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

function hasSignificantWordOverlap(a, b) {
  const skipWords = new Set(['the','le','la','les','de','du','des','and','et','a','an','un','une','dans','en','on']);
  const aw = normalizeTitle(a).split(/\s+/).filter(w => w.length > 3 && !skipWords.has(w));
  const bw = normalizeTitle(b).split(/\s+/).filter(w => w.length > 3 && !skipWords.has(w));
  const overlap = aw.filter(w => bw.includes(w));
  if (overlap.length > 0) {
    console.log(`[MERGE] Overlap: "${a}" <-> "${b}" | Words: ${overlap.join(', ')}`);
    return true;
  }
  return false;
}

// 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;
}

function mergeResults(arrays, query = '', limit = 5) {
  const merged = [];
  arrays.flat().forEach(entry => {
    const entryYear = entry.year ? entry.year.toString() : '';
    let foundIdx = -1;
    for (let i = 0; i < merged.length; i++) {
      const m = merged[i];
      // Match same year AND at least one significant word in common
      if (
        (m.year ? m.year.toString() : '') === entryYear &&
        hasSignificantWordOverlap(entry.title, m.title)
      ) {
        foundIdx = i;
        break;
      }
    }
    if (foundIdx >= 0) {
      console.log(`[MERGE] ${entry.title} (${entryYear}) merged with ${merged[foundIdx].title} (${entryYear})`);
      merged[foundIdx].results.push({ source: entry.source, ...entry });
    } else {
      merged.push({
        title: entry.title,
        year: entry.year,
        results: [{ source: entry.source, ...entry }],
        __raw: entry // For tie-break
      });
    }
  });

  let out = merged;
  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 };