Assistant/backend.tests/ScriptedRealtimeUpstream.cs

using System.Text.Json.Nodes;
using System.Threading.Channels;
using backend.Realtime;

namespace backend.tests;

public class ScriptedRealtimeUpstream : IRealtimeUpstream
{
    private readonly Channel<JsonObject> _toRelay =
        Channel.CreateUnbounded<JsonObject>(new UnboundedChannelOptions { SingleReader = true });

    private readonly Channel<JsonObject> _fromRelay =
        Channel.CreateUnbounded<JsonObject>(new UnboundedChannelOptions { SingleWriter = true });

    public IList<JsonObject> Sent { get; } = new List<JsonObject>();
    public bool IsClosed => _toRelay.Reader.Completion.IsCompleted;
    public string? CloseReason => IsClosed ? "scripted upstream closed" : null;

    public Task SendJsonAsync(JsonObject envelope, CancellationToken ct)
    {
        Sent.Add(envelope);
        return _fromRelay.Writer.WriteAsync(envelope, ct).AsTask();
    }

    public async Task<JsonObject?> ReceiveJsonAsync(CancellationToken ct)
    {
        try
        {
            return await _toRelay.Reader.ReadAsync(ct);
        }
        catch (ChannelClosedException)
        {
            return null;
        }
    }

    public void Push(JsonObject evt) => _toRelay.Writer.TryWrite(evt);
    public void CloseUpstream() => _toRelay.Writer.TryComplete();

    public async Task<JsonObject> WaitForSentAsync(string type, CancellationToken ct)
    {
        await foreach (var item in _fromRelay.Reader.ReadAllAsync(ct))
        {
            if ((string?)item["type"] == type) return item;
        }
        throw new TimeoutException($"never saw outbound {type}");
    }

    public ValueTask DisposeAsync()
    {
        _toRelay.Writer.TryComplete();
        _fromRelay.Writer.TryComplete();
        return ValueTask.CompletedTask;
    }
}