// Sinh src-tauri/icons/favicon.ico tu app/templates/favicon.svg (icon exe).
// Dung: node tools/gen_favicon_ico.js
// (Can @resvg/resvg-js — npm install @resvg/resvg-js trong thu muc lam viec,
// hoac chay trong thu muc da cai. Output: src-tauri/icons/favicon.ico.)
// ICO chua cac size 16/24/32/48/64/128 — Windows dung cho exe icon.
const fs = require('fs');
const path = require('path');

const ROOT = path.resolve(__dirname, '..');
const SVG = path.join(ROOT, 'app', 'templates', 'favicon.svg');
const OUT = path.join(ROOT, 'src-tauri', 'icons', 'favicon.ico');

let Resvg;
try {
  ({ Resvg } = require('@resvg/resvg-js'));
} catch (e) {
  console.error('Thieu @resvg/resvg-js. Chay: npm install @resvg/resvg-js');
  process.exit(1);
}

const svg = fs.readFileSync(SVG, 'utf8');
const SIZES = [16, 24, 32, 48, 64, 128];

function buildIco(images) {
  const header = Buffer.alloc(6);
  header.writeUInt16LE(0, 0);
  header.writeUInt16LE(1, 2);
  header.writeUInt16LE(images.length, 4);
  const entries = [];
  const datas = [];
  let offset = 6 + 16 * images.length;
  for (const { size, data } of images) {
    const entry = Buffer.alloc(16);
    const dim = size >= 256 ? 0 : size;
    entry.writeUInt8(dim, 0);
    entry.writeUInt8(dim, 1);
    entry.writeUInt8(0, 2);
    entry.writeUInt8(0, 3);
    entry.writeUInt16LE(1, 4);
    entry.writeUInt16LE(32, 6);
    entry.writeUInt32LE(data.length, 8);
    entry.writeUInt32LE(offset, 12);
    entries.push(entry);
    datas.push(data);
    offset += data.length;
  }
  return Buffer.concat([header, ...entries, ...datas]);
}

const pngs = SIZES.map(s => ({
  size: s,
  data: new Resvg(svg, { fitTo: { mode: 'width', value: s }, background: 'rgba(0,0,0,0)' }).render().asPng(),
}));
fs.writeFileSync(OUT, buildIco(pngs));
console.log('favicon.ico ->', OUT, fs.statSync(OUT).size, 'bytes');