import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';

import '../providers/attendance_provider.dart';
import '../providers/shift_countdown_provider.dart';

/// A persistent banner that shows a countdown to the shift start time.
///
/// Activated when [shiftCountdownProvider] is set to a non-null [DateTime].
/// Auto-dismisses when the countdown reaches zero or the provider is cleared
/// (e.g., when the user checks in).
class ShiftCountdownBanner extends ConsumerStatefulWidget {
  const ShiftCountdownBanner({required this.child, super.key});

  final Widget child;

  @override
  ConsumerState<ShiftCountdownBanner> createState() =>
      _ShiftCountdownBannerState();
}

class _ShiftCountdownBannerState extends ConsumerState<ShiftCountdownBanner> {
  Timer? _timer;
  Duration _remaining = Duration.zero;

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }

  void _startTimer(DateTime target) {
    _timer?.cancel();
    _updateRemaining(target);
    _timer = Timer.periodic(const Duration(seconds: 1), (_) {
      _updateRemaining(target);
    });
  }

  void _updateRemaining(DateTime target) {
    final now = DateTime.now();
    final diff = target.difference(now);
    if (diff.isNegative || diff == Duration.zero) {
      _timer?.cancel();
      // Clear the provider when countdown finishes
      ref.read(shiftCountdownProvider.notifier).state = null;
      if (mounted) setState(() => _remaining = Duration.zero);
      return;
    }
    if (mounted) setState(() => _remaining = diff);
  }

  String _formatDuration(Duration d) {
    final minutes = d.inMinutes.remainder(60).toString().padLeft(2, '0');
    final seconds = d.inSeconds.remainder(60).toString().padLeft(2, '0');
    if (d.inHours > 0) {
      return '${d.inHours}:$minutes:$seconds';
    }
    return '$minutes:$seconds';
  }

  @override
  Widget build(BuildContext context) {
    final target = ref.watch(shiftCountdownProvider);

    // Start/stop timer when target changes
    ref.listen<DateTime?>(shiftCountdownProvider, (previous, next) {
      if (next != null) {
        _startTimer(next);
      } else {
        _timer?.cancel();
        if (mounted) setState(() => _remaining = Duration.zero);
      }
    });

    // Auto-dismiss when user checks in today (attendance stream updates)
    ref.listen(attendanceLogsProvider, (previous, next) {
      if (target == null) return;
      final logs = next.valueOrNull ?? [];
      final today = DateTime.now();
      final checkedInToday = logs.any(
        (log) =>
            log.checkInAt.year == today.year &&
            log.checkInAt.month == today.month &&
            log.checkInAt.day == today.day,
      );
      if (checkedInToday) {
        ref.read(shiftCountdownProvider.notifier).state = null;
      }
    });

    // Initialize timer on first build if target is already set
    if (target != null && _timer == null) {
      WidgetsBinding.instance.addPostFrameCallback((_) {
        _startTimer(target);
      });
    }

    final showBanner = target != null && _remaining > Duration.zero;

    return Column(
      children: [
        if (showBanner)
          Material(
            child: InkWell(
              onTap: () => context.go('/attendance'),
              child: Container(
                width: double.infinity,
                padding:
                    const EdgeInsets.symmetric(horizontal: 16, vertical: 10),
                decoration: BoxDecoration(
                  color: Theme.of(context).colorScheme.primaryContainer,
                ),
                child: Row(
                  children: [
                    Icon(
                      Icons.timer_outlined,
                      size: 20,
                      color:
                          Theme.of(context).colorScheme.onPrimaryContainer,
                    ),
                    const SizedBox(width: 8),
                    Expanded(
                      child: Text(
                        'Shift starts in ${_formatDuration(_remaining)}',
                        style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                              color: Theme.of(context)
                                  .colorScheme
                                  .onPrimaryContainer,
                              fontWeight: FontWeight.w600,
                            ),
                      ),
                    ),
                    Text(
                      'Tap to check in',
                      style: Theme.of(context).textTheme.bodySmall?.copyWith(
                            color: Theme.of(context)
                                .colorScheme
                                .onPrimaryContainer
                                .withValues(alpha: 0.7),
                          ),
                    ),
                    const SizedBox(width: 4),
                    Icon(
                      Icons.chevron_right,
                      size: 18,
                      color: Theme.of(context)
                          .colorScheme
                          .onPrimaryContainer
                          .withValues(alpha: 0.7),
                    ),
                  ],
                ),
              ),
            ),
          ),
        Expanded(child: widget.child),
      ],
    );
  }
}