import 'package:flutter/foundation.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:uuid/uuid.dart';

import '../brick/cache_helpers.dart';
import '../models/programmer_task.model.dart';
import '../models/programmer_task_activity_log.model.dart';
import '../utils/snackbar.dart' show isOfflineSaveError;
import 'connectivity_provider.dart';
import 'profile_provider.dart';
import 'realtime_controller.dart';
import 'stream_recovery.dart';
import 'supabase_provider.dart';

/// Lifecycle action types that determine whether a task is currently paused.
const _pauseStateActions = ['started', 'paused', 'resumed', 'completed', 'cancelled'];

int _statusRank(String status) {
  switch (status) {
    case ProgrammerTaskStatus.inProgress:
      return 0;
    case ProgrammerTaskStatus.queued:
      return 1;
    case ProgrammerTaskStatus.completed:
      return 2;
    case ProgrammerTaskStatus.cancelled:
      return 3;
    default:
      return 4;
  }
}

void _sortTasks(List<ProgrammerTask> tasks) {
  tasks.sort((a, b) {
    final r = _statusRank(a.status).compareTo(_statusRank(b.status));
    if (r != 0) return r;
    return b.createdAt.compareTo(a.createdAt);
  });
}

// ---------------------------------------------------------------------------
// Offline-pending state (merged into the live stream; replayed on reconnect)
// ---------------------------------------------------------------------------

final offlinePendingProgrammerTasksProvider =
    StateProvider<List<ProgrammerTask>>((ref) => const []);

final offlinePendingProgrammerTaskRawProvider =
    StateProvider<List<Map<String, dynamic>>>((ref) => const []);

final offlinePendingProgrammerTaskUpdatesProvider =
    StateProvider<Map<String, Map<String, dynamic>>>((ref) => const {});

final offlinePendingProgrammerTaskLogsProvider =
    StateProvider<List<Map<String, dynamic>>>((ref) => const []);

// ---------------------------------------------------------------------------
// Stream providers
// ---------------------------------------------------------------------------

final programmerTasksProvider = StreamProvider<List<ProgrammerTask>>((ref) {
  final userId = ref.watch(currentUserIdProvider);
  if (userId == null) return const Stream.empty();
  final client = ref.watch(supabaseClientProvider);

  final pendingNew = ref.watch(offlinePendingProgrammerTasksProvider);
  final pendingUpdates = ref.watch(offlinePendingProgrammerTaskUpdatesProvider);

  List<ProgrammerTask> applyPending(List<ProgrammerTask> rows) {
    final byId = {for (final r in rows) r.id: r};
    pendingUpdates.forEach((id, fields) {
      final existing = byId[id];
      if (existing == null) return;
      byId[id] = _applyUpdateFields(existing, fields);
    });
    for (final p in pendingNew) {
      byId.putIfAbsent(p.id, () => p);
    }
    final result = byId.values.toList();
    _sortTasks(result);
    return result;
  }

  final wrapper = StreamRecoveryWrapper<ProgrammerTask>(
    stream: client
        .from('programmer_tasks')
        .stream(primaryKey: ['id'])
        .order('created_at', ascending: false),
    onPollData: () async {
      final data = await client
          .from('programmer_tasks')
          .select()
          .order('created_at', ascending: false)
          .range(0, 199);
      return data.map(ProgrammerTask.fromMap).toList();
    },
    fromMap: ProgrammerTask.fromMap,
    channelName: 'programmer_tasks',
    onStatusChanged: ref.read(realtimeControllerProvider).handleChannelStatus,
    onOfflineData: () async {
      final all = await cachedListFromBrick<ProgrammerTask>();
      return applyPending(all);
    },
    onCacheMirror: (rows) =>
        mirrorBatchToBrick<ProgrammerTask>(rows, tag: 'programmer_tasks'),
  );

  ref.onDispose(wrapper.dispose);

  // Reconnect-replay: POST queued items directly, bypassing Brick's queue.
  ref.listen<bool>(isOnlineProvider, (wasOnline, isNowOnline) async {
    if (wasOnline == true || !isNowOnline) return;

