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

const ROOT = path.resolve('public');
const SKIP = new Set(['favicon.ico']);
const MAX_W = 1920; // cap any image wider than this

const exts = new Set(['.jpg', '.jpeg', '.png', '.gif', '.webp']);
let convertedCount = 0;
let savedBytes = 0;
let skippedCount = 0;

async function walk(dir) {
  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);
    else if (exts.has(path.extname(p).toLowerCase())) await compress(p);
  }
}

function qualityFor(bytes) {
  if (bytes > 700 * 1024) return 70;
  if (bytes > 300 * 1024) return 75;
  if (bytes > 120 * 1024) return 78;
  return 82;
}

async function compress(input) {
  const base = path.basename(input);
  if (SKIP.has(base)) return;
  const ext = path.extname(input).toLowerCase();
  const isGif = ext === '.gif';
  const relRoot = path.relative(process.cwd(), input).split(path.sep).join('/');

  try {
    const stIn = await fs.stat(input);
    if (stIn.size < 8 * 1024) {
      // tiny: leave
      return;
    }
    const target = input.slice(0, -ext.length) + '.webp';
    // Read into memory first, then close handle
    const srcBuf = await fs.readFile(input);
    const meta = await sharp(srcBuf, { animated: isGif }).metadata();
    let pipeline = sharp(srcBuf, { animated: isGif });
    if (meta.width && meta.width > MAX_W) {
      pipeline = pipeline.resize({ width: MAX_W, withoutEnlargement: true });
    }
    const q = qualityFor(stIn.size);
    pipeline = pipeline.webp({
      quality: q,
      alphaQuality: 88,
      effort: 6,
      smartSubsample: true,
      ...(isGif ? { loop: 0 } : {}),
    });
    const buf = await pipeline.toBuffer();
    if (buf.length >= stIn.size && ext === '.webp') {
      skippedCount++;
      return;
    }
    // write via temp file then rename for atomicity
    const tmp = target + '.tmp';
    await fs.writeFile(tmp, buf);
    if (target !== input) {
      try { await fs.unlink(input); } catch {}
    }
    await fs.rename(tmp, target);
    convertedCount++;
    savedBytes += stIn.size - buf.length;
    const inKB = (stIn.size / 1024).toFixed(0);
    const outKB = (buf.length / 1024).toFixed(0);
    console.log(`OK  q=${q}  ${relRoot}  ${inKB}KB -> ${outKB}KB${meta.width && meta.width > MAX_W ? '  (resized)' : ''}`);
  } catch (err) {
    console.log(`FAIL ${relRoot}: ${err.message}`);
  }
}

await walk(ROOT);
const savedMB = (savedBytes / 1024 / 1024).toFixed(2);
console.log('\n---');
console.log(`compressed: ${convertedCount}  skipped: ${skippedCount}`);
console.log(`saved: ${savedMB} MB`);