const nativeRaf = window.requestAnimationFrame ||
   window.webkitRequestAnimationFrame ||
   window.mozRequestAnimationFrame;

const nativeCancelRaf = window.cancelAnimationFrame ||
  window.webkitCancelAnimationFrame ||
  window.webkitCancelRequestAnimationFrame;

export const raf = nativeRaf || function(callback) {
    let timeCurrent = (new Date()).getTime(),
        timeDelta;

    /* Dynamically set delay on a per-tick basis to match 60fps. */
    /* Technique by Erik Moller. MIT license: https://gist.github.com/paulirish/1579671 */
    timeDelta = Math.max(0, 16 - (timeCurrent - timeLast));
    timeLast = timeCurrent + timeDelta;

    return setTimeout(function() { callback(timeCurrent + timeDelta); }, timeDelta);
}

export const rafCancel = nativeRaf ? nativeCancelRaf : function(id) {
  return window.cancelTimeout(id);
}

export function rafPromise() {
  return new Promise(resolve => raf(resolve));
}

export let CSS = {};
(function() {
  // transform
  var i, keys = ['webkitTransform', 'transform', '-webkit-transform', 'webkit-transform',
                 '-moz-transform', 'moz-transform', 'MozTransform', 'mozTransform', 'msTransform'];

  for (i = 0; i < keys.length; i++) {
    if (document.documentElement.style[keys[i]] !== undefined) {
      CSS.transform = keys[i];
      break;
    }
  }

  // transition
  keys = ['webkitTransition', 'mozTransition', 'msTransition', 'transition'];
  for (i = 0; i < keys.length; i++) {
    if (document.documentElement.style[keys[i]] !== undefined) {
      CSS.transition = keys[i];
      break;
    }
  }

  // The only prefix we care about is webkit for transitions.
  var isWebkit = CSS.transition.indexOf('webkit') > -1;

  CSS.prefix = isWebkit ? '-webkit-' : '';

  // transition duration
  CSS.transitionDuration = (isWebkit ? '-webkit-' : '') + 'transition-duration';

  // To be sure transitionend works everywhere, include *both* the webkit and non-webkit events
  CSS.transitionEnd = (isWebkit ? 'webkitTransitionEnd ' : '') + 'transitionend';
})();

if (window.onanimationend === undefined && window.onwebkitanimationend !== undefined) {
  CSS.animation = 'WebkitAnimation';
  CSS.animationStart = 'webkitAnimationStart animationstart';
  CSS.animationEnd = 'webkitAnimationEnd animationend';
} else {
  CSS.animation = 'animation';
  CSS.animationStart = 'animationstart';
  CSS.animationEnd = 'animationend';
}

export function transitionEnd(el:Element) {
  return cssPromise(el, CSS.transitionEnd);
}

export function animationStart(el:Element, animationName) {
  return cssPromise(el, CSS.animationStart, animationName);
}

export function animationEnd(el:Element, animationName) {
  return cssPromise(el, CSS.animationEnd, animationName);
}

function cssPromise(el:Element, eventNames, animationName) {
  return new Promise(resolve => {
    eventNames.split(' ').forEach(eventName => {
      el.addEventListener(eventName, onEvent);
    })
    function onEvent(ev) {
      if (ev.animationName && animationName) {
        // do not resolve if a bubbled up ev.animationName
        // is not the same as the passed in animationName arg
        if (ev.animationName !== animationName) {
          return;
        }
      } else if (ev.target !== el) {
        // do not resolve if the event's target element is not
        // the same as the element the listener was added to
        return;
      }
      ev.stopPropagation();
      eventNames.split(' ').forEach(eventName => {
        el.removeEventListener(eventName, onEvent);
      })
      resolve(ev);
    }
  });
}

export function ready(callback) {
  let promise = null;

  if (!callback) {
    // a callback wasn't provided, so let's return a promise instead
    promise = new Promise(resolve => { callback = resolve; });
  }

  if (document.readyState === 'complete' || document.readyState === 'interactive') {
    callback();

  } else {
    function completed() {
      document.removeEventListener('DOMContentLoaded', completed, false);
      window.removeEventListener('load', completed, false);
      callback();
    }

    document.addEventListener('DOMContentLoaded', completed, false);
    window.addEventListener('load', completed, false);
  }

  return promise;
}

export function windowLoad(callback) {
  let promise = null;

  if (!callback) {
    // a callback wasn't provided, so let's return a promise instead
    promise = new Promise(resolve => { callback = resolve; });
  }

  if (document.readyState === 'complete') {
    callback();

