//EAN-8
//(c) 2010 by Tomasz Lubinski
//www.algorytm.org

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

  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]
  ];
          
function convert(EAN8) {
    
    /* inccorect length or check sum, return null */
    if ((EAN8 == null) ||
      (EAN8.length != 8) || 
      (checkSum(EAN8) == false)) {
      return null;
    }
    
    var bars = new Array(67);
    for (i=0; i<67; i++) {
        bars[i] = 0;
    }
    

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

    for (i=0; i<4; i++) {
       for (j=0; j<7; j++) {
            bars[i*7 + 3 + j] = left[EAN8[i]][j];
       }
    }

    bars[31] = 0;
    bars[32] = 1;
    bars[33] = 0;
    bars[34] = 1;
    bars[35] = 0;

    for (i=4; i<8; i++) {
        for (j=0; j<7; j++) {
            bars[(i-4)*7 + 36 + j] = right[EAN8[i]][j];
        }
    }

    bars[64] = 1;
    bars[65] = 0;
    bars[66] = 1;       
        
    return bars;
}

  
/**
 * calculates checksum of EAN13
 */
function checkSum(EAN8) {
var sum = 3 * EAN8[0] + 
          1 * EAN8[1] +
          3 * EAN8[2] +
          1 * EAN8[3] +
          3 * EAN8[4] +
          1 * EAN8[5] +
          3 * EAN8[6];
        sum %= 10;
        sum = 10 - sum;
        sum %= 10;
        
    if (sum == EAN8[7]) {
      return true;
    }
    else {
      return false;
    }
}
  
  
//initialize data
function generate(EAN8)
{
  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(EAN8);
  if (bars != null)
  {
    for (i=0; i<bars.length; i++) {
      if ((i >= 0 && i<= 2) ||
          (i >= 31 && i<= 35) ||
          (i >= 64 && i<= 66)) {
        length = 100;
      } else {
        length = 90;
      }           
      if (bars[i] == 1) {
        ctx.fillRect(i*2+20, 10, 2, length);
      }
    }
    for (i=0; i<4; i++) {
      ctx.fillText(EAN8[i], i*14+30, 105);
    }
    for (i=4; i<8; i++) {
      ctx.fillText(EAN8[i], i*14+40, 105);
    } 
  }
  else
  {
    ctx.fillText("Nieprawidłowy numer", 50, 80);
    ctx.fillText("Incorrect number", 50, 100);
  }
}