/* globals define jQuery */
(function (factory) {
  if (typeof define === 'function' && define.amd) {
    // AMD. Register as an anonymous module.
    define(['jquery'], factory)
  } else {
    // Browser globals
    factory(jQuery)
  }
}(function ($) {
  $.widget('ui.rotatable', $.ui.mouse, {
    widgetEventPrefix: 'rotate',

    options: {
      angle: false,       // specify an angle in radians (for backward compatability)
      degrees: false,     // specify angle in degrees
      handle: false,      // an image to use for a handle
      handleOffset: {     // where the handle should appear
        top: 0,
        left: 0
      },
      radians: false,     // specify angle in radians
      rotate: null,       // a callback for during rotation
      rotationCenterOffset: {   // offset the center of the element for rotation
        top: 0,
        left: 0
      },
      snap: false,        // boolean flag, should the element snap to a certain rotation?
      start: null,        // callback when rotation starts
      step: 22.5,         // angle in degrees that the rotation should be snapped to
      stop: null,         // callback when rotation stops
      transforms: null,   // other transforms to performed on the element
      wheelRotate: true   // boolean flag, should the element rotate when the mousewheel is rotated?
    },

    // accessor for the angle in radians
    angle: function (angle) {
      if (angle === undefined) {
        return this.options.angle
      }
      this.options.angle = angle
      this.elementCurrentAngle = angle
      this._performRotation(this.options.angle)
    },

    // calculates the element center if needed and returns it
    getElementCenter: function () {
      this.elementCenter = this._calculateElementCenter()
      return this.elementCenter
    },

    // accessor for the handle
    handle: function (handle) {
      if (handle === undefined) {
        return this.options.handle
      }
      this.options.handle = handle
    },

    plugins: {},

    /* accessor for the center of rotation
    * takes an object with keys of top and left
    */
    rotationCenterOffset: function (offset) {
      if (offset === undefined) {
        return this.options.rotationCenterOffset
      }
      if (offset.top !== null) {
        this.options.rotationCenterOffset.top = offset.top
      }
      if (offset.left !== null) {
        this.options.rotationCenterOffset.left = offset.left
      }
    },

    // listener for rotating the element
    rotateElement: function (event) {
      if (!this.element || this.element.disabled || this.options.disabled) {
        return false
      }

      if (!event.which) {
        this.stopRotate(event)
        return false
      }

      var rotateAngle = this._calculateRotateAngle(event)
      var previousRotateAngle = this.elementCurrentAngle
      this.elementCurrentAngle = rotateAngle

      // Plugins callbacks need to be called first.
      this._propagate('rotate', event)

      if (this._propagate('rotate', event) === false) {
        this.elementCurrentAngle = previousRotateAngle
        return false
      }
      var ui = this.ui()
      if (this._trigger('rotate', event, ui) === false) {
        this.elementCurrentAngle = previousRotateAngle
        return false
      } else if (ui.angle.current !== rotateAngle) {
        rotateAngle = ui.angle.current
        this.elementCurrentAngle = rotateAngle
      }

      this._performRotation(rotateAngle)

      if (previousRotateAngle !== rotateAngle) {
        this.hasRotated = true
      }

      return false
    },

    // listener for starting rotation
    startRotate: function (event) {
      var center = this.getElementCenter()
      var startXFromCenter = event.pageX - center.x
      var startYFromCenter = event.pageY - center.y
      this.mouseStartAngle = Math.atan2(startYFromCenter, startXFromCenter)
      this.elementStartAngle = this.elementCurrentAngle
      this.hasRotated = false

      this._propagate('start', event)

      $(document).bind('mousemove', this.listeners.rotateElement)
      $(document).bind('mouseup', this.listeners.stopRotate)

      return false
    },

    // listener for stopping rotation
    stopRotate: function (event) {
      if (!this.element || this.element.disabled) {
        return
      }

      $(document).unbind('mousemove', this.listeners.rotateElement)
      $(document).unbind('mouseup', this.listeners.stopRotate)

      this.elementStopAngle = this.elementCurrentAngle

      this._propagate('stop', event)

      setTimeout(function () { this.element = false }, 10)
      return false
    },

    // listener for mousewheel rotation
    wheelRotate: function (event) {
      if (!this.element || this.element.disabled || this.options.disabled) {
        return
      }
      event.preventDefault()
      var angle = this._angleInRadians(Math.round(event.originalEvent.deltaY / 10))
      if (this.options.snap || event.shiftKey) {
        angle = this._calculateSnap(angle)
      }
      angle = this.elementCurrentAngle + angle
      this.angle(angle)
      this._trigger('rotate', event, this.ui())
    },

    // for callbacks
    ui: function () {
      return {
        api: this,
        element: this.element,
        angle: {
          start: this.elementStartAngle,
          current: this.elementCurrentAngle,
          degrees: this._normalizeDegrees(this._angleInDegrees(this.elementCurrentAngle)),
          stop: this.elementStopAngle
        }
      }
    },

    /* *********************** private functions ************************** */
    // calculates the radians for a given angle in degrees
    _angleInRadians: function (degrees) {
      return degrees * Math.PI / 180
    },

    // calculates the degrees for a given angle in radians
    _angleInDegrees: function (radians) {
      return radians * 180 / Math.PI
    },

    _normalizeDegrees: function (degrees) {
      return ((degrees % 360) + 360) % 360;
    },

