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

// QUICServerCredentials{selfSigned = true} from a cold cache, in several
// processes at once. The pair used to be made by the openssl CLI straight
// into the fixed /tmp/crafter-network-quic-cert/{key,cert}.pem, guarded by an
// in-process mutex only: test binaries started together each found no pair,
// each ran openssl over the same two files, and one could load another run's
// key with its own certificate, failing in ConfigurationLoadCredential. The
// directory was shared by every user of the machine, and without the openssl
// CLI there was no certificate at all.
//
// Six processes, forked before any thread or msquic exists, are released at
// once; each starts two threads that create a selfSigned listener together,
// against an empty cache (XDG_CACHE_HOME pointed at a fresh directory) and
// with no openssl on PATH, and connects to both. Every listener must serve,
// and every process must report the same certificate: one made the pair and
// the rest read it. Then:
//  - the directory is the user's alone (0700) and so is the key (0600);
//  - a process started later serves the same certificate, so a browser's
//    pinned hash survives a restart;
//  - a mismatched pair left on disk, what the race used to leave behind, is
//    replaced by the next process rather than loaded.
//
// The parent never starts msquic or a thread, so forking stays safe: every
// listener lives in a child, which answers with one line through a pipe.

#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <cerrno>
#include <cstdio>
#include <cstdlib>

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;
}

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

std::string Hex(const std::array<std::uint8_t, 32>& bytes) {
    std::string text;
    for (std::uint8_t byte : bytes) text += std::format("{:02x}", byte);
    return text;
}

// One child: wait for the byte on `go`, start `listeners` selfSigned
// listeners together on threads of their own, reach each with a client, and
// write "OK <certificate hash> <certificate path>" or "FAIL <why>" to
// `report`.
[[noreturn]] void Child(int go, int report, int listeners) {
    // A child that hangs dies and so answers nothing, which the parent
    // counts as a failure, inside the runner's 60 s.
    alarm(40);
    char byte = 0;
    while (read(go, &byte, 1) < 0 && errno == EINTR) {}
    close(go);

    std::string line;
    try {
        ThreadPool::Start();
        std::latch together(listeners);
        std::vector<std::string> problems(static_cast<std::size_t>(listeners));
        std::vector<std::thread> threads;
        for (int i = 0; i < listeners; ++i) {
            threads.emplace_back([&, i] {
                try {
                    together.arrive_and_wait();
                    QUICServerCredentials serverCreds;
                    serverCreds.selfSigned = true;
                    ListenerQUIC listener("127.0.0.1", 0, alpn, serverCreds, [](ClientQUIC* peer) {
                        peer->OnStream([](QUICStream stream) {
                            try {
                                std::vector<char> got = stream.RecieveUntilCloseSync();
                                stream.SendSync(got.data(), static_cast<std::uint32_t>(got.size()), true);
                            } catch (...) {}
                        });
                    });
                    listener.ListenAsyncAsync();
                    QUICClientCredentials clientCreds;
                    clientCreds.insecureNoServerValidation = true;
                    ClientQUIC client("127.0.0.1", listener.Port(), alpn, clientCreds);
                    QUICStream stream = client.OpenStream();
                    stream.SendSync("hi", 2, true);
                    std::vector<char> echoed = stream.RecieveUntilCloseSync();
                    if (std::string(echoed.begin(), echoed.end()) != "hi") problems[static_cast<std::size_t>(i)] = "no echo";
                } catch (const std::exception& e) {
                    problems[static_cast<std::size_t>(i)] = e.what();
                }
            });
        }
        for (std::thread& thread : threads) thread.join();
        std::string problem;
        for (const std::string& p : problems) if (!p.empty()) problem = p;
        if (problem.empty()) {
            const std::string path = GetSelfSignedCertificatePath();
            line = std::format("OK {} {}", Hex(ComputeCertificateHashSHA256(path)), path);
        } else {
            line = "FAIL " + problem;
        }
    } catch (const std::exception& e) {
        line = std::string("FAIL ") + e.what();
    }
    line += '\n';
    for (std::size_t written = 0; written < line.size();) {
        const ssize_t put = write(report, line.data() + written, line.size() - written);
        if (put < 0) {
            if (errno == EINTR) continue;
            break;
        }
        written += static_cast<std::size_t>(put);
    }
    // The accepted peers are still open: skip msquic's static teardown,
    // which would wait for their idle timeout.
    std::_Exit(0);
}

