/* Add stylesheet to page */

var presStyle = document.createElement('link');
presStyle.type = 'text/css';
presStyle.rel = 'stylesheet';
presStyle.href = '/presentation.css';
document.head.appendChild(presStyle);

/* Print button */

const printBtn = document.getElementById('printBtn');

printBtn.onclick = function() {
	window.print();
}

/* Next and previous buttons */

const prevSlideBtn = document.getElementById('prevSlideBtn');
const nextSlideBtn = document.getElementById('nextSlideBtn');

const slides = document.getElementsByClassName('slide');
var slideIndex = 0;

function showSlide(mod) {
	slides[slideIndex].classList.remove('absolute-slide');
	slideIndex = (slides.length + slideIndex + mod) % slides.length;
	slides[slideIndex].classList.add('absolute-slide');
}

prevSlideBtn.onclick = function() {
	showSlide(-1);
}

nextSlideBtn.onclick = function() {
	showSlide(+1);
}

/* Present button */

const presentCont = document.getElementById('presentCont');
const presentBtn = document.getElementById('presentBtn');

presentBtn.onclick = function() {
	// Hide the whole page
	document.body.classList.toggle('invisible');
	document.body.classList.toggle('no-overflow');
	// Fix background color
	document.body.classList.toggle('body-bg-color');
	// Show the slide controller
	presentCont.classList.toggle('absolute-cont');
	prevSlideBtn.classList.toggle('nodisplay');
	nextSlideBtn.classList.toggle('nodisplay');
	// Show the first slide
	slides[slideIndex].classList.toggle('absolute-slide');
	slideIndex = 0;
	window.scrollTo(0, 0); // Alignment of presentation to screen
}