// started on main page load
function init() {
	init_board();
}

var revision;

// helper for breaking feedback loop
var caretpos = 0;

function showQRWindow()
{
 document.getElementById("qrwindow").style.display = 'block';
}

function hideQRWindow()
{
 document.getElementById("qrwindow").style.display = 'none';
}

var websocket;

//
// Callbacks for websocket data of different types
//

function on_getfile(data, rev, pos)
{
	var board = document.getElementById("board");
	if (board.value != data) {
		board.value = data;
	}
	textAreaSetPos("board", pos);
	revision = rev;
}

function on_newid(id)
{
	var new_location = document.location.origin + document.location.pathname + '?id=' + id;
	window.location.href = new_location;
}

function on_qrcode(png)
{
	var blob = new Blob([png], {type: 'image/png'});
	var url = URL.createObjectURL(blob);
	var img = document.getElementById("qrcode");
	img.src = url;
	showQRWindow();
}

function on_modify_ack(rev)
{
	revision = rev;
}

function on_message(e) {
	var parser = new DOMParser();
	var xmlDocument = parser.parseFromString(e.data, "text/xml");
	
	var type = xmlDocument.getElementsByTagName("type")[0].textContent;

	if (type == "getfile") {
		on_getfile(xmlDocument.getElementsByTagName("data")[0].textContent,
			   parseInt(xmlDocument.getElementsByTagName("revision")[0].textContent),
			   parseInt(xmlDocument.getElementsByTagName("cursorpos")[0].textContent));
	} else if (type == "modify") {
		on_modify_ack(parseInt(xmlDocument.getElementsByTagName("revision")[0].textContent));
	} else if (type == "newid") {
		on_newid(xmlDocument.getElementsByTagName("id")[0].textContent);
	} else if (type == "qrcode") {
		on_qrcode(xmlDocument.getElementsByTagName("png")[0].textContent);
	} else if (type == "error") {
		alert(xmlDocument.getElementsByTagName("message")[0].textContent);
	} else {
		alert("Unhandled message type: " + e.data + "|" + type);
	}
}

function handleSelection() {
  const activeElement = document.activeElement

  if (activeElement && activeElement.id === 'board') {
    if (caretpos != activeElement.selectionStart) {
      on_selectionchange(activeElement.selectionStart);
      caretpos = activeElement.selectionStart;
    }
  }
}

function init_board() {
	var newlocation = location.origin + location.pathname;
	newlocation = newlocation.replace(/^http/, 'ws');
	if (newlocation.slice(-1) != "/")
		newlocation += "/";
	newlocation += "websocket";
	websocket = new WebSocket(newlocation);

	websocket.onmessage = function(e) { on_message(e); };

	websocket.onopen = function(e) {
		const searchParams = (new URL(document.location)).searchParams;
		if (!searchParams.has('id')) {
			redirect_to_new_page();
			return;
		}

		var board = document.getElementById("board");
		board.addEventListener("input", function() {on_input(); });
                // Need this workaround (different from direct on_selectionchange) for Chrome.
		// Otherwise, callback will not be called on Chrome.
		document.addEventListener("selectionchange", handleSelection);
		//board.addEventListener("selectionchange", function() {on_selectionchange(); });

		websocket.send("<request><command>getfile</command><id>" + get_id() + "</id></request>");
	};
	
	websocket.onclose = function(e) {
		alert("Server connection closed.");
	};

	websocket.onerror = function(e) {
		alert("Error: Server connection closed.");
	};

        document.getElementById("qrwindow").onclick = function() {
         hideQRWindow();
        }

        document.onkeydown = function(evt) {
         if (evt.key == "Escape") {
          hideQRWindow();
         }
        }

	document.getElementById("board").focus();
}

function get_id()
{
        const searchParams = (new URL(document.location)).searchParams;
        return searchParams.get('id');
}

// from html
function on_new_page()
{
	redirect_to_new_page();
}

function redirect_to_new_page()
{
	websocket.send("<request><command>newid</command></request>");
}

// local change done
function on_input()
{
	var parser = new DOMParser();
	var xmlDocument = parser.parseFromString("<request></request>", "text/xml");
	
	var requestElement = xmlDocument.getElementsByTagName("request")[0];

	var commandElement = xmlDocument.createElement("command");
	commandElement.appendChild(document.createTextNode("modify"));
	requestElement.appendChild(commandElement);

	var idElement = xmlDocument.createElement("id");
	idElement.appendChild(document.createTextNode(get_id()));
	requestElement.appendChild(idElement);

	var dataElement = xmlDocument.createElement("data");
	dataElement.appendChild(document.createTextNode(document.getElementById("board").value));
	requestElement.appendChild(dataElement);

	websocket.send(new XMLSerializer().serializeToString(xmlDocument));
}

// for cursor position
function on_selectionchange(pos)
{
	var parser = new DOMParser();
	var xmlDocument = parser.parseFromString("<request></request>", "text/xml");
	
	var requestElement = xmlDocument.getElementsByTagName("request")[0];

	var commandElement = xmlDocument.createElement("command");
	commandElement.appendChild(document.createTextNode("cursorpos"));
	requestElement.appendChild(commandElement);

	var idElement = xmlDocument.createElement("id");
	idElement.appendChild(document.createTextNode(get_id()));
	requestElement.appendChild(idElement);

	var dataElement = xmlDocument.createElement("pos");
	dataElement.appendChild(document.createTextNode(pos));
	requestElement.appendChild(dataElement);

	websocket.send(new XMLSerializer().serializeToString(xmlDocument));
}

function textAreaSetPos(id, pos)
{
	if (document.getElementById(id).selectionStart != pos) {
		document.getElementById(id).selectionStart = pos;
		document.getElementById(id).selectionEnd = pos;
		caretpos = pos;
	}
}

// HTML button
function on_qrcode()
{
	var parser = new DOMParser();
	var xmlDocument = parser.parseFromString("<request></request>", "text/xml");
	
	var requestElement = xmlDocument.getElementsByTagName("request")[0];

	var commandElement = xmlDocument.createElement("command");
	commandElement.appendChild(document.createTextNode("qrcode"));
	requestElement.appendChild(commandElement);

	var idElement = xmlDocument.createElement("url");
	idElement.appendChild(document.createTextNode(document.location));
	requestElement.appendChild(idElement);

	websocket.send(new XMLSerializer().serializeToString(xmlDocument));
}