Simple relay import

NostrRelay/INostrRelay.cs

@@ -0,0 +1,35 @@
+using System.Net;
+using System.Net.WebSockets;
+using Nostr.Client.Messages;
+using Nostr.Client.Requests;
+
+namespace NostrRelay;
+
+public record NostrClientContext(WebSocket WebSocket, IPAddress Ip, string UserAgent);
+public record HandleEventResponse(bool Ok, string? Message);
+
+public interface INostrRelay
+{
+    /// <summary>
+    /// If we should handle this connection
+    /// </summary>
+    /// <param name="context"></param>
+    /// <returns></returns>
+    ValueTask<bool> AcceptConnection(NostrClientContext context);
+
+    /// <summary>
+    /// Respond to a request for content
+    /// </summary>
+    /// <param name="context"></param>
+    /// <param name="req"></param>
+    /// <returns></returns>
+    IAsyncEnumerable<NostrEvent> HandleRequest(NostrClientContext context, NostrRequest req);
+
+    /// <summary>
+    /// Handle new event publish
+    /// </summary>
+    /// <param name="context"></param>
+    /// <param name="ev"></param>
+    /// <returns></returns>
+    ValueTask<HandleEventResponse> HandleEvent(NostrClientContext context, NostrEvent ev);
+}

NostrRelay/NostrRelay.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net8.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <PackageReference Include="Nostr.Client" Version="2.0.0" />
+    </ItemGroup>
+
+</Project>

NostrRelay/Relay.cs

@@ -0,0 +1,95 @@
+using System.Buffers;
+using System.Net.WebSockets;
+using System.Text;
+using Microsoft.Extensions.Logging;
+using Newtonsoft.Json;
+using Nostr.Client.Json;
+using Nostr.Client.Requests;
+using Nostr.Client.Responses;
+
+namespace NostrRelay;
+
+public class NostrRelay<THandler> where THandler : INostrRelay
+{
+    private readonly ILogger<NostrRelay<THandler>> _logger;
+    private readonly CancellationTokenSource _cts = new();
+    private readonly THandler _handler;
+    private readonly NostrClientContext _ctx;
+
+    public NostrRelay(THandler handler, NostrClientContext ctx, CancellationToken ct, ILogger<NostrRelay<THandler>> logger)
+    {
+        _handler = handler;
+        _ctx = ctx;
+        _logger = logger;
+        ct.Register(() => _cts.Cancel());
+    }
+
+    private async Task WriteResponse<T>(T obj)
+    {
+        var rspJson = JsonConvert.SerializeObject(obj, NostrSerializer.Settings);
+        _logger.LogDebug("Sending {msg}", rspJson);
+        await _ctx.WebSocket.SendAsync(Encoding.UTF8.GetBytes(rspJson), WebSocketMessageType.Text, true, _cts.Token);
+    }
+
+    public async Task Read()
+    {
+        if (!await _handler.AcceptConnection(_ctx)) return;
+
+        var offset = 0;
+        var mem = MemoryPool<byte>.Shared.Rent(1024 * 1024);
+        while (!_cts.IsCancellationRequested)
+        {
+            var msg = await _ctx.WebSocket.ReceiveAsync(mem.Memory[offset..], _cts.Token);
+            if (msg.MessageType is WebSocketMessageType.Text)
+            {
+                var buff = mem.Memory[..(offset + msg.Count)];
+                offset = !msg.EndOfMessage ? offset + msg.Count : 0;
+                if (!msg.EndOfMessage) continue;
+
+                var str = Encoding.UTF8.GetString(buff.Span);
+                _logger.LogDebug("Got msg {msg}", str);
+                if (str.StartsWith("[\"REQ\""))
+                {
+                    var req = JsonConvert.DeserializeObject<NostrRequest>(str, NostrSerializer.Settings);
+                    if (req != default)
+                    {
+                        await foreach (var ev in _handler.HandleRequest(_ctx, req))
+                        {
+                            await WriteResponse(new NostrEventResponse()
+                            {
+                                MessageType = "EVENT",
+                                Subscription = req.Subscription,
+                                Event = ev
+                            });
+                        }
+
+                        var rsp = new NostrEoseResponse
+                        {
+                            MessageType = "EOSE",
+                            Subscription = req.Subscription
+                        };
+
+                        await WriteResponse(rsp);
+                    }
+                }
+                else if (str.StartsWith("[\"EVENT\""))
+                {
+                    var req = JsonConvert.DeserializeObject<NostrEventRequest>(str, NostrSerializer.Settings);
+                    if (req != default)
+                    {
+                        var result = await _handler.HandleEvent(_ctx, req.Event);
+                        var rsp = new NostrOkResponse()
+                        {
+                            MessageType = "OK",
+                            EventId = req.Event.Id,
+                            Accepted = result.Ok,
+                            Message = result.Message ?? ""
+                        };
+
+                        await WriteResponse(rsp);
+                    }
+                }
+            }
+        }
+    }
+}