Issue3: Added a socket that will report when the ladder has changed and can be used to provide realtime notifications on the website.

Author: kirby561

Beef/BeefApi/ApiServer.cs

@@ -2,25 +2,38 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Net;
+using System.Net.Sockets;
 using System.Text;
 using System.Threading.Tasks;
 
 
 namespace Beef.BeefApi {
+    /// <summary>
+    /// The ApiServer hosts a REST endpoint at /beef-ladder that returns a json representation
+    /// of the current ladder rankings. It also provides a socket that can be connected to at
+    /// the configured port in order to be notified realtime when the ladder has been changed.
+    /// </summary>
     public class ApiServer {
         private String _configFilePath;
         private SynchronizationContext _mainContext;
         private BeefUserConfigManager _beefUserManager;
         private PresentationManager _ladderManager;
         private WebApplication _application;
         private Thread _thread;
+        private SynchronizationContext _threadContext;
+        private int _eventSocket; // set from the config file
+        private List<Socket> _eventClients = new List<Socket>();
         private object _lock = new object();
 
         public ApiServer(String configFilePath, SynchronizationContext mainContext, PresentationManager ladderManager, BeefUserConfigManager beefUserManager) {
             _configFilePath = configFilePath;
             _mainContext = mainContext;
             _ladderManager = ladderManager;
             _beefUserManager = beefUserManager;
+
+            // Subscribe to the ladder changed event
+            _ladderManager.LadderChanged += OnLadderChanged;
         }
 
         public void Start() {
@@ -51,9 +64,13 @@ public void Stop() {
         }
 
         private void ThreadStart() {
+            SynchronizationContext.SetSynchronizationContext(new SynchronizationContext());
+            _threadContext = SynchronizationContext.Current;
+
             lock (_lock) {
                 var builder = WebApplication.CreateBuilder();
                 builder.Configuration.AddJsonFile(_configFilePath);
+                _eventSocket = builder.Configuration.GetValue<int>("LadderChangedEventPort", 5002);
 
                 _application = builder.Build();
                 Monitor.PulseAll(_lock);
@@ -117,7 +134,85 @@ await Task.Run(() => {
                 await context.Response.WriteAsJsonAsync(response);
             });
 
+            _threadContext.Post(async (object? state) => {
+                IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Any, _eventSocket);
+                Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+                listener.Bind(localEndPoint);
+                listener.Listen();
+
+                while (true) {
+                    Socket client = await listener.AcceptAsync();
+
+                    lock (_eventClients) {
+                        _eventClients.Add(client);
+                    }
+                }
+            }, null);
+
             _application.Run();
         }
+
+        private void NotifyLadderChanged() {
+            List<Socket> clientsToRemove = new List<Socket>();
+            lock (_eventClients) {
+                foreach (Socket client in _eventClients) {
+                    if (!client.Connected) {
+                        clientsToRemove.Add(client);
+                        continue;
+                    }
+
+                    try {
+                        String eventMessage = "{ \"Message\": \"OnLadderChanged\" }";
+                        int messageLength = eventMessage.Length;
+                        byte[] lengthBytes = GetBytesInNetworkOrder(messageLength);
+                        byte[] messageBytes = Encoding.UTF8.GetBytes(eventMessage);
+
+                        SendBytesOrDie(lengthBytes, client);
+                        SendBytesOrDie(messageBytes, client);
+                    } catch (Exception) {
+                        // Any exception should just close the connection and keep going
+                        clientsToRemove.Add(client);
+                    }
+                }
+
+                // Cleanup anyone that has disconnected
+                foreach (Socket client in clientsToRemove) {
+                    _eventClients.Remove(client);
+                }
+            }
+        }
+
+        private byte[] GetBytesInNetworkOrder(int number) {
+            byte[] numberBytes = BitConverter.GetBytes(number);
+            if (BitConverter.IsLittleEndian)
+                Array.Reverse(numberBytes);
+            return numberBytes;
+        }
+
+        private void OnLadderChanged(List<BeefEntry> entries) {
+            _threadContext.Post((object? state) => {
+                NotifyLadderChanged();
+            }, null);
+        }
+
+        /// <summary>
+        /// Sends the given bytes to the given socket. If all the bytes aren't sent, an
+        /// exception is thrown. Note that in the event the buffer was sent in stages and
+        /// an error occurs inbetween the stages, some bytes could have been sent prior to the exception.
+        /// </summary>
+        /// <param name="bytes">The bytes to send to the socket.</param>
+        /// <param name="socket">The socket to write to. It is assumed it's already connected.</param>
+        private void SendBytesOrDie(byte[] bytes, Socket socket) {
+            int bytesSent = 0;
+            int index = 0;
+            while (bytesSent < bytes.Length) {
+                int result = socket.Send(bytes, index, bytes.Length - index, SocketFlags.None);
+                if (result <= 0) {
+                    throw new SocketException(result);
+                } else {
+                    bytesSent += result;
+                }
+            }
+        }
     }
 }

Beef/BeefApiConfig.json.example

@@ -8,5 +8,6 @@
         "Url": "https://localhost:5001"
       }
     }
-  }
+  },
+  "LadderChangedEventPort": 5002
 }

Beef/PresentationManager.cs

@@ -34,6 +34,9 @@ public class PresentationManager {
         private Dictionary<String, Tuple<ProfileInfo, LadderInfo>> _mmrDictionary;
         private Dictionary<int, String> _rankToObjectId; // A map of rank to the ID of the object in the slide representing that rank
 
+        public delegate void OnLadderChanged(List<BeefEntry> entries);
+        public event OnLadderChanged LadderChanged;
+
         /// <summary>
         /// Creates a PresentationManager with the given information.
         /// </summary>
@@ -576,6 +579,10 @@ public ErrorCode SubmitRequests(bool backup) {
             }
 
             _requestList.Clear();
+
+            // Notify listeners
+            LadderChanged.Invoke(_entries);
+
             return result;
         }