import { promises as fs } from 'node:fs';
import path from 'node:path';

// Build map: relative path that ORIGINALLY existed but now only has .webp
// Walk /public for .webp files, compute their candidate original ext (.jpg/.png/.gif)
// If the candidate no longer exists on disk, that's a swap target.

const PUBLIC_ROOT = path.resolve('public');
const SRC_ROOT = path.resolve('src');

async function walk(dir, out) {
  const entries = await fs.readdir(dir, { withFileTypes: true });
  for (const e of entries) {
    const p = path.join(dir, e.name);
    if (e.isDirectory()) await walk(p, out);
    else out.push(p);
  }
}

// 1. Find .webp files and detect which original ext is missing
const all = [];
await walk(PUBLIC_ROOT, all);
const webps = all.filter((p) => p.toLowerCase().endsWith('.webp'));
const existing = new Set(all.map((p) => p.toLowerCase()));

const swaps = []; // { from: /images/foo.jpg, to: /images/foo.webp }
for (const wp of webps) {
  const base = wp.slice(0, -5); // strip .webp
  for (const ext of ['.jpg', '.jpeg', '.png', '.gif']) {
    const candidate = base + ext;
    if (!existing.has(candidate.toLowerCase())) {
      // Candidate gone => it was converted
      const rel = '/' + path.relative(PUBLIC_ROOT, candidate).split(path.sep).join('/');
      const relWebp = '/' + path.relative(PUBLIC_ROOT, wp).split(path.sep).join('/');
      swaps.push({ from: rel, to: relWebp });
    }
  }
}

console.log(`detected ${swaps.length} swap pairs`);

// 2. Walk /src for ts/tsx/js/jsx/json/md/css and apply replacements
const srcExts = new Set(['.ts', '.tsx', '.js', '.jsx', '.json', '.md', '.css', '.html', '.mjs']);
const srcFiles = [];
await walk(SRC_ROOT, srcFiles);
const targets = srcFiles.filter((p) => srcExts.has(path.extname(p).toLowerCase()));

let totalReplacements = 0;
let touchedFiles = 0;
for (const file of targets) {
  let text = await fs.readFile(file, 'utf8');
  let count = 0;
  for (const s of swaps) {
    if (text.includes(s.from)) {
      const before = text;
      text = text.split(s.from).join(s.to);
      const occurrences = (before.length - text.length) / (s.from.length - s.to.length);
      count += occurrences;
    }
  }
  if (count > 0) {
    await fs.writeFile(file, text, 'utf8');
    totalReplacements += count;
    touchedFiles++;
    const rel = path.relative(process.cwd(), file).split(path.sep).join('/');
    console.log(`UPDATE ${rel}  (${count} swaps)`);
  }
}
console.log('---');
console.log(`replaced ${totalReplacements} references across ${touchedFiles} files`);