import type { DecisionKind, LetterTemplate, OutgoingLetter } from "./types";

export type StatusKind = "hired" | "withdrawn" | "other";

/**
 * "Hired", "hired " and "HIRED" are the same decision. "Offer accepted" is a
 * different one and is never read as Hired. With normalisation off (tests only)
 * the comparison is exact.
 */
export function statusKind(raw: string, normalized = true): StatusKind {
  const s = normalized ? raw.trim().replace(/\s+/g, " ").toLowerCase() : raw;
  if (s === (normalized ? "hired" : "Hired")) return "hired";
  if (s === (normalized ? "withdrawn" : "Withdrawn")) return "withdrawn";
  return "other";
}

export function normalizeAddress(a: string): string {
  return a.trim().toLowerCase();
}

// Deliberately plain: one @, a dot in the domain, no spaces. The mail service is the final judge.
export function looksLikeAddress(a: string): boolean {
  return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(a.trim());
}

export function decisionKind(raw: string): DecisionKind | null {
  const s = raw.trim().toLowerCase();
  if (s === "send again") return "send-again";
  if (s === "confirm sent") return "confirm-sent";
  if (s === "approve new address") return "approve-new-address";
  return null;
}

const MONTHS = [
  "January", "February", "March", "April", "May", "June",
  "July", "August", "September", "October", "November", "December",
];
const DAYS = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];

/** "2026-10-05" -> "Monday, October 5". Computed in UTC so page and Apps Script agree. */
export function longDate(iso: string): string {
  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(iso);
  if (!m) return iso;
  const d = new Date(Date.UTC(+m[1], +m[2] - 1, +m[3]));
  return `${DAYS[d.getUTCDay()]}, ${MONTHS[d.getUTCMonth()]} ${d.getUTCDate()}`;
}

/** A real calendar date written YYYY-MM-DD ("2026-10-32" is not one). */
export function isRealDate(iso: string): boolean {
  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(iso.trim());
  if (!m) return false;
  const d = new Date(Date.UTC(+m[1], +m[2] - 1, +m[3]));
  return d.getUTCFullYear() === +m[1] && d.getUTCMonth() === +m[2] - 1 && d.getUTCDate() === +m[3];
}

export function firstName(fullName: string): string {
  return fullName.trim().split(/\s+/)[0] ?? "";
}

/** A short, stable fingerprint of the letter text, stored with each attempt. */
export function letterVersion(t: LetterTemplate): string {
  let h = 5381;
  const s = `${t.subject}\u0000${t.body}`;
  for (let i = 0; i < s.length; i++) h = ((h << 5) + h + s.charCodeAt(i)) >>> 0;
  return `v-${h.toString(36)}`;
}

export function renderLetter(
  t: LetterTemplate,
  a: { therapist: string; startDate: string; welcomeEmail: string },
): OutgoingLetter {
  const fill = (s: string) =>
    s.replace(/\{\{\s*first_name\s*\}\}/g, firstName(a.therapist)).replace(/\{\{\s*start_date\s*\}\}/g, longDate(a.startDate));
  return {
    to: a.welcomeEmail.trim(),
    subject: fill(t.subject),
    body: fill(t.body),
    senderName: t.senderName,
    replyTo: t.replyTo,
  };
}