/* Copyright (c) 2015 Hyunje Alex Jun and other contributors
 * Licensed under the MIT License
 */
'use strict';

var h = require('../../lib/helper')
  , instances = require('../instances')
  , updateGeometry = require('../update-geometry')
  , updateScroll = require('../update-scroll');

function bindClickRailHandler(element, i) {
  function pageOffset(el) {
    return el.getBoundingClientRect();
  }
  var stopPropagation = window.Event.prototype.stopPropagation.bind;

  if (i.settings.stopPropagationOnClick) {
    i.event.bind(i.scrollbarY, 'click', stopPropagation);
  }
  i.event.bind(i.scrollbarYRail, 'click', function (e) {
    var halfOfScrollbarLength = h.toInt(i.scrollbarYHeight / 2);
    var positionTop = i.railYRatio * (e.pageY - window.scrollY - pageOffset(i.scrollbarYRail).top - halfOfScrollbarLength);
    var maxPositionTop = i.railYRatio * (i.railYHeight - i.scrollbarYHeight);
    var positionRatio = positionTop / maxPositionTop;

    if (positionRatio < 0) {
      positionRatio = 0;
    } else if (positionRatio > 1) {
      positionRatio = 1;
    }

    updateScroll(element, 'top', (i.contentHeight - i.containerHeight) * positionRatio);
    updateGeometry(element);

    e.stopPropagation();
  });

  if (i.settings.stopPropagationOnClick) {
    i.event.bind(i.scrollbarX, 'click', stopPropagation);
  }
  i.event.bind(i.scrollbarXRail, 'click', function (e) {
    var halfOfScrollbarLength = h.toInt(i.scrollbarXWidth / 2);
    var positionLeft = i.railXRatio * (e.pageX - window.scrollX - pageOffset(i.scrollbarXRail).left - halfOfScrollbarLength);
    var maxPositionLeft = i.railXRatio * (i.railXWidth - i.scrollbarXWidth);
    var positionRatio = positionLeft / maxPositionLeft;

    if (positionRatio < 0) {
      positionRatio = 0;
    } else if (positionRatio > 1) {
      positionRatio = 1;
    }

    updateScroll(element, 'left', ((i.contentWidth - i.containerWidth) * positionRatio) - i.negativeScrollAdjustment);
    updateGeometry(element);

    e.stopPropagation();
  });
}

module.exports = function (element) {
  var i = instances.get(element);
  bindClickRailHandler(element, i);
};