Daily streak: track consecutive claim days

lib/claim.dart

@@ -6,6 +6,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter_svg/flutter_svg.dart';
 import 'package:geolocator/geolocator.dart';
 import 'package:postbox_game/app_preferences.dart';
+import 'package:postbox_game/streak_service.dart';
 import 'package:postbox_game/james_controller.dart';
 import 'package:postbox_game/theme.dart';
 
@@ -77,6 +78,7 @@ class ClaimState extends State<Claim> with SingleTickerProviderStateMixin {
       FirebaseFunctions.instance.httpsCallable('nearbyPostboxes');
   final HttpsCallable _claimCallable =
       FirebaseFunctions.instance.httpsCallable('startScoring');
+  final StreakService _streakService = StreakService();
 
   Future<Position> _getPosition() async {
     bool serviceEnabled = await Geolocator.isLocationServiceEnabled();
@@ -147,6 +149,11 @@ class ClaimState extends State<Claim> with SingleTickerProviderStateMixin {
         currentStage = ClaimStage.claimed;
       });
       _successController.forward(from: 0);
+      try {
+        await _streakService.updateStreakAfterClaim();
+      } catch (e) {
+        debugPrint('Streak update failed (non-fatal): $e');
+      }
       if (mounted) {
         final msg = _pointsEarned >= 50
             ? "Oh ho — a rare one! That's a find. Well done."
@@ -291,6 +298,39 @@ class ClaimState extends State<Claim> with SingleTickerProviderStateMixin {
         child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
           children: [
+            StreamBuilder<int?>(
+              stream: _streakService.streakStream(),
+              builder: (context, snapshot) {
+                final streak = snapshot.data;
+                if (streak == null || streak == 0) return const SizedBox.shrink();
+                return Padding(
+                  padding: const EdgeInsets.only(bottom: AppSpacing.md),
+                  child: Container(
+                    padding: const EdgeInsets.symmetric(
+                        horizontal: AppSpacing.md, vertical: AppSpacing.sm),
+                    decoration: BoxDecoration(
+                      color: postalRed.withValues(alpha: 0.08),
+                      borderRadius: BorderRadius.circular(20),
+                      border: Border.all(color: postalRed.withValues(alpha: 0.25)),
+                    ),
+                    child: Row(
+                      mainAxisSize: MainAxisSize.min,
+                      children: [
+                        const Text('🔥', style: TextStyle(fontSize: 18)),
+                        const SizedBox(width: AppSpacing.xs),
+                        Text(
+                          '$streak-day streak',
+                          style: Theme.of(context).textTheme.labelLarge?.copyWith(
+                                color: postalRed,
+                                fontWeight: FontWeight.w600,
+                              ),
+                        ),
+                      ],
+                    ),
+                  ),
+                );
+              },
+            ),
             SvgPicture.asset(
               'assets/postbox.svg',
               height: 100,
@@ -646,6 +686,21 @@ class ClaimState extends State<Claim> with SingleTickerProviderStateMixin {
                   ),
             ),
             const SizedBox(height: AppSpacing.sm),
+            StreamBuilder<int?>(
+              stream: _streakService.streakStream(),
+              builder: (context, snap) {
+                final streak = snap.data ?? 0;
+                if (streak < 2) return const SizedBox.shrink();
+                return Padding(
+                  padding: const EdgeInsets.only(top: 8),
+                  child: Text(
+                    '🔥 $streak-day streak!',
+                    style: Theme.of(context).textTheme.titleMedium,
+                    textAlign: TextAlign.center,
+                  ),
+                );
+              },
+            ),
             if (_pointsEarned > 0)
               Container(
                 padding: const EdgeInsets.symmetric(

lib/streak_service.dart

@@ -0,0 +1,73 @@
+import 'package:cloud_firestore/cloud_firestore.dart';
+import 'package:firebase_auth/firebase_auth.dart';
+
+/// Updates and reads daily claim streak for the current user.
+class StreakService {
+  StreakService({FirebaseFirestore? firestore, FirebaseAuth? auth})
+      : _firestore = firestore ?? FirebaseFirestore.instance,
+        _auth = auth ?? FirebaseAuth.instance;
+
+  final FirebaseFirestore _firestore;
+  final FirebaseAuth _auth;
+
+  static String get _today {
+    final now = DateTime.now().toUtc();
+    // Approximate BST: last Sunday March → last Sunday October
+    // BST = UTC+1, GMT = UTC+0
+    final month = now.month;
+    final isDstCandidate = month > 3 && month < 10 ||
+        (month == 3 && now.day > 24) || // last week of March (rough)
+        (month == 10 && now.day <= 24); // first 3 weeks of October (rough)
+    final london = isDstCandidate
+        ? now.add(const Duration(hours: 1))
+        : now;
+    return london.toIso8601String().split('T').first;
+  }
+
+  /// Call after user successfully claims (e.g. startScoring returned found with claims).
+  Future<void> updateStreakAfterClaim() async {
+    final user = _auth.currentUser;
+    if (user == null) return;
+
+    final today = _today;
+    final todayDate = DateTime.parse(today);
+    final yesterday = todayDate
+        .subtract(const Duration(days: 1))
+        .toIso8601String()
+        .split('T')
+        .first;
+
+    final ref = _firestore.collection('users').doc(user.uid);
+    await _firestore.runTransaction((tx) async {
+      final doc = await tx.get(ref);
+      final data = doc.data() ?? {};
+      final lastClaimDate = data['lastClaimDate'] as String?;
+      final currentStreak = (data['streak'] as int?) ?? 0;
+
+      int newStreak;
+      if (lastClaimDate == today) {
+        return; // Already claimed today
+      } else if (lastClaimDate == yesterday) {
+        newStreak = currentStreak + 1;
+      } else {
+        newStreak = 1;
+      }
+
+      tx.set(ref, {
+        'lastClaimDate': today,
+        'streak': newStreak,
+      }, SetOptions(merge: true));
+    });
+  }
+
+  /// Stream of the current user's streak (for UI).
+  Stream<int?> streakStream() {
+    final uid = _auth.currentUser?.uid;
+    if (uid == null) return Stream<int?>.value(null);
+    return _firestore.collection('users').doc(uid).snapshots().map((s) {
+      final d = s.data();
+      if (d == null || d['streak'] is! int) return null;
+      return d['streak'] as int;
+    });
+  }
+}