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

// The machine as the driver sees it.
//
// - Shared files: an atomic write never leaves half a file and gives the
//   temp file the mode asked for; LockedUpdate re-reads under the lock, keeps
//   keys it does not know, falls back on a damaged file, and serialises
//   concurrent writers — including another process holding flock(2) on the
//   same side file, as every driver on the machine does.
// - /proc: the start time read after the last ')' (a command name may hold
//   spaces and parentheses), a zombie reading as gone, MemInfo in MB.
// - Identity: natively a driver's own pid and start time; in the sandbox the
//   instance's host pid from bwrapinfo.json with the start time of /proc/1.
//   On a fake /proc and a fake instance directory, because the suite itself
//   runs inside `flatpak build` in the Flatpak.
// - The lifetime lock: held while its driver lives, refused to a second
//   driver under the same name, gone when it ends, and a stale one reads as
//   dead.
// - The host XDG directories coming back in the sandbox.

#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>

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;
        }
    }

    void Write(const fs::path& path, std::string_view text) {
        fs::create_directories(path.parent_path());
        std::ofstream(path, std::ios::binary) << text;
    }

    // A /proc/<pid>/stat whose command name is designed to trip a naive split.
    std::string Stat(std::int64_t pid, char state, std::int64_t start) {
        std::string fields = std::format("{} (we (ird) name) {} 1", pid, state);
        for (std::int32_t field = 5; field <= 21; ++field) fields += " 0";
        return std::format("{} {} 0 0\n", fields, start);
    }
}

int main() {
    const fs::path dir = fs::temp_directory_path() / std::format("crafter-review-platform-{}", getpid());
    fs::remove_all(dir);
    fs::create_directories(dir);
    Platform::SetMode(Platform::Mode::Native);

    {
        const mode_t previous = umask(022);
        const fs::path file = dir / "atomic.json";
        Platform::WriteAtomic(file, "{\"a\": 1}", 0600);
        struct stat info {};
        stat(file.c_str(), &info);
        Check(Platform::ReadFile(file) == "{\"a\": 1}", "the atomic write lands");
        Check((info.st_mode & 0777) == 0600, std::format("with the mode asked for ({:o})", info.st_mode & 0777));
        Check(!fs::exists(std::format("{}.{}.tmp", file.string(), Platform::PublishedPid())), "and leaves no temp file");
        umask(previous);
    }

    {
        const fs::path file = dir / "board.json";
        Write(file, "{\"version\": 1, \"cost7d\": 3.5, \"seats\": {}}");
        const Json seen = Platform::LockedUpdate(file, [](Json& data) {
            data["seats"]["local"] = { { "id", "local" } };
            return true;
        }, Json::object(), 0600, {});
        const Json back = Json::parse(*Platform::ReadFile(file));
        Check(back["cost7d"] == 3.5 && back["seats"]["local"]["id"] == "local", "a key this driver does not know survives the rewrite");
        Check(*Platform::ReadFile(file) == DumpFile(back), "written in DumpFile's layout");
        Check(seen == back, "LockedUpdate returns what the change saw");

        Write(file, "{not json");
        const Json fallback = { { "version", 1 } };
        Platform::LockedUpdate(file, [](Json& data) {
            return data.contains("version");
        }, fallback, 0600, {});
        Check(Json::parse(*Platform::ReadFile(file)) == fallback, "a damaged file is replaced by the fallback the change kept");

        const std::string before = *Platform::ReadFile(file);
        Platform::LockedUpdate(file, [](Json& data) {
            data["ignored"] = true;
            return false;
        }, Json::object(), 0600, {});
        Check(*Platform::ReadFile(file) == before, "a change that returns false leaves the file alone");
    }

    {
        // Two writers in one process: flock is per open file description, so
        // two FileLocks exclude each other just as two processes would.
        const fs::path file = dir / "counter.json";
        Write(file, "{\"n\": 0}");
        auto bump = [&file] {
            for (std::int32_t i = 0; i < 100; ++i) {
                Platform::LockedUpdate(file, [](Json& data) {
                    data["n"] = data["n"].get<std::int64_t>() + 1;
                    return true;
                }, Json::object(), 0600, {});
            }
        };
        std::thread a(bump);
        std::thread b(bump);
        a.join();
        b.join();
        Check(Json::parse(*Platform::ReadFile(file))["n"] == 200, "concurrent read-modify-writes lose nothing");
    }

    {
        // Another process holds flock on the side file for a moment (flock(1),
        // util-linux): the lock here must wait for it, as every driver on the
        // machine shares these files.
        const fs::path file = dir / "shared.json";
        const fs::path lock = std::format("{}.lock", file.string());
        const fs::path ready = dir / "other-holds";
        try {
            const Process::Child other = Process::Start({ .argv = { "flock", lock.string(), "sh", "-c", "touch \"$1\" && sleep 0.4", "sh", ready.string() } });
            for (std::int32_t i = 0; i < 100 && !fs::exists(ready); ++i) std::this_thread::sleep_for(20ms);
            const auto start = std::chrono::steady_clock::now();
            {
                const Platform::FileLock ours(lock);
                Check(ours.Held(), "the lock is taken once the other process lets go");
            }
            const auto waited = std::chrono::steady_clock::now() - start;
            Process::Wait(other.pid);
            Check(waited >= 200ms, std::format("and not before: flock(2) excludes the other process's flock ({} ms)", std::chrono::duration_cast<std::chrono::milliseconds>(waited).count()));
        } catch (const std::runtime_error&) {
            std::println("SKIP  no flock here to hold the other end of the lock");
        }
    }

