#!/usr/bin/env node
// Generates minimal PNG icons for the PWA manifest.
// Uses pure Node.js — no canvas or image library needed.
// Output: valid PNG icons with an "H" monogram on black background with volt (#faff69) color.
// For production, replace with properly designed icons.

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

function makePNG(size, bgHex, fgHex) {
  // PNG signature
  const sig = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10])

  // IHDR chunk
  const ihdrData = Buffer.alloc(13)
  ihdrData.writeUInt32BE(size, 0)
  ihdrData.writeUInt32BE(size, 4)
  ihdrData[8] = 8   // bit depth
  ihdrData[9] = 2   // color type RGB
  ihdrData[10] = 0  // compression
  ihdrData[11] = 0  // filter
  ihdrData[12] = 0  // interlace
  const ihdr = makeChunk('IHDR', ihdrData)

  // IDAT chunk — raw RGB pixel data, filtered (filter byte 0 = none per row)
  const bg = hexToRgb(bgHex)
  const fg = hexToRgb(fgHex)
  const rawRows = []
  const margin = Math.floor(size * 0.2)
  for (let y = 0; y < size; y++) {
    const row = [0] // filter byte
    for (let x = 0; x < size; x++) {
      // Simple "H" monogram in the center
      const inMargin = x >= margin && x < size - margin && y >= margin && y < size - margin
      const isStroke =
        inMargin &&
        ((x < margin + Math.floor(size * 0.08) || x > size - margin - Math.floor(size * 0.08)) ||
         (Math.abs(y - size / 2) < Math.floor(size * 0.06)))
      const c = isStroke ? fg : bg
      row.push(c[0], c[1], c[2])
    }
    rawRows.push(Buffer.from(row))
  }
  const rawData = Buffer.concat(rawRows)
  const compressed = zlib.deflateSync(rawData)
  const idat = makeChunk('IDAT', compressed)

  // IEND
  const iend = makeChunk('IEND', Buffer.alloc(0))

  return Buffer.concat([sig, ihdr, idat, iend])
}

function makeChunk(type, data) {
  const len = Buffer.alloc(4)
  len.writeUInt32BE(data.length)
  const typeBytes = Buffer.from(type)
  const crc = crc32(Buffer.concat([typeBytes, data]))
  const crcBuf = Buffer.alloc(4)
  crcBuf.writeInt32BE(crc)
  return Buffer.concat([len, typeBytes, data, crcBuf])
}

function hexToRgb(hex) {
  const n = parseInt(hex.replace('#', ''), 16)
  return [(n >> 16) & 0xff, (n >> 8) & 0xff, n & 0xff]
}

function crc32(buf) {
  let crc = 0xffffffff
  const table = makeCRCTable()
  for (const b of buf) crc = (crc >>> 8) ^ table[(crc ^ b) & 0xff]
  return (crc ^ 0xffffffff) | 0
}

function makeCRCTable() {
  const t = new Int32Array(256)
  for (let i = 0; i < 256; i++) {
    let c = i
    for (let j = 0; j < 8; j++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1
    t[i] = c
  }
  return t
}

const iconsDir = path.join(__dirname, '..', 'public', 'icons')
fs.mkdirSync(iconsDir, { recursive: true })
fs.writeFileSync(path.join(iconsDir, 'icon-192.png'), makePNG(192, '#000000', '#faff69'))
fs.writeFileSync(path.join(iconsDir, 'icon-512.png'), makePNG(512, '#000000', '#faff69'))
console.log('Icons generated: icon-192.png, icon-512.png')