    // calculates the center of the element
    _calculateElementCenter: function () {
      var elementOffset = this._getElementOffset()

      // Rotation center given via options
      if (this._isRotationCenterSet()) {
        return {
          x: elementOffset.left + this.rotationCenterOffset().left,
          y: elementOffset.top + this.rotationCenterOffset().top
        }
      }

      // Deduce rotation center from transform-origin
      if (this.element.css('transform-origin') !== undefined) {
        var originPx = this.element.css('transform-origin').match(/([\d.]+)px +([\d.]+)px/)
        if (originPx != null) {
          return {
            x: elementOffset.left + parseFloat(originPx[1]),
            y: elementOffset.top + parseFloat(originPx[2])
          }
        }
      }

      // Default rotation center: middle of the element
      return {
        x: elementOffset.left + this.element.width() / 2,
        y: elementOffset.top + this.element.height() / 2
      }
    },

    // calculates the angle that the element should snap to and returns it in radians
    _calculateSnap: function (radians) {
      var degrees = this._angleInDegrees(radians)
      degrees = Math.round(degrees / this.options.step) * this.options.step
      return this._angleInRadians(degrees)
    },

    // calculates the angle to rotate the element to, based on input
    _calculateRotateAngle: function (event) {
      var center = this.getElementCenter()

      var xFromCenter = event.pageX - center.x
      var yFromCenter = event.pageY - center.y
      var mouseAngle = Math.atan2(yFromCenter, xFromCenter)
      var rotateAngle = mouseAngle - this.mouseStartAngle + this.elementStartAngle

      if (this.options.snap || event.shiftKey) {
        rotateAngle = this._calculateSnap(rotateAngle)
      }

      return rotateAngle
    },

    // constructor
    _create: function () {
      var handle
      if (!this.options.handle) {
        handle = $(document.createElement('div'))
        handle.addClass('ui-rotatable-handle')
        if (this.options.handleOffset.top !== 0 || this.options.handleOffset.left !== 0) {
          handle.css('position', 'relative')
          handle.css('top', this.options.handleOffset.top + 'px')
          handle.css('left', this.options.handleOffset.left + 'px')
        }
      } else {
        handle = this.options.handle
      }

      this.listeners = {
        rotateElement: $.proxy(this.rotateElement, this),
        startRotate: $.proxy(this.startRotate, this),
        stopRotate: $.proxy(this.stopRotate, this),
        wheelRotate: $.proxy(this.wheelRotate, this)
      }

      if (this.options.wheelRotate) {
        this.element.bind('wheel', this.listeners.wheelRotate)
      }

      handle.draggable({ helper: 'clone', start: this._dragStart, handle: handle })
      handle.bind('mousedown', this.listeners.startRotate)

      if (!handle.closest(this.element).length) {
        handle.appendTo(this.element)
      }
      this.rotationCenterOffset(this.options.rotationCenterOffset)

      if (this.options.degrees) {
        this.elementCurrentAngle = this._angleInRadians(this.options.degrees)
      }
      else {
        this.elementCurrentAngle = this.options.radians || this.options.angle || 0
      }
      this._performRotation(this.elementCurrentAngle)
    },

    // destructor
    _destroy: function () {
      this.element.removeClass('ui-rotatable')
      this.element.find('.ui-rotatable-handle').remove()

      if (this.options.wheelRotate) {
        this.element.unbind('wheel', this.listeners.wheelRotate)
      }
    },

    // used for the handle
    _dragStart: function (event) {
      if (this.element) {
        return false
      }
    },

    // retrieves the element offset
    _getElementOffset: function () {
      this._performRotation(0)
      var offset = this.element.offset()
      this._performRotation(this.elementCurrentAngle)
      return offset
    },

    _getTransforms: function (angle) {
      var transforms = 'rotate(' + angle + 'rad)'

      if (this.options.transforms) {
        transforms += ' ' + (function (transforms) {
          var t = []
          for (var i in transforms) {
            if (transforms.hasOwnProperty(i) && transforms[i]) {
              t.push(i + '(' + transforms[i] + ')')
            }
          }
          return t.join(' ')
        }(this.options.transforms))
      }
      return transforms
    },

    // checks to see if the element has a rotationCenterOffset set
    _isRotationCenterSet: function () {
      return (this.options.rotationCenterOffset.top !== 0 || this.options.rotationCenterOffset.left !== 0)
    },

    // performs the actual rotation on the element
    _performRotation: function (angle) {
      if (this._isRotationCenterSet()) {
        this.element.css('transform-origin', this.options.rotationCenterOffset.left + 'px ' + this.options.rotationCenterOffset.top + 'px')
        this.element.css('-ms-transform-origin', this.options.rotationCenterOffset.left + 'px ' + this.options.rotationCenterOffset.top + 'px') /* IE 9 */
        this.element.css('-webkit-transform-origin', this.options.rotationCenterOffset.left + 'px ' + this.options.rotationCenterOffset + 'px') /* Chrome, Safari, Opera */
      }

      var transforms = this._getTransforms(angle)

      this.element.css('transform', transforms)
      this.element.css('-moz-transform', transforms)
      this.element.css('-webkit-transform', transforms)
      this.element.css('-o-transform', transforms)
    },

    // propagates events
    _propagate: function (n, event) {
      $.ui.plugin.call(this, n, [event, this.ui()]);
      (n !== 'rotate' && this._trigger(n, event, this.ui()))
    }
  })

  return $.ui.rotatable
}))