let input = document.getElementById('select-json');
let textInput = document.getElementById('text-json');
let text = document.getElementById('text');
let simulation;
let links;
let nodes;
let context;

textInput.onchange = function change() {
	try {
		json = JSON.parse(this.value);
		nodes = buildNodes(json);
		links = buildLinks(json);
	} catch (e) {
		alert(e.message);
		return;
	}
	render(json);
}

input.onchange = function change() {

	var reader = new FileReader();
	reader.onload = () => {
		let text = reader.result;
		try {
			json = JSON.parse(text);
			nodes = buildNodes(json);
			links = buildLinks(json);
		} catch (e) {
			alert(e.message);
			return;
		}
		render(json);
	}
	reader.readAsText(this.files[0]);
};

function buildNodes(json) {
	let keys = Object.keys(json);
	return keys.map(key => ({ id: key, group: 1 }));
}

function buildLinks(json) {
	let keys = Object.keys(json);
	let lengths = {};
	keys.forEach(key => lengths[key] = json[key].length);
	return keys.reduce((acc, key) => {
			let list = [];
			json[key].forEach(t => {
				if (keys.indexOf(t) > -1) {
					list.push({ source: key, target: t });
				}
			});
			return acc.concat(list);
		}, []);
}

function render(json) {	
	let n = nodes.length;
	text.innerText = `Total of ${n} nodes`;
	let canvas = document.querySelector("canvas");

	let width = window.innerWidth,
		height = window.innerHeight;

	context = canvas.getContext("2d");
	d3.select(canvas)
        .attr('width', width * window.devicePixelRatio)
        .attr('height', height * window.devicePixelRatio)
        .style('width', width + 'px')
        .style('height', height + 'px');
    context.scale(window.devicePixelRatio, window.devicePixelRatio);

	simulation = d3.forceSimulation()
		.force('link', d3.forceLink().id(d => d.id).distance(300))
		.force('charge', d3.forceManyBody())
		.force('center', d3.forceCenter(width / 2, height / 2));

	simulation.nodes(nodes)
		.on('tick', ticked);

	simulation.force('link')
		.links(links);

	d3.select(canvas)
		.call(d3.drag()
			.container(canvas)
			.subject(dragsubject)
			.on('start', dragstarted)
			.on('drag', dragged)
			.on('end', dragended));

	function ticked() {
		context.clearRect(0, 0, width, height);

		
		links.forEach(drawLink);	
		nodes.forEach(drawNode);
  	}

  	function dragsubject() {
  		return simulation.find(d3.event.x, d3.event.y);
  	}
}

function dragstarted() {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  d3.event.subject.fx = d3.event.subject.x;
  d3.event.subject.fy = d3.event.subject.y;
}

function dragged() {
  d3.event.subject.fx = d3.event.x;
  d3.event.subject.fy = d3.event.y;
}

function dragended() {
  if (!d3.event.active) simulation.alphaTarget(0);
  d3.event.subject.fx = null;
  d3.event.subject.fy = null;
}

function drawLink(d) {
	context.beginPath();
	context.moveTo(d.source.x, d.source.y);
	context.lineTo(d.target.x, d.target.y);
	context.lineWidth = 3;
	if (d.target.id === "127.0.0.1" || d.source.id === "127.0.0.1") {
		context.strokeStyle = "red";
	} else if (d.target.id === "127.0.0.2" || d.source.id === "127.0.0.2") {
		context.strokeStyle = "green";
	} else {
		context.strokeStyle = "#aaa";
	}
	context.stroke();

}

function drawNode(d) {
	context.beginPath();
	context.moveTo(d.x + 10, d.y);
	context.arc(d.x, d.y, 10, 0, 2 * Math.PI);
	context.lineWidth = 1;
	if (d.id === "127.0.0.1") {
		context.fillStyle = "red";
	} else if (d.id === "127.0.0.2" ) {
	    context.fillStyle = "green";
    } else {
		context.fillStyle = "black";
	}
	context.fill();
	context.strokeStyle = "#fff";
	context.stroke();
}