'use strict';

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

function bindMouseScrollXHandler(element, i) {
  var currentLeft = null;
  var currentPageX = null;

  function updateScrollLeft(deltaX) {
    var newLeft = currentLeft + (deltaX * i.railXRatio);
    var maxLeft = Math.max(0, i.scrollbarXRail.getBoundingClientRect().left) + (i.railXRatio * (i.railXWidth - i.scrollbarXWidth));

    if (newLeft < 0) {
      i.scrollbarXLeft = 0;
    } else if (newLeft > maxLeft) {
      i.scrollbarXLeft = maxLeft;
    } else {
      i.scrollbarXLeft = newLeft;
    }

    var scrollLeft = _.toInt(i.scrollbarXLeft * (i.contentWidth - i.containerWidth) / (i.containerWidth - (i.railXRatio * i.scrollbarXWidth))) - i.negativeScrollAdjustment;
    updateScroll(element, 'left', scrollLeft);
  }

  var mouseMoveHandler = function (e) {
    updateScrollLeft(e.pageX - currentPageX);
    updateGeometry(element);
    e.stopPropagation();
    e.preventDefault();
  };

  var mouseUpHandler = function () {
    _.stopScrolling(element, 'x');
    i.event.unbind(i.ownerDocument, 'mousemove', mouseMoveHandler);
  };

  i.event.bind(i.scrollbarX, 'mousedown', function (e) {
    currentPageX = e.pageX;
    currentLeft = _.toInt(dom.css(i.scrollbarX, 'left')) * i.railXRatio;
    _.startScrolling(element, 'x');

    i.event.bind(i.ownerDocument, 'mousemove', mouseMoveHandler);
    i.event.once(i.ownerDocument, 'mouseup', mouseUpHandler);

    e.stopPropagation();
    e.preventDefault();
  });
}

function bindMouseScrollYHandler(element, i) {
  var currentTop = null;
  var currentPageY = null;

  function updateScrollTop(deltaY) {
    var newTop = currentTop + (deltaY * i.railYRatio);
    var maxTop = Math.max(0, i.scrollbarYRail.getBoundingClientRect().top) + (i.railYRatio * (i.railYHeight - i.scrollbarYHeight));

    if (newTop < 0) {
      i.scrollbarYTop = 0;
    } else if (newTop > maxTop) {
      i.scrollbarYTop = maxTop;
    } else {
      i.scrollbarYTop = newTop;
    }

    var scrollTop = _.toInt(i.scrollbarYTop * (i.contentHeight - i.containerHeight) / (i.containerHeight - (i.railYRatio * i.scrollbarYHeight)));
    updateScroll(element, 'top', scrollTop);
  }

  var mouseMoveHandler = function (e) {
    updateScrollTop(e.pageY - currentPageY);
    updateGeometry(element);
    e.stopPropagation();
    e.preventDefault();
  };

  var mouseUpHandler = function () {
    _.stopScrolling(element, 'y');
    i.event.unbind(i.ownerDocument, 'mousemove', mouseMoveHandler);
  };

  i.event.bind(i.scrollbarY, 'mousedown', function (e) {
    currentPageY = e.pageY;
    currentTop = _.toInt(dom.css(i.scrollbarY, 'top')) * i.railYRatio;
    _.startScrolling(element, 'y');

    i.event.bind(i.ownerDocument, 'mousemove', mouseMoveHandler);
    i.event.once(i.ownerDocument, 'mouseup', mouseUpHandler);

    e.stopPropagation();
    e.preventDefault();
  });
}

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