var Exercise = Exercise || function(json) {
  this.name = json.name || '';
  this.color = json.color || [255, 128, 255];
  //this.color_string = 'rgba('+this.color[0]+','+this.color[1]+','+this.color[2]+')';
  this.color_string = '#'+(this.color[0].toString(16))+(this.color[1].toString(16))+(this.color[2].toString(16));
  this.sets = [];
  this.parent = null;                     // Page this owns this
  if (typeof json.sets !== 'undefined') {
    for (var i = 0; i < json.sets.length; i++) {
      this.createSet(json.sets[i]);
    }
  } else {
    this.createSet({});
  }
};
Exercise.prototype.getJSON = function() {
  var json = {
    name: this.name,
    color: this.color,
    sets: []
  };
  for (var i = 0; i < this.sets.length; i++) {
    json.sets.push(this.sets[i].getJSON());
  }
  return json;
};
Exercise.prototype.createSet = function(json) {
  var set = new ESet(json);
  set.parent = this;
  this.sets.push(set);
  return set;
};
Exercise.prototype.removeSet = function(index) {
  if (index < 0 || index >= this.sets.length) return;
  this.sets.splice(index, 1);
};