//SPDX-License-Identifier: LGPL-3.0-only
//SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

// ~ClientQUIC lets the streams its owner already stopped finish before it
// closes the connection. It used to shut the connection down at once, and
// msquic aborts every stream with the connection, along with whatever of
// theirs it had not sent yet: a server that answered with
// SendAsync(..., finish = true), let the stream go and deleted the
// connection lost the answer whenever the shutdown, queued right behind the
// send, reached msquic's worker before the flush that would have sent it.
// Crafter.Debug's session, which answers every request still waiting when
// it ends and then closes its connections, lost that answer in 4 runs of 30.
//
// Twenty connections in turn. On each, the client sends a request; the
// server answers 64 KiB with SendAsync(finish = true), destroys the stream
// wrapper and deletes its ClientQUIC at once, as such a server does. The
// client must get every byte and a clean end each time, and the deletes
// must stay quick: a stopped stream finishes about a round trip after its
// last send, well inside the 1 s bound.

#include <cstdio>

import Crafter.Network;
import Crafter.Thread;
import std;
using namespace Crafter;

namespace {

int failures = 0;

void Check(bool ok, std::string_view what) {
    std::println("{}  {}", ok ? "PASS" : "FAIL", what);
    if (!ok) ++failures;
}

// What the client's stream received, and how it ended.
struct Seen {
    std::mutex mutex;
    std::condition_variable changed;
    std::size_t bytes = 0;
    bool ended = false;
    bool clean = false;
};

// The server's side of the connection being tested, handed over by the
// accept thread and the pool task that delivers the stream.
struct Accepted {
    std::mutex mutex;
    std::condition_variable changed;
    ClientQUIC* peer = nullptr;
    std::optional<QUICStream> stream;
};

} // namespace

int main() {
    ThreadPool::Start();
    std::thread([] {
        std::this_thread::sleep_for(std::chrono::seconds(45));
        std::println("FAIL  timed out");
        std::fflush(stdout);
        std::_Exit(1);
    }).detach();

    const std::string alpn = "crafter/test-finish-stopped";
    QUICServerCredentials serverCreds;
    serverCreds.selfSigned = true;
    QUICClientCredentials clientCreds;
    clientCreds.insecureNoServerValidation = true;

    constexpr std::size_t answerSize = 64 * 1024;
    const std::string answer(answerSize, 'a');
    auto accepted = std::make_shared<Accepted>();

    try {
        ListenerQUIC listener("127.0.0.1", 0, alpn, serverCreds, [accepted](ClientQUIC* peer) {
            peer->OnStream([accepted](QUICStream stream) {
                {
                    std::lock_guard lock(accepted->mutex);
                    accepted->stream.emplace(std::move(stream));
                }
                accepted->changed.notify_all();
            });
            {
                std::lock_guard lock(accepted->mutex);
                accepted->peer = peer;
            }
            accepted->changed.notify_all();
        });
        listener.ListenAsyncSync();

        int whole = 0;
        std::chrono::milliseconds slowestDelete{ 0 };
        for (int i = 0; i < 20; ++i) {
            ClientQUIC client("127.0.0.1", listener.Port(), alpn, clientCreds);
            auto seen = std::make_shared<Seen>();
            QUICStream request = client.OpenStream();
            request.OnRecieve(
                [seen](std::span<const char> data) {
                    std::lock_guard lock(seen->mutex);
                    seen->bytes += data.size();
                },
                [seen](bool clean) {
                    {
                        std::lock_guard lock(seen->mutex);
                        seen->ended = true;
                        seen->clean = clean;
                    }
                    seen->changed.notify_all();
                });
            request.SendSync("ask", 3, true);

            ClientQUIC* peer = nullptr;
            std::optional<QUICStream> stream;
            {
                std::unique_lock lock(accepted->mutex);
                if (!accepted->changed.wait_for(lock, std::chrono::seconds(5), [&] { return accepted->peer != nullptr && accepted->stream.has_value(); })) {
                    std::println("      connection {}: the server never saw the stream", i);
                    break;
                }
                peer = std::exchange(accepted->peer, nullptr);
                stream = std::move(accepted->stream);
                accepted->stream.reset();
            }

            // The server's last word, and then the end of it all at once.
            stream->SendAsync(answer.data(), static_cast<std::uint32_t>(answer.size()), true, {});
            stream.reset();
            const auto deleting = std::chrono::steady_clock::now();
            delete peer;
            slowestDelete = std::max(slowestDelete, std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now() - deleting));

            std::unique_lock lock(seen->mutex);
            seen->changed.wait_for(lock, std::chrono::seconds(5), [&] { return seen->ended; });
            if (seen->ended && seen->clean && seen->bytes == answerSize) {
                ++whole;
            } else {
                std::println("      connection {}: {} of {} bytes, {}", i, seen->bytes, answerSize,
                             !seen->ended ? "no end" : seen->clean ? "a clean end" : "reset");
            }
        }
        Check(whole == 20, std::format("each of 20 answers arrived whole before its connection closed ({} did)", whole));
        Check(slowestDelete < std::chrono::milliseconds(500), std::format("each delete waited only for its answer (slowest {} ms)", slowestDelete.count()));
    } catch (const std::exception& e) {
        Check(false, std::format("threw: {}", e.what()));
    }

    std::println("{}", failures == 0 ? "all checks passed" : "check(s) failed");
    // msquic's static teardown would wait on what the listener still holds.
    std::fflush(stdout);
    std::_Exit(failures == 0 ? 0 : 1);
}