    {
        const fs::path proc = dir / "proc";
        Write(proc / "4242" / "stat", Stat(4242, 'S', 987654));
        Write(proc / "4243" / "stat", Stat(4243, 'Z', 5));
        Write(proc / "sys" / "kernel" / "random" / "boot_id", "0123456789abcdef-the-rest\n");
        Write(dir / "meminfo", "MemTotal:       65536000 kB\nMemAvailable:   32768000 kB\nHugePages_Total:       0\n");
        Platform::SetPaths({ .proc = proc, .flatpakInfo = dir / "no-flatpak-info", .runtimeDir = dir / "run" });
        Check(Platform::ProcStart(4242) == 987654, "the start time is field 22, read after the last ')'");
        Check(!Platform::ProcStart(4243).has_value(), "a zombie reads as gone");
        Check(!Platform::ProcStart(4244).has_value(), "so does a pid that is not there");
        Check(Platform::BootId() == "01234567", "boot_id's first eight characters");
        const auto memory = Platform::MemInfo(dir / "meminfo");
        Check(memory.at("MemTotal") == 64000 && memory.at("MemAvailable") == 32000 && memory.at("HugePages_Total") == 0, "meminfo in MB, unitless fields as they are");

        Write(proc / std::to_string(getpid()) / "stat", Stat(getpid(), 'R', 111));
        Platform::SetMode(Platform::Mode::Native);
        const std::optional<Platform::Identity> native = Platform::Self();
        Check(native && native->pid == getpid() && native->start == 111 && native->Key() == std::format("{}:111", getpid()), "natively a driver is its own pid and start time");

        Write(dir / "flatpak-info", "[Application]\nname=net.catcrafts.CrafterReview\n\n[Instance]\ninstance-id=2509661707\napp-path=/x\n");
        Write(dir / "run" / ".flatpak" / "2509661707" / "bwrapinfo.json", "{\n    \"child-pid\": 416559,\n    \"pid-namespace\": 4026536671\n}\n");
        Write(proc / "1" / "stat", Stat(1, 'S', 841601));
        Platform::SetPaths({ .proc = proc, .flatpakInfo = dir / "flatpak-info", .runtimeDir = dir / "run" });
        Platform::SetMode(Platform::Mode::Sandbox);
        const std::optional<Platform::Identity> sandboxed = Platform::Self();
        Check(sandboxed && sandboxed->Key() == "416559:841601", "in the sandbox: the instance's host pid and /proc/1's start time");

        fs::remove(dir / "run" / ".flatpak" / "2509661707" / "bwrapinfo.json");
        Check(!Platform::Self().has_value(), "no bwrapinfo.json (flatpak build): no identity a host driver could check");
        Platform::SetMode(Platform::Mode::Native);
    }

    {
        const fs::path drivers = dir / "drivers";
        const Platform::Identity me { .pid = 416559, .start = 841601 };
        {
            const Platform::LifetimeLock lock(drivers, me);
            Check(fs::exists(drivers / "416559-841601.lock"), "the lifetime lock is named <pid>-<start>.lock");
            Check(Platform::ProbeLifetimeLock(drivers, me.pid, me.start) == true, "a probe finds it held");
            bool refused = false;
            try {
                const Platform::LifetimeLock second(drivers, me);
            } catch (const std::runtime_error&) {
                refused = true;
            }
            Check(refused, "a second driver under the same name is refused");
            const std::vector<fs::directory_entry> entries(fs::directory_iterator(drivers), {});
            Check(entries.size() == 1, "and leaves no temp file behind");
        }
        Check(!Platform::ProbeLifetimeLock(drivers, me.pid, me.start).has_value(), "a driver that ended leaves no lock file");
        Write(Platform::LifetimeLockFile(drivers, 7, 8), "");
        Check(Platform::ProbeLifetimeLock(drivers, 7, 8) == false, "a lock file nobody holds is a dead driver's");
        Check(!Platform::ProbeLifetimeLock(drivers, 9, 9).has_value(), "no lock file: a driver that takes none");
    }

    {
        const std::string home = Platform::Home();
        setenv("XDG_CONFIG_HOME", "/home/x/.var/app/net.catcrafts.CrafterReview/config", 1);
        setenv("XDG_CACHE_HOME", "/home/x/.var/app/net.catcrafts.CrafterReview/cache", 1);
        setenv("HOST_XDG_CONFIG_HOME", "/elsewhere/config", 1);
        unsetenv("HOST_XDG_CACHE_HOME");
        Platform::RestoreHostXdg();
        Check(Platform::GetEnv("XDG_CONFIG_HOME") == "/elsewhere/config", "a host XDG directory the host set comes back");
        Check(Platform::GetEnv("XDG_CACHE_HOME") == Dyn::JoinPath(home, ".cache"), "one it left unset is the XDG default under $HOME");
        Check(Platform::GetEnv("XDG_STATE_HOME") == Dyn::JoinPath(home, ".local/state"), "state too");
    }

    {
        const std::string today = Platform::TodayIso();
        Check(today.size() == 10 && today[4] == '-' && today[7] == '-', "date.today().isoformat()");
        Check(Platform::LocalTime("%H:%M:%S", 0).size() == 8, "strftime in local time");
        Check(Platform::SelfExe().is_absolute(), "the running binary's path");
    }

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