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

// ClientTCP's receive calls return exactly the bytes that arrived:
//  - RecieveSync(bufferSize) returned the whole buffer when fewer bytes had
//    arrived, so the caller read garbage after them.
//  - RecieveUntilCloseSync kept the unused end of its first buffer, and then
//    cut everything it had read down to the size of the last read.
//  - A signal arriving while a receive waited made it throw "Interrupted
//    system call", where the receive should simply wait on.
//  - RecieveSync(bufferSize, buffer) returned recv's -1 or 0 where the other
//    receives throw: it now returns the count and throws the same way. A
//    receive of no bytes returns at once: recv's 0 for it isn't a close.
//  - The *Async receives let a closed peer's exception escape the thread
//    pool's task, which ended the whole program; it now goes to onError,
//    and without an onError it's dropped.
//
// Everything runs over loopback.

#include <arpa/inet.h>
#include <netinet/in.h>
#include <pthread.h>
#include <signal.h>
#include <sys/socket.h>
#include <unistd.h>
#include <cstdlib>

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

namespace {

int failures = 0;

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

// A connected pair: a ClientTCP and the socket the listener accepted for it.
struct Connection {
    int listener = -1;
    int peer = -1;
    std::optional<ClientTCP> client;

    Connection() {
        listener = socket(AF_INET, SOCK_STREAM, 0);
        sockaddr_in address {};
        address.sin_family = AF_INET;
        address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
        bind(listener, reinterpret_cast<sockaddr*>(&address), sizeof(address));
        listen(listener, 1);
        socklen_t length = sizeof(address);
        getsockname(listener, reinterpret_cast<sockaddr*>(&address), &length);
        client.emplace("127.0.0.1", ntohs(address.sin_port));
        peer = accept(listener, nullptr, nullptr);
    }
    ~Connection() {
        if (peer != -1) close(peer);
        close(listener);
    }
    void Send(std::string_view bytes) const {
        send(peer, bytes.data(), bytes.size(), 0);
    }
    void ClosePeer() {
        close(peer);
        peer = -1;
    }
};

std::string_view Text(const std::vector<char>& bytes) {
    return std::string_view(bytes.data(), bytes.size());
}

// What a receive threw, by kind.
std::string Kind(std::exception_ptr error) {
    try {
        std::rethrow_exception(error);
    } catch (const SocketClosedException&) {
        return "closed";
    } catch (const SocketTimeoutException&) {
        return "timeout";
    } catch (const std::exception& e) {
        return std::string("other: ") + e.what();
    }
}

// An async receive's outcome. Shared with the callbacks, so it outlives
// whichever thread sets it.
struct Outcome {
    std::mutex mutex;
    std::condition_variable done;
    std::optional<std::string> value;

    void Set(std::string what) {
        {
            std::lock_guard lock(mutex);
            value = std::move(what);
        }
        done.notify_all();
    }
    std::string Wait() {
        std::unique_lock lock(mutex);
        done.wait_for(lock, 2s, [&] { return value.has_value(); });
        return value.value_or("nothing within 2 s");
    }
};

void IgnoreSignal(int) {}

} // namespace

int main() {
    // ── A short read returns only what arrived ───────────────────────────────
    {
        Connection connection;
        connection.Send("hello");
        std::this_thread::sleep_for(20ms);
        const std::vector<char> received = connection.client->RecieveSync(64);
        Check(Text(received) == "hello", std::format("RecieveSync(64) returns the 5 bytes that arrived (got {})", received.size()));
    }

    // ── Until close: every chunk, in order, nothing more ─────────────────────
    {
        Connection connection;
        std::thread sender([&] {
            connection.Send("abc");
            std::this_thread::sleep_for(30ms);
            connection.Send("defgh");
            std::this_thread::sleep_for(30ms);
            connection.Send("ij");
            std::this_thread::sleep_for(30ms);
            connection.ClosePeer();
        });
        const std::vector<char> received = connection.client->RecieveUntilCloseSync();
        sender.join();
        Check(Text(received) == "abcdefghij",
              std::format("RecieveUntilCloseSync returns the three chunks it was sent ({} bytes)", received.size()));
    }

    // ── A signal doesn't break a waiting receive ─────────────────────────────
    {
        // No SA_RESTART, so the signal makes recv return EINTR.
        struct sigaction action {};
        action.sa_handler = IgnoreSignal;
        sigemptyset(&action.sa_mask);
        sigaction(SIGUSR1, &action, nullptr);

        Connection connection;
        std::string outcome;
        std::thread reader([&] {
            try {
                outcome = Text(connection.client->RecieveUntilFullSync(4));
            } catch (const std::exception& e) {
                outcome = std::string("threw: ") + e.what();
            }
        });
        std::this_thread::sleep_for(50ms);
        pthread_kill(reader.native_handle(), SIGUSR1);
        std::this_thread::sleep_for(50ms);
        connection.Send("data");
        reader.join();
        Check(outcome == "data", std::format("a receive interrupted by a signal waits on for its data ({})", outcome));
    }

