module.exports={distanceToXpLevel,getXpLevel,getXpRequired,getBaseXpFromLevel};

function distanceToXpLevel(xp, toLevel) {
  var level = getXpLevel(xp);
  if (!toLevel) toLevel = level+1;
  var levelBaseXp = getBaseXpFromLevel(level);
  var requiredXp = getXpRequired(level, toLevel);
  return (xp - levelBaseXp) / requiredXp;
}

function getXpLevel(xp) {
  // I have to use quadratic equation to reverse the equation from getBaseXpFromLevel(). Ugh.
  var a;
  var b;
  var c;
  if (xp < 352) { // 352 == Experience at level 16
    a = 1;
    b = 6;
    c = 0;
  } else if (xp < 1507) { // 1507 == Experience at level 31
    a = 2.5;
    b = -40.5;
    c = 360;
  } else { // Level 32+
    a = 4.5;
    b = -162.5;
    c = 2220;
  }
  c -= xp;
  return Math.floor((-b + Math.sqrt(b*b - 4*a*c)) / (2 * a)); // Math class was useful I guess mmph
}

function getXpRequired(level, toLevel) {
  if (!toLevel) toLevel = level + 1;
  return getBaseXpFromLevel(toLevel) - getBaseXpFromLevel(level);
}

function getBaseXpFromLevel(level){
  // The equations in this function are stupid and directly from the MC Wiki
  // http://minecraft.gamepedia.com/Experience#Leveling_up
  if (level <= 16) {
    return level*level + 6*level;
  } else if (level <= 31) {
    return 2.5*level*level - 40.5*level + 360;
  } else { // 32+
    return 4.5*level*level - 162.5*level + 2220;
  }
}