Gateway client basics

Discord.API/Gateway/GatewayClient.cs

@@ -0,0 +1,76 @@
+using System.Collections.Specialized;
+using System.Text.Json;
+using Serilog;
+using Websocket.Client;
+
+namespace Discord.API;
+
+public class GatewayClient {
+
+    private const int ApiVersion = 10;
+
+    private string ApiKey;
+    private WebsocketClient Websocket;
+    private CancellationTokenSource? heartbeat_cts;
+    private ulong? Sequence = null;
+
+    public GatewayClient(string url, string api_key){
+        this.ApiKey=api_key;
+        UriBuilder uriBuilder = new(url);
+        NameValueCollection query = System.Web.HttpUtility.ParseQueryString("");
+        query.Add("v", ApiVersion.ToString());
+        query.Add("encoding", "json");
+        uriBuilder.Query=query.ToString();
+        Websocket = new WebsocketClient(uriBuilder.Uri);
+        Websocket.DisconnectionHappened.Subscribe(DisconnectionHandler);
+        Websocket.ReconnectionHappened.Subscribe(ReconnectionHandler);
+        Websocket.MessageReceived.Subscribe(MessageReceivedHandler);
+
+        Log.Debug("GATEWAY: Created new gateway, with url: {url}", uriBuilder.ToString());
+    }
+
+    private void DisconnectionHandler(DisconnectionInfo info){
+        Log.Information("GATEWAY: Disconnected. Type: {DisconnectionType}", info.Type);
+    }
+    private void ReconnectionHandler(ReconnectionInfo info){
+        Log.Information("GATEWAY: (Re)Connected to server. Url: {url}, Type: {Type}", Websocket.Url, info.Type);
+    }
+    private void MessageReceivedHandler(ResponseMessage msg){
+        if(msg.MessageType != System.Net.WebSockets.WebSocketMessageType.Text) return;
+        try{
+            GatewayPacket packet = JsonSerializer.Deserialize(msg.Text!, SourceGenerationContext.Default.GatewayPacket)
+                ?? throw new Exception("Failed to deserialize packet"); // This can be optimized //TODO
+
+            switch(packet){
+                case HelloPacket helloPacket:
+                    HelloPacketHandler(helloPacket);
+                    break;
+            }
+        }catch(Exception ex){
+            Log.Warning(ex, "GATEWAY: Error processing gateway event");
+        }
+    }
+
+    private void HelloPacketHandler(HelloPacket packet){
+        StartHeartbeat((int)packet.Data.HeartbeatInterval);
+    }
+
+    private void StartHeartbeat(int heartbeat_interval){
+        heartbeat_cts?.Cancel();
+        heartbeat_cts = new CancellationTokenSource();
+        CancellationToken ct = heartbeat_cts.Token;
+        Task.Run(async ()=>{
+            await Task.Delay(Random.Shared.Next(1, heartbeat_interval));
+            using PeriodicTimer pd = new(TimeSpan.FromMilliseconds(heartbeat_interval));
+            do{
+                HeartbeatPacket packet = new HeartbeatPacket(){
+                    Sequence=this.Sequence
+                };
+                if(Websocket.IsRunning)
+                    if(!Websocket.Send(JsonSerializer.Serialize(packet, SourceGenerationContext.Default.HeartbeatPacket))){
+                        Log.Warning("GATEWAY: Failed to queue heartbeat message");
+                    }
+            }while(await pd.WaitForNextTickAsync(ct) && !ct.IsCancellationRequested);
+        });
+    }
+}