'use client';

import { useState, useRef, useEffect } from 'react';
import { ChevronLeft, ChevronRight, Calendar } from 'lucide-react';

interface MonthPickerProps {
  value: string;
  onChange: (value: string) => void;
  placeholder?: string;
}

const MONTHS = ['1月', '2月', '3月', '4月', '5月', '6月', '7月', '8月', '9月', '10月', '11月', '12月'];

export function MonthPicker({ value, onChange, placeholder = '选择月份' }: MonthPickerProps) {
  const [open, setOpen] = useState(false);
  const [year, setYear] = useState(() => {
    if (value) return parseInt(value.slice(0, 4));
    return new Date().getFullYear();
  });
  const ref = useRef<HTMLDivElement>(null);

  useEffect(() => {
    const handler = (e: MouseEvent) => {
      if (ref.current && !ref.current.contains(e.target as Node)) setOpen(false);
    };
    document.addEventListener('mousedown', handler);
    return () => document.removeEventListener('mousedown', handler);
  }, []);

  const selectedMonth = value ? parseInt(value.slice(5, 7)) : null;
  const selectedYear = value ? parseInt(value.slice(0, 4)) : null;

  const handleSelect = (month: number) => {
    const m = String(month).padStart(2, '0');
    onChange(`${year}-${m}`);
    setOpen(false);
  };

  const handleClear = (e: React.MouseEvent) => {
    e.stopPropagation();
    onChange('');
    setOpen(false);
  };

  const displayText = value
    ? `${selectedYear}年${selectedMonth}月`
    : '';

  return (
    <div ref={ref} className="relative">
      <button
        type="button"
        onClick={() => setOpen(!open)}
        className="flex h-8 items-center gap-2 rounded-lg border border-[var(--line)] bg-[var(--bg-card)] px-3 text-[12px] text-[var(--ink-soft)] hover:border-[var(--accent)] transition-colors min-w-[120px]"
      >
        <Calendar className="h-3.5 w-3.5 text-[var(--ink-muted)]" />
        <span className={displayText ? 'text-[var(--ink)]' : 'text-[var(--ink-muted)]'}>
          {displayText || placeholder}
        </span>
        {value && (
          <span
            onClick={handleClear}
            className="ml-auto text-[var(--ink-muted)] hover:text-[var(--ink)] text-[10px] leading-none"
          >
            ✕
          </span>
        )}
      </button>

      {open && (
        <div className="absolute top-full left-0 mt-1 z-50 w-[240px] rounded-xl border border-[var(--line)] bg-[var(--bg-card)] shadow-[var(--shadow-md)] p-3">
          {/* Year nav */}
          <div className="flex items-center justify-between mb-3">
            <button
              type="button"
              onClick={() => setYear(year - 1)}
              className="p-1 rounded-md hover:bg-[var(--bg-subtle)] text-[var(--ink-muted)] hover:text-[var(--ink)]"
            >
              <ChevronLeft className="h-4 w-4" />
            </button>
            <span className="text-[13px] font-semibold text-[var(--ink)]">{year}年</span>
            <button
              type="button"
              onClick={() => setYear(year + 1)}
              className="p-1 rounded-md hover:bg-[var(--bg-subtle)] text-[var(--ink-muted)] hover:text-[var(--ink)]"
            >
              <ChevronRight className="h-4 w-4" />
            </button>
          </div>

          {/* Month grid */}
          <div className="grid grid-cols-3 gap-1.5">
            {MONTHS.map((label, i) => {
              const month = i + 1;
              const isSelected = selectedYear === year && selectedMonth === month;
              const isCurrent = new Date().getFullYear() === year && new Date().getMonth() === i;
              return (
                <button
                  key={month}
                  type="button"
                  onClick={() => handleSelect(month)}
                  className={`h-8 rounded-lg text-[12px] font-medium transition-colors ${
                    isSelected
                      ? 'bg-[var(--accent)] text-white'
                      : isCurrent
                        ? 'border border-[var(--accent)] text-[var(--accent)] hover:bg-[var(--accent-soft)]'
                        : 'text-[var(--ink-soft)] hover:bg-[var(--bg-subtle)] hover:text-[var(--ink)]'
                  }`}
                >
                  {label}
                </button>
              );
            })}
          </div>
        </div>
      )}
    </div>
  );
}