import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:go_router/go_router.dart';
import 'package:focusflow_shared/focusflow_shared.dart';

import '../../../../core/theme/app_colors.dart';
import '../../../../core/widgets/reward_popup.dart';
import '../bloc/next_task_cubit.dart';

/// THE core ADHD feature — "Just do the next thing."
///
///  - Single task displayed, nothing else.
///  - Large title text centered.
///  - Energy level indicator.
///  - Estimated time.
///  - Big "Done!" button (green, satisfying).
///  - "Skip" button (smaller, gray, no guilt).
///  - "I need a break" option.
///  - Timer showing elapsed time (gentle, not anxiety-inducing).
///  - On completion: reward popup appears.
///  - After reward: auto-loads next task or shows "All done!" celebration.
class FocusModeScreen extends StatefulWidget {
  const FocusModeScreen({super.key});

  @override
  State<FocusModeScreen> createState() => _FocusModeScreenState();
}

class _FocusModeScreenState extends State<FocusModeScreen> {
  late final NextTaskCubit _cubit;
  final Stopwatch _stopwatch = Stopwatch();
  Timer? _timer;
  bool _showReward = false;
  int _elapsedSeconds = 0;

  @override
  void initState() {
    super.initState();
    _cubit = NextTaskCubit()..loadNext();
    _startTimer();
  }

  void _startTimer() {
    _stopwatch.start();
    _timer = Timer.periodic(const Duration(seconds: 1), (_) {
      if (mounted) {
        setState(() => _elapsedSeconds = _stopwatch.elapsed.inSeconds);
      }
    });
  }

  void _resetTimer() {
    _stopwatch.reset();
    setState(() => _elapsedSeconds = 0);
  }

  @override
  void dispose() {
    _timer?.cancel();
    _stopwatch.stop();
    _cubit.close();
    super.dispose();
  }

  String _formatElapsed() {
    final minutes = _elapsedSeconds ~/ 60;
    final seconds = _elapsedSeconds % 60;
    return '${minutes}m ${seconds.toString().padLeft(2, '0')}s so far';
  }

  Color _energyColor(String level) {
    switch (level) {
      case 'low':
        return AppColors.energyLow;
      case 'high':
        return AppColors.energyHigh;
      default:
        return AppColors.energyMedium;
    }
  }

  String _energyEmoji(String level) {
    switch (level) {
      case 'low':
        return 'Low energy';
      case 'high':
        return 'High energy';
      default:
        return 'Medium energy';
    }
  }

  Future<void> _onComplete() async {
    _stopwatch.stop();
    setState(() => _showReward = true);
  }

  void _dismissReward() {
    setState(() => _showReward = false);
    _resetTimer();
    _stopwatch.start();
    _cubit.complete();
  }

  void _onSkip() {
    _resetTimer();
    _cubit.skip();
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return BlocProvider.value(
      value: _cubit,
      child: Scaffold(
        backgroundColor: theme.scaffoldBackgroundColor,
        appBar: AppBar(
          leading: IconButton(
            icon: const Icon(Icons.close_rounded),
            onPressed: () => context.go('/'),
            tooltip: 'Exit focus mode',
          ),
          title: const Text('Focus Mode'),
          centerTitle: true,
        ),
        body: Stack(
          children: [
            BlocBuilder<NextTaskCubit, NextTaskState>(
              builder: (context, state) {
                if (state is NextTaskLoading) {
                  return const Center(child: CircularProgressIndicator());
                }

                if (state is NextTaskError) {
                  return Center(
                    child: Padding(
                      padding: const EdgeInsets.all(32),
                      child: Column(
                        mainAxisSize: MainAxisSize.min,
                        children: [
                          const Icon(Icons.cloud_off_rounded,
                              size: 56, color: AppColors.skipped),
                          const SizedBox(height: 12),
                          Text(state.message,
                              style: theme.textTheme.bodyLarge,
                              textAlign: TextAlign.center),
                          const SizedBox(height: 16),
                          FilledButton(
                            onPressed: () => _cubit.loadNext(),
                            child: const Text('Try again'),
                          ),
                        ],
                      ),
                    ),
                  );
                }

                if (state is NextTaskEmpty) {
                  return _AllDoneView(onGoBack: () => context.go('/'));
                }

                if (state is NextTaskLoaded) {
                  return _TaskFocusView(
                    task: state.task,
                    elapsed: _formatElapsed(),
                    energyColor: _energyColor(state.task.energyLevel),
                    energyLabel: _energyEmoji(state.task.energyLevel),
                    onComplete: _onComplete,
                    onSkip: _onSkip,
                    onBreak: () {
                      _stopwatch.stop();
                      ScaffoldMessenger.of(context).showSnackBar(
                        SnackBar(
                          content: const Text(
                              'Take your time. Tap anywhere when you\'re ready.'),
                          action: SnackBarAction(
                            label: 'Resume',
                            onPressed: () => _stopwatch.start(),
                          ),
                        ),
                      );
                    },
                  );
                }

                return const SizedBox.shrink();
              },
            ),

            // ── Reward overlay ───────────────────────────────────
            if (_showReward)
              Container(
                color: Colors.black.withAlpha(120),
                child: RewardPopup(
                  reward: Reward(
                    id: 'local-${DateTime.now().millisecondsSinceEpoch}',
                    userId: '',
                    rewardType: 'points',
                    magnitude: 10,
                    title: 'Task complete!',
                    createdAt: DateTime.now(),
                  ),
                  onDismiss: _dismissReward,
                ),
              ),
          ],
        ),
      ),
    );
  }
}

