feat(battle-node): WebSocket endpoint at /socket.io/ + DI extension methods

SVSim.BattleNode/Hosting/BattleNodeExtensions.cs

@@ -0,0 +1,32 @@
+// SVSim.BattleNode/Hosting/BattleNodeExtensions.cs
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.BattleNode.Bridge;
+using SVSim.BattleNode.Sessions;
+
+namespace SVSim.BattleNode.Hosting;
+
+public static class BattleNodeExtensions
+{
+    public static IServiceCollection AddBattleNode(this IServiceCollection services, Action<BattleNodeOptions>? configure = null)
+    {
+        var options = new BattleNodeOptions();
+        configure?.Invoke(options);
+        services.AddSingleton(options);
+        services.AddSingleton<IBattleSessionStore, InMemoryBattleSessionStore>();
+        services.AddSingleton<IMatchingBridge, MatchingBridge>();
+        services.AddSingleton<BattleNodeWebSocketHandler>();
+        return services;
+    }
+
+    public static IApplicationBuilder UseBattleNode(this IApplicationBuilder app)
+    {
+        app.UseWebSockets();
+        app.Map("/socket.io", branch => branch.Run(async ctx =>
+        {
+            var handler = ctx.RequestServices.GetRequiredService<BattleNodeWebSocketHandler>();
+            await handler.HandleAsync(ctx);
+        }));
+        return app;
+    }
+}

SVSim.BattleNode/Hosting/BattleNodeWebSocketHandler.cs

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+// SVSim.BattleNode/Hosting/BattleNodeWebSocketHandler.cs
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Logging;
+using SVSim.BattleNode.Sessions;
+using SVSim.BattleNode.Wire;
+
+namespace SVSim.BattleNode.Hosting;
+
+public sealed class BattleNodeWebSocketHandler
+{
+    private readonly IBattleSessionStore _store;
+    private readonly ILogger<BattleNodeWebSocketHandler> _log;
+    private readonly ILoggerFactory _loggerFactory;
+
+    public BattleNodeWebSocketHandler(IBattleSessionStore store, ILoggerFactory loggerFactory)
+    {
+        _store = store;
+        _loggerFactory = loggerFactory;
+        _log = loggerFactory.CreateLogger<BattleNodeWebSocketHandler>();
+    }
+
+    public async Task HandleAsync(HttpContext ctx)
+    {
+        if (!ctx.WebSockets.IsWebSocketRequest)
+        {
+            ctx.Response.StatusCode = StatusCodes.Status400BadRequest;
+            return;
+        }
+
+        var battleId = ctx.Request.Query["BattleId"].ToString();
+        var encryptedViewerId = ctx.Request.Query["viewerId"].ToString();
+        if (string.IsNullOrEmpty(battleId) || string.IsNullOrEmpty(encryptedViewerId))
+        {
+            ctx.Response.StatusCode = StatusCodes.Status400BadRequest;
+            return;
+        }
+
+        long viewerId;
+        try
+        {
+            var plain = NodeCrypto.DecryptForNode(encryptedViewerId);
+            viewerId = long.Parse(plain);
+        }
+        catch (Exception ex)
+        {
+            _log.LogWarning(ex, "viewerId query param failed to decrypt");
+            ctx.Response.StatusCode = StatusCodes.Status400BadRequest;
+            return;
+        }
+
+        var pending = _store.TryGetPending(battleId);
+        if (pending is null || pending.ViewerId != viewerId)
+        {
+            _log.LogWarning("Unknown battle/viewer pair: {Bid}/{Vid}", battleId, viewerId);
+            ctx.Response.StatusCode = StatusCodes.Status400BadRequest;
+            return;
+        }
+
+        var ws = await ctx.WebSockets.AcceptWebSocketAsync();
+        _store.RemovePending(battleId);
+        var session = new BattleSession(ws, battleId, viewerId, _loggerFactory.CreateLogger<BattleSession>());
+        await session.RunAsync(ctx.RequestAborted);
+    }
+}