import type { AgentSettlementCycle } from "@/lib/agent-settlement-cycle";

export type SettlementPeriodPresetKey = "this_week" | "last_week" | "this_month";

/** `datetime-local` 控件取值格式 */
export function toDateTimeLocalValue(date: Date): string {
  const pad = (n: number) => String(n).padStart(2, "0");

  return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}T${pad(date.getHours())}:${pad(date.getMinutes())}`;
}

function startOfDay(date: Date): Date {
  const d = new Date(date);
  d.setHours(0, 0, 0, 0);

  return d;
}

function endOfDay(date: Date): Date {
  const d = new Date(date);
  d.setHours(23, 59, 0, 0);

  return d;
}

/** 周一为一周起始（与产品文档「周结」一致） */
function startOfWeekMonday(date: Date): Date {
  const d = startOfDay(date);
  const day = d.getDay();
  const diff = day === 0 ? -6 : 1 - day;
  d.setDate(d.getDate() + diff);

  return d;
}

function addDays(date: Date, days: number): Date {
  const d = new Date(date);
  d.setDate(d.getDate() + days);

  return d;
}

function startOfMonth(date: Date): Date {
  const d = startOfDay(date);
  d.setDate(1);

  return d;
}

function endOfMonth(date: Date): Date {
  const d = startOfDay(date);
  d.setMonth(d.getMonth() + 1);
  d.setDate(0);

  return endOfDay(d);
}

export function settlementPeriodPresetRange(
  key: SettlementPeriodPresetKey,
  now: Date = new Date(),
): { period_start: string; period_end: string } {
  switch (key) {
    case "this_week": {
      const start = startOfWeekMonday(now);
      const end = endOfDay(addDays(start, 6));

      return {
        period_start: toDateTimeLocalValue(start),
        period_end: toDateTimeLocalValue(end),
      };
    }
    case "last_week": {
      const thisStart = startOfWeekMonday(now);
      const start = addDays(thisStart, -7);
      const end = endOfDay(addDays(start, 6));

      return {
        period_start: toDateTimeLocalValue(start),
        period_end: toDateTimeLocalValue(end),
      };
    }
    case "this_month": {
      const start = startOfMonth(now);
      const end = endOfMonth(now);

      return {
        period_start: toDateTimeLocalValue(start),
        period_end: toDateTimeLocalValue(end),
      };
    }
  }
}

/** 按代理结算周期推荐默认快捷开期（周结优先） */
export function defaultSettlementPeriodPreset(
  cycle: AgentSettlementCycle,
): SettlementPeriodPresetKey {
  if (cycle === "monthly") {
    return "this_month";
  }

  return "this_week";
}

export function formatSettlementPeriodSpan(
  periodStart: string | undefined,
  periodEnd: string | undefined,
): string {
  const start = periodStart?.slice(0, 10) ?? "—";
  const end = periodEnd?.slice(0, 10) ?? "—";

  return `${start} ~ ${end}`;
}