/**
 * The two indexing judgements the site makes, in one place.
 *
 * Both are imported by more than one file on purpose. `isIndexableMint` decides a mint
 * page's `robots` meta *and* whether the sitemap lists it, and those two must agree:
 * a sitemap entry for a page that says `noindex` is a contradiction a crawler notices.
 * `check-hreflang.mjs` verifies the agreement from the built HTML, so the invariant is
 * enforced rather than merely intended.
 *
 * Pure functions, no `t()`: `check-i18n.mjs` treats every `.ts` under `lib/` as island
 * code and would hold any key here to the client-namespace rule.
 */

/**
 * Is this mint's page worth a place in the index?
 *
 * No, in exactly one case: the site has never once reached it *and* nobody has ever
 * reviewed it. Such a page has no operator name, no description, no version, no NUT
 * list and no reviews, because every one of those comes from a mint that answered or a
 * person who wrote something. What is left is the site's own furniture and a URL, which
 * is the same page as the next never-reached mint's.
 *
 * It stays listed on /mints, stays linked, stays searchable on the site and stays
 * reviewable — the rule that offline mints must remain findable is about this site's
 * own listings, and nothing here changes them. Only search engines skip it, and only
 * until the mint answers once or someone reviews it, at which point the next build
 * puts it back.
 */
export function isIndexableMint(mint: {
  last_online: number | null;
  review_count: number;
}): boolean {
  return !(mint.last_online === null && mint.review_count === 0);
}

/**
 * Names that say nothing about which mint they belong to.
 *
 * Anchored, so a mint genuinely called "Bolverker Mint" or "Mint Cuba Bitcoin" is left
 * alone; only a name that is *entirely* a generic noun matches. Two mints currently
 * publish `name: "Cashu mint"`, which produced two identical `<title>`s competing with
 * each other for the same query.
 */
const GENERIC_NAME = /^(cashu[\s-]?mint|mint|cashu|ecash[\s-]?mint|test(\s?mint)?)$/i;

/** Names published by more than one mint, lowercased. Built once from the full list. */
export function nameCollisions(mints: Array<{ name: string | null }>): Set<string> {
  const seen = new Map<string, number>();
  for (const mint of mints) {
    const key = mint.name?.trim().toLowerCase();
    if (!key) continue;
    seen.set(key, (seen.get(key) ?? 0) + 1);
  }
  return new Set([...seen].filter(([, count]) => count > 1).map(([key]) => key));
}

/**
 * The name a `<title>` should use for a mint.
 *
 * The operator's own name, unless it identifies nothing — either because it is missing,
 * or because it is a generic noun, or because another mint publishes the same one. In
 * those cases the domain does the identifying, since that is what actually tells two
 * mints apart.
 *
 * This is for the title and the description only. The `<h1>` keeps the operator's name
 * verbatim: the heading is the mint's name for itself, and rewriting it would be
 * putting words in their mouth. The title is this site's label for its own page.
 */
export function seoName(
  name: string | null,
  domain: string,
  collisions: Set<string>,
): string {
  const raw = name?.trim() ?? '';
  if (raw === '' || GENERIC_NAME.test(raw)) return domain;
  if (collisions.has(raw.toLowerCase())) return `${raw} (${domain})`;
  return raw;
}

/**
 * Trim to a length without cutting a word in half.
 *
 * Meta descriptions are truncated by the search engine anyway, but a description stored
 * ending mid-word reads as broken in every other consumer of it (link previews, feed
 * readers) where nothing re-truncates.
 */
export function clampWords(value: string, max: number): string {
  if (value.length <= max) return value;
  const cut = value.slice(0, max);
  const lastSpace = cut.lastIndexOf(' ');
  return (lastSpace > max * 0.6 ? cut.slice(0, lastSpace) : cut).trimEnd();
}

/**
 * A mint's own description, made fit to open a meta description.
 *
 * It is operator-written text headed for a `content` attribute and a link preview, so
 * everything that does not belong in either comes out: HTML tags and control
 * characters are stripped, whitespace collapses, and only the first sentence
 * survives — a meta description quoting three sentences of marketing leaves no room
 * for the rating and status that make the snippet useful. (Astro does the actual
 * attribute escaping; this removes what escaping would merely neutralise.)
 *
 * Two judgement calls:
 *
 *   - SHOUTING is normalised to sentence case. A description that is ≥80% capitals
 *     reads as noise in a search result, and the mint's page still shows the original.
 *   - The sentence split requires whitespace after the terminator, so "mint.example.com"
 *     inside a sentence does not end it.
 *
 * Returns null when nothing usable is left, and the caller falls back to its own copy.
 */
export function cleanMintDescription(value: string | null | undefined, max = 70): string | null {
  if (!value) return null;

  let clean = value
    .replace(/<[^>]*>/g, ' ')
    .replace(/[\u0000-\u001f\u007f-\u009f]/g, ' ')
    .replace(/\s+/g, ' ')
    .trim();
  if (clean === '') return null;

  const sentence = /^.*?[.!?](?=\s|$)/.exec(clean);
  clean = (sentence?.[0] ?? clean).trim();

  const letters = clean.replace(/[^\p{L}]/gu, '');
  if (letters.length >= 8 && letters.replace(/\p{Ll}/gu, '').length / letters.length > 0.8) {
    clean = clean.toLowerCase();
    clean = clean[0]!.toUpperCase() + clean.slice(1);
  }

  clean = clampWords(clean, max);
  if (!/[.!?]$/.test(clean)) clean += '.';
  return clean;
}