var Page = Page || function() {
  this.entry_count = 6;    // count of entries (basically workout dates)
  this.entries = [];        // entry titles
  this.exercises = [];      // exercises
  this.start_weight = 0;    // starting weight
  this.end_weight = 50;     // ending weight
  this.step_weight = 5;     // demarcation steps
  this.input = null;        // input element
  this.tab   = null;        // tab element
  this.element = document.createElement('div'); // bogus element for events
};
Page.prototype.loadJSON = function(json) {
  this.entry_count = json.entry_count || this.entry_count;
  this.entries = json.entries || this.entries;
  this.start_weight = json.start_weight || this.start_weight;
  this.end_weight = json.end_weight || this.end_weight;
  this.step_weight = json.step_weight || this.step_weight;
  this.input.value = json.name || 'swolitude';
  if (typeof json.exercises !== 'undefined') {
    for (var i = 0; i < json.exercises.length; i++) {
      var exercise = this.createExercise(json.exercises[i]);
    }
  }
};
Page.prototype.getJSON = function() {
  var json = {
    entry_count: this.entry_count,
    entries: this.entries,
    start_weight: this.start_weight,
    end_weight: this.end_weight,
    step_weight: this.step_weight,
    name: this.input.value,
    exercises: []
  };
  for (var i = 0; i < this.exercises.length; i++) {
    json.exercises.push(this.exercises[i].getJSON());
  }
  return json;
};
Page.prototype.createExercise = function(json) {
  var exercise = new Exercise(json);
  exercise.parent = this;
  this.exercises.push(exercise);
  return exercise;
};
Page.prototype.removeExercise = function(index) {
  if (index instanceof Exercise) {
    index = this.exercises.indexOf(index);
  }
  if (index < 0 || index >= this.exercises.length) return;
  this.exercises.splice(index, 1);
};