const PNG = require('pngjs').PNG;
const path = require('path');
const fs = require('fs');
const { arrayToString } = require('./util');
const {
  TILE_WIDTH,
  TILE_HEIGHT
} = require('./common');


const getPixelValue = (pixel) => {
  if(pixel.g === 188) return 0;
  if(pixel.g === 172) return 1;
  if(pixel.g === 98) return 2;
  if(pixel.g === 56) return 3;
  throw new Error();
}

const png2gb = (fileIn, dirOut, name) => {
  const data = fs.readFileSync(fileIn);
  const png = PNG.sync.read(data);

  // Convert PNG pixels into 0x00-0x03
  const pixels = [];
  for(let y = 0; y < png.height; y++) {
    for(let x = 0; x < png.width; x++) {
      const id = x + (y * png.width);
      const idx = id << 2;
      const r = png.data[idx];
      const g = png.data[idx+1];
      const b = png.data[idx+2];
      const value = getPixelValue({ r, g, b });
      pixels.push(value);
    }
  }

  // Now take these raw pixels and extract the tiles themselves
  let rearranged = [];
  const columns = (png.width / TILE_WIDTH);
  const rows = (png.height / TILE_HEIGHT);
  let n = 0;
  for(let i = 0; i < columns * rows; i++) {
    const tileX = i % columns;
    const tileY = Math.floor(i / columns) % rows;
    
    for(let y = 0; y < TILE_HEIGHT; y++) {
      for(let x = 0; x < TILE_WIDTH; x++) {
        const px = (tileX * TILE_WIDTH) + x;
        const py = (tileY * TILE_HEIGHT) + y;
        const pi = (py * png.width) + px;
        rearranged[n++] = pixels[pi];
      }
    }
  }

  // Now turn into a tileset
  const bits = [];
  for(let i = 0; i < rearranged.length; i += TILE_WIDTH) {
    let lowBits = 0x00;
    let highBits = 0x00;
    for(let j = 0; j < TILE_WIDTH; j++) {
      const pixel = rearranged[i + j];
      lowBits = lowBits | ((pixel & 0x01) << (7-j));
      highBits = highBits | ((pixel & 0x02) >> 1 << (7-j));
    }
    bits.push(lowBits, highBits);
  }

  let outH = '';
  outH += `#include "libs.h"\n\n`
  outH += `#define ${name}_IMAGE_WIDTH ${png.width}\n`;
  outH += `#define ${name}_IMAGE_HEIGHT ${png.height}\n`;
  outH += `#define ${name}_IMAGE_COLUMNS ${png.width / TILE_WIDTH}\n`;
  outH += `#define ${name}_IMAGE_ROWS ${png.height / TILE_HEIGHT}\n`;
  outH += `#define ${name}_IMAGE_TILES ${columns * rows}\n`;
  outH += `extern const uint8_t ${name}_IMAGE[];`;

  let outC = `#include "${name}.h"\n`;
  outC += `\nconst uint8_t ${name}_IMAGE[] = {\n${arrayToString(bits)}};`;

  const fileH = path.join(dirOut, name + '.h');
  const fileC = path.join(dirOut, name + '.c');

  fs.writeFileSync(fileH, outH);
  fs.writeFileSync(fileC, outC);
  return { fileH, fileC };
}

module.exports = {
  png2gb
}

// convert('images/sm.png', 'out.c', 'PENNY');