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

// Child processes and their lifetime.
//
// SIGKILL to the claude process alone would leave the Playwright server and
// Chromium under it running after a timeout, and every pass running after a
// SIGKILLed driver, so a pass runs under a supervisor that is the subreaper
// of its tree. This test starts a target that leaves a detached grandchild —
// `setsid sleep`, a process group of its own, the way Playwright starts
// Chromium — and checks the grandchild is gone when the target exits, when
// the supervisor is told to stop, and when the driver above it is SIGKILLed.
//
// Also: return codes (minus the signal for a killed child), a missing
// program reported with its errno text, captured output from both streams
// without a deadlock, a timeout, nothing but the three streams reaching the
// child, and the child getting SIGPIPE back at its default with an empty
// signal mask while the driver ignores SIGPIPE.
//
// The test binary plays the supervisor (`__supervise`) and the driver
// (`--as-driver`) itself, by re-running its own executable.

#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <cerrno>

import std;
import Crafter.Review;
namespace fs = std::filesystem;
using namespace Crafter::Review;
using namespace std::chrono_literals;

namespace {
    std::int32_t Failures = 0;

    void Check(bool cond, std::string_view msg) {
        if (!cond) {
            std::println(std::cerr, "FAIL: {}", msg);
            ++Failures;
        }
    }

    fs::path Stage() {
        const fs::path dir = fs::temp_directory_path() / std::format("crafter-review-process-{}", getpid());
        fs::remove_all(dir);
        fs::create_directories(dir);
        return dir;
    }

    bool Alive(std::int64_t pid) {
        return pid > 0 && kill(static_cast<pid_t>(pid), 0) == 0;
    }

    // The pid a target wrote to `file`, waited for up to 5 s.
    std::int64_t PidFrom(const fs::path& file) {
        for (std::int32_t i = 0; i < 100; ++i) {
            if (const std::optional<std::string> text = Platform::ReadFile(file)) {
                if (const std::optional<std::int64_t> pid = Dyn::ParseInt(*text); pid && *pid > 0) return *pid;
            }
            std::this_thread::sleep_for(50ms);
        }
        return 0;
    }

    bool GoneWithin(std::int64_t pid, std::chrono::milliseconds limit) {
        const auto deadline = std::chrono::steady_clock::now() + limit;
        while (std::chrono::steady_clock::now() < deadline) {
            if (!Alive(pid)) return true;
            std::this_thread::sleep_for(20ms);
        }
        return !Alive(pid);
    }

    // `sh -c '<script>'` under a supervisor, started the way the pool starts
    // a pass: SIGTERM as its death signal.
    Process::Child StartSupervised(const std::string& script) {
        const std::vector<std::string> target { "sh", "-c", script };
        Process::Spec spec { .argv = Process::Supervised(target) };
        spec.deathSignal = SIGTERM;
        return Process::Start(spec);
    }

    // The driver this test SIGKILLs: it starts a supervised target that
    // leaves a detached grandchild, then waits to be killed.
    std::int32_t AsDriver(std::string_view pidFile) {
        Process::BecomeSubreaper();
        StartSupervised(std::format("setsid sleep 300 & echo $! > {}; wait", pidFile));
        std::this_thread::sleep_for(60s);
        return 0;
    }

    std::uint64_t HexMask(const std::string& status, std::string_view field) {
        for (const std::string& line : Dyn::SplitLines(status)) {
            if (!line.starts_with(field)) continue;
            return std::stoull(Dyn::Strip(line.substr(field.size())), nullptr, 16);
        }
        return ~0ULL;
    }
}

int main(int argc, char** argv) {
    const std::vector<std::string_view> args(argv, argv + argc);
    if (args.size() > 1 && args[1] == Process::SuperviseVerb) return Process::SuperviseMain(std::span(args).subspan(2));
    if (args.size() > 2 && args[1] == "--as-driver") return AsDriver(args[2]);

    Process::InstallSignalThread([](std::int32_t) {});
    const fs::path dir = Stage();

    {
        const Process::Child child = Process::Start({ .argv = { "sh", "-c", "exit 3" } });
        Check(Process::Wait(child.pid) == 3, "an exit status comes back as the return code");
        const Process::Child killed = Process::Start({ .argv = { "sh", "-c", "kill -TERM $$" } });
        Check(Process::Wait(killed.pid) == -15, "a child killed by a signal returns minus the signal, as Popen does");
    }

    {
        std::string message;
        try {
            Process::Start({ .argv = { "no-such-program-for-crafter-review" } });
        } catch (const std::runtime_error& e) {
            message = e.what();
        }
        Check(message == "[Errno 2] No such file or directory: 'no-such-program-for-crafter-review'",
              std::format("a missing program fails the way Popen fails ({})", message));
    }