// Forks `count` children, releases them together, and returns their lines,
// "FAIL no answer" for one that died first.
std::vector<std::string> RunChildren(int count, int listeners) {
    int go[2];
    if (pipe(go) != 0) return std::vector<std::string>(static_cast<std::size_t>(count), "FAIL pipe");
    std::vector<std::pair<pid_t, int>> children;
    for (int i = 0; i < count; ++i) {
        int report[2];
        if (pipe(report) != 0) break;
        const pid_t pid = fork();
        if (pid == 0) {
            close(go[1]);
            close(report[0]);
            for (const auto& [sibling, siblingReport] : children) close(siblingReport);
            Child(go[0], report[1], listeners);
        }
        close(report[1]);
        children.emplace_back(pid, report[0]);
    }
    close(go[0]);
    const std::string release(children.size(), 'x');
    (void)!write(go[1], release.data(), release.size());
    close(go[1]);

    std::vector<std::string> lines;
    for (const auto& [pid, report] : children) {
        std::string line;
        char buffer[512];
        for (;;) {
            const ssize_t got = read(report, buffer, sizeof(buffer));
            if (got == 0) break;
            if (got < 0) {
                if (errno == EINTR) continue;
                break;
            }
            line.append(buffer, static_cast<std::size_t>(got));
        }
        close(report);
        int status = 0;
        while (waitpid(pid, &status, 0) < 0 && errno == EINTR) {}
        if (!line.empty() && line.back() == '\n') line.pop_back();
        lines.push_back(line.empty() ? "FAIL no answer" : line);
    }
    return lines;
}

bool Ok(const std::string& line) { return line.starts_with("OK "); }

// The hash in an "OK <hash> <path>" line.
std::string HashOf(const std::string& line) { return Ok(line) ? line.substr(3, 64) : std::string(); }

// The path in an "OK <hash> <path>" line.
std::string PathOf(const std::string& line) { return Ok(line) && line.size() > 68 ? line.substr(68) : std::string(); }

} // namespace

int main() {
    // The watchdog, without a thread: SIGALRM's default action ends the
    // process, which the runner counts as a failure.
    alarm(55);

    char scratch[] = "/tmp/crafter-network-certificate-XXXXXX";
    if (mkdtemp(scratch) == nullptr) {
        std::println("FAIL  mkdtemp: {}", std::strerror(errno));
        return 1;
    }
    const std::filesystem::path cache = scratch;
    const std::filesystem::path directory = cache / "crafter-network" / "quic-cert";
    setenv("XDG_CACHE_HOME", scratch, 1);
    // No openssl to fall back on, wherever it is installed.
    setenv("PATH", (cache / "no-programs-here").c_str(), 1);

    // ── Six processes, two listeners each, from cold ─────────────────────────
    const std::vector<std::string> cold = RunChildren(6, 2);
    for (const std::string& line : cold) std::println("      {}", line);
    Check(std::ranges::all_of(cold, Ok),
          "twelve listeners in six processes started together from an empty cache, with no openssl CLI, were all served");
    std::set<std::string> hashes;
    for (const std::string& line : cold) hashes.insert(HashOf(line));
    Check(hashes.size() == 1 && !hashes.begin()->empty(),
          "and all six processes serve one certificate: one made it, the rest read it");
    const std::string first = HashOf(cold.front());
    Check(PathOf(cold.front()) == (directory / "cert.pem").string(),
          std::format("it lives under XDG_CACHE_HOME ({})", PathOf(cold.front())));

    // ── The directory is the user's alone ────────────────────────────────────
    struct stat info {};
    Check(stat(directory.c_str(), &info) == 0 && (info.st_mode & 0777) == 0700 && info.st_uid == geteuid(),
          "the certificate directory is the user's, mode 0700");
    Check(stat((directory / "key.pem").c_str(), &info) == 0 && (info.st_mode & 077) == 0,
          "the key is readable by the user alone");
    bool leftovers = false;
    std::error_code error;
    for (const auto& entry : std::filesystem::directory_iterator(directory, error)) {
        leftovers = leftovers || entry.path().extension() == ".new";
    }
    Check(!leftovers, "no temporary file is left behind");

    // ── A restart keeps the certificate ──────────────────────────────────────
    const std::vector<std::string> restart = RunChildren(1, 1);
    std::println("      {}", restart.front());
    Check(Ok(restart.front()) && HashOf(restart.front()) == first,
          "a process started later serves the same certificate, so a pinned hash survives a restart");

    // ── A mismatched pair is replaced, not loaded ────────────────────────────
    // Another valid P-256 key, of the TLS partition's certificate: what a
    // torn replacement leaves on disk.
    {
        std::ofstream key(directory / "key.pem", std::ios::binary | std::ios::trunc);
        key << GetSelfSignedCertificatePem().privateKey;
    }
    const std::vector<std::string> mismatched = RunChildren(1, 1);
    std::println("      {}", mismatched.front());
    Check(Ok(mismatched.front()) && HashOf(mismatched.front()) != first,
          "a mismatched pair left on disk is replaced by a new one, which serves");
    try {
        Check(Hex(ComputeCertificateHashSHA256((directory / "cert.pem").string())) == HashOf(mismatched.front()),
              "and the new certificate is the one on disk");
    } catch (const std::exception& e) {
        Check(false, std::format("hashing the certificate on disk threw: {}", e.what()));
    }

    std::filesystem::remove_all(cache, error);
    std::println("{}", failures == 0 ? "all checks passed" : "check(s) failed");
    std::fflush(stdout);
    return failures == 0 ? 0 : 1;
}