OPC/ControlPlane.Api/Endpoints/TenantLogEndpoints.cs

using Docker.DotNet;
using Docker.DotNet.Models;
using ControlPlane.Core.Services;

namespace ControlPlane.Api.Endpoints;

public static class TenantLogEndpoints
{
    public static IEndpointRouteBuilder MapTenantLogEndpoints(this IEndpointRouteBuilder app)
    {
        app.MapGet("/api/tenants/{subdomain}/logs", StreamTenantLogs).WithTags("Tenants");
        return app;
    }

    private static async Task StreamTenantLogs(
        string subdomain,
        IConfiguration config,
        TenantRegistryService registry,
        HttpContext ctx,
        CancellationToken cancellationToken)
    {
        var tenant = registry.GetAll().FirstOrDefault(t => t.Subdomain == subdomain);
        if (tenant is null)
        {
            ctx.Response.StatusCode = 404;
            return;
        }

        var containerName = tenant.ContainerName;
        if (string.IsNullOrWhiteSpace(containerName))
        {
            ctx.Response.StatusCode = 404;
            return;
        }

        ctx.Response.Headers.ContentType  = "text/event-stream";
        ctx.Response.Headers.CacheControl = "no-cache";
        ctx.Response.Headers.Connection   = "keep-alive";

        var socketUri = config["Docker:Socket"] ?? "npipe://./pipe/docker_engine";
        using var docker = new DockerClientConfiguration(new Uri(socketUri)).CreateClient();

        var logParams = new ContainerLogsParameters
        {
            ShowStdout = true,
            ShowStderr = true,
            Follow     = true,
            Tail       = "200",
            Timestamps = true,
        };

        try
        {
            using var stream = await docker.Containers.GetContainerLogsAsync(
                containerName, tty: false, logParams, cancellationToken);

            // MultiplexedStream exposes CopyOutputToAsync which separates stdout/stderr
            var stdoutBuf = new System.IO.MemoryStream();
            var stderrBuf = new System.IO.MemoryStream();

            // Stream with Follow=true won't complete until cancelled — use a pipe instead
            var stdoutPipe = new System.IO.Pipelines.Pipe();
            var stderrPipe = new System.IO.Pipelines.Pipe();

            _ = Task.Run(async () =>
            {
                try
                {
                    await stream.CopyOutputToAsync(
                        System.IO.Stream.Null,
                        stdoutPipe.Writer.AsStream(),
                        stderrPipe.Writer.AsStream(),
                        cancellationToken);
                }
                finally
                {
                    stdoutPipe.Writer.Complete();
                    stderrPipe.Writer.Complete();
                }
            }, cancellationToken);

            // Merge both pipes into SSE — read stdout line by line
            var stdoutReader = new System.IO.StreamReader(stdoutPipe.Reader.AsStream());
            var stderrReader = new System.IO.StreamReader(stderrPipe.Reader.AsStream());

            var stdoutTask = ReadLinesAsync(stdoutReader, ctx, cancellationToken);
            var stderrTask = ReadLinesAsync(stderrReader, ctx, cancellationToken);
            await Task.WhenAll(stdoutTask, stderrTask);
        }
        catch (OperationCanceledException) { /* client disconnected — normal */ }
    }

    private static async Task ReadLinesAsync(
        System.IO.StreamReader reader,
        HttpContext ctx,
        CancellationToken ct)
    {
        while (!ct.IsCancellationRequested)
        {
            var line = await reader.ReadLineAsync(ct);
            if (line is null) break;
            if (string.IsNullOrWhiteSpace(line)) continue;

            await ctx.Response.WriteAsync($"data: {line}\n\n", ct);
            await ctx.Response.Body.FlushAsync(ct);
        }
    }
}