import 'dart:async';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../auth/auth_providers.dart';
import 'group_ride_models.dart';
import 'group_ride_service.dart';

/// Provider for GroupRideService.
final groupRideServiceProvider = Provider<GroupRideService>((ref) {
  return GroupRideService();
});

/// Stream of a specific Group Ride by ID.
final groupRideStreamProvider =
    StreamProvider.family<GroupRide?, String>((ref, rideId) {
  final service = ref.watch(groupRideServiceProvider);
  return service.groupRideStream(rideId);
});

/// Stream of participants for a specific Group Ride.
/// Uses bounded point-document listeners per UID discovered via parent GroupRide.accessUids
/// (plus the signed-in user's own UID if available) to ensure zero collection list queries
/// and complete peer block isolation.
final groupRideParticipantsProvider =
    StreamProvider.family.autoDispose<List<GroupRideParticipant>, String>((ref, rideId) {
  final service = ref.watch(groupRideServiceProvider);
  final rideAsync = ref.watch(groupRideStreamProvider(rideId));
  final currentUser = ref.watch(currentUserProvider);

  final controller = StreamController<List<GroupRideParticipant>>();
  final participantSubscriptions = <String, StreamSubscription<GroupRideParticipant?>>{};
  final activeParticipants = <String, GroupRideParticipant>{};

  void emitCurrent() {
    if (controller.isClosed) return;
    final list = activeParticipants.values.toList()
      ..sort((a, b) {
        if (a.role == GroupRideRole.organizer) return -1;
        if (b.role == GroupRideRole.organizer) return 1;
        return a.createdAt.compareTo(b.createdAt);
      });
    controller.add(list);
  }

  void reconcileCandidates(List<String> candidateUids) {
    final candidateSet = candidateUids.toSet();
    if (currentUser != null && !currentUser.isAnonymous) {
      candidateSet.add(currentUser.uid);
    }

    final existingUids = participantSubscriptions.keys.toList();
    for (final uid in existingUids) {
      if (!candidateSet.contains(uid)) {
        participantSubscriptions.remove(uid)?.cancel();
        activeParticipants.remove(uid);
      }
    }

    for (final uid in candidateSet) {
      if (!participantSubscriptions.containsKey(uid)) {
        final stream = service.participantDocStream(groupRideId: rideId, participantUid: uid);
        participantSubscriptions[uid] = stream.listen(
          (participant) {
            if (participant != null) {
              activeParticipants[uid] = participant;
            } else {
              activeParticipants.remove(uid);
            }
            emitCurrent();
          },
          onError: (_) {
            activeParticipants.remove(uid);
            emitCurrent();
          },
        );
      }
    }
    emitCurrent();
  }

  rideAsync.when(
    data: (ride) {
      if (ride == null) {
        for (final sub in participantSubscriptions.values) {
          sub.cancel();
        }
        participantSubscriptions.clear();
        activeParticipants.clear();
        emitCurrent();
        return;
      }
      reconcileCandidates(ride.accessUids);
    },
    error: (e, st) {
      if (!controller.isClosed) controller.addError(e, st);
    },
    loading: () {},
  );

  ref.onDispose(() {
    for (final sub in participantSubscriptions.values) {
      sub.cancel();
    }
    participantSubscriptions.clear();
    activeParticipants.clear();
    controller.close();
  });

  return controller.stream;
});

/// FutureProvider fetching pending join requests for a GroupRide (organizer or club leadership only).
final groupRideJoinRequestsProvider =
    FutureProvider.family.autoDispose<List<GroupRideJoinRequest>, String>((ref, rideId) async {
  final user = ref.watch(currentUserProvider);
  if (user == null || user.isAnonymous) {
    return const [];
  }
  final authService = ref.watch(authServiceProvider);
  final token = await authService.getIdToken();
  final service = ref.watch(groupRideServiceProvider);
  const definedUrl = String.fromEnvironment('MOTORSIGNAL_API_BASE_URL');
  final baseUrl = definedUrl.isNotEmpty ? definedUrl : null;
  try {
    return await service.fetchJoinRequests(
      groupRideId: rideId,
      idToken: token,
      baseUrl: baseUrl,
    );
  } catch (e) {
    return const [];
  }
});

/// Stream of upcoming Group Rides for the current user.
final upcomingGroupRidesProvider = StreamProvider<List<GroupRide>>((ref) {
  final user = ref.watch(currentUserProvider);
  if (user == null || user.isAnonymous) {
    return Stream.value([]);
  }
  final service = ref.watch(groupRideServiceProvider);
  return service.upcomingRidesStream(callerUid: user.uid);
});

/// Stream of Group Rides organized by the current user.
final myGroupRidesProvider = StreamProvider<List<GroupRide>>((ref) {
  final user = ref.watch(currentUserProvider);
  if (user == null || user.isAnonymous) {
    return Stream.value([]);
  }
  final service = ref.watch(groupRideServiceProvider);
  return service.myRidesStream(callerUid: user.uid);
});


/// Stream of live presence records for all accepted participants in a specific Group Ride.
/// Uses bounded point-document listeners per candidate UID discovered via parent GroupRide.accessUids.
/// Isolates peer permission-denied / sharing-off events to the specific peer and recovers cleanly.
final groupRideLivePresenceProvider =
    StreamProvider.family.autoDispose<List<LiveGroupPresence>, String>((ref, rideId) {
  final service = ref.watch(groupRideServiceProvider);
  final rideAsync = ref.watch(groupRideStreamProvider(rideId));

  final controller = StreamController<List<LiveGroupPresence>>();
  final activeSubscriptions = <String, StreamSubscription<LiveGroupPresence?>>{};
  final activePresences = <String, LiveGroupPresence>{};
  final retryTimers = <String, Timer>{};
  final participantSubscriptions = <String, StreamSubscription<GroupRideParticipant?>>{};
  final acceptedUids = <String>{};

  void emitCurrent() {
    if (controller.isClosed) return;
    final now = DateTime.now();
    final freshList = activePresences.values
        .where((p) => p.sharingEnabled && p.updatedAt.isAfter(now.subtract(const Duration(seconds: 120))))
        .toList();
    controller.add(freshList);
  }