    // 1. Replay offline-created tasks.
    final pendingRaw = List<Map<String, dynamic>>.from(
      ref.read(offlinePendingProgrammerTaskRawProvider),
    );
    if (pendingRaw.isNotEmpty) {
      final syncedIds = <String>[];
      for (final payload in pendingRaw) {
        final id = payload['id'] as String;
        try {
          await client.from('programmer_tasks').insert(payload);
          try {
            await client.from('programmer_task_activity_logs').insert({
              'task_id': id,
              'actor_id': payload['creator_id'],
              'action_type': 'created',
            });
          } catch (_) {}
          syncedIds.add(id);
        } catch (e) {
          final msg = e.toString();
          if (msg.contains('23505') || msg.contains('duplicate key')) {
            syncedIds.add(id);
          } else {
            debugPrint('[programmerTasksProvider] failed to sync id=$id: $e');
          }
        }
      }
      if (syncedIds.isNotEmpty) {
        ref.read(offlinePendingProgrammerTaskRawProvider.notifier).state =
            List.unmodifiable(
              ref
                  .read(offlinePendingProgrammerTaskRawProvider)
                  .where((p) => !syncedIds.contains(p['id'] as String)),
            );
        ref.read(offlinePendingProgrammerTasksProvider.notifier).state =
            List.unmodifiable(
              ref
                  .read(offlinePendingProgrammerTasksProvider)
                  .where((t) => !syncedIds.contains(t.id)),
            );
      }
    }

    // 2. Replay offline field/status updates.
    final pendingUpdatesMap = Map<String, Map<String, dynamic>>.from(
      ref.read(offlinePendingProgrammerTaskUpdatesProvider),
    );
    if (pendingUpdatesMap.isNotEmpty) {
      final syncedIds = <String>[];
      for (final entry in pendingUpdatesMap.entries) {
        try {
          await client
              .from('programmer_tasks')
              .update(entry.value)
              .eq('id', entry.key);
          syncedIds.add(entry.key);
        } catch (e) {
          debugPrint(
            '[programmerTasksProvider] failed to sync update id=${entry.key}: $e',
          );
        }
      }
      if (syncedIds.isNotEmpty) {
        final remaining = Map<String, Map<String, dynamic>>.from(
          ref.read(offlinePendingProgrammerTaskUpdatesProvider),
        );
        for (final id in syncedIds) {
          remaining.remove(id);
        }
        ref.read(offlinePendingProgrammerTaskUpdatesProvider.notifier).state =
            remaining;
      }
    }

    // 3. Replay queued activity logs (started/paused/resumed/etc.).
    final pendingLogs = List<Map<String, dynamic>>.from(
      ref.read(offlinePendingProgrammerTaskLogsProvider),
    );
    if (pendingLogs.isNotEmpty) {
      final synced = <Map<String, dynamic>>[];
      for (final log in pendingLogs) {
        try {
          await client.from('programmer_task_activity_logs').insert(log);
          synced.add(log);
        } catch (e) {
          debugPrint('[programmerTasksProvider] failed to sync log: $e');
        }
      }
      if (synced.isNotEmpty) {
        ref.read(offlinePendingProgrammerTaskLogsProvider.notifier).state =
            List.unmodifiable(
              ref
                  .read(offlinePendingProgrammerTaskLogsProvider)
                  .where((l) => !synced.contains(l)),
            );
      }
    }
  });

  return wrapper.stream.map((result) => applyPending(result.data));
});

final programmerTaskByIdProvider = Provider.family<ProgrammerTask?, String>((
  ref,
  id,
) {
  final tasks = ref.watch(programmerTasksProvider).valueOrNull;
  if (tasks == null) return null;
  try {
    return tasks.firstWhere((t) => t.id == id);
  } catch (_) {
    return null;
  }
});

/// The current user's actively-running task id (status in_progress AND latest
/// activity log is not a pause), or null. Lets the list distinguish a *running*
/// task from a *paused* one (both share the `in_progress` status). Re-queries
/// whenever the task list changes. Given the single-active invariant, at most
/// one task is running per user.
final myRunningProgrammerTaskIdProvider = FutureProvider<String?>((ref) async {
  // Re-run whenever tasks change (a start/pause/resume mutates a row).
  ref.watch(programmerTasksProvider);
  final running =
      await ref.watch(programmerTasksControllerProvider).findRunningTaskForCurrentUser();
  return running?.id;
});

