//EAN-2
//(c) 2011 by Tomasz Lubinski
//www.algorytm.org

  var left = [
    [
        [0, 0, 0, 1, 1, 0, 1],
        [0, 0, 1, 1, 0, 0, 1],
        [0, 0, 1, 0, 0, 1, 1],
        [0, 1, 1, 1, 1, 0, 1],
        [0, 1, 0, 0, 0, 1, 1],
        [0, 1, 1, 0, 0, 0, 1],
        [0, 1, 0, 1, 1, 1, 1],
        [0, 1, 1, 1, 0, 1, 1],
        [0, 1, 1, 0, 1, 1, 1],
        [0, 0, 0, 1, 0, 1, 1]
    ],
    [
        [0, 1, 0, 0, 1, 1, 1],
        [0, 1, 1, 0, 0, 1, 1],
        [0, 0, 1, 1, 0, 1, 1],
        [0, 1, 0, 0, 0, 0, 1],
        [0, 0, 1, 1, 1, 0, 1],
        [0, 1, 1, 1, 0, 0 ,1],
        [0, 0, 0, 0, 1, 0, 1],
        [0, 0, 1, 0, 0, 0 ,1],
        [0, 0, 0, 1, 0, 0, 1],
        [0, 0, 1, 0, 1, 1, 1]
    ]
   ];

  var checksumTable = [
    [0, 0],
    [0, 1],
    [1, 0],
    [1, 1]
  ];

function convert(EAN2) {

    /* inccorect length return null */
    if ((EAN2 == null) ||
        (EAN2.length != 2)) {
      return null;
    }

    try {

        var checkSum = EAN2[0]*10 + EAN2[1];
        checkSum %= 4;

        var bars = new Array(20);
        for (i=0; i<20; i++) {
            bars[i] = 0;
        }

        bars[0] = 1;
        bars[1] = 0;
        bars[2] = 1;
        bars[3] = 1;

        for (i=0; i<2; i++) {
           for (j=0; j<7; j++) {
              bars[i*9 + 4 + j] = left[checksumTable[checkSum][i]][EAN2[i]][j];
           }
           if (i<1) {
              bars[i*9 + 11] = 0;
              bars[i*9 + 12] = 1;
           }       
        }
    } catch(e) {
        return null;
    }

    return bars;
}

//initialize data
function generate(EAN2)
{
  var canvas = document.getElementById("canvas");
  var ctx = canvas.getContext("2d");

  /* clear canvas */
  canvas.width = canvas.width;

  /* prepare style */
  ctx.fillStyle    = "rgb(0,0,0)";
  ctx.font         = "10pt Arial";
  ctx.textBaseline = "top";
  ctx.textAlign    = "left";

  var bars = convert(EAN2);
  if (bars != null)
  {
    for (i=0; i<bars.length; i++) {
      if (bars[i] == 1) {
        ctx.fillRect(i*2+20, 40, 2, 60);
      }
    }
    
    for (i=0; i<2; i++) {
      ctx.fillText(EAN2[i], i*17+30, 20);
    }
  }
  else
  {
    ctx.fillText("Nieprawidłowy", 10, 10);
    ctx.fillText("numer", 10, 25);
    ctx.fillText("Incorrect", 10, 50);
    ctx.fillText("number", 10, 65);
  }
}