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: Column(
              children: List.generate(6, (row) {
                return Expanded(
                  child: Row(
                    children: List.generate(7, (col) {
                      final index = row * 7 + col;
                      final dayNumber = index - offset + 1;

                      if (dayNumber < 1 || dayNumber > daysInMonth) {
                        return const Expanded(child: SizedBox.shrink());
                      }

                      final isToday = dayNumber == now.day;

                      return Expanded(
                        child: Container(
                          margin: const EdgeInsets.all(2),
                          decoration: isToday
                              ? BoxDecoration(
                                  color: Theme.of(context).colorScheme.primary,
                                  shape: BoxShape.circle,
                                )
                              : null,
                          child: Center(
                            child: FittedBox(
                              fit: BoxFit.scaleDown,
                              child: Text(
                                '$dayNumber',
                                style: TextStyle(
                                  color: isToday ? Colors.black : Colors.white,
                                  fontWeight: isToday
                                      ? FontWeight.bold
                                      : FontWeight.normal,
                                  fontSize: 12,
                                ),
                              ),
                            ),
                          ),
                        ),
                      );
                    }),
                  ),
                );
              }),
            ),
          ),
        ],
      ),
    );
  }
}