import React, { useState, useMemo, useEffect } from 'react';
import { Transaction, TransactionType, BillReminder } from '../types';
import { Solar } from 'lunar-javascript';

interface CalendarViewProps {
  transactions: Transaction[];
  reminders?: BillReminder[];
  viewDate?: string; // Format: YYYY-MM
}

const formatAmount = (num: number): string => {
    // 如果金额超过 10 万（十万单位），显示为 X.Y万，最多显示小数点后一位
    if (num >= 100000) {
        return (num / 10000).toFixed(1).replace(/\.0$/, '') + '万';
    }
    // 否则显示完整数字（四舍五入）
    return Math.round(num).toString();
};

const CalendarView: React.FC<CalendarViewProps> = ({ transactions, reminders = [], viewDate }) => {
  // Initialize from prop or current date
  const [currentDate, setCurrentDate] = useState(() => {
    if (viewDate) {
      const [y, m] = viewDate.split('-').map(Number);
      return new Date(y, m - 1, 1);
    }
    return new Date();
  });

  // Sync internal state when prop changes
  useEffect(() => {
    if (viewDate) {
      const [y, m] = viewDate.split('-').map(Number);
      setCurrentDate(new Date(y, m - 1, 1));
    }
  }, [viewDate]);

  const year = currentDate.getFullYear();
  const month = currentDate.getMonth();

  const daysInMonth = new Date(year, month + 1, 0).getDate();
  const firstDayOfMonth = new Date(year, month, 1).getDay(); // 0 is Sunday

  const handlePrevMonth = () => setCurrentDate(new Date(year, month - 1, 1));
  const handleNextMonth = () => setCurrentDate(new Date(year, month + 1, 1));

  // Helper to get Lunar Date text
  const getLunarText = (y: number, m: number, d: number) => {
      try {
        const solar = Solar.fromYmd(y, m + 1, d);
        const lunar = solar.getLunar();
        const day = lunar.getDayInChinese();
        if (day === '初一') {
            return lunar.getMonthInChinese() + '月';
        }
        return day;
      } catch (e) {
          return '';
      }
  };

  // Aggregate stats by date
  const dailyStats = useMemo(() => {
    const map = new Map<string, { income: number; expense: number; reminderTitle?: string }>();
    
    // Process Transactions
    transactions.forEach(t => {
      const existing = map.get(t.date) || { income: 0, expense: 0 };
      if (t.type === TransactionType.EXPENSE) {
        existing.expense += t.amount;
      } else {
        existing.income += t.amount;
      }
      map.set(t.date, existing);
    });

    // Process Reminders
    reminders.forEach(r => {
        let dateKey = '';
        if (r.frequency === 'monthly') {
            const day = parseInt(r.targetDate);
            if (day <= daysInMonth) {
                dateKey = `${year}-${String(month + 1).padStart(2, '0')}-${String(day).padStart(2, '0')}`;
            }
        } else {
            dateKey = r.targetDate;
        }

        if (dateKey) {
             const existing = map.get(dateKey) || { income: 0, expense: 0 };
             if (!r.isCompleted && !existing.reminderTitle) {
                 existing.reminderTitle = r.title;
             }
             map.set(dateKey, existing);
        }
    });

    return map;
  }, [transactions, reminders, year, month, daysInMonth]);

  const renderDays = () => {
    const days = [];
    for (let i = 0; i < firstDayOfMonth; i++) {
      days.push(<div key={`empty-${i}`} className="h-24 bg-gray-50/20 border border-gray-100/30"></div>);
    }

    for (let d = 1; d <= daysInMonth; d++) {
      const dateStr = `${year}-${String(month + 1).padStart(2, '0')}-${String(d).padStart(2, '0')}`;
      const stat = dailyStats.get(dateStr) || { income: 0, expense: 0 };
      const isToday = new Date().toISOString().split('T')[0] === dateStr;
      const lunarText = getLunarText(year, month, d);

      days.push(
        <div key={d} className={`h-24 border border-gray-100 p-1 flex flex-col justify-between relative overflow-hidden transition-colors ${isToday ? 'bg-indigo-50/40 ring-1 ring-inset ring-indigo-100' : 'bg-white'}`}>
          <div className="flex flex-col w-full items-center pt-1">
             <div className="flex flex-col items-center leading-none">
                 <span className={`text-[11px] font-black w-5 h-5 flex items-center justify-center rounded-full mb-0.5 ${isToday ? 'bg-indigo-600 text-white' : 'text-gray-700'}`}>
                    {d}
                 </span>
                 <span className="text-[8px] text-gray-300 font-bold scale-90">{lunarText}</span>
             </div>
             {stat.reminderTitle && (
                 <div className="w-full px-0.5 mt-1 text-center">
                     <span className="block text-[8px] font-black text-rose-500 bg-rose-50 border border-rose-100 rounded px-0.5 py-0.5 whitespace-nowrap overflow-hidden leading-none uppercase tracking-tighter">
                        {stat.reminderTitle.slice(0, 4)}
                     </span>
                 </div>
             )}
          </div>
          <div className="flex flex-col items-end w-full px-0.5 gap-0.5 pb-1">
              {stat.income > 0 && (
                  <div className="flex items-center gap-0.5 w-full justify-end">
                      <span className="text-[9px] font-black text-emerald-500 leading-none whitespace-nowrap overflow-visible">
                        ¥{formatAmount(stat.income)}
                      </span>
                  </div>
              )}
              {stat.expense > 0 && (
                  <div className="flex items-center gap-0.5 w-full justify-end">
                      <span className="text-[9px] font-black text-rose-400 leading-none whitespace-nowrap overflow-visible">
                        ¥{formatAmount(stat.expense)}
                      </span>
                  </div>
              )}
          </div>
        </div>
      );
    }
    return days;
  };

  return (
    <div className="bg-white rounded-[2rem] shadow-sm border border-gray-100 overflow-hidden">
      <div className="flex items-center justify-between p-4 border-b border-gray-100 bg-white">
        <button onClick={handlePrevMonth} className="p-2 hover:bg-gray-50 rounded-xl text-gray-300 hover:text-indigo-600 transition-colors">
          <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor"><path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15 19l-7-7 7-7" /></svg>
        </button>
        <h3 className="font-black text-gray-800 text-sm tracking-widest uppercase">
          {year} / {String(month + 1).padStart(2, '0')}
        </h3>
        <button onClick={handleNextMonth} className="p-2 hover:bg-gray-50 rounded-xl text-gray-300 hover:text-indigo-600 transition-colors">
          <svg className="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke="currentColor"><path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 5l7 7-7 7" /></svg>
        </button>
      </div>
      <div className="grid grid-cols-7 bg-gray-50/30">
        {['日', '一', '二', '三', '四', '五', '六'].map(day => (
          <div key={day} className="py-2.5 text-center text-[9px] font-black text-gray-400 uppercase tracking-widest">
            {day}
          </div>
        ))}
      </div>
      <div className="grid grid-cols-7 border-t border-gray-50">
        {renderDays()}
      </div>
    </div>
  );
};

export default CalendarView;