const invocation = new XMLHttpRequest();
	const url = 'https://pad.xpub.nl/p/special_issue_8_cnn/export/txt';

	function findCategories(data){
		// Return categories that this page is part of
		// by doing a reversed dictionary lookup
		var current_url = window.location.href;
		var keys = Object.keys(data)
		var categories = [];
		for(var i=0; i<keys.length; i++){
			var urls = data[keys[i]];
			for(var x=0; x<urls.length; x++){
				if(urls[x] === current_url){
					console.log('MATCH:', keys[i]);
					categories.push(keys[i]);
				}
			}
		}
		return categories;
	}

	function CategoryNetworkNavigator(data){
		// Pick two categories that this page is part of
		// and insert links to other pages of the same category

		var data = JSON.parse(data);

		// Find categories that this page is part of
		var categories = findCategories(data);

		if ( categories.length > 0 && categories.length < 2){
			//if we have only one category we add another one at random
			var keys = Object.keys(data)
			keys.splice(categories[1], 1)
			categories.push(keys[Math.floor(Math.random() * keys.length)])
		}

		// Select a pseudo-randomised category for buttonA
		var buttonA = categories[Math.floor(Math.random() * categories.length)];
		document.querySelectorAll('#buttonA button')[0].textContent = buttonA;
		
		// Select another category for buttonB
		var indexA = categories.indexOf(buttonA);
		categories.splice(indexA, 1);
		var buttonB = categories[Math.floor(Math.random() * categories.length)];
		document.querySelectorAll('#buttonB button')[0].textContent = buttonB;

		// Insert a link for each button
		// to another page of the same category
		var linksA = data[buttonA];
		var linksB = data[buttonB];
		linksA.splice(window.location.href, 1);
		linksB.splice(window.location.href, 1);
		document.getElementById("buttonA").href = linksA[Math.floor(Math.random() * linksA.length)];
		document.getElementById("buttonB").href = linksB[Math.floor(Math.random() * linksB.length)];
	}

 	function readEtherpadJSON(){
		if (invocation){
			invocation.open( "GET", url, true ); 
			invocation.onreadystatechange = function() {
				console.log('ready!');
				if (invocation.readyState === 4 && invocation.status === 200) {
					console.log('invocation:', invocation);
					CategoryNetworkNavigator(invocation.responseText);
				}
			};
			invocation.send();
		}
		return invocation;
	}

	function insertCNN(cnn_template){
		document.body.innerHTML = cnn_template + document.body.innerHTML;
		readEtherpadJSON();
	}

	var cnn_template = '<!-- START CNN -->\
		<div id="cnn">\
			<div class="button_container">\
				<a id="buttonA" href="http://b-e-e-t.r-o-o-t.net/pages/please_to_foshan.html"><button class="cnn-button">WHAT IS A NETWORK?</button></a>\
			</div>\
			<div class="button_container">\
				<a id="buttonB" href="http://richfolks.club/"><button class="cnn-button">AUTONOMY AND ITS CONTINGENCIES</button></a>\
			</div>\
			<a id="sitemap" href="https://issue.xpub.nl/08/"><button class="cnn-button">netmap</button></a>\
		</div>\
		<link rel="stylesheet" type="text/css" href="https://issue.xpub.nl/08/cnn/cnn.css">\
		<!-- END CNN -->'

	insertCNN(cnn_template);