Basic login functionality

owe.js

@@ -72,6 +72,11 @@ function getUsernameFromCookie() {
     return null;
 }
 
+function deleteUsernameCookie() {
+    // Set the 'owe_user' cookie to expire by setting its expiration date to a time in the past
+    document.cookie = 'owe_user=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=.;';
+}
+
 
 function onReloadClicked() {
 	loadSentences();
@@ -246,16 +251,34 @@ async function getLastTimeFromArchive(archiveFileUrl) {
     }
 }
 
+function logoutUser() {
+    deleteUsernameCookie();
+    initializeLoginArea(); // Reload everything in the login area 
+}
 
 async function initializeLoginArea() {
     var loginArea = document.getElementById('login_area');
 
+    var sendButton = document.getElementById('sendbut');
+    sendButton.style.display = "unset"
+    var wordInput = document.getElementById('wordinput');
+    wordInput.disabled = false;
+
     // Use async/await to wait for the result of getNextPlayer
     try {
+        var loggedInPlayer = getUsernameFromCookie();
         var nextPlayer = await getNextPlayer();
         var relative_time = await getTimeSinceLast();
     	// Clear the login area
     	loginArea.innerHTML = "";
+        if (loggedInPlayer != null) {
+            loginArea.innerHTML += "Du bist angemeldet als " + loggedInPlayer + "."
+            loginArea.innerHTML += " <button onclick='logoutUser()'>abmelden</button><br>\n";
+            if (loggedInPlayer != nextPlayer) {
+                sendButton.style.display = "none";
+                wordInput.disabled = true;
+            }
+        }
         loginArea.innerHTML += nextPlayer + " ist dran!<br>\n";
 
         var days = Math.floor(relative_time / (3600 * 24));