#!/usr/bin/env node
/**
 * Generates appicon.png (512x512) — a vermilion tile with a white play glyph.
 * No image libraries: encodes a PNG by hand with Node's zlib.
 *
 * After running this, expand it into all platform sizes with the Tauri CLI:
 *   npm run tauri icon ./appicon.png
 */
const fs = require('fs');
const path = require('path');
const zlib = require('zlib');

const SIZE = 512;

// CRC32 (PNG chunk checksums)
const CRC_TABLE = (() => {
  const t = new Uint32Array(256);
  for (let n = 0; n < 256; n++) {
    let c = n;
    for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
    t[n] = c >>> 0;
  }
  return t;
})();
function crc32(buf) {
  let c = 0xffffffff;
  for (let i = 0; i < buf.length; i++) c = CRC_TABLE[(c ^ buf[i]) & 0xff] ^ (c >>> 8);
  return (c ^ 0xffffffff) >>> 0;
}
function chunk(type, data) {
  const len = Buffer.alloc(4);
  len.writeUInt32BE(data.length, 0);
  const typeBuf = Buffer.from(type, 'ascii');
  const crc = Buffer.alloc(4);
  crc.writeUInt32BE(crc32(Buffer.concat([typeBuf, data])), 0);
  return Buffer.concat([len, typeBuf, data, crc]);
}

// --- paint pixels (RGBA) ---
const px = Buffer.alloc(SIZE * SIZE * 4);
function set(x, y, r, g, b, a = 255) {
  const i = (y * SIZE + x) * 4;
  px[i] = r; px[i + 1] = g; px[i + 2] = b; px[i + 3] = a;
}

// Background: subtle vertical vermilion gradient (#ff6a52 -> #d4321d)
for (let y = 0; y < SIZE; y++) {
  const t = y / SIZE;
  const r = Math.round(0xff + (0xd4 - 0xff) * t);
  const g = Math.round(0x6a + (0x32 - 0x6a) * t);
  const b = Math.round(0x52 + (0x1d - 0x52) * t);
  for (let x = 0; x < SIZE; x++) set(x, y, r, g, b);
}

// White play triangle, centered, slightly right-nudged for optical balance.
const ax = 196, ay = 150, bx = 196, by = 362, cx = 384, cy = 256;
function edge(px1, py1, px2, py2, x, y) {
  return (x - px1) * (py2 - py1) - (y - py1) * (px2 - px1);
}
for (let y = 120; y < 392; y++) {
  for (let x = 170; x < 400; x++) {
    const w0 = edge(bx, by, cx, cy, x, y);
    const w1 = edge(cx, cy, ax, ay, x, y);
    const w2 = edge(ax, ay, bx, by, x, y);
    if ((w0 <= 0 && w1 <= 0 && w2 <= 0) || (w0 >= 0 && w1 >= 0 && w2 >= 0)) {
      set(x, y, 255, 255, 255);
    }
  }
}

// --- encode ---
const raw = Buffer.alloc((SIZE * 4 + 1) * SIZE);
for (let y = 0; y < SIZE; y++) {
  raw[y * (SIZE * 4 + 1)] = 0; // filter: none
  px.copy(raw, y * (SIZE * 4 + 1) + 1, y * SIZE * 4, (y + 1) * SIZE * 4);
}
const ihdr = Buffer.alloc(13);
ihdr.writeUInt32BE(SIZE, 0);
ihdr.writeUInt32BE(SIZE, 4);
ihdr[8] = 8;  // bit depth
ihdr[9] = 6;  // color type RGBA
const png = Buffer.concat([
  Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
  chunk('IHDR', ihdr),
  chunk('IDAT', zlib.deflateSync(raw, { level: 9 })),
  chunk('IEND', Buffer.alloc(0)),
]);

const out = path.join(__dirname, '..', 'appicon.png');
fs.writeFileSync(out, png);
console.log(`Wrote ${out} (${SIZE}x${SIZE}).`);
console.log('Now run:  npm run tauri icon ./appicon.png');