const path = require('path');
const { imageCreate, imageWrite, imageLoad, imageCopy } = require('./../utils/image');
const fs = require('fs');
const xml = require('xml-js');
const { args } = require('./../utils/args');
const { mkdirp } = require('../utils/file');

// Parse Args
if(!args.root) throw new Error(`Missing root argument`);
if(!args.assets) throw new Error(`Missing assets argument`);
if(!args.in) throw new Error(`Missing in argument`);
if(!args.out) throw new Error(`Missing out argument`);
if(!args.in.endsWith('xml')) throw new Error(`Invalid in XML`);
if(!args.out.endsWith('png')) throw new Error(`Invalid out PNG`);

// Determine in and out.
const root = path.resolve(args.root);
const file = path.resolve(args.root, args.assets, args.in);
if(!fs.existsSync(file)) throw new Error(`Could not find ${file}`);
const outFile = path.resolve(args.assets, args.out);
if(fs.existsSync(outFile)) return;

// Load XML
const data = xml.xml2js(fs.readFileSync(file, 'utf-8'));
const [ character ] = data.elements;

// Validate file.
if(!character.attributes.context) throw new Error(`Missing context`)
const dir = path.resolve(root, args.assets, character.attributes.context);

// Parse base and layers
const base = character.elements.find(e => e.name == 'base').attributes;
if(!base) throw new Error(`Failed to find base`);
const layers = character.elements
  .filter(e => e.name == 'layer')
  .map(e => e.attributes)
  .map(e => ({
    ...e,
    x: parseInt(e.x),
    y: parseInt(e.y),
    width: parseInt(e.width),
    height: parseInt(e.height)
  }))
;

(async () => {
  // Load the base
  const baseImage = await imageLoad(path.join(dir, base.file));

  let columnsMax = 0;
  let widthMax = 0;
  layers.forEach((layer,row) => {
    if(!layer.width || !layer.height || !layer.x || !layer.y) {
      throw new Error(`Missing layer info`);
    }

    const layerDir = path.join(dir, layer.directory);
    const scan = fs.readdirSync(layerDir);
    columnsMax = Math.max(scan.length, columnsMax);
    widthMax = Math.max(widthMax, layer.width);
  });

  // Create the output buffer
  const out = imageCreate(
    baseImage.width + (columnsMax * widthMax),
    baseImage.height
  );

  // Copy the base
  imageCopy(out, baseImage, 0, 0);
  
  // Now begin copying the children, row is defined by the directory
  let y = 0;
  for(let row = 0; row < layers.length; row++) {
    const layer = layers[row];
    const layerDir = path.join(dir, layer.directory);
    const scan = fs.readdirSync(layerDir);

    // Column defined by the file index
    for(let col = 0; col < scan.length; col++) {
      const img = await imageLoad(path.join(layerDir, scan[col]));
      console.log('Copying', scan[col]);
      imageCopy(out, img,
        baseImage.width+(col*layer.width), y,
        layer
      );
    }

    y += layer.height;
  }

  mkdirp(outFile);
  await imageWrite(out, outFile);
})().catch(console.error);