(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global.pullToRefresh = factory());
}(this, (function () { 'use strict';

  function ontouchpan (_ref) {
    var element = _ref.element,
        onpanstart = _ref.onpanstart,
        onpanmove = _ref.onpanmove,
        onpanend = _ref.onpanend;

    var touchId = void 0,
        startX = void 0,
        startY = void 0,
        panstartCalled = void 0;

    function calcMovement(e) {
      var touch = Array.prototype.slice.call(e.changedTouches).filter(function (touch) {
        return touch.identifier === touchId;
      })[0];
      if (!touch) return false;

      e.deltaX = touch.screenX - startX;
      e.deltaY = touch.screenY - startY;
      return true;
    }

    function touchstart(e) {
      var touch = e.changedTouches[0];
      touchId = touch.identifier;
      startX = touch.screenX;
      startY = touch.screenY;
    }

    function touchmove(e) {
      if (calcMovement(e)) {
        if (onpanstart && !panstartCalled) {
          onpanstart(e);
          panstartCalled = true;
        }

        onpanmove(e);
      }
    }

    function touchend(e) {
      if (calcMovement(e)) onpanend(e);
    }

    element.addEventListener('touchstart', touchstart);
    if (onpanmove) element.addEventListener('touchmove', touchmove);
    if (onpanend) element.addEventListener('touchend', touchend);

    return function () {
      element.removeEventListener('touchstart', touchstart);
      if (onpanmove) element.removeEventListener('touchmove', touchmove);
      if (onpanend) element.removeEventListener('touchend', touchend);
    };
  }

  function pullToRefresh (opts) {
    opts = Object.assign({
      // https://bugs.chromium.org/p/chromium/issues/detail?id=766938
      scrollable: document.body,
      threshold: 150,
      onStateChange: function onStateChange() {/* noop */}
    }, opts);

    var _opts = opts,
        container = _opts.container,
        scrollable = _opts.scrollable,
        threshold = _opts.threshold,
        refresh = _opts.refresh,
        onStateChange = _opts.onStateChange,
        animates = _opts.animates;


    var distance = void 0,
        offset = void 0,
        state = void 0; // state: pulling, aborting, reached, refreshing, restoring

    function addClass(cls) {
      container.classList.add('pull-to-refresh--' + cls);
    }

    function removeClass(cls) {
      container.classList.remove('pull-to-refresh--' + cls);
    }

    function scrollTop() {
      if (!scrollable || [window, document, document.body, document.documentElement].includes(scrollable)) {
        return document.documentElement.scrollTop || document.body.scrollTop;
      } else {
        return scrollable.scrollTop;
      }
    }

    return ontouchpan({
      element: container,

      onpanmove: function onpanmove(e) {
        var d = e.deltaY;

        if (scrollTop() > 0 || d < 0 && !state || state in { aborting: 1, refreshing: 1, restoring: 1 }) return;

        if (e.cancelable) {
          e.preventDefault();
        }

        if (distance == null) {
          offset = d;
          state = 'pulling';
          addClass(state);
          onStateChange(state, opts);
        }

        d = d - offset;
        if (d < 0) d = 0;
        distance = d;

        if (d >= threshold && state !== 'reached' || d < threshold && state !== 'pulling') {
          removeClass(state);
          state = state === 'reached' ? 'pulling' : 'reached';
          addClass(state);
          onStateChange(state, opts);
        }

        animates.pulling(d, opts);
      },
      onpanend: function onpanend() {
        if (state == null) return;

        if (state === 'pulling') {
          removeClass(state);
          state = 'aborting';
          onStateChange(state);
          addClass(state);
          animates.aborting(opts).then(function () {
            removeClass(state);
            distance = state = offset = null;
            onStateChange(state);
          });
        } else if (state === 'reached') {
          removeClass(state);
          state = 'refreshing';
          addClass(state);
          onStateChange(state, opts);
          animates.refreshing(opts);

          refresh().then(function () {
            removeClass(state);
            state = 'restoring';
            addClass(state);
            onStateChange(state);

            animates.restoring(opts).then(function () {
              removeClass(state);
              distance = state = offset = null;
              onStateChange(state);
            });
          });
        }
      }
    });
  }

  return pullToRefresh;

})));