using System;
using System.Diagnostics;
using System.Threading.Tasks;

using Grpc.Core;
using Grpc.Core.Interceptors;

namespace FrostFS.SDK.Client;

[System.Diagnostics.CodeAnalysis.SuppressMessage("Design", "CA1062:Validate arguments of public methods",
        Justification = "parameters are provided by GRPC infrastructure")]
public class MetricsInterceptor(Action<CallStatistics> callback) : Interceptor
{
    public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(
        TRequest request,
        ClientInterceptorContext<TRequest, TResponse> context,
        AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
    {
        var call = continuation(request, context);

        return new AsyncUnaryCall<TResponse>(
            HandleUnaryResponse(call),
            call.ResponseHeadersAsync,
            call.GetStatus,
            call.GetTrailers,
            call.Dispose);
    }

    public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(
        ClientInterceptorContext<TRequest, TResponse> context,
        AsyncClientStreamingCallContinuation<TRequest, TResponse> continuation)
    {
        var call = continuation(context);

        return new AsyncClientStreamingCall<TRequest, TResponse>(
            call.RequestStream,
            HandleStreamResponse(call),
            call.ResponseHeadersAsync,
            call.GetStatus,
            call.GetTrailers,
            call.Dispose);
    }

    private async Task<TResponse> HandleUnaryResponse<TResponse>(AsyncUnaryCall<TResponse> call)
    {
        var watch = new Stopwatch();
        watch.Start();

        var response = await call;

        watch.Stop();

        var elapsed = watch.ElapsedTicks * 1_000_000 / Stopwatch.Frequency;

        callback(new CallStatistics { MethodName = call.ToString(), ElapsedMicroSeconds = elapsed });

        return response;
    }

    private async Task<TResponse> HandleStreamResponse<TRequest, TResponse>(AsyncClientStreamingCall<TRequest, TResponse> call)
    {
        var watch = new Stopwatch();
        watch.Start();

        var response = await call;

        watch.Stop();

        var elapsed = watch.ElapsedTicks * 1_000_000 / Stopwatch.Frequency;

        callback(new CallStatistics { MethodName = call.ToString(), ElapsedMicroSeconds = elapsed });

        return response;
    }
}