final programmerTaskActivityLogsProvider =
    StreamProvider.family<List<ProgrammerTaskActivityLog>, String>((ref, taskId) {
      final client = ref.watch(supabaseClientProvider);

      final wrapper = StreamRecoveryWrapper<ProgrammerTaskActivityLog>(
        stream: client
            .from('programmer_task_activity_logs')
            .stream(primaryKey: ['id'])
            .eq('task_id', taskId)
            .order('created_at', ascending: false),
        onPollData: () async {
          final data = await client
              .from('programmer_task_activity_logs')
              .select()
              .eq('task_id', taskId)
              .order('created_at', ascending: false);
          return data.map(ProgrammerTaskActivityLog.fromMap).toList();
        },
        fromMap: ProgrammerTaskActivityLog.fromMap,
        channelName: 'programmer_task_activity_logs_$taskId',
        onStatusChanged: ref
            .read(realtimeControllerProvider)
            .handleChannelStatus,
        onOfflineData: () async {
          final all = await cachedListFromBrick<ProgrammerTaskActivityLog>();
          return all.where((l) => l.taskId == taskId).toList()
            ..sort((a, b) => b.createdAt.compareTo(a.createdAt));
        },
        onCacheMirror: (rows) => mirrorBatchToBrick<ProgrammerTaskActivityLog>(
          rows,
          tag: 'programmer_task_activity_logs',
        ),
      );

      ref.onDispose(wrapper.dispose);
      return wrapper.stream.map((result) => result.data);
    });

// ---------------------------------------------------------------------------
// Controller
// ---------------------------------------------------------------------------

final programmerTasksControllerProvider = Provider<ProgrammerTasksController>((
  ref,
) {
  final client = ref.watch(supabaseClientProvider);
  return ProgrammerTasksController(client, ref);
});

class ProgrammerTasksController {
  ProgrammerTasksController(this._client, [this._ref]);

  final dynamic _client;
  final Ref? _ref;

  bool get _isOnline => _ref?.read(isOnlineProvider) ?? true;

  /// Whether [taskId]'s most recent lifecycle event is a pause (i.e. the task
  /// is in_progress but not actively running).
  Future<bool> _isCurrentlyPaused(String taskId) async {
    try {
      final rows = await _client
          .from('programmer_task_activity_logs')
          .select('action_type, created_at')
          .eq('task_id', taskId)
          .inFilter('action_type', _pauseStateActions)
          .order('created_at', ascending: false)
          .limit(1);
      if (rows is List && rows.isNotEmpty) {
        return (rows.first['action_type']?.toString() ?? '') == 'paused';
      }
    } catch (_) {}
    return false;
  }

  Future<void> _insertLog(
    String taskId,
    String actionType, {
    Map<String, dynamic>? meta,
  }) async {
    final row = <String, dynamic>{
      'task_id': taskId,
      'actor_id': _client.auth.currentUser?.id,
      'action_type': actionType,
      'meta': ?meta,
    };
    if (!_isOnline) {
      _queueLog(row);
      return;
    }
    try {
      await _client.from('programmer_task_activity_logs').insert(row);
    } catch (e) {
      if (isOfflineSaveError(e)) {
        _queueLog(row);
      } else {
        rethrow;
      }
    }
  }

  /// Creates a task. [assigneeId] defaults to the current user (self-logged);
  /// pass another programmer's id to assign it to them. Returns the task id.
  Future<String> createTask({
    required String title,
    required String category,
    String? description,
    String? assigneeId,
    String? projectId,
    int priority = 1,
  }) async {
    final userId = _client.auth.currentUser?.id;
    if (userId == null) throw Exception('Not authenticated');

    final id = const Uuid().v4();
    final assignee = assigneeId ?? userId;
    final payload = <String, dynamic>{
      'id': id,
      'title': title,
      'description': description,
      'category': category,
      'status': ProgrammerTaskStatus.queued,
      'priority': priority,
      'assignee_id': assignee,
      'creator_id': userId,
      'project_id': ?projectId,
    };

    try {
      await _client.from('programmer_tasks').insert(payload);
      await _insertLog(id, 'created');
      if (assignee != userId) {
        await _insertLog(id, 'assigned', meta: {'assignee_id': assignee});
      }
      return id;
    } catch (e) {
      if (!isOfflineSaveError(e)) rethrow;
      final now = DateTime.now().toUtc();
      final local = ProgrammerTask(
        id: id,
        title: title,
        description: description,
        category: category,
        status: ProgrammerTaskStatus.queued,
        priority: priority,
        assigneeId: assignee,
        creatorId: userId,
        projectId: projectId,
        createdAt: now,
        updatedAt: now,
      );
      _queueNewTask(local, payload);
      return id;
    }
  }

