#!/usr/bin/env node
var
  fs = require('fs'),
  imagediff = require('../imagediff.js'),
  Canvas = require('canvas');

commandLine(process.argv.slice(2));

function do_exit (is_equal) {
  process.exit(is_equal ? 0 : 1);
}

function loadImage (url, callback) {
  var
    image = new Canvas.Image();
  fs.readFile(url, function (error, data) {
    if (error) throw error;
    image.onload = function () {
      callback(image);
    };
    image.onerror = function () {
      throw 'Error loading image buffer.'
    };
    image.src = data;
  });
  return image;
}

function commandLine (args) {

  if (args.length < 3) {
    console.log("Invalid parameters:");
    console.log("imagediff [-e|equal] [-t|tolerance VALUE] FILE_A FILE_B");
    console.log("imagediff [-d|diff] FILE_A FILE_B OUTPUT_FILE");
    return;
  }

  var
    t = 0,
    aName, bName, i, fn, output;

  for (i = args.length - 2; i--;) {
    switch (args[i]) {
      case '-d':
      case 'diff':
      case '--diff':
        fn = 'diff';
        break;
      case '-e':
      case 'equal':
      case '--equal':
        fn = 'equal'
        break;
      case '-t':
      case 'tolerance':
      case '--tolerance':
        t = args[i + 1];
        break;
    }
  }

  if (fn === 'diff') {
    if (args.length < 4) throw '-d option expects an output';
    output = args.pop();
  }
  bName = args.pop();
  aName = args.pop();

  loadImage(bName, function (b) {
    loadImage(aName, function (a) {
      var
        aData = imagediff.toImageData(a),
        bData = imagediff.toImageData(b),
        equal = imagediff.equal(aData, bData, t),
        result;

      if (fn === 'equal') {
        process.stdout.write(equal ? 'true\n' : 'false\n');
        do_exit(equal);
      } else if (fn === 'diff') {
        result = imagediff.diff(aData, bData, t);
        imagediff.imageDataToPNG(result, output, function () {
          do_exit(equal);
          process.stdout.write('Diff of ' + aName + ' and ' + bName + ' rendered to ' + output + '\n');
        });
      }
    });
  });
};