(function (window, document, exportName, undefined) {
  'use strict'

  var isMultiTouch = false
  var multiTouchStartPos
  var eventTarget
  var touchElements = {}

  // polyfills
  if (!document.createTouch) {
    document.createTouch = function (view, target, identifier, pageX, pageY, screenX, screenY, clientX, clientY) {
      // auto set
      if (clientX == undefined || clientY == undefined) {
        clientX = pageX - window.pageXOffset
        clientY = pageY - window.pageYOffset
      }

      return new Touch(target, identifier, {
        pageX: pageX,
        pageY: pageY,
        screenX: screenX,
        screenY: screenY,
        clientX: clientX,
        clientY: clientY
      })
    }
  }

  if (!document.createTouchList) {
    document.createTouchList = function () {
      var touchList = new TouchList()
      for (var i = 0; i < arguments.length; i++) {
        touchList[i] = arguments[i]
      }
      touchList.length = arguments.length
      return touchList
    }
  }

  /**
     * create an touch point
     * @constructor
     * @param target
     * @param identifier
     * @param pos
     * @param deltaX
     * @param deltaY
     * @returns {Object} touchPoint
     */
  function Touch (target, identifier, pos, deltaX, deltaY) {
    deltaX = deltaX || 0
    deltaY = deltaY || 0

    this.identifier = identifier
    this.target = target
    this.clientX = pos.clientX + deltaX
    this.clientY = pos.clientY + deltaY
    this.screenX = pos.screenX + deltaX
    this.screenY = pos.screenY + deltaY
    this.pageX = pos.pageX + deltaX
    this.pageY = pos.pageY + deltaY
  }

  /**
     * create empty touchlist with the methods
     * @constructor
     * @returns touchList
     */
  function TouchList () {
    var touchList = []

    touchList.item = function (index) {
      return this[index] || null
    }

    // specified by Mozilla
    touchList.identifiedTouch = function (id) {
      return this[id + 1] || null
    }

    return touchList
  }

  /**
     * Simple trick to fake touch event support
     * this is enough for most libraries like Modernizr and Hammer
     */
  function fakeTouchSupport () {
    var objs = [window, document.documentElement]
    var props = ['ontouchstart', 'ontouchmove', 'ontouchcancel', 'ontouchend']

    for (var o = 0; o < objs.length; o++) {
      for (var p = 0; p < props.length; p++) {
        if (objs[o] && objs[o][props[p]] == undefined) {
          objs[o][props[p]] = null
        }
      }
    }
  }

  /**
     * we don't have to emulate on a touch device
     * @returns {boolean}
     */
  function hasTouchSupport () {
    return ('ontouchstart' in window) || // touch events
            (window.Modernizr && window.Modernizr.touch) || // modernizr
            (navigator.msMaxTouchPoints || navigator.maxTouchPoints) > 2 // pointer events
  }

  /**
     * disable mouseevents on the page
     * @param ev
     */
  function preventMouseEvents (ev) {
    ev.preventDefault()
    ev.stopPropagation()
  }

  /**
     * only trigger touches when the left mousebutton has been pressed
     * @param touchType
     * @returns {Function}
     */
  function onMouse (touchType) {
    return function (ev) {
      // prevent mouse events
      // 过滤 输入框 和 可编辑元素
      // preventMouseEvents(ev);
      ev.stopPropagation()
      var computedStyle
      var target = ev.target
      if (target.tagName !== 'INPUT' && target.tagName !== 'TEXTAREA' && (computedStyle = window.getComputedStyle(target)) && (computedStyle['user-modify'] || computedStyle['-webkit-user-modify']).indexOf('write') < 0) {
        ev.preventDefault()
      }

      if (ev.which !== 1) {
        return
      }

      // The EventTarget on which the touch point started when it was first placed on the surface,
      // even if the touch point has since moved outside the interactive area of that element.
      // also, when the target doesnt exist anymore, we update it
      if (ev.type == 'mousedown' || !eventTarget || (eventTarget && !eventTarget.dispatchEvent)) {
        eventTarget = ev.target
      }

      // shiftKey has been lost, so trigger a touchend
      if (isMultiTouch && !ev.shiftKey) {
        triggerTouch('touchend', ev)
        isMultiTouch = false
      }

      triggerTouch(touchType, ev)

      // we're entering the multi-touch mode!
      if (!isMultiTouch && ev.shiftKey) {
        isMultiTouch = true
        multiTouchStartPos = {
          pageX: ev.pageX,
          pageY: ev.pageY,
          clientX: ev.clientX,
          clientY: ev.clientY,
          screenX: ev.screenX,
          screenY: ev.screenY
        }
        triggerTouch('touchstart', ev)
      }

      // reset
      if (ev.type == 'mouseup') {
        multiTouchStartPos = null
        isMultiTouch = false
        eventTarget = null
      }
    }
  }