  /// The current user's actively-running task (status in_progress, latest event
  /// not a pause), or null. Used to drive the pause-on-switch prompt. Online
  /// only — returns null offline (the prompt is a best-effort UX aid).
  Future<ProgrammerTask?> findRunningTaskForCurrentUser() async {
    final userId = _client.auth.currentUser?.id;
    if (userId == null || !_isOnline) return null;
    try {
      final rows = await _client
          .from('programmer_tasks')
          .select()
          .eq('assignee_id', userId)
          .eq('status', ProgrammerTaskStatus.inProgress);
      if (rows is! List) return null;
      for (final row in rows) {
        final task = ProgrammerTask.fromMap(row as Map<String, dynamic>);
        if (!await _isCurrentlyPaused(task.id)) return task;
      }
    } catch (_) {}
    return null;
  }

  /// Moves a queued task to in_progress (sets started_at on first start) and
  /// logs a `started` event.
  Future<void> startTask({required String taskId}) async {
    final updates = <String, dynamic>{
      'status': ProgrammerTaskStatus.inProgress,
      'started_at': DateTime.now().toUtc().toIso8601String(),
    };
    await _updateTaskRow(taskId, updates, onlyIfStartNull: true);
    await _insertLog(taskId, 'started');
  }

  /// Logs a `paused` event for a running task (idempotent).
  Future<void> pauseTask({required String taskId}) async {
    if (_isOnline && await _isCurrentlyPaused(taskId)) return;
    await _insertLog(taskId, 'paused');
  }

  /// Logs a `resumed` event for a paused task (idempotent).
  Future<void> resumeTask({required String taskId}) async {
    if (_isOnline && !await _isCurrentlyPaused(taskId)) return;
    await _insertLog(taskId, 'resumed');
  }

  Future<void> completeTask({required String taskId}) async {
    await _updateTaskRow(taskId, {
      'status': ProgrammerTaskStatus.completed,
      'completed_at': DateTime.now().toUtc().toIso8601String(),
    });
    await _insertLog(taskId, 'completed');
  }

  Future<void> cancelTask({
    required String taskId,
    required String reason,
  }) async {
    await _updateTaskRow(taskId, {
      'status': ProgrammerTaskStatus.cancelled,
      'cancelled_at': DateTime.now().toUtc().toIso8601String(),
      'cancellation_reason': reason,
    });
    await _insertLog(taskId, 'cancelled', meta: {'reason': reason});
  }

  Future<void> reassign({
    required String taskId,
    required String newAssigneeId,
  }) async {
    await _updateTaskRow(taskId, {'assignee_id': newAssigneeId});
    await _insertLog(taskId, 'reassigned', meta: {'assignee_id': newAssigneeId});
  }

  Future<void> updateTask({
    required String taskId,
    String? title,
    String? description,
    String? category,
    int? priority,
  }) async {
    final updates = <String, dynamic>{};
    if (title != null) updates['title'] = title;
    if (description != null) updates['description'] = description;
    if (category != null) updates['category'] = category;
    if (priority != null) updates['priority'] = priority;
    if (updates.isEmpty) return;
    await _updateTaskRow(taskId, updates);
    await _insertLog(taskId, 'updated', meta: {'fields': updates.keys.toList()});
  }

  /// Assigns the task to a project (pass null to clear it).
  Future<void> setProject({
    required String taskId,
    required String? projectId,
  }) async {
    await _updateTaskRow(taskId, {'project_id': projectId});
    await _insertLog(taskId, 'updated', meta: {
      'fields': ['project_id'],
    });
  }

  /// Records a time adjustment (negative [seconds]) against a task's worked
  /// duration — e.g. when the current user helped on another task and chose to
  /// deduct that time from their own running task.
  Future<void> addAdjustment({
    required String taskId,
    required int seconds,
    String? reason,
    String? sourceTaskId,
  }) async {
    await _insertLog(taskId, 'adjustment', meta: {
      'seconds': seconds,
      'reason': ?reason,
      'source_task_id': ?sourceTaskId,
    });
  }