  } else {
    function completed() {
      window.removeEventListener('load', completed, false);
      callback();
    }

    window.addEventListener('load', completed, false);
  }

  return promise;
}

export function pointerCoord(ev) {
  // get coordinates for either a mouse click
  // or a touch depending on the given event
  let c = { x: 0, y: 0 };
  if (ev) {
    const touches = ev.touches && ev.touches.length ? ev.touches : [ev];
    const e = (ev.changedTouches && ev.changedTouches[0]) || touches[0];
    if (e) {
      c.x = e.clientX || e.pageX || 0;
      c.y = e.clientY || e.pageY || 0;
    }
  }
  return c;
}

export function hasPointerMoved(threshold, startCoord, endCoord) {
  return startCoord && endCoord &&
         (Math.abs(startCoord.x - endCoord.x) > threshold || Math.abs(startCoord.y - endCoord.y) > threshold);
}

export function hasFocus(ele) {
  return !!(ele && (document.activeElement === ele.nativeElement || document.activeElement === ele));
}

export function isTextInput(ele) {
  return !!ele &&
         (ele.tagName == 'TEXTAREA' ||
          ele.contentEditable === 'true' ||
          (ele.tagName == 'INPUT' && !(/^(radio|checkbox|range|file|submit|reset|color|image|button)$/i).test(ele.type)));
}

export function hasFocusedTextInput() {
  let ele = document.activeElement;
  if (isTextInput(ele)) {
    return (ele.parentElement.querySelector(':focus') === ele);
  }
  return false;
}

export function closest(ele, selector) {
  var matchesFn;

  // find vendor prefix
  ['matches','webkitMatchesSelector','mozMatchesSelector','msMatchesSelector','oMatchesSelector'].some(function(fn) {
    if (typeof document.body[fn] == 'function') {
      matchesFn = fn;
      return true;
    }
    return false;
  })

  // traverse parents
  while (ele !== null) {
    parent = ele.parentElement;
    if (parent!==null && parent[matchesFn](selector)) {
      return parent;
    }
    ele = parent;
  }

  return null;
}

export function removeElement(ele) {
  ele && ele.parentNode && ele.parentNode.removeChild(ele);
}


/**
 * Get the element offsetWidth and offsetHeight. Values are cached
 * to reduce DOM reads. Cache is cleared on a window resize.
 * @param {TODO} ele  TODO
 */
export function getDimensions(ion) {
  if (!ion._dimId) {
    ion._dimId = ++dimensionIds;
    if (ion._dimId % 100 === 0) {
      // periodically flush dimensions
      flushDimensionCache();
    }
  }

  let dimensions = dimensionCache[ion._dimId];
  if (!dimensions) {
    let ele = ion.getNativeElement();
    dimensions = dimensionCache[ion._dimId] = {
      width: ele.offsetWidth,
      height: ele.offsetHeight,
      left: ele.offsetLeft,
      top: ele.offsetTop
    };
  }

  return dimensions;
}

export function windowDimensions() {
  if (!dimensionCache.win) {
    dimensionCache.win = {
      width: window.innerWidth,
      height: window.innerHeight
    };
  }
  return dimensionCache.win;
}

export function flushDimensionCache() {
  dimensionCache = {};
}

let dimensionCache = {};
let dimensionIds = 0;

function getStyle(el, cssprop) {
  if (el.currentStyle) { //IE
    return el.currentStyle[cssprop];
  } else if (window.getComputedStyle) {
    return window.getComputedStyle(el)[cssprop];
  }
  // finally try and get inline style
  return el.style[cssprop];
}

function isStaticPositioned(element) {
  return (getStyle(element, 'position') || 'static') === 'static';
}

/**
 * returns the closest, non-statically positioned parentOffset of a given element
 * @param element
 */
export function parentOffsetEl(element) {
  var offsetParent = element.offsetParent || document;
  while (offsetParent && offsetParent !== document && isStaticPositioned(offsetParent)) {
    offsetParent = offsetParent.offsetParent;
  }
  return offsetParent || document;
};

/**
 * Get the current coordinates of the element, relative to the offset parent.
 * Read-only equivalent of [jQuery's position function](http://api.jquery.com/position/).
 * @param {element} element The element to get the position of.
 * @returns {object} Returns an object containing the properties top, left, width and height.
 */
export function position(element) {
  var elBCR = offset(element);
  var offsetParentBCR = { top: 0, left: 0 };
  var offsetParentEl = parentOffsetEl(element);
  if (offsetParentEl != document) {
    offsetParentBCR = offset(offsetParentEl);
    offsetParentBCR.top += offsetParentEl.clientTop - offsetParentEl.scrollTop;
    offsetParentBCR.left += offsetParentEl.clientLeft - offsetParentEl.scrollLeft;
  }

  var boundingClientRect = element.getBoundingClientRect();
  return {
    width: boundingClientRect.width || element.prop('offsetWidth'),
    height: boundingClientRect.height || element.prop('offsetHeight'),
    top: elBCR.top - offsetParentBCR.top,
    left: elBCR.left - offsetParentBCR.left
  };
}

/**
* Get the current coordinates of the element, relative to the document.
* Read-only equivalent of [jQuery's offset function](http://api.jquery.com/offset/).
* @param {element} element The element to get the offset of.
* @returns {object} Returns an object containing the properties top, left, width and height.
*/
export function offset(element) {
 var boundingClientRect = element.getBoundingClientRect();
 return {
   width: boundingClientRect.width || element.prop('offsetWidth'),
   height: boundingClientRect.height || element.prop('offsetHeight'),
   top: boundingClientRect.top + (window.pageYOffset || document.documentElement.scrollTop),
   left: boundingClientRect.left + (window.pageXOffset || document.documentElement.scrollLeft)
 };
}