import {
  addShanghaiDays,
  previousShanghaiMonth,
  previousShanghaiWeek,
  shanghaiMonthRange,
  shanghaiWeekRange,
  shanghaiWeekday,
  shanghaiYearMonth,
  shanghaiYmd,
  startOfShanghaiDay,
} from './shanghai-date';

export const WECOM_REPORT_KINDS = ['daily', 'weekly', 'monthly'] as const;
export type WecomReportKind = (typeof WECOM_REPORT_KINDS)[number];

export function isWecomReportKind(v: string): v is WecomReportKind {
  return (WECOM_REPORT_KINDS as readonly string[]).includes(v);
}

export type WecomReportStats = {
  usersTotal: number;
  usersIncrement: number;
  partnersTotal: number;
  partnersIncrement: number;
  storesTotal: number;
  storesIncrement: number;
  ordersTotal: number;
  ordersIncrement: number;
  orderAmountTotal: number;
  orderAmountIncrement: number;
  redeemsTotal: number;
  redeemsIncrement: number;
  redeemAmountTotal: number;
  redeemAmountIncrement: number;
};

export type WecomReportPeriod = {
  kind: WecomReportKind;
  start: Date;
  endExclusive: Date;
  periodKey: string;
  title: string;
  rangeLabel: string;
  incrementLabel: string;
};

export type WecomReportSchedule = {
  enabled: boolean;
  sendHour: number;
  sendMinute: number;
  /** 1=周一 … 7=周日，仅周报 */
  sendWeekday: number;
  /** 1–31，仅月报 */
  sendMonthDay: number;
  lastSentPeriod: string | null;
};

function pad2(n: number): string {
  return String(n).padStart(2, '0');
}

function shanghaiDateTime(ymd: string, hour: number, minute: number): Date {
  return new Date(`${ymd}T${pad2(hour)}:${pad2(minute)}:00+08:00`);
}

function lastDayOfShanghaiMonth(year: number, month: number): number {
  return Number(shanghaiYmd(new Date(shanghaiMonthRange(year, month).endExclusive.getTime() - 1)).slice(8, 10));
}

/** 日报=当天；周报=上一自然周；月报=上一自然月（北京日历） */
export function wecomReportPeriod(kind: WecomReportKind, now = new Date()): WecomReportPeriod {
  if (kind === 'daily') {
    const start = startOfShanghaiDay(now);
    const ymd = shanghaiYmd(start);
    return {
      kind,
      start,
      endExclusive: addShanghaiDays(start, 1),
      periodKey: ymd,
      title: `日报（${ymd}）`,
      rangeLabel: ymd,
      incrementLabel: '当日新增',
    };
  }
  if (kind === 'weekly') {
    const { start, endExclusive } = previousShanghaiWeek(now);
    const from = shanghaiYmd(start);
    const to = shanghaiYmd(new Date(endExclusive.getTime() - 1));
    return {
      kind,
      start,
      endExclusive,
      periodKey: from,
      title: `周报（${from} ~ ${to}）`,
      rangeLabel: `${from} ~ ${to}`,
      incrementLabel: '本期新增',
    };
  }
  const { year, month } = previousShanghaiMonth(now);
  const { start, endExclusive } = shanghaiMonthRange(year, month);
  return {
    kind,
    start,
    endExclusive,
    periodKey: `${year}-${pad2(month)}`,
    title: `月报（${year}年${month}月）`,
    rangeLabel: `${shanghaiYmd(start)} ~ ${shanghaiYmd(new Date(endExclusive.getTime() - 1))}`,
    incrementLabel: '本期新增',
  };
}

/** 进行中的周期截到 now，已结束的周期用期末 */
export function wecomReportCutoff(period: WecomReportPeriod, now = new Date()): Date {
  return now.getTime() < period.endExclusive.getTime() ? now : period.endExclusive;
}

export function wecomReportDueAt(kind: WecomReportKind, schedule: WecomReportSchedule, now = new Date()): Date {
  const hour = Math.min(23, Math.max(0, Math.floor(schedule.sendHour)));
  const minute = Math.min(59, Math.max(0, Math.floor(schedule.sendMinute)));
  if (kind === 'daily') {
    return shanghaiDateTime(shanghaiYmd(now), hour, minute);
  }
  if (kind === 'weekly') {
    const { start } = shanghaiWeekRange(now);
    const iso = Math.min(7, Math.max(1, Math.floor(schedule.sendWeekday) || 1));
    const day = addShanghaiDays(start, iso - 1);
    return shanghaiDateTime(shanghaiYmd(day), hour, minute);
  }
  const { year, month } = shanghaiYearMonth(now);
  const last = lastDayOfShanghaiMonth(year, month);
  const day = Math.min(last, Math.max(1, Math.floor(schedule.sendMonthDay) || 1));
  return shanghaiDateTime(`${year}-${pad2(month)}-${pad2(day)}`, hour, minute);
}

export function wecomReportShouldFire(
  kind: WecomReportKind,
  schedule: WecomReportSchedule,
  now = new Date(),
): boolean {
  if (!schedule.enabled) return false;
  const period = wecomReportPeriod(kind, now);
  if (schedule.lastSentPeriod === period.periodKey) return false;
  return now.getTime() >= wecomReportDueAt(kind, schedule, now).getTime();
}

function fmtCount(n: number): string {
  return Math.round(n).toLocaleString('zh-CN');
}

function fmtMoney(n: number): string {
  return Number(n || 0).toFixed(2);
}

function line(label: string, total: number, inc: number, incLabel: string, money = false): string {
  const fmt = money ? fmtMoney : fmtCount;
  return `${label}：${fmt(total)}（${incLabel} ${fmt(inc)}）`;
}

export function formatWecomReportMarkdown(period: WecomReportPeriod, stats: WecomReportStats): string {
  const inc = period.incrementLabel;
  return [
    `**杜康好客 · ${period.title}**`,
    `统计区间：${period.rangeLabel}（北京时间）`,
    '',
    line('用户数量', stats.usersTotal, stats.usersIncrement, inc),
    line('合伙人数量', stats.partnersTotal, stats.partnersIncrement, inc),
    line('门店数量', stats.storesTotal, stats.storesIncrement, inc),
    line('订单数量', stats.ordersTotal, stats.ordersIncrement, inc),
    line('订单金额', stats.orderAmountTotal, stats.orderAmountIncrement, inc, true),
    line('核销单数量', stats.redeemsTotal, stats.redeemsIncrement, inc),
    line('核销单金额', stats.redeemAmountTotal, stats.redeemAmountIncrement, inc, true),
  ].join('\n');
}

/** 仅用于单测：避免把 shanghaiWeekday 的周日=0 与 ISO 周一=1 搞混 */
export function wecomReportIsoWeekday(d: Date): number {
  const wd = shanghaiWeekday(d);
  return wd === 0 ? 7 : wd;
}