    {
        const Process::Captured both = Process::Run({ "sh", "-c", "echo out; echo err >&2; exit 4" });
        Check(both.out == "out\n" && both.err == "err\n" && both.returnCode == 4, "both streams and the return code are captured");
        const Process::Captured fed = Process::Run({ "cat" }, std::nullopt, std::nullopt, "fed through stdin");
        Check(fed.out == "fed through stdin", "input reaches the child's stdin");
        const Process::Captured large = Process::Run({ "sh", "-c", "head -c 300000 /dev/zero; head -c 300000 /dev/zero >&2" });
        Check(large.out.size() == 300000 && large.err.size() == 300000, "large output on both streams does not stall the child");
        const auto start = std::chrono::steady_clock::now();
        const Process::Captured slow = Process::Run({ "sleep", "5" }, std::nullopt, 200ms);
        Check(slow.timedOut && std::chrono::steady_clock::now() - start < 3s, "a timeout kills the child and comes back promptly");
        const Process::Captured where = Process::Run({ "pwd" }, dir);
        Check(Dyn::Strip(where.out) == fs::canonical(dir).string(), "the child runs in the directory asked for");
        const Process::Captured env = Process::Run({ "sh", "-c", "echo $ONLY_HERE" }, std::nullopt, std::nullopt, {},
                                                   std::map<std::string, std::string> { { "ONLY_HERE", "yes" }, { "PATH", "/usr/bin:/bin" } });
        Check(Dyn::Strip(env.out) == "yes", "an environment given replaces this process's");
    }

    {
        // An fd this process left open without O_CLOEXEC must not reach the child.
        const std::int32_t leaked = open("/dev/null", O_RDONLY);
        const std::int32_t high = dup2(leaked, 57);
        const Process::Captured fds = Process::Run({ "sh", "-c", "ls /proc/$$/fd" });
        const std::vector<std::string> open = Dyn::Split(fds.out);
        Check(std::ranges::find(open, "57") == open.end() && open.size() <= 4, std::format("only the three streams reach the child (it had: {})", fds.out));
        close(high);
        close(leaked);
    }

    {
        const Process::Captured status = Process::Run({ "sh", "-c", "cat /proc/self/status" });
        const std::uint64_t ignored = HexMask(status.out, "SigIgn:");
        const std::uint64_t blocked = HexMask(status.out, "SigBlk:");
        Check((ignored & (1ULL << (SIGPIPE - 1))) == 0, "the child has SIGPIPE back at its default");
        Check(blocked == 0, "the child's signal mask is empty");
    }

    {
        // The target exits and leaves a detached grandchild behind.
        const fs::path pidFile = dir / "left-behind";
        const Process::Child supervisor = StartSupervised(std::format("setsid sleep 300 & echo $! > {}", pidFile.string()));
        const std::int64_t grandchild = PidFrom(pidFile);
        const std::optional<std::int32_t> code = Process::Wait(supervisor.pid, 10s);
        Check(grandchild > 0 && code == 0, "a supervised target's exit status comes back");
        Check(GoneWithin(grandchild, 2s), "what a target leaves behind dies with it, a detached process group included");
    }

    {
        // A timeout or an abort: SIGTERM to the supervisor.
        const fs::path pidFile = dir / "terminated";
        const Process::Child supervisor = StartSupervised(std::format("setsid sleep 300 & echo $! > {}; sleep 300", pidFile.string()));
        const std::int64_t grandchild = PidFrom(pidFile);
        Check(grandchild > 0 && Alive(grandchild), "the grandchild runs while the target does");
        Process::Signal(supervisor.pid, SIGTERM);
        const std::optional<std::int32_t> code = Process::Wait(supervisor.pid, 10s);
        Check(code.has_value() && Process::SupervisedReturnCode(*code) == -SIGKILL, std::format("a stopped target reports the kill (supervisor exit {})", code.value_or(-1)));
        Check(GoneWithin(grandchild, 2s), "SIGTERM to the supervisor takes the whole tree down");
    }

    {
        // The driver itself is SIGKILLed: nothing of the pass may outlive it.
        const fs::path pidFile = dir / "driver-killed";
        const Process::Child driver = Process::Start({ .argv = { Platform::SelfExe().string(), "--as-driver", pidFile.string() } });
        const std::int64_t grandchild = PidFrom(pidFile);
        Check(grandchild > 0 && Alive(grandchild), "the driver's pass is running");
        Process::Signal(driver.pid, SIGKILL);
        Process::Wait(driver.pid, 10s);
        Check(GoneWithin(grandchild, 3s), "a SIGKILLed driver's pass dies with it, through the supervisor's death signal");
    }

    {
        const Process::Child running = Process::Start({ .argv = { "sleep", "5" } });
        Check(!Process::Wait(running.pid, 100ms).has_value(), "a wait that times out leaves the child running");
        Process::Signal(running.pid, SIGKILL);
        Check(Process::Wait(running.pid, 5s) == -SIGKILL, "and the child can still be waited for");
        Check(Process::SupervisedReturnCode(137) == -9 && Process::SupervisedReturnCode(3) == 3, "a supervisor's 128+n is signal n");
    }

    fs::remove_all(dir);
    return Failures == 0 ? 0 : 1;
}