/// GitHub-style contribution heatmap for one calendar month of transactions.
library;

import 'package:flutter/material.dart';

import '../utils/helpers.dart';
import '../utils/tx_calendar.dart';

class TxHeatmap extends StatelessWidget {
  const TxHeatmap({
    super.key,
    required this.month,
    required this.counts,
    required this.canGoForward,
    this.selectedDay,
    required this.onPreviousMonth,
    required this.onNextMonth,
    required this.onSelectDay,
  });

  final DateTime month;
  final Map<DateTime, int> counts;
  final bool canGoForward;
  final DateTime? selectedDay;
  final VoidCallback onPreviousMonth;
  final VoidCallback onNextMonth;
  final ValueChanged<DateTime?> onSelectDay;

  static const _weekdays = ['M', 'T', 'W', 'T', 'F', 'S', 'S'];

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final scheme = theme.colorScheme;
    final cells = monthGrid(month);
    final today = dateOnly(DateTime.now());
    final weeks = cells.length ~/ 7;

    return Card(
      margin: const EdgeInsets.fromLTRB(0, 8, 0, 8),
      child: Padding(
        padding: const EdgeInsets.fromLTRB(12, 8, 12, 12),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Row(
              children: [
                IconButton(
                  tooltip: 'Previous month',
                  onPressed: onPreviousMonth,
                  icon: const Icon(Icons.chevron_left),
                ),
                Expanded(
                  child: Text(
                    formatMonthYear(month),
                    textAlign: TextAlign.center,
                    style: theme.textTheme.titleMedium,
                  ),
                ),
                IconButton(
                  tooltip: 'Next month',
                  onPressed: canGoForward ? onNextMonth : null,
                  icon: const Icon(Icons.chevron_right),
                ),
              ],
            ),
            const SizedBox(height: 4),
            Row(
              children: [
                for (final label in _weekdays)
                  Expanded(
                    child: Text(
                      label,
                      textAlign: TextAlign.center,
                      style: theme.textTheme.labelMedium,
                    ),
                  ),
              ],
            ),
            const SizedBox(height: 4),
            for (var week = 0; week < weeks; week++)
              Padding(
                padding: const EdgeInsets.only(top: 4),
                child: Row(
                  children: [
                    for (var weekday = 0; weekday < 7; weekday++)
                      Expanded(
                        child: Padding(
                          padding: const EdgeInsets.symmetric(horizontal: 2),
                          child: _HeatCell(
                            date: cells[week * 7 + weekday],
                            count: cells[week * 7 + weekday] == null
                                ? 0
                                : counts[cells[week * 7 + weekday]] ?? 0,
                            today: today,
                            selectedDay: selectedDay,
                            onSelect: onSelectDay,
                          ),
                        ),
                      ),
                  ],
                ),
              ),
            const SizedBox(height: 12),
            Row(
              children: [
                Text('Less', style: theme.textTheme.labelMedium),
                const SizedBox(width: 6),
                for (var level = 0; level <= 4; level++)
                  Padding(
                    padding: const EdgeInsets.only(right: 3),
                    child: Container(
                      width: 12,
                      height: 12,
                      decoration: BoxDecoration(
                        color: _fillForLevel(scheme, level),
                        borderRadius: BorderRadius.circular(3),
                      ),
                    ),
                  ),
                Text('More', style: theme.textTheme.labelMedium),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

class _HeatCell extends StatelessWidget {
  const _HeatCell({
    required this.date,
    required this.count,
    required this.today,
    required this.selectedDay,
    required this.onSelect,
  });

  final DateTime? date;
  final int count;
  final DateTime today;
  final DateTime? selectedDay;
  final ValueChanged<DateTime?> onSelect;

  @override
  Widget build(BuildContext context) {
    if (date == null) {
      return const SizedBox(height: 36);
    }

    final scheme = Theme.of(context).colorScheme;
    final level = heatmapLevel(count);
    final selected = selectedDay != null && isSameDay(date!, selectedDay!);
    final isToday = isSameDay(date!, today);
    final fill = _fillForLevel(scheme, level);
    final textColor = level >= 3
        ? scheme.onPrimary
        : scheme.onSurface.withValues(alpha: count == 0 ? 0.45 : 1);

    return Tooltip(
      message: count == 0
          ? formatDate(date!)
          : '${formatDate(date!)} · ${count == 1 ? '1 tx' : '$count txs'}',
      child: InkWell(
        onTap: () => onSelect(selected ? null : date),
        borderRadius: BorderRadius.circular(6),
        child: AnimatedContainer(
          duration: const Duration(milliseconds: 150),
          height: 36,
          alignment: Alignment.center,
          decoration: BoxDecoration(
            color: fill,
            borderRadius: BorderRadius.circular(6),
            border: Border.all(
              color: selected
                  ? scheme.primary
                  : isToday
                      ? scheme.outline
                      : Colors.transparent,
              width: selected ? 2 : 1,
            ),
          ),
          child: Text(
            '${date!.day}',
            style: Theme.of(context).textTheme.labelMedium?.copyWith(
                  color: textColor,
                  fontWeight: isToday || selected
                      ? FontWeight.w700
                      : FontWeight.w500,
                  fontSize: 11,
                ),
          ),
        ),
      ),
    );
  }
}

Color _fillForLevel(ColorScheme scheme, int level) {
  if (level <= 0) return scheme.surfaceContainerHighest;
  final t = (level / 4).clamp(0.28, 1.0);
  return Color.lerp(scheme.primary.withValues(alpha: 0.22), scheme.primary, t)!;
}