    // ── Into a buffer: the count, and the same exceptions ────────────────────
    {
        Connection connection;
        connection.Send("hello");
        std::this_thread::sleep_for(20ms);
        std::array<char, 64> buffer {};
        const std::uint32_t got = connection.client->RecieveSync(buffer.size(), buffer.data());
        Check(got == 5 && std::string_view(buffer.data(), got) == "hello", std::format("RecieveSync(64, buffer) returns the 5 bytes that arrived ({})", got));
        connection.ClosePeer();
        std::string closed;
        try {
            (void)connection.client->RecieveSync(buffer.size(), buffer.data());
        } catch (...) {
            closed = Kind(std::current_exception());
        }
        Check(closed == "closed", std::format("and throws SocketClosedException once the peer has closed ({})", closed.empty() ? "returned" : closed));
    }
    {
        Connection connection;
        std::array<char, 16> buffer {};
        std::string outcome = "returned";
        try {
            const bool empty = connection.client->RecieveSync(0).empty() && connection.client->RecieveSync(0, buffer.data()) == 0;
            if (!empty) outcome = "bytes";
        } catch (...) {
            outcome = Kind(std::current_exception());
        }
        Check(outcome == "returned", std::format("a receive of no bytes returns nothing on a live connection ({})", outcome));
    }
    {
        Connection connection;
        connection.client->SetReceiveTimeout(50ms);
        std::array<char, 16> buffer {};
        std::string timedOut;
        try {
            (void)connection.client->RecieveSync(buffer.size(), buffer.data());
        } catch (...) {
            timedOut = Kind(std::current_exception());
        }
        Check(timedOut == "timeout", std::format("and SocketTimeoutException when nothing comes in time ({})", timedOut.empty() ? "returned" : timedOut));
    }

    // ── Async: data to the callback, failures to onError ─────────────────────
    ThreadPool::Start(3);
    {
        Connection connection;
        connection.Send("hi");
        auto outcome = std::make_shared<Outcome>();
        connection.client->RecieveAsync(64, [outcome](std::vector<char> data) { outcome->Set(std::string(Text(data))); },
                                        [outcome](std::exception_ptr error) { outcome->Set(Kind(error)); });
        const std::string got = outcome->Wait();
        Check(got == "hi", std::format("RecieveAsync hands the data to its callback ({})", got));
    }
    {
        Connection connection;
        connection.ClosePeer();
        auto outcome = std::make_shared<Outcome>();
        connection.client->RecieveAsync(64, [outcome](std::vector<char>) { outcome->Set("data"); },
                                        [outcome](std::exception_ptr error) { outcome->Set(Kind(error)); });
        const std::string got = outcome->Wait();
        Check(got == "closed", std::format("and a closed peer to onError, the program carrying on ({})", got));
    }
    {
        Connection connection;
        connection.Send("ab");
        connection.ClosePeer();
        auto outcome = std::make_shared<Outcome>();
        connection.client->RecieveUntilFullAsync(4, [outcome](std::vector<char>) { outcome->Set("data"); },
                                                 [outcome](std::exception_ptr error) { outcome->Set(Kind(error)); });
        const std::string got = outcome->Wait();
        Check(got == "closed", std::format("RecieveUntilFullAsync reports a peer that closes early to onError ({})", got));
    }
    {
        Connection connection;
        connection.Send("xyz");
        std::array<char, 16> buffer {};
        auto outcome = std::make_shared<Outcome>();
        connection.client->RecieveAsync(buffer.size(), [outcome, &buffer](std::uint32_t count) { outcome->Set(std::string(buffer.data(), count)); },
                                        buffer.data(), [outcome](std::exception_ptr error) { outcome->Set(Kind(error)); });
        const std::string got = outcome->Wait();
        Check(got == "xyz", std::format("the buffer RecieveAsync hands its callback the count ({})", got));
    }
    {
        Connection connection;
        connection.ClosePeer();
        auto outcome = std::make_shared<Outcome>();
        connection.client->RecieveUntilCloseAsync([outcome](std::vector<char>) { outcome->Set("data"); },
                                                  [outcome](std::exception_ptr error) { outcome->Set(Kind(error)); });
        const std::string got = outcome->Wait();
        Check(got == "closed", std::format("RecieveUntilCloseAsync on a peer that sent nothing goes to onError ({})", got));
    }
    {
        Connection connection;
        connection.ClosePeer();
        connection.client->RecieveAsync(64, [](std::vector<char>) {}, {});
        // Calling the empty onError ended the program from the pool's task.
        std::this_thread::sleep_for(300ms);
        Check(true, "without an onError, a closed peer's exception is dropped, the program carrying on");
    }
    ThreadPool::Stop();

    std::println("{}", failures == 0 ? "all checks passed" : "check(s) failed");
    return failures == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
}