// Replicates the query parsing logic shared by api.php and search.php:
//   - extract a year (last (19|20)\d{2} match, ignoring 1080/2160)
//   - extract an episode marker (SxxExxx, SxxExx, Sxx, partN, NxN, Exxx)
//   - choose movie vs tv accordingly
//   - extract titlein from the bytes before the year/episode

import { FILTER_RE } from './titleFilter.js';

const YEAR_RE = /(19|20)\d{2}/g;
// Single-pass regex matching the PHP behaviour:
//   - S/s and E/e and "part" are case-insensitive  ([Ss], [Ee], [Pp]art)
//   - the lowercase 'x' in NxN, and uppercase 'E' in standalone Exxx, are case-sensitive
// Greedy left-to-right alternation means "S01E02" is consumed whole, so the
// trailing "E02" alternative cannot match inside it.
const EPISODE_RE = /[Ss][0-9]{1,2}.?[Ee][0-9]{1,3}|[Ss][0-9]{2}|[Pp]art\.?[0-9]{1,3}|[0-9]{1,2}x[0-9]{1,3}|E[0-9]{1,3}/g;

// PHP uses byte offsets (substr). To stay byte-faithful, work on the UTF-8 bytes.
const utf8 = (s) => Buffer.from(s, 'utf8');
const sliceBytes = (s, end) => utf8(s).slice(0, end).toString('utf8');

function findAll(re, str) {
  const out = [];
  re.lastIndex = 0;
  let m;
  while ((m = re.exec(str)) !== null) {
    out.push({ value: m[0], byteOffset: Buffer.byteLength(str.slice(0, m.index), 'utf8') });
    if (m.index === re.lastIndex) re.lastIndex++;
  }
  return out;
}

function stripFilter(s) {
  return s.replace(FILTER_RE, '');
}

export function parseQuery(query) {
  if (!query) return null;

  let yearin = 0;
  let yearpos = -1;
  let titlein = '';

  const years = findAll(YEAR_RE, query).reverse();
  for (const m of years) {
    if (m.value === '1080' || m.value === '2160') continue;
    yearin = parseInt(m.value, 10);
    yearpos = m.byteOffset;
    titlein = sliceBytes(query, yearpos);
    break;
  }

  let episodein = '';
  let episodepos = -1;
  const eps = findAll(EPISODE_RE, query).reverse();
  for (const m of eps) {
    episodein = m.value;
    episodepos = m.byteOffset;
    break;
  }

  if (episodein) {
    if (!yearin) {
      titlein = sliceBytes(query, episodepos);
    } else if (episodepos > yearpos) {
      titlein = sliceBytes(query, yearpos);
      if (!stripFilter(titlein)) {
        titlein = sliceBytes(query, episodepos);
        yearin = 0;
      }
    } else {
      titlein = sliceBytes(query, episodepos);
      if (!stripFilter(titlein)) {
        titlein = sliceBytes(query, yearpos);
        episodein = '';
      }
    }
  }

  if (!yearin && !episodein) {
    return { error: 'Year or episode not found in query', titlein, yearin, episodein };
  }

  const type = episodein ? 'tv' : 'movie';
  return { type, titlein, yearin, episodein };
}