// AttendanceCalendar：月度考勤日历
// 依据：02-architecture-design.md §15.5 AttendanceCalendar 设计
// - 月历视图，每天用颜色点标记考勤状态
// - present=success / late=warning / absent=danger / leave=ink-subtle
// - 支持月份导航（可选 month + onMonthChange props）

"use client";

import { useMemo } from "react";
import type { AttendanceRecord } from "@/types";
import { cn } from "@/lib/utils";

interface AttendanceCalendarProps {
  records: AttendanceRecord[];
  /** YYYY-MM 格式，未传则使用当前月 */
  month?: string;
  /** 月份切换回调，传入则显示导航按钮 */
  onMonthChange?: (month: string) => void;
}

const STATUS_STYLES: Record<AttendanceRecord["status"], string> = {
  present: "bg-success",
  late: "bg-warning",
  absent: "bg-danger",
  leave: "bg-ink-subtle",
};

const STATUS_LABELS: Record<AttendanceRecord["status"], string> = {
  present: "出勤",
  late: "迟到",
  absent: "缺勤",
  leave: "请假",
};

const WEEKDAYS = ["日", "一", "二", "三", "四", "五", "六"];

function parseMonth(month: string): { year: number; month: number } {
  const [yearStr, monthStr] = month.split("-");
  return {
    year: parseInt(yearStr ?? "0", 10),
    month: parseInt(monthStr ?? "1", 10) - 1,
  };
}

function formatMonth(year: number, month: number): string {
  return `${year}-${String(month + 1).padStart(2, "0")}`;
}

function shiftMonth(month: string, delta: number): string {
  const { year, month: m } = parseMonth(month);
  const date = new Date(year, m + delta, 1);
  return formatMonth(date.getFullYear(), date.getMonth());
}

export function AttendanceCalendar({
  records,
  month,
  onMonthChange,
}: AttendanceCalendarProps) {
  const {
    year,
    month: monthLabel,
    days,
    recordMap,
  } = useMemo(() => {
    const now = new Date();
    const target = month
      ? parseMonth(month)
      : { year: now.getFullYear(), month: now.getMonth() };
    const y = target.year;
    const m = target.month;
    const firstDay = new Date(y, m, 1);
    const lastDay = new Date(y, m + 1, 0);
    const startWeekday = firstDay.getDay();
    const totalDays = lastDay.getDate();

    const dayCells: (number | null)[] = [];
    for (let i = 0; i < startWeekday; i++) dayCells.push(null);
    for (let d = 1; d <= totalDays; d++) dayCells.push(d);
    while (dayCells.length % 7 !== 0) dayCells.push(null);

    const map = new Map<string, AttendanceRecord>();
    for (const r of records) {
      map.set(r.date, r);
    }

    return { year: y, month: m, days: dayCells, recordMap: map };
  }, [records, month]);

  // 统计
  const stats = useMemo(() => {
    const counts = { present: 0, late: 0, absent: 0, leave: 0 };
    for (const r of records) {
      counts[r.status]++;
    }
    return counts;
  }, [records]);

  return (
    <div className="rounded border border-rule bg-paper-elevated p-4">
      <div className="flex items-center justify-between">
        <div className="flex items-center gap-2">
          {onMonthChange && (
            <button
              type="button"
              onClick={() =>
                onMonthChange(shiftMonth(formatMonth(year, monthLabel), -1))
              }
              className="rounded px-2 py-1 text-sm text-ink-muted hover:text-ink"
              aria-label="上一月"
            >
              ‹
            </button>
          )}
          <h3 className="font-serif text-base">
            {year}年{monthLabel + 1}月考勤
          </h3>
          {onMonthChange && (
            <button
              type="button"
              onClick={() =>
                onMonthChange(shiftMonth(formatMonth(year, monthLabel), 1))
              }
              className="rounded px-2 py-1 text-sm text-ink-muted hover:text-ink"
              aria-label="下一月"
            >
              ›
            </button>
          )}
        </div>
        <div className="flex gap-3 text-xs">
          {(Object.keys(STATUS_LABELS) as AttendanceRecord["status"][]).map(
            (s) => (
              <span key={s} className="flex items-center gap-1">
                <span
                  className={cn(
                    "inline-block h-2 w-2 rounded-full",
                    STATUS_STYLES[s],
                  )}
                />
                {STATUS_LABELS[s]}
              </span>
            ),
          )}
        </div>
      </div>

      {/* 日历网格 */}
      <div className="mt-4">
        <div className="grid grid-cols-7 gap-1 text-center text-xs text-ink-muted">
          {WEEKDAYS.map((w) => (
            <div key={w} className="py-1">
              {w}
            </div>
          ))}
        </div>
        <div className="mt-1 grid grid-cols-7 gap-1">
          {days.map((day, idx) => {
            if (day === null) {
              return <div key={idx} style={{ aspectRatio: "1 / 1" }} />;
            }
            const dateStr = `${year}-${String(monthLabel + 1).padStart(2, "0")}-${String(day).padStart(2, "0")}`;
            const record = recordMap.get(dateStr);
            return (
              <div
                key={idx}
                className="flex flex-col items-center justify-center rounded text-sm"
                style={{ aspectRatio: "1 / 1" }}
                title={record ? STATUS_LABELS[record.status] : undefined}
              >
                <span className="text-xs">{day}</span>
                {record && (
                  <span
                    className={cn(
                      "mt-0.5 inline-block h-1.5 w-1.5 rounded-full",
                      STATUS_STYLES[record.status],
                    )}
                  />
                )}
              </div>
            );
          })}
        </div>
      </div>

      {/* 统计 */}
      <div className="mt-4 flex gap-4 border-t border-rule pt-3 text-sm">
        <span className="text-ink-muted">
          出勤 <span className="font-mono text-success">{stats.present}</span>
        </span>
        <span className="text-ink-muted">
          迟到 <span className="font-mono text-warning">{stats.late}</span>
        </span>
        <span className="text-ink-muted">
          缺勤 <span className="font-mono text-danger">{stats.absent}</span>
        </span>
        <span className="text-ink-muted">
          请假 <span className="font-mono">{stats.leave}</span>
        </span>
      </div>
    </div>
  );
}

export default AttendanceCalendar;