// Generates simple PNG icons using pure Node.js (no external packages needed).
'use strict';
const fs   = require('fs');
const path = require('path');
const zlib = require('zlib');

const outDir = path.join(__dirname, 'public', 'icons');
if (!fs.existsSync(outDir)) fs.mkdirSync(outDir, { recursive: true });

function writePNG(filePath, size) {
  const channels = 4; // RGBA
  const row = size * channels;
  const raw = Buffer.alloc(size * row);

  // Background: dark green #145228
  const bgR = 0x14, bgG = 0x52, bgB = 0x28;
  // Heart color: red #e53935
  const hR = 0xe5, hG = 0x39, hB = 0x35;

  // Draw pixel by pixel: background + centered heart shape
  // Heart expressed as two overlapping circles + a downward triangle
  const cx = size / 2;
  const cy = size / 2 + size * 0.05;
  const r  = size * 0.22;

  // Two circle centers
  const lx = cx - r * 0.6, ly = cy - r * 0.35;
  const rx = cx + r * 0.6, ry = cy - r * 0.35;
  // Triangle tip
  const tipY = cy + r * 1.1;

  for (let y = 0; y < size; y++) {
    for (let x = 0; x < size; x++) {
      const px = (y * size + x) * channels;
      const nx = x + 0.5, ny = y + 0.5;

      // Rounded corners (radius ~20% of size)
      const cr = size * 0.2;
      const inCorner = (nx < cr && ny < cr && Math.hypot(nx - cr, ny - cr) > cr) ||
                       (nx > size - cr && ny < cr && Math.hypot(nx - (size - cr), ny - cr) > cr) ||
                       (nx < cr && ny > size - cr && Math.hypot(nx - cr, ny - (size - cr)) > cr) ||
                       (nx > size - cr && ny > size - cr && Math.hypot(nx - (size - cr), ny - (size - cr)) > cr);
      if (inCorner) { raw[px+3] = 0; continue; }

      // Heart: point in left circle OR right circle OR downward triangle region
      const inL = Math.hypot(nx - lx, ny - ly) <= r;
      const inR = Math.hypot(nx - rx, ny - ry) <= r;
      // Triangle: below the circle union and above the tip
      // Approximate with two lines from the outer circle edges to the tip
      const inT = ny >= Math.min(ly, ry) && nx >= lx - r + (nx - (lx - r)) * 0 &&
                  (ny - (cy - r * 0.35)) / (tipY - (cy - r * 0.35)) <=
                  1 - Math.abs(nx - cx) / (r * 1.2);

      const inHeart = inL || inR || inT;

      if (inHeart) {
        raw[px]   = hR;
        raw[px+1] = hG;
        raw[px+2] = hB;
        raw[px+3] = 255;
      } else {
        raw[px]   = bgR;
        raw[px+1] = bgG;
        raw[px+2] = bgB;
        raw[px+3] = 255;
      }
    }
  }

  // Encode to PNG
  const chunks = [];

  // PNG signature
  chunks.push(Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]));

  function crc32(buf) {
    let c = 0xffffffff;
    const table = crc32.table || (crc32.table = (() => {
      const t = new Uint32Array(256);
      for (let i = 0; i < 256; i++) {
        let v = i;
        for (let k = 0; k < 8; k++) v = v & 1 ? 0xedb88320 ^ (v >>> 1) : v >>> 1;
        t[i] = v;
      }
      return t;
    })());
    for (let i = 0; i < buf.length; i++) c = table[(c ^ buf[i]) & 0xff] ^ (c >>> 8);
    return (c ^ 0xffffffff) >>> 0;
  }

  function chunk(type, data) {
    const len = Buffer.alloc(4); len.writeUInt32BE(data.length);
    const tp  = Buffer.from(type);
    const crc = Buffer.alloc(4);
    crc.writeUInt32BE(crc32(Buffer.concat([tp, data])));
    return Buffer.concat([len, tp, data, crc]);
  }

  // IHDR
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(size, 0);
  ihdr.writeUInt32BE(size, 4);
  ihdr[8]  = 8;  // bit depth
  ihdr[9]  = 6;  // RGBA
  ihdr[10] = 0; ihdr[11] = 0; ihdr[12] = 0;
  chunks.push(chunk('IHDR', ihdr));

  // IDAT: add filter byte (0) before each row
  const filtered = Buffer.alloc(size * (row + 1));
  for (let y = 0; y < size; y++) {
    filtered[y * (row + 1)] = 0; // None filter
    raw.copy(filtered, y * (row + 1) + 1, y * row, (y + 1) * row);
  }
  const compressed = zlib.deflateSync(filtered);
  chunks.push(chunk('IDAT', compressed));

  // IEND
  chunks.push(chunk('IEND', Buffer.alloc(0)));

  fs.writeFileSync(filePath, Buffer.concat(chunks));
  console.log(`${path.basename(filePath)} written (${size}×${size})`);
}

writePNG(path.join(outDir, 'icon-192.png'), 192);
writePNG(path.join(outDir, 'icon-512.png'), 512);
console.log('Icons generated.');