text: /*\
  title: $:/core/modules/utils/dom/scroller.js
  type: application/javascript
  module-type: utils
  
  Module that creates a $tw.utils.Scroller object prototype that manages scrolling in the browser
  
  \*/
  (function(){
  
  /*jslint node: true, browser: true */
  /*global $tw: false */
  "use strict";
  
  /*
  Event handler for when the `tm-scroll` event hits the document body
  */
  var PageScroller = function() {
  	this.idRequestFrame = null;
  	this.requestAnimationFrame = window.requestAnimationFrame ||
  		window.webkitRequestAnimationFrame ||
  		window.mozRequestAnimationFrame ||
  		function(callback) {
  			return window.setTimeout(callback, 1000/60);
  		};
  	this.cancelAnimationFrame = window.cancelAnimationFrame ||
  		window.webkitCancelAnimationFrame ||
  		window.webkitCancelRequestAnimationFrame ||
  		window.mozCancelAnimationFrame ||
  		window.mozCancelRequestAnimationFrame ||
  		function(id) {
  			window.clearTimeout(id);
  		};
  };
  
  PageScroller.prototype.isScrolling = function() {
  	return this.idRequestFrame !== null;
  }
  
  PageScroller.prototype.cancelScroll = function(srcWindow) {
  	if(this.idRequestFrame) {
  		this.cancelAnimationFrame.call(srcWindow,this.idRequestFrame);
  		this.idRequestFrame = null;
  	}
  };
  
  /*
  Handle an event
  */
  PageScroller.prototype.handleEvent = function(event) {
  	if(event.type === "tm-scroll") {
  		var options = {};
  		if($tw.utils.hop(event.paramObject,"animationDuration")) {
  			options.animationDuration = event.paramObject.animationDuration;
  		}
  		if(event.paramObject && event.paramObject.selector) {
  			this.scrollSelectorIntoView(null,event.paramObject.selector,null,options);
  		} else {
  			this.scrollIntoView(event.target,null,options);
  		}
  		return false; // Event was handled
  	}
  	return true;
  };
  
  /*
  Handle a scroll event hitting the page document
  */
  PageScroller.prototype.scrollIntoView = function(element,callback,options) {
  	var self = this,
  		duration = $tw.utils.hop(options,"animationDuration") ? parseInt(options.animationDuration) : $tw.utils.getAnimationDuration(),
  		srcWindow = element ? element.ownerDocument.defaultView : window;
  	try {
  		$tw.utils.addClass(element,"tc-navigating");
  		var scrollIntoView = function() {
  			element.scrollIntoView({inline: "start"});
  		};
  		this.requestAnimationFrame.call(srcWindow,scrollIntoView);
  		setTimeout(function() {
  			$tw.utils.removeClass(element,"tc-navigating");
  		},$tw.utils.getAnimationDuration() * 1);
  	} catch(e) {
  		console.log(e);
  		// Now get ready to scroll the body
  		this.cancelScroll(srcWindow);
  		this.startTime = Date.now();
  		// Get the height of any position:fixed toolbars
  		var toolbar = srcWindow.document.querySelector(".tc-adjust-top-of-scroll"),
  			offset = 0;
  		if(toolbar) {
  			offset = toolbar.offsetHeight;
  		}
  		// Get the client bounds of the element and adjust by the scroll position
  		var getBounds = function() {
  				var clientBounds = typeof callback === 'function' ? callback() : element.getBoundingClientRect(),
  					scrollPosition = $tw.utils.getScrollPosition(srcWindow);
  				return {
  					left: clientBounds.left + scrollPosition.x,
  					top: clientBounds.top + scrollPosition.y - offset,
  					width: clientBounds.width,
  					height: clientBounds.height
  				};
  			},
  			// We'll consider the horizontal and vertical scroll directions separately via this function
  			// targetPos/targetSize - position and size of the target element
  			// currentPos/currentSize - position and size of the current scroll viewport
  			// returns: new position of the scroll viewport
  			getEndPos = function(targetPos,targetSize,currentPos,currentSize) {
  				var newPos = targetPos;
  				// If we are scrolling within 50 pixels of the top/left then snap to zero
  				if(newPos < 50) {
  					newPos = 0;
  				}
  				return newPos;
  			},
  			drawFrame = function drawFrame() {
  				var t;
  				if(duration <= 0) {
  					t = 1;
  				} else {
  					t = ((Date.now()) - self.startTime) / duration;
  				}
  				if(t >= 1) {
  					self.cancelScroll(srcWindow);
  					t = 1;
  				}
  				t = $tw.utils.slowInSlowOut(t);
  				var scrollPosition = $tw.utils.getScrollPosition(srcWindow),
  					bounds = getBounds(),
  					endX = getEndPos(bounds.left,bounds.width,scrollPosition.x,srcWindow.innerWidth),
  					endY = getEndPos(bounds.top,bounds.height,scrollPosition.y,srcWindow.innerHeight);
  				srcWindow.scrollTo(scrollPosition.x + (endX - scrollPosition.x) * t,scrollPosition.y + (endY - scrollPosition.y) * t);
  				if(t < 1) {
  					self.idRequestFrame = self.requestAnimationFrame.call(srcWindow,drawFrame);
  				}
  			};
  		drawFrame();
  	}
  };
  
  PageScroller.prototype.scrollSelectorIntoView = function(baseElement,selector,callback,options) {
  	baseElement = baseElement || document.body;
  	var element = baseElement.querySelector(selector);
  	if(element) {
  		this.scrollIntoView(element,callback,options);
  	}
  };
  
  exports.PageScroller = PageScroller;
  
  })();
  