// Worker thread used by lib/searchEngine.js. Equivalent to one fork in
// searchmultithreads.php: load one search chunk and emit candidate matches.

import { readFileSync } from 'node:fs';
import { parentPort, workerData } from 'node:worker_threads';
import { LEV_DEL, LEV_INS, LEV_REP, LEV_SCALE, TITLE_TOLERANCE, YEAR_TOLERANCE } from '../config.js';
import { mbLevenshtein, mbStrlen } from './mbLevenshtein.js';

const TMDB = 0;
const TITLE = 1;
const ENGLISHTITLE = 2;
const ORIGINALTITLE = 3;
const FILTEREDTITLE = 4;
const FILTEREDENGLISHTITLE = 5;
const FILTEREDORIGINALTITLE = 6;
const YEAR = 7;
const POPULARITY = 8;

let chunkPath;
let chunk = null;

if (workerData?.chunkPath) {
  chunkPath = workerData.chunkPath;
}

function loadChunk() {
  if (chunk) return chunk;
  chunk = JSON.parse(readFileSync(chunkPath, 'utf8'));
  return chunk;
}

function score(filteredIn, target, ftiLen) {
  if (!target) return 0;
  const tlen = mbStrlen(target);
  return (
    100 -
    (mbLevenshtein(filteredIn, target, LEV_INS, LEV_REP, LEV_DEL) / (Math.max(ftiLen, tlen) * LEV_SCALE)) *
      100
  );
}

function search({ filteredTitleIn, yearIn }) {
  const db = loadChunk();
  const out = [];
  const ftiLen = mbStrlen(filteredTitleIn);

  for (const row of db) {
    let deltaYear = 0;
    if (yearIn) {
      let ok = false;
      for (const y of row[YEAR]) {
        const dy = Math.abs(yearIn - y);
        if (dy <= YEAR_TOLERANCE) {
          ok = true;
          deltaYear = dy;
          break;
        }
      }
      if (!ok) continue;
    }

    const fT = row[FILTEREDTITLE];
    const fE = row[FILTEREDENGLISHTITLE];
    const fO = row[FILTEREDORIGINALTITLE];

    const pO = score(filteredTitleIn, fO, ftiLen);

    let pT;
    if (fT) {
      pT = fT === fO ? pO : score(filteredTitleIn, fT, ftiLen);
    } else pT = 0;

    let pE;
    if (fE) {
      if (fE === fO) pE = pO;
      else if (fE === fT) pE = pT;
      else pE = score(filteredTitleIn, fE, ftiLen);
    } else pE = 0;

    const dT = 100 - pT;
    const dE = 100 - pE;
    const dO = 100 - pO;
    const delta = Math.min(dT, dE, dO);
    if (delta > TITLE_TOLERANCE) continue;

    out.push({
      delta,
      pop: -row[POPULARITY],
      deltaYear,
      tmdb: row[TMDB],
      title: row[TITLE],
      englishTitle: row[ENGLISHTITLE],
      originalTitle: row[ORIGINALTITLE],
      filteredTitle: fT,
      filteredEnglishTitle: fE,
      filteredOriginalTitle: fO,
      year: row[YEAR][0],
    });
  }
  return out;
}

if (parentPort) {
  parentPort.on('message', (msg) => {
    if (msg?.type === 'search') {
      try {
        const results = search(msg.payload);
        parentPort.postMessage({ type: 'result', id: msg.id, results });
      } catch (err) {
        parentPort.postMessage({ type: 'error', id: msg.id, error: err.message });
      }
    }
  });
}