// ── Single-task focus view ─────────────────────────────────────────

class _TaskFocusView extends StatelessWidget {
  final Task task;
  final String elapsed;
  final Color energyColor;
  final String energyLabel;
  final VoidCallback onComplete;
  final VoidCallback onSkip;
  final VoidCallback onBreak;

  const _TaskFocusView({
    required this.task,
    required this.elapsed,
    required this.energyColor,
    required this.energyLabel,
    required this.onComplete,
    required this.onSkip,
    required this.onBreak,
  });

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return SafeArea(
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 28),
        child: Column(
          children: [
            const Spacer(flex: 2),

            // ── Energy indicator ─────────────────────────────────
            Container(
              padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 6),
              decoration: BoxDecoration(
                color: energyColor.withAlpha(30),
                borderRadius: BorderRadius.circular(20),
              ),
              child: Row(
                mainAxisSize: MainAxisSize.min,
                children: [
                  Icon(Icons.bolt_rounded, size: 18, color: energyColor),
                  const SizedBox(width: 4),
                  Text(energyLabel,
                      style: TextStyle(
                          color: energyColor, fontWeight: FontWeight.w600)),
                ],
              ),
            ),
            const SizedBox(height: 24),

            // ── Task title ───────────────────────────────────────
            Text(
              task.title,
              style: theme.textTheme.headlineMedium?.copyWith(
                fontWeight: FontWeight.w700,
              ),
              textAlign: TextAlign.center,
            ),
            const SizedBox(height: 12),

            // ── Estimated time ───────────────────────────────────
            if (task.estimatedMinutes != null)
              Text(
                '~${task.estimatedMinutes} min estimated',
                style: theme.textTheme.bodyLarge?.copyWith(
                  color: AppColors.primary,
                ),
              ),
            const SizedBox(height: 20),

            // ── Elapsed time (gentle) ────────────────────────────
            Text(
              elapsed,
              style: theme.textTheme.bodyMedium?.copyWith(
                fontWeight: FontWeight.w500,
                color: AppColors.primary,
              ),
            ),

            const Spacer(flex: 3),

            // ── Done button ──────────────────────────────────────
            SizedBox(
              width: double.infinity,
              height: 64,
              child: FilledButton(
                onPressed: onComplete,
                style: FilledButton.styleFrom(
                  backgroundColor: AppColors.completed,
                  shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(20),
                  ),
                  textStyle: theme.textTheme.titleLarge?.copyWith(
                    fontWeight: FontWeight.w700,
                    color: Colors.white,
                  ),
                ),
                child: const Text('Done!', style: TextStyle(fontSize: 22, color: Colors.white)),
              ),
            ),
            const SizedBox(height: 12),

            // ── Skip button (smaller, gray, no guilt) ────────────
            SizedBox(
              width: double.infinity,
              height: 52,
              child: OutlinedButton(
                onPressed: onSkip,
                style: OutlinedButton.styleFrom(
                  foregroundColor: AppColors.skipped,
                  side: const BorderSide(color: AppColors.skipped),
                  shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(16),
                  ),
                ),
                child: const Text('Skip for now'),
              ),
            ),
            const SizedBox(height: 8),

            // ── Break button ─────────────────────────────────────
            TextButton.icon(
              onPressed: onBreak,
              icon: const Icon(Icons.self_improvement_rounded, size: 20),
              label: const Text('I need a break'),
            ),

            const Spacer(),
          ],
        ),
      ),
    );
  }
}

// ── All done celebration ───────────────────────────────────────────

class _AllDoneView extends StatelessWidget {
  final VoidCallback onGoBack;
  const _AllDoneView({required this.onGoBack});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return Center(
      child: Padding(
        padding: const EdgeInsets.all(32),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(Icons.celebration_rounded, size: 80, color: AppColors.rewardGold),
            const SizedBox(height: 20),
            Text(
              'All done for today!',
              style: theme.textTheme.headlineMedium?.copyWith(fontWeight: FontWeight.w700),
              textAlign: TextAlign.center,
            ),
            const SizedBox(height: 8),
            Text(
              'You showed up and that matters. Enjoy your free time!',
              style: theme.textTheme.bodyLarge,
              textAlign: TextAlign.center,
            ),
            const SizedBox(height: 28),
            FilledButton(
              onPressed: onGoBack,
              child: const Text('Back to dashboard'),
            ),
          ],
        ),
      ),
    );
  }
}