import 'package:flutter/material.dart';
import 'package:intl/intl.dart';

class CalendarWidget extends StatelessWidget {
  const CalendarWidget({super.key});

  @override
  Widget build(BuildContext context) {
    final now = DateTime.now();
    final firstDayOfMonth = DateTime(now.year, now.month, 1);
    final lastDayOfMonth = DateTime(now.year, now.month + 1, 0);
    final daysInMonth = lastDayOfMonth.day;
    final startingWeekday = firstDayOfMonth.weekday; // Mon=1, Sun=7

    // Simple calendar logic
    // We need to pad the beginning with empty slots
    // If week starts on Sunday, adjust accordingly. Let's assume Mon start for now or use locale.
    // Let's assume standard Sun-Sat or Mon-Sun. Let's go with Sun-Sat for standard calendar view often seen in KR/US.
    // DateTime.weekday: Mon=1, Sun=7.
    // If we want Sun start: Sun=0, Mon=1...
    // Let's adjust so Sunday is first.

    int offset =
        startingWeekday %
        7; // If startingWeekday is 7 (Sun), offset is 0. If 1 (Mon), offset is 1.

    return Container(
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: Theme.of(context).cardTheme.color,
        borderRadius: BorderRadius.circular(16),
      ),
      child: Column(
        children: [
          // Header
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              Text(
                DateFormat('MMMM yyyy').format(now),
                style: Theme.of(context).textTheme.titleLarge?.copyWith(
                  fontWeight: FontWeight.bold,
                  color: Colors.white,
                ),
              ),
              const Icon(Icons.calendar_today, color: Colors.white54),
            ],
          ),
          const SizedBox(height: 16),
          // Days Header
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: ['S', 'M', 'T', 'W', 'T', 'F', 'S'].map((day) {
              return Expanded(
                child: Center(
                  child: Text(
                    day,
                    style: const TextStyle(
                      color: Colors.white54,
                      fontWeight: FontWeight.bold,
                    ),
                  ),
                ),
              );
            }).toList(),
          ),
          const SizedBox(height: 8),
          // Days Grid
          Expanded(
            child: GridView.builder(
              physics: const NeverScrollableScrollPhysics(),
              gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
                crossAxisCount: 7,
                childAspectRatio: 1.0,
              ),
              itemCount: 42, // 6 rows max to be safe
              itemBuilder: (context, index) {
                final dayNumber = index - offset + 1;
                if (dayNumber < 1 || dayNumber > daysInMonth) {
                  return const SizedBox.shrink();
                }

                final isToday = dayNumber == now.day;

                return Container(
                  margin: const EdgeInsets.all(4),
                  decoration: isToday
                      ? BoxDecoration(
                          color: Theme.of(context).colorScheme.primary,
                          shape: BoxShape.circle,
                        )
                      : null,
                  child: Center(
                    child: Text(
                      '$dayNumber',
                      style: TextStyle(
                        color: isToday ? Colors.black : Colors.white,
                        fontWeight: isToday
                            ? FontWeight.bold
                            : FontWeight.normal,
                      ),
                    ),
                  ),
                );
              },
            ),
          ),
        ],
      ),
    );
  }
}