  // Periodic sweep for stale presences (> 120s)
  final ttlTimer = Timer.periodic(const Duration(seconds: 15), (_) => emitCurrent());

  void stopPresenceListener(String uid) {
    retryTimers.remove(uid)?.cancel();
    activeSubscriptions.remove(uid)?.cancel();
    activePresences.remove(uid);
    emitCurrent();
  }

  void startPresenceListener(String uid) {
    if (activeSubscriptions.containsKey(uid) || !acceptedUids.contains(uid)) return;
    retryTimers.remove(uid)?.cancel();

    final stream = service.livePresenceDocStream(groupRideId: rideId, targetUid: uid);
    activeSubscriptions[uid] = stream.listen(
      (presence) {
        if (presence != null && presence.sharingEnabled) {
          activePresences[uid] = presence;
        } else {
          activePresences.remove(uid);
        }
        emitCurrent();
      },
      onError: (e) {
        // Peer error (sharing disabled, mutual block, or permission-denied)
        activePresences.remove(uid);
        emitCurrent();
        activeSubscriptions.remove(uid)?.cancel();

        // Bounded retry to recover when sharing is toggled back ON
        if (!controller.isClosed && acceptedUids.contains(uid)) {
          retryTimers[uid] = Timer(const Duration(seconds: 10), () {
            if (!controller.isClosed && acceptedUids.contains(uid)) {
              startPresenceListener(uid);
            }
          });
        }
      },
    );
  }

  void reconcileCandidates(List<String> candidateUids) {
    final candidateSet = candidateUids.toSet();

    // 1. Remove participant listeners and presence listeners for candidates no longer present
    final existingUids = participantSubscriptions.keys.toList();
    for (final uid in existingUids) {
      if (!candidateSet.contains(uid)) {
        participantSubscriptions.remove(uid)?.cancel();
        acceptedUids.remove(uid);
        stopPresenceListener(uid);
      }
    }

    // 2. Add participant listener for new candidate UIDs
    for (final uid in candidateSet) {
      if (!participantSubscriptions.containsKey(uid)) {
        final pStream = service.participantDocStream(groupRideId: rideId, participantUid: uid);
        participantSubscriptions[uid] = pStream.listen(
          (participant) {
            final wasAccepted = acceptedUids.contains(uid);
            final isNowAccepted = participant?.status == ParticipantStatus.accepted;

            if (isNowAccepted) {
              acceptedUids.add(uid);
              if (!wasAccepted || !activeSubscriptions.containsKey(uid)) {
                startPresenceListener(uid);
              }
            } else {
              acceptedUids.remove(uid);
              stopPresenceListener(uid);
            }
          },
          onError: (err) {
            // If participant document itself is denied (e.g. mutual block on roster), exclude UID
            acceptedUids.remove(uid);
            stopPresenceListener(uid);
          },
        );
      }
    }
  }

  rideAsync.when(
    data: (ride) {
      if (ride == null || ride.isCompleted || ride.isCanceled) {
        for (final sub in participantSubscriptions.values) {
          sub.cancel();
        }
        participantSubscriptions.clear();
        for (final sub in activeSubscriptions.values) {
          sub.cancel();
        }
        activeSubscriptions.clear();
        for (final timer in retryTimers.values) {
          timer.cancel();
        }
        retryTimers.clear();
        acceptedUids.clear();
        activePresences.clear();
        emitCurrent();
        return;
      }

      reconcileCandidates(ride.accessUids);
    },
    error: (e, st) {
      if (!controller.isClosed) controller.addError(e, st);
    },
    loading: () {},
  );

  ref.onDispose(() {
    ttlTimer.cancel();
    for (final timer in retryTimers.values) {
      timer.cancel();
    }
    retryTimers.clear();
    for (final sub in participantSubscriptions.values) {
      sub.cancel();
    }
    participantSubscriptions.clear();
    for (final sub in activeSubscriptions.values) {
      sub.cancel();
    }
    activeSubscriptions.clear();
    controller.close();
  });

  return controller.stream;
});

/// Master privacy setting: whether group ride live location sharing is permitted by user.
/// Defaults to false (explicit opt-in required).
final groupRideLiveSharingAllowedProvider = StateProvider<bool>((ref) {
  return false;
});

/// Active Group Ride ID currently being broadcasted to by the local rider, if any.
final activeLiveRideSharingIdProvider = StateProvider<String?>((ref) {
  return null;
});

/// Provider that returns the first active group ride for the current user (assembling or underway).
final activeUserGroupRideProvider = Provider<GroupRide?>((ref) {
  final upcomingAsync = ref.watch(upcomingGroupRidesProvider);
  final activeSharingId = ref.watch(activeLiveRideSharingIdProvider);

  return upcomingAsync.when(
    data: (rides) {
      if (activeSharingId != null) {
        try {
          return rides.firstWhere((r) => r.id == activeSharingId);
        } catch (_) {}
      }
      try {
        return rides.firstWhere((r) =>
            r.status == GroupRideStatus.underway ||
            r.status == GroupRideStatus.assembling);
      } catch (_) {
        return null;
      }
    },
    loading: () => null,
    error: (_, _) => null,
  );
});