using w4c_workflows.Services;
using w4c_workflows.Services.Messaging;
using Xunit;

namespace w4c_workflows.Tests;

/// <summary>
/// Backlog-bound regression tests: a stalled in-memory consumer must not be able
/// to grow server memory without limit. Both channels are bounded and drop the
/// oldest entry under pressure.
/// </summary>
public class BoundedChannelTests
{
    [Fact]
    public void RealtimeEventHub_bounds_the_per_client_backlog()
    {
        var hub = new RealtimeEventHub();
        var (id, reader) = hub.AddClient("tenant-a");

        for (var i = 0; i < 300; i++)
            hub.Publish("tenant-a", "workflow", i.ToString(), DateTime.UtcNow);

        var received = 0;
        while (reader.TryRead(out _))
            received++;

        // Client channel capacity is 256 and DropOldest keeps the newest entries.
        Assert.Equal(256, received);

        hub.RemoveClient("tenant-a", id);
    }

    [Fact]
    public async Task InMemoryTransport_bounds_the_job_backlog()
    {
        var transport = new InMemoryTransport();

        for (var i = 0; i < 10_500; i++)
            await transport.EnqueueAsync("tenant-b", new Dictionary<string, string> { ["n"] = i.ToString() }, default);

        var drained = await transport.ReadGroupAsync("tenant-b", "consumer", 20_000, default);

        Assert.True(drained.Count > 0, "no messages were readable");
        Assert.True(drained.Count <= 10_000, $"job backlog was not bounded: {drained.Count}");
    }
}