var gPosition = 0;
var gProgress = 0;
var gCurrentPage = 0;
var gPageCount = 0;
var gClientHeight = null;

const kMaxFont = 0;

function getPosition()
{
	return gPosition;
}

function getProgress()
{
	return gProgress;
}

function getPageCount()
{
	return gPageCount;
}

function getCurrentPage()
{
	return gCurrentPage;
}

/**
 * Setup the columns and calculate the total page count;
 */

function setupBookColumns()
{
	var body = document.getElementsByTagName('body')[0].style;
	body.marginLeft = 0;
	body.marginRight = 0;
	body.marginTop = 0;
	body.marginBottom = 0;
	
    var bc = document.getElementById('book-columns').style;
    bc.width = (window.innerWidth * 2) + 'px !important';
	bc.height = (window.innerHeight-kMaxFont) + 'px !important';
    bc.marginTop = '0px !important';
    bc.webkitColumnWidth = window.innerWidth + 'px !important';
    bc.webkitColumnGap = '0px';
	bc.overflow = 'visible';

	gCurrentPage = 1;
	gProgress = gPosition = 0;
	
	var bi = document.getElementById('book-inner').style;
	bi.marginLeft = '0px';
	bi.marginRight = '0px';
	bi.padding = '0';

	gPageCount = document.body.scrollWidth / window.innerWidth;

	// Adjust the page count to 1 in case the initial bool-columns.clientHeight is less than the height of the screen. We only do this once.2

	if (gClientHeight < (window.innerHeight-kMaxFont)) {
		gPageCount = 1;
	}
}

/**
 * Columnize the document and move to the first page. The position and progress are reset/initialized
 * to 0. This should be the initial pagination request when the document is initially shown.
 */

function paginate()
{	
	// Get the height of the page. We do this only once. In setupBookColumns we compare this
	// value to the height of the window and then decide wether to force the page count to one.
	
	if (gClientHeight == undefined) {
		gClientHeight = document.getElementById('book-columns').clientHeight;
	}
	
	setupBookColumns();
}

/**
 * Paginate the document again and maintain the current progress. This needs to be used when
 * the content view changes size. For example because of orientation changes. The page count
 * and current page are recalculated based on the current progress.
 */

function paginateAndMaintainProgress()
{
	var savedProgress = gProgress;
	setupBookColumns();
	goProgress(savedProgress);
}

/**
 * Update the progress based on the current page and page count. The progress is calculated
 * based on the top left position of the page. So the first page is 0% and the last page is
 * always below 1.0.
 */

function updateProgress()
{
	gProgress = (gCurrentPage - 1.0) / gPageCount;
}

/**
 * Move a page back if possible. The position, progress and page count are updated accordingly.
 */

function goBack()
{
	if (gCurrentPage > 1)
	{
		gCurrentPage--;
		gPosition -= window.innerWidth;
		window.scrollTo(gPosition, 0);
		updateProgress();
	}
}

/**
 * Move a page forward if possible. The position, progress and page count are updated accordingly.
 */

function goForward()
{
	if (gCurrentPage < gPageCount)
	{
		gCurrentPage++;
		gPosition += window.innerWidth;
		window.scrollTo(gPosition, 0);
		updateProgress();
	}
}

/**
 * Move directly to a page. Remember that there are no real page numbers in a reflowed
 * EPUB document. Use this only in the context of the current document.
 */

function goPage(pageNumber)
{
	if (pageNumber > 0 && pageNumber <= gPageCount)
	{
		gCurrentPage = pageNumber;
		gPosition = (gCurrentPage - 1) * window.innerWidth;
		window.scrollTo(gPosition, 0);
		updateProgress();
	}
}

/**
 * Go the the page with respect to progress. Assume everything has been setup.
 */

function goProgress(progress)
{
	progress += 0.0001;
	
	var progressPerPage = 1.0 / gPageCount;
	var newPage = 0;
	
	for (var page = 0; page < gPageCount; page++) {
		var low = page * progressPerPage;
		var high = low + progressPerPage;
		if (progress >= low && progress < high) {
			newPage = page;
			break;
		}
	}
		
	gCurrentPage = newPage + 1;
	gPosition = (gCurrentPage - 1) * window.innerWidth;
	window.scrollTo(gPosition, 0);
	updateProgress();		
}

//Set font family
function setFontFamily(newFont) {
	document.body.style.fontFamily = newFont + " !important";
	paginateAndMaintainProgress();
}

//Sets font size to a relative size
function setFontSize(toSize) {
	document.getElementById('book-inner').style.fontSize = toSize + "em !important";
	//To prevent 1 page chapters from not reflowing to additional pages when increasing the font size:
	if (toSize > 1) {
		gClientHeight = document.getElementById('book-columns').clientHeight;
	}
	paginateAndMaintainProgress();
}

//Sets line height relative to font size
function setLineHeight(toHeight) {
	document.getElementById('book-inner').style.lineHeight = toHeight + "em !important";
	paginateAndMaintainProgress();
}

//Enables night reading mode
function enableNightReading() {
	document.body.style.backgroundColor = "#000000";
	var theDiv = document.getElementById('book-inner');
	theDiv.style.color = "#ffffff";
	
	var anchorTags;
	anchorTags = theDiv.getElementsByTagName('a');
	
	for (var i = 0; i < anchorTags.length; i++) {
		anchorTags[i].style.color = "#ffffff";
	}
}