import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../../../core/providers/mood_provider.dart';

const _moodColors = [
  Color(0xFFE57373),
  Color(0xFFFFB74D),
  Color(0xFFFFD54F),
  Color(0xFF81C784),
  Color(0xFF4DB6AC),
];

class CalendarHeatmap extends ConsumerWidget {
  const CalendarHeatmap({
    super.key,
    required this.month,
    required this.selectedDay,
    required this.onDayTap,
  });

  final DateTime month;
  final DateTime selectedDay;
  final ValueChanged<DateTime> onDayTap;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final start = DateTime(month.year, month.month, 1);
    final end = DateTime(month.year, month.month + 1, 0, 23, 59, 59);
    final averagesAsync =
        ref.watch(dailyAveragesProvider((start: start, end: end)));

    return averagesAsync.when(
      data: (averages) => _HeatmapGrid(
        month: month,
        averages: averages,
        selectedDay: selectedDay,
        onDayTap: onDayTap,
      ),
      loading: () =>
          const SizedBox(height: 280, child: Center(child: CircularProgressIndicator())),
      error: (_, __) => const SizedBox(height: 280),
    );
  }
}

class _HeatmapGrid extends StatelessWidget {
  const _HeatmapGrid({
    required this.month,
    required this.averages,
    required this.selectedDay,
    required this.onDayTap,
  });

  final DateTime month;
  final Map<DateTime, double> averages;
  final DateTime selectedDay;
  final ValueChanged<DateTime> onDayTap;

  @override
  Widget build(BuildContext context) {
    final cs = Theme.of(context).colorScheme;
    final daysInMonth = DateTime(month.year, month.month + 1, 0).day;
    final leadingBlanks = DateTime(month.year, month.month, 1).weekday - 1;
    final today = DateTime.now();
    final todayNorm = DateTime(today.year, today.month, today.day);

    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 4, 16, 16),
      child: Column(
        children: [
          Row(
            children: ['Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa', 'Su']
                .map((l) => Expanded(
                      child: Center(
                        child: Text(
                          l,
                          style: Theme.of(context)
                              .textTheme
                              .labelSmall
                              ?.copyWith(color: cs.outline),
                        ),
                      ),
                    ))
                .toList(),
          ),
          const SizedBox(height: 6),
          GridView.builder(
            shrinkWrap: true,
            physics: const NeverScrollableScrollPhysics(),
            gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount: 7,
              mainAxisSpacing: 4,
              crossAxisSpacing: 4,
            ),
            itemCount: leadingBlanks + daysInMonth,
            itemBuilder: (context, i) {
              if (i < leadingBlanks) return const SizedBox.shrink();
              final day = i - leadingBlanks + 1;
              final date = DateTime(month.year, month.month, day);
              final avg = averages[date];
              final isSelected = date == selectedDay;
              final isToday = date == todayNorm;

              Color? fill;
              if (avg != null) {
                final idx = (avg.clamp(1.0, 5.0) - 1).round().clamp(0, 4);
                fill = _moodColors[idx].withValues(alpha: 0.85);
              }

              return GestureDetector(
                onTap: () => onDayTap(date),
                child: Container(
                  decoration: BoxDecoration(
                    shape: BoxShape.circle,
                    color: fill ??
                        cs.surfaceContainerHighest.withValues(alpha: 0.5),
                    border: isSelected
                        ? Border.all(color: cs.primary, width: 2.5)
                        : isToday
                            ? Border.all(color: cs.outline, width: 1)
                            : null,
                  ),
                  child: Center(
                    child: Text(
                      '$day',
                      style: Theme.of(context).textTheme.labelSmall?.copyWith(
                            color: fill != null ? Colors.white : cs.onSurfaceVariant,
                            fontWeight: isSelected || isToday
                                ? FontWeight.bold
                                : FontWeight.normal,
                          ),
                    ),
                  ),
                ),
              );
            },
          ),
        ],
      ),
    );
  }
}