import { createReadStream, statSync } from 'node:fs';
import { createInterface } from 'node:readline';
import { IMDB_RATINGS } from '../config.js';

let cache = null;
let cacheMtime = 0;

export async function loadRatings(filePath = IMDB_RATINGS) {
  const map = new Map();
  const stream = createReadStream(filePath, { encoding: 'utf8' });
  const rl = createInterface({ input: stream, crlfDelay: Infinity });
  let first = true;
  for await (const line of rl) {
    if (first) { first = false; continue; }
    if (!line) continue;
    const tab1 = line.indexOf('\t');
    if (tab1 < 0) continue;
    const tab2 = line.indexOf('\t', tab1 + 1);
    if (tab2 < 0) continue;
    const id = line.slice(0, tab1);
    const rating = line.slice(tab1 + 1, tab2);
    const votes = line.slice(tab2 + 1);
    map.set(id, [rating, votes]);
  }
  return map;
}

export async function getRatings() {
  try {
    const st = statSync(IMDB_RATINGS);
    if (cache && st.mtimeMs === cacheMtime) return cache;
    cache = await loadRatings(IMDB_RATINGS);
    cacheMtime = st.mtimeMs;
    return cache;
  } catch (err) {
    if (cache) return cache;
    throw err;
  }
}

export function lookupRating(map, imdbId) {
  if (!imdbId) return { rating: 0, votes: 0 };
  const row = map.get(imdbId);
  if (!row) return { rating: 0, votes: 0 };
  return {
    rating: parseFloat(row[0]) || 0,
    votes: parseInt(row[1], 10) || 0,
  };
}