  /// Applies a field patch to a task row. When [onlyIfStartNull] is set,
  /// `started_at` is dropped if the task already has one (preserves the first
  /// execution start across pause/resume cycles).
  Future<void> _updateTaskRow(
    String taskId,
    Map<String, dynamic> updates, {
    bool onlyIfStartNull = false,
  }) async {
    var payload = updates;
    if (!_isOnline) {
      _queueUpdate(taskId, payload);
      return;
    }
    try {
      if (onlyIfStartNull && payload.containsKey('started_at')) {
        final existing = await _client
            .from('programmer_tasks')
            .select('started_at')
            .eq('id', taskId)
            .maybeSingle();
        if (existing is Map && existing['started_at'] != null) {
          payload = Map<String, dynamic>.from(payload)..remove('started_at');
        }
      }
      await _client.from('programmer_tasks').update(payload).eq('id', taskId);
    } catch (e) {
      if (isOfflineSaveError(e)) {
        _queueUpdate(taskId, payload);
      } else {
        rethrow;
      }
    }
  }

  // ------------------------------------------------------------------ queues

  void _queueNewTask(ProgrammerTask model, Map<String, dynamic> payload) {
    final ref = _ref;
    if (ref == null) return;
    ref.read(offlinePendingProgrammerTasksProvider.notifier).state =
        List.unmodifiable([
          ...ref.read(offlinePendingProgrammerTasksProvider),
          model,
        ]);
    ref.read(offlinePendingProgrammerTaskRawProvider.notifier).state =
        List.unmodifiable([
          ...ref.read(offlinePendingProgrammerTaskRawProvider),
          payload,
        ]);
    mirrorBatchToBrick<ProgrammerTask>([model], tag: 'offline_programmer_task');
  }

  void _queueUpdate(String taskId, Map<String, dynamic> fields) {
    final ref = _ref;
    if (ref == null) return;
    final current = Map<String, Map<String, dynamic>>.from(
      ref.read(offlinePendingProgrammerTaskUpdatesProvider),
    );
    current[taskId] = {...?current[taskId], ...fields};
    ref.read(offlinePendingProgrammerTaskUpdatesProvider.notifier).state =
        current;
  }

  void _queueLog(Map<String, dynamic> row) {
    final ref = _ref;
    if (ref == null) return;
    ref.read(offlinePendingProgrammerTaskLogsProvider.notifier).state =
        List.unmodifiable([
          ...ref.read(offlinePendingProgrammerTaskLogsProvider),
          row,
        ]);
  }
}

// ---------------------------------------------------------------------------
// Field-patch helper for optimistic offline updates
// ---------------------------------------------------------------------------

ProgrammerTask _applyUpdateFields(ProgrammerTask t, Map<String, dynamic> f) {
  DateTime? parseOpt(String key) {
    if (!f.containsKey(key)) return null;
    final v = f[key];
    return v == null ? null : DateTime.parse(v as String).toUtc();
  }

  return ProgrammerTask(
    id: t.id,
    title: (f['title'] as String?) ?? t.title,
    description: f.containsKey('description')
        ? f['description'] as String?
        : t.description,
    category: (f['category'] as String?) ?? t.category,
    status: (f['status'] as String?) ?? t.status,
    priority: (f['priority'] as num?)?.toInt() ?? t.priority,
    assigneeId:
        f.containsKey('assignee_id') ? f['assignee_id'] as String? : t.assigneeId,
    creatorId: t.creatorId,
    projectId:
        f.containsKey('project_id') ? f['project_id'] as String? : t.projectId,
    createdAt: t.createdAt,
    startedAt: f.containsKey('started_at') ? parseOpt('started_at') : t.startedAt,
    completedAt:
        f.containsKey('completed_at') ? parseOpt('completed_at') : t.completedAt,
    cancelledAt:
        f.containsKey('cancelled_at') ? parseOpt('cancelled_at') : t.cancelledAt,
    cancellationReason: f.containsKey('cancellation_reason')
        ? f['cancellation_reason'] as String?
        : t.cancellationReason,
    updatedAt: DateTime.now().toUtc(),
  );
}