  /**
     * trigger a touch event
     * @param eventName
     * @param mouseEv
     */
  function triggerTouch (eventName, mouseEv) {
    var touchEvent = document.createEvent('Event')
    touchEvent.initEvent(eventName, true, true)

    touchEvent.altKey = mouseEv.altKey
    touchEvent.ctrlKey = mouseEv.ctrlKey
    touchEvent.metaKey = mouseEv.metaKey
    touchEvent.shiftKey = mouseEv.shiftKey

    touchEvent.touches = getActiveTouches(mouseEv, eventName)
    touchEvent.targetTouches = getActiveTouches(mouseEv, eventName)
    touchEvent.changedTouches = getChangedTouches(mouseEv, eventName)

    eventTarget.dispatchEvent(touchEvent)
  }

  /**
     * create a touchList based on the mouse event
     * @param mouseEv
     * @returns {TouchList}
     */
  function createTouchList (mouseEv) {
    var touchList = new TouchList()

    if (isMultiTouch) {
      var f = TouchEmulator.multiTouchOffset
      var deltaX = multiTouchStartPos.pageX - mouseEv.pageX
      var deltaY = multiTouchStartPos.pageY - mouseEv.pageY

      touchList.push(new Touch(eventTarget, 1, multiTouchStartPos, (deltaX * -1) - f, (deltaY * -1) + f))
      touchList.push(new Touch(eventTarget, 2, multiTouchStartPos, deltaX + f, deltaY - f))
    } else {
      touchList.push(new Touch(eventTarget, 1, mouseEv, 0, 0))
    }

    return touchList
  }

  /**
     * receive all active touches
     * @param mouseEv
     * @returns {TouchList}
     */
  function getActiveTouches (mouseEv, eventName) {
    // empty list
    if (mouseEv.type == 'mouseup') {
      return new TouchList()
    }

    var touchList = createTouchList(mouseEv)
    if (isMultiTouch && mouseEv.type != 'mouseup' && eventName == 'touchend') {
      touchList.splice(1, 1)
    }
    return touchList
  }

  /**
     * receive a filtered set of touches with only the changed pointers
     * @param mouseEv
     * @param eventName
     * @returns {TouchList}
     */
  function getChangedTouches (mouseEv, eventName) {
    var touchList = createTouchList(mouseEv)

    // we only want to return the added/removed item on multitouch
    // which is the second pointer, so remove the first pointer from the touchList
    //
    // but when the mouseEv.type is mouseup, we want to send all touches because then
    // no new input will be possible
    if (isMultiTouch && mouseEv.type != 'mouseup' &&
            (eventName == 'touchstart' || eventName == 'touchend')) {
      touchList.splice(0, 1)
    }

    return touchList
  }

  /**
     * show the touchpoints on the screen
     */
  function showTouches (ev) {
    var touch, i, el, styles

    // first all visible touches
    for (i = 0; i < ev.touches.length; i++) {
      touch = ev.touches[i]
      el = touchElements[touch.identifier]
      if (!el) {
        el = touchElements[touch.identifier] = document.createElement('div')
        document.body.appendChild(el)
      }

      styles = TouchEmulator.template(touch)
      for (var prop in styles) {
        el.style[prop] = styles[prop]
      }
    }

    // remove all ended touches
    if (ev.type == 'touchend' || ev.type == 'touchcancel') {
      for (i = 0; i < ev.changedTouches.length; i++) {
        touch = ev.changedTouches[i]
        el = touchElements[touch.identifier]
        if (el) {
          el.parentNode.removeChild(el)
          delete touchElements[touch.identifier]
        }
      }
    }
  }

  /**
     * TouchEmulator initializer
     */
  function TouchEmulator () {
    if (hasTouchSupport()) {
      return
    }

    fakeTouchSupport()

    window.addEventListener('mousedown', onMouse('touchstart'), true)
    window.addEventListener('mousemove', onMouse('touchmove'), true)
    window.addEventListener('mouseup', onMouse('touchend'), true)

    window.addEventListener('mouseenter', preventMouseEvents, true)
    window.addEventListener('mouseleave', preventMouseEvents, true)
    window.addEventListener('mouseout', preventMouseEvents, true)
    window.addEventListener('mouseover', preventMouseEvents, true)

    // it uses itself!
    // 关闭触摸显示
    // window.addEventListener("touchstart", showTouches, false);
    // window.addEventListener("touchmove", showTouches, false);
    // window.addEventListener("touchend", showTouches, false);
    // window.addEventListener("touchcancel", showTouches, false);
  }

  // start distance when entering the multitouch mode
  TouchEmulator.multiTouchOffset = 75

  /**
     * css template for the touch rendering
     * @param touch
     * @returns object
     */
  TouchEmulator.template = function (touch) {
    var size = 30
    var transform = 'translate(' + (touch.clientX - (size / 2)) + 'px, ' + (touch.clientY - (size / 2)) + 'px)'
    return {
      position: 'fixed',
      left: 0,
      top: 0,
      background: '#fff',
      border: 'solid 1px #999',
      opacity: 0.6,
      borderRadius: '100%',
      height: size + 'px',
      width: size + 'px',
      padding: 0,
      margin: 0,
      display: 'block',
      overflow: 'hidden',
      pointerEvents: 'none',
      webkitUserSelect: 'none',
      mozUserSelect: 'none',
      userSelect: 'none',
      webkitTransform: transform,
      mozTransform: transform,
      transform: transform
    }
  }

  // export
  // 直接启用
  // if (typeof define == "function" && define.amd) {
  //     define(function() {
  //         return TouchEmulator;
  //     });
  // } else if (typeof module != "undefined" && module.exports) {
  //     module.exports = TouchEmulator;
  // } else {
  //     window[exportName] = TouchEmulator;
  // }
  TouchEmulator()
})(window, document, 'TouchEmulator')