const fs = require('fs');
const path = require('path');
const zlib = require('zlib');

const buildDir = path.join(__dirname, '..', 'build');
const pngPath = path.join(buildDir, 'icon.png');
const icoPath = path.join(buildDir, 'icon.ico');

function crc32(buffer) {
  let crc = 0xffffffff;
  for (let i = 0; i < buffer.length; i++) {
    crc ^= buffer[i];
    for (let j = 0; j < 8; j++) {
      const mask = -(crc & 1);
      crc = (crc >>> 1) ^ (0xedb88320 & mask);
    }
  }
  return (crc ^ 0xffffffff) >>> 0;
}

function makeChunk(type, data) {
  const length = Buffer.alloc(4);
  length.writeUInt32BE(data.length, 0);
  const typeBuffer = Buffer.from(type, 'ascii');
  const crcBuffer = Buffer.alloc(4);
  const crc = crc32(Buffer.concat([typeBuffer, data]));
  crcBuffer.writeUInt32BE(crc, 0);
  return Buffer.concat([length, typeBuffer, data, crcBuffer]);
}

function drawLine(raw, rowStride, color, x0, y0, x1, y1, thickness = 2) {
  const dx = Math.abs(x1 - x0);
  const dy = Math.abs(y1 - y0);
  const sx = x0 < x1 ? 1 : -1;
  const sy = y0 < y1 ? 1 : -1;
  let err = dx - dy;

  const setPixel = (x, y) => {
    if (x < 0 || y < 0 || x >= 256 || y >= 256) return;
    for (let ty = -Math.floor(thickness / 2); ty <= Math.floor(thickness / 2); ty++) {
      for (let tx = -Math.floor(thickness / 2); tx <= Math.floor(thickness / 2); tx++) {
        const xx = x + tx;
        const yy = y + ty;
        if (xx < 0 || yy < 0 || xx >= 256 || yy >= 256) continue;
        const rowStart = yy * rowStride;
        const idx = rowStart + 1 + xx * 4;
        raw[idx] = color[0];
        raw[idx + 1] = color[1];
        raw[idx + 2] = color[2];
        raw[idx + 3] = color[3];
      }
    }
  };

  while (true) {
    setPixel(x0, y0);
    if (x0 === x1 && y0 === y1) break;
    const e2 = 2 * err;
    if (e2 > -dy) { err -= dy; x0 += sx; }
    if (e2 < dx) { err += dx; y0 += sy; }
  }
}

function createIconPng(width, height) {
  const signature = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);

  const ihdrData = Buffer.alloc(13);
  ihdrData.writeUInt32BE(width, 0);
  ihdrData.writeUInt32BE(height, 4);
  ihdrData[8] = 8; // Bit depth
  ihdrData[9] = 6; // Color type RGBA
  const ihdrChunk = makeChunk('IHDR', ihdrData);

  const rowStride = width * 4 + 1;
  const raw = Buffer.alloc(rowStride * height);
  const bg = [79, 70, 229, 255]; // blue/indigo
  for (let y = 0; y < height; y++) {
    const rowStart = y * rowStride;
    raw[rowStart] = 0; // No filter
    for (let x = 0; x < width; x++) {
      const idx = rowStart + 1 + x * 4;
      raw[idx] = bg[0];
      raw[idx + 1] = bg[1];
      raw[idx + 2] = bg[2];
      raw[idx + 3] = bg[3];
    }
  }

  // White checkmark
  const check = [255, 255, 255, 255];
  drawLine(raw, rowStride, check, Math.floor(width * 0.22), Math.floor(height * 0.55), Math.floor(width * 0.42), Math.floor(height * 0.72), 10);
  drawLine(raw, rowStride, check, Math.floor(width * 0.42), Math.floor(height * 0.72), Math.floor(width * 0.78), Math.floor(height * 0.32), 10);

  const idatData = zlib.deflateSync(raw);
  const idatChunk = makeChunk('IDAT', idatData);
  const iendChunk = makeChunk('IEND', Buffer.alloc(0));

  return Buffer.concat([signature, ihdrChunk, idatChunk, iendChunk]);
}

function buildIcoFromPng(pngBuffer) {
  const header = Buffer.alloc(6);
  header.writeUInt16LE(0, 0); // Reserved
  header.writeUInt16LE(1, 2); // Type = icon
  header.writeUInt16LE(1, 4); // Image count

  const entry = Buffer.alloc(16);
  entry[0] = 0; // Width 256 (0 means 256 in ICO format)
  entry[1] = 0; // Height 256
  entry[2] = 0; // Palette
  entry[3] = 0; // Reserved
  entry.writeUInt16LE(1, 4); // Color planes
  entry.writeUInt16LE(32, 6); // Bits per pixel
  entry.writeUInt32LE(pngBuffer.length, 8); // PNG byte size
  entry.writeUInt32LE(header.length + entry.length, 12); // Offset to PNG

  return Buffer.concat([header, entry, pngBuffer]);
}

function ensureBuildAssets() {
  fs.mkdirSync(buildDir, { recursive: true });

  // Always regenerate to ensure latest icon style
  const pngBuffer = createIconPng(256, 256);
  fs.writeFileSync(pngPath, pngBuffer);
  console.log(`Wrote PNG icon at ${pngPath}`);

  const icoBuffer = buildIcoFromPng(pngBuffer);
  fs.writeFileSync(icoPath, icoBuffer);
  console.log(`Wrote ICO icon at ${icoPath}`);
}

ensureBuildAssets();