(function() {
  'use strict'

  function noop() {}

  var Waypoint = window.Waypoint

  /* http://imakewebthings.com/waypoints/shortcuts/inview */
  function Inview(options) {
    this.options = Waypoint.Adapter.extend({}, Inview.defaults, options)
    this.axis = this.options.horizontal ? 'horizontal' : 'vertical'
    this.waypoints = []
    this.createWaypoints()
  }

  /* Private */
  Inview.prototype.createWaypoints = function() {
    var configs = {
      vertical: [{
        down: 'enter',
        up: 'exited',
        offset: '100%'
      }, {
        down: 'entered',
        up: 'exit',
        offset: 'bottom-in-view'
      }, {
        down: 'exit',
        up: 'entered',
        offset: 0
      }, {
        down: 'exited',
        up: 'enter',
        offset: function() {
          return -this.adapter.outerHeight()
        }
      }],
      horizontal: [{
        right: 'enter',
        left: 'exited',
        offset: '100%'
      }, {
        right: 'entered',
        left: 'exit',
        offset: 'right-in-view'
      }, {
        right: 'exit',
        left: 'entered',
        offset: 0
      }, {
        right: 'exited',
        left: 'enter',
        offset: function() {
          return -this.adapter.outerWidth()
        }
      }]
    }

    for (var i = 0, end = configs[this.axis].length; i < end; i++) {
      var config = configs[this.axis][i]
      this.createWaypoint(config)
    }
  }

  /* Private */
  Inview.prototype.createWaypoint = function(config) {
    var self = this
    this.waypoints.push(new Waypoint({
      element: this.options.element,
      handler: (function(config) {
        return function(direction) {
          self.options[config[direction]].call(this, direction)
        }
      }(config)),
      offset: config.offset,
      horizontal: this.options.horizontal
    }))
  }

  /* Public */
  Inview.prototype.destroy = function() {
    for (var i = 0, end = this.waypoints.length; i < end; i++) {
      this.waypoints[i].destroy()
    }
    this.waypoints = []
  }

  Inview.defaults = {
    enter: noop,
    entered: noop,
    exit: noop,
    exited: noop
  }

  Waypoint.Inview = Inview
}())
