// JavaScript Document
var currentSection = "photo1-page";
var tabTag = "-tab";
var paneTag = "-page";

function ScrollSection(link, scrollArea, offset) {

	// Store the last section, and update the current section
	if(currentSection == link) {
		return;
	}
	lastSection = currentSection;
	currentSection = link;
	
	// Change the section highlight.
	// Extract the root section name, and use that to change the background image to 'top', revealing the alt. state
	sectionTab = currentSection.split("-")[0] + tabTag;
	document.getElementById(sectionTab).className = "active";
	if(lastSection) {
		lastTab = lastSection.split("-")[0] + tabTag;
		document.getElementById(lastTab).className = "inactive";
	}
    
	// Get the element we want to scroll, get the position of the element to scroll to
	theScroll = document.getElementById(scrollArea);
	position = findElementPos(document.getElementById(link));

	// Get the position of the offset div -- the div at the far left.
	// This is the amount we compensate for when scrolling
	if(offset != "") {
		offsetPos = findElementPos(document.getElementById(offset));
		position[0] = position[0] - offsetPos[0];
	}

	scrollStart(theScroll, theScroll.scrollLeft, position[0], "horiz");
	// return false;
}

// Scroll the page using the arrows
function ScrollArrow(direction, toolbar, scrollArea, offset) {

	toolbarElem = document.getElementById(toolbar);
	toolbarNames = new Array();
    
	// Find all the <li> elements in the toolbar, and extract their id's into an array.
	if(toolbarElem.hasChildNodes()) {
		var children = toolbarElem.childNodes;
		for(var i = 0; i < children.length; i++) {
			if(toolbarElem.childNodes[i].tagName == "LI") {
				toolbarNames.push(toolbarElem.childNodes[i].id.split("-")[0]);
			}
		}
	}

	// Now iterate through our array of tab names, find matches, and determine where to go.
	for(var i = 0; i < toolbarNames.length; i++) {
		if(toolbarNames[i] == currentSection.split("-")[0]) {
			if(direction == "left") {
				if(i - 1 < 0) {
					gotoTab = toolbarNames[toolbarNames.length - 1];
				} else {
					gotoTab = toolbarNames[i - 1];
				}
			} else {
				if((i + 1) > (toolbarNames.length - 1)) {
					gotoTab = toolbarNames[0];
				} else {
					gotoTab = toolbarNames[i + 1];
				}
			}
		}
	}
	
	// Go to the section name!
	ScrollSection(gotoTab+paneTag, scrollArea, offset);
}

// Animated Scroll Functions
// Scrolls are synchronous -- only one at a time.
var scrollanim = {time:0, begin:0, change:0.0, duration:0.0, element:null, timer:null};

function scrollStart(elem, start, end, direction) {
	if (scrollanim.timer != null) {
		clearInterval(scrollanim.timer);
		scrollanim.timer = null;
	}
	scrollanim.time = 0;
	scrollanim.begin = start;
	scrollanim.change = end - start;
	scrollanim.duration = 25;
	scrollanim.element = elem;
	
	if(direction == "horiz") {
		scrollanim.timer = setInterval("scrollHorizAnim();", 45);
	} else {
		scrollanim.timer = setInterval("scrollVertAnim();", 45);
	}
}

function scrollVertAnim() {
	if(scrollanim.time > scrollanim.duration) {
		clearInterval(scrollanim.timer);
		scrollanim.timer = null;
	} else {
		move = sineInOut(scrollanim.time, scrollanim.begin, scrollanim.change, scrollanim.duration);
		scrollanim.element.scrollTop = move; 
		scrollanim.time++;
	}
}

function scrollHorizAnim() {
	if(scrollanim.time > scrollanim.duration) {
		clearInterval(scrollanim.timer);
		scrollanim.timer = null;
	} else {
		move = sineInOut(scrollanim.time, scrollanim.begin, scrollanim.change, scrollanim.duration);
		scrollanim.element.scrollLeft = move;
		scrollanim.time++;
	}
}

function findElementPos(elemFind) {
	var elemX = 0;
	var elemY = 0;
	do {
		elemX += elemFind.offsetLeft;
		elemY += elemFind.offsetTop;
	} while(elemFind = elemFind.offsetParent)

	return Array(elemX, elemY);
}

function sineInOut(t, b, c, d) {
	return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
}