'use strict';

const crypto = require('node:crypto');

const SCHEME = 'mangacircus-work-v1';
const KINDS = new Set(['anilist', 'mangadex', 'weebcentral', 'hoster', 'origin']);

function normalizeWorkIdentity(value) {
  if (!value || typeof value !== 'object' || value.scheme !== SCHEME
    || !KINDS.has(value.kind) || typeof value.value !== 'string'
    || !value.value.trim() || value.value.length > 300) return null;
  return { scheme: SCHEME, kind: value.kind, value: value.value.trim() };
}

function resolveWorkIdentity(meta = {}, mangaId, serverId) {
  const carried = normalizeWorkIdentity(meta['x-work-identity']);
  if (carried) return carried;

  const anilist = meta['x-anilist']?.id ?? meta['x-scraper']?.ids?.anilist;
  if (anilist != null && String(anilist).trim()) return { scheme: SCHEME, kind: 'anilist', value: String(anilist).trim() };

  const ids = meta['x-scraper']?.ids || {};
  for (const source of ['mangadex', 'weebcentral']) {
    if (ids[source] != null && String(ids[source]).trim()) {
      return { scheme: SCHEME, kind: source, value: String(ids[source]).trim() };
    }
  }
  for (const source of Object.keys(ids).sort()) {
    if (!['anilist', 'mangadex', 'weebcentral'].includes(source) && !source.startsWith('peer-')
      && ids[source] != null && String(ids[source]).trim()) {
      return { scheme: SCHEME, kind: 'hoster', value: `${source}:${String(ids[source]).trim()}` };
    }
  }

  // A private, stable lineage ID lets a title safely make a round trip even if
  // neither server has external metadata. It reveals neither the folder nor title.
  if (typeof mangaId === 'string' && mangaId && typeof serverId === 'string' && serverId) {
    const value = crypto.createHash('sha256').update(`${serverId}\0${mangaId}`).digest('hex');
    return { scheme: SCHEME, kind: 'origin', value };
  }
  return null;
}

function sameWorkIdentity(left, right) {
  const a = normalizeWorkIdentity(left), b = normalizeWorkIdentity(right);
  return !!a && !!b && a.scheme === b.scheme && a.kind === b.kind && a.value === b.value;
}

module.exports = { SCHEME, normalizeWorkIdentity, resolveWorkIdentity, sameWorkIdentity };