using System.Diagnostics;

namespace FinalFactory.Rendezvous.Server.Observability;

internal sealed class TelemetryMiddleware(
    RequestDelegate next,
    RendezvousTelemetry telemetry)
{
    public async Task InvokeAsync(HttpContext context)
    {
        string operation = context.GetEndpoint()?.Metadata.GetMetadata<IEndpointNameMetadata>()
            ?.EndpointName ?? "Unmatched";
        long started = Stopwatch.GetTimestamp();
        using Activity? activity = telemetry.StartActivity(
            $"HTTP {operation}",
            ActivityKind.Server);
        string correlationId = activity?.TraceId.ToString() ?? Guid.NewGuid().ToString("N");
        context.Response.Headers["X-Rendezvous-Correlation-ID"] = correlationId;
        activity?.SetTag("rendezvous.operation", operation);
        try
        {
            await next(context).ConfigureAwait(false);
        }
        finally
        {
            telemetry.RecordHttp(
                operation,
                context.Response.StatusCode,
                Stopwatch.GetElapsedTime(started).TotalMilliseconds);
        }
    }
}