/**
 * Shared date parsing for Stampli M/D/YY and MM/DD/YYYY formats.
 * Ported from payments-dashboard/src/dates.js — both formats must parse;
 * anything else returns null (never pass through garbage).
 */

export type ParsedMDY = {
  year: number;
  month: number;
  day: number;
};

/** Parse "M/D/YY" or "MM/DD/YYYY" into { year, month, day }, or null. */
export function parseMDY(value: string | null | undefined): ParsedMDY | null {
  const match = /^(\d{1,2})\/(\d{1,2})\/(\d{2}|\d{4})$/.exec(String(value ?? "").trim());
  if (!match) return null;
  const month = Number.parseInt(match[1]!, 10);
  const day = Number.parseInt(match[2]!, 10);
  let year = Number.parseInt(match[3]!, 10);
  if (match[3]!.length === 2) year += 2000;
  const dt = new Date(year, month - 1, day);
  if (dt.getFullYear() !== year || dt.getMonth() !== month - 1 || dt.getDate() !== day) {
    return null;
  }
  return { year, month, day };
}

/** "YYYY-MM-DD" or null. */
export function toISODate(value: string | null | undefined): string | null {
  const p = parseMDY(value);
  if (!p) return null;
  return `${p.year}-${String(p.month).padStart(2, "0")}-${String(p.day).padStart(2, "0")}`;
}

/** Canonical "MM/DD/YYYY" or null. Stored form for send_payment_on / CSV. */
export function toCanonicalMDY(value: string | null | undefined): string | null {
  const p = parseMDY(value);
  if (!p) return null;
  return `${String(p.month).padStart(2, "0")}/${String(p.day).padStart(2, "0")}/${p.year}`;
}

/**
 * Plausibility window for ingested send dates.
 * Relative to the current year (7 years back, 2 years forward).
 */
export function isPlausibleSendYear(
  value: string | null | undefined,
  nowYear: number = new Date().getFullYear(),
): boolean {
  const p = parseMDY(value);
  if (p === null) return false;
  return p.year >= nowYear - 7 && p.year <= nowYear + 2;
}