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

// ListenerQUIC can be told which local address to listen on. Before, it
// always listened on every address of both families
// (QUIC_ADDRESS_FAMILY_UNSPEC), so a server meant for this machine's own
// processes, such as a debug server embedded in an app, was reachable from
// the network.
//
// msquic binds the UDP port on every address whatever it is given and
// filters by the address a connection was sent to at its own layer, so what
// is checked is the connection: one to 127.0.0.1 is served, while one to
// this machine's LAN address, or to ::1, fails, and fails at once (msquic
// refuses it outright) rather than after the handshake timeout.
//
// Also: ::1 works as a bind address, a name is refused, and only the
// connections that were served reach connectCallback.

#include <arpa/inet.h>
#include <ifaddrs.h>
#include <netinet/in.h>
#include <sys/socket.h>
#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;
}

// An IPv4 address of this host that is not loopback, if it has one.
std::optional<std::string> NonLoopbackIPv4() {
    ifaddrs* interfaces = nullptr;
    if (getifaddrs(&interfaces) != 0) return std::nullopt;
    std::optional<std::string> found;
    for (const ifaddrs* entry = interfaces; entry != nullptr && !found; entry = entry->ifa_next) {
        if (entry->ifa_addr == nullptr || entry->ifa_addr->sa_family != AF_INET) continue;
        const auto* v4 = reinterpret_cast<const sockaddr_in*>(entry->ifa_addr);
        if (ntohl(v4->sin_addr.s_addr) >> 24 == 127) continue;
        char text[INET_ADDRSTRLEN] = {};
        inet_ntop(AF_INET, &v4->sin_addr, text, sizeof(text));
        found = std::string(text);
    }
    freeifaddrs(interfaces);
    return found;
}

bool HasIPv6Loopback() {
    ifaddrs* interfaces = nullptr;
    if (getifaddrs(&interfaces) != 0) return false;
    bool found = false;
    for (const ifaddrs* entry = interfaces; entry != nullptr && !found; entry = entry->ifa_next) {
        if (entry->ifa_addr == nullptr || entry->ifa_addr->sa_family != AF_INET6) continue;
        const auto* v6 = reinterpret_cast<const sockaddr_in6*>(entry->ifa_addr);
        found = IN6_IS_ADDR_LOOPBACK(&v6->sin6_addr);
    }
    freeifaddrs(interfaces);
    return found;
}

const std::string alpn = "crafter/test-bind";

QUICClientCredentials ClientCredentials() {
    QUICClientCredentials creds;
    creds.insecureNoServerValidation = true;
    // Long enough that a connection msquic silently dropped would show as
    // slow below, short enough to stay inside the watchdog.
    creds.settings.handshakeIdleTimeoutMs = 6000;
    return creds;
}

// One stream to host:port and back. Empty when the echo did not come back.
std::string Echo(const std::string& host, std::uint16_t port, std::string_view text) {
    ClientQUIC client(host, port, alpn, ClientCredentials());
    QUICStream stream = client.OpenStream();
    stream.SendSync(text.data(), static_cast<std::uint32_t>(text.size()), true);
    std::vector<char> echoed = stream.RecieveUntilCloseSync();
    return std::string(echoed.begin(), echoed.end());
}

// Connects to host:port and reports how long it took to be refused; nullopt
// when the connection was served instead.
std::optional<std::chrono::milliseconds> RefusedAfter(const std::string& host, std::uint16_t port) {
    const auto start = std::chrono::steady_clock::now();
    try {
        ClientQUIC client(host, port, alpn, ClientCredentials());
        return std::nullopt;
    } catch (const QUICException& e) {
        const auto took = std::chrono::duration_cast<std::chrono::milliseconds>(
            std::chrono::steady_clock::now() - start);
        std::println("      ({} refused after {} ms: {})", host, took.count(), e.what());
        return took;
    }
}

} // 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();

    QUICServerCredentials serverCreds;
    serverCreds.selfSigned = true;
    std::atomic<int> accepted = 0;
    auto serve = [&](ClientQUIC* peer) {
        ++accepted;
        peer->OnStream([](QUICStream stream) {
            try {
                std::vector<char> got = stream.RecieveUntilCloseSync();
                stream.SendSync(got.data(), static_cast<std::uint32_t>(got.size()), true);
            } catch (...) {}
        });
    };
    // A refusal well inside the handshake timeout is msquic turning the
    // connection away; one at the timeout is a silent drop.
    constexpr std::chrono::milliseconds atOnce{ 3000 };

    try {
        // ── 127.0.0.1 ────────────────────────────────────────────────────────
        ListenerQUIC loopback("127.0.0.1", 0, alpn, serverCreds, serve);
        loopback.ListenAsyncAsync();
        const std::uint16_t port = loopback.Port();
        Check(port != 0, std::format("a listener on 127.0.0.1 at port 0 reports its port ({})", port));
        Check(Echo("127.0.0.1", port, "loopback") == "loopback", "it serves a client that connects through 127.0.0.1");

        if (const std::optional<std::string> lan = NonLoopbackIPv4()) {
            const std::optional<std::chrono::milliseconds> refused = RefusedAfter(*lan, port);
            Check(refused.has_value(), std::format("a client that connects through this host's LAN address {} is not served", *lan));
            Check(refused && *refused < atOnce, "and is refused at once, not timed out");
        } else {
            std::println("skipping the LAN half: this host has no IPv4 address but loopback");
        }
        if (HasIPv6Loopback()) {
            const std::optional<std::chrono::milliseconds> refused = RefusedAfter("::1", port);
            Check(refused.has_value() && *refused < atOnce, "nor is one through ::1, the other loopback address");
        }
        Check(accepted.load() == 1, std::format("only the served connection reached connectCallback ({})", accepted.load()));

        // ── ::1 ──────────────────────────────────────────────────────────────
        if (HasIPv6Loopback()) {
            ListenerQUIC loopback6("::1", 0, alpn, serverCreds, serve);
            loopback6.ListenAsyncAsync();
            Check(Echo("::1", loopback6.Port(), "v6") == "v6", "a listener on ::1 serves a client that connects through ::1");
            const std::optional<std::chrono::milliseconds> refused = RefusedAfter("127.0.0.1", loopback6.Port());
            Check(refused.has_value() && *refused < atOnce, "and refuses one through 127.0.0.1");
        } else {
            std::println("skipping the ::1 half: this host has no IPv6 loopback");
        }

        // ── A name ───────────────────────────────────────────────────────────
        bool threw = false;
        try {
            ListenerQUIC named("localhost", 0, alpn, serverCreds, serve);
        } catch (const QUICException& e) {
            threw = true;
            std::println("      ({})", e.what());
        }
        Check(threw, "a name such as localhost is refused as a bind address");
    } catch (const std::exception& e) {
        Check(false, std::format("threw: {}", e.what()));
    }

    std::println("{}", failures == 0 ? "all checks passed" : "check(s) failed");
    // As the other QUIC tests: skip the static teardown, which waits for the
    // accepted peers' idle timeout. _Exit doesn't flush.
    std::fflush(stdout);
    std::_Exit(failures == 0 ? 0 : 1);
}