateTime.parse(date);
+    return _dateOnly(parsed);
+  }
+
+  static String _formatDateOnly(DateTime date) {
+    return '${date.year.toString().padLeft(4, '0')}-'
+        '${date.month.toString().padLeft(2, '0')}-'
+        '${date.day.toString().padLeft(2, '0')}';
+  }
+
+  static int _computeLongest(List<DateTime> daysSortedAsc) {
+    if (daysSortedAsc.isEmpty) return 0;
+    var longest = 1;
+    var run = 1;
+
+    for (var i = 1; i < daysSortedAsc.length; i++) {
+      final prev = daysSortedAsc[i - 1];
+      final curr = daysSortedAsc[i];
+      final delta = curr.difference(prev).inDays;
+
+      if (delta == 1) {
+        run++;
+        if (run > longest) longest = run;
+      } else if (delta > 1) {
+        run = 1;
+      }
+    }
+    return longest;
+  }
+
+  static int _countBackwardsFrom(Set<DateTime> days, DateTime endDay) {
+    var count = 0;
+    var cursor = endDay;
+    while (days.contains(cursor)) {
+      count++;
+      cursor = cursor.subtract(const Duration(days: 1));
+    }
+    return count;
+  }
 }

lib/features/study/data/review_session_summary_repository_provider.dart

@@ -0,0 +1,7 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:lapse/features/study/data/review_session_summary_repository.dart';
+
+final reviewSessionSummaryRepositoryProvider =
+    Provider<ReviewSessionSummaryRepository>((ref) {
+      return ReviewSessionSummaryRepository();
+    });

lib/features/study/domain/review_session_summary.dart

@@ -60,8 +60,9 @@ class ReviewSessionSummary extends Equatable {
     required int reviewCount,
     String userId = '',
   }) {
+    // Streaks are completion-based: count the day the session finishes.
     final date =
-        '${startedAt.year}-${startedAt.month.toString().padLeft(2, '0')}-${startedAt.day.toString().padLeft(2, '0')}';
+        '${endedAt.year}-${endedAt.month.toString().padLeft(2, '0')}-${endedAt.day.toString().padLeft(2, '0')}';
     return ReviewSessionSummary(
       userId: userId,
       date: date,

lib/features/study/domain/review_streak.dart

@@ -0,0 +1,21 @@
+import 'package:equatable/equatable.dart';
+
+class ReviewStreak extends Equatable {
+  final int currentStreak;
+  final int longestStreak;
+  final String? lastCompletedDate; // YYYY-MM-DD
+
+  const ReviewStreak({
+    required this.currentStreak,
+    required this.longestStreak,
+    required this.lastCompletedDate,
+  });
+
+  const ReviewStreak.empty()
+    : currentStreak = 0,
+      longestStreak = 0,
+      lastCompletedDate = null;
+
+  @override
+  List<Object?> get props => [currentStreak, longestStreak, lastCompletedDate];
+}

lib/features/study/presentation/providers/review_streak_provider.dart

@@ -0,0 +1,8 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:lapse/features/study/data/review_session_summary_repository_provider.dart';
+import 'package:lapse/features/study/domain/review_streak.dart';
+
+final reviewStreakProvider = FutureProvider<ReviewStreak>((ref) async {
+  final repo = ref.watch(reviewSessionSummaryRepositoryProvider);
+  return repo.getStreak();
+});