function normalizeTitle(str) {
  return str ? str.toLowerCase().replace(/[^a-z0-9]/g, '') : '';
}

// Compute match score: exact > startsWith > includes > other
function getMatchScore(film, query) {
  const nTitle = normalizeTitle(film.title);
  const nQuery = normalizeTitle(query);
  if (nTitle === nQuery) return 100;
  if (nTitle.startsWith(nQuery)) return 80;
  if (nTitle.includes(nQuery)) return 60;
  return 10;
}

// Merge and rank by match
function mergeResults(arrays, query = '', limit = 5) {
  const map = {};
  arrays.flat().forEach(entry => {
    const key = normalizeTitle(entry.title) + (entry.year ? '|' + entry.year : '');
    if (!map[key]) {
      map[key] = {
        title: entry.title,
        year: entry.year,
        results: [],
        __raw: entry // For tie-break
      };
    }
    map[key].results.push({
      source: entry.source,
      ...entry
    });
  });
  let out = Object.values(map);
  if (query) {
    out.forEach(f => f.__score = getMatchScore(f, query));
    out = out.sort((a, b) => b.__score - a.__score);
  }
  // Remove internals, trim to limit
  return out.slice(0, limit).map(f => {
    delete f.__score; delete f.__raw;
    return f;
  });
}

module.exports = { mergeResults };