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

module;
#include <fcntl.h>
#include <pwd.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <stdio.h>
#include <unistd.h>
#include <cerrno>
#include <cstdlib>
#include <ctime>

module Crafter.Review:Platform_impl;
import :Platform;
import :Json;
import :Text;
import :Crypto;
import std;

namespace fs = std::filesystem;

namespace Crafter::Review::Platform {
    namespace {
        Mode CurrentModeValue = Mode::Native;

        SystemPaths& PathsValue() {
            static SystemPaths paths = [] {
                SystemPaths defaults;
                if (const char* runtime = std::getenv("XDG_RUNTIME_DIR"); runtime && *runtime) {
                    defaults.runtimeDir = runtime;
                } else {
                    defaults.runtimeDir = std::format("/run/user/{}", getuid());
                }
                return defaults;
            }();
            return paths;
        }

        // [section] key=value, as GLib's key files are written.
        std::optional<std::string> KeyFileValue(std::string_view text, std::string_view section, std::string_view key) {
            bool inSection = false;
            for (const std::string& line : Dyn::SplitLines(text)) {
                const std::string_view view(line);
                if (view.starts_with('[')) {
                    inSection = view == std::format("[{}]", section);
                    continue;
                }
                if (!inSection) continue;
                const std::size_t equals = view.find('=');
                if (equals == std::string_view::npos) continue;
                if (Dyn::Strip(view.substr(0, equals)) == key) return Dyn::Strip(view.substr(equals + 1));
            }
            return std::nullopt;
        }

        std::optional<std::int64_t> ToInt(std::string_view text) {
            std::int64_t value = 0;
            const auto [end, error] = std::from_chars(text.data(), text.data() + text.size(), value);
            if (error != std::errc() || end != text.data() + text.size()) return std::nullopt;
            return value;
        }
    }

    void Init() {
        CurrentModeValue = fs::exists(PathsValue().flatpakInfo) ? Mode::Sandbox : Mode::Native;
        if (CurrentModeValue == Mode::Sandbox) {
            RestoreHostXdg();
            RestoreShell();
        }
    }

    Mode CurrentMode() {
        return CurrentModeValue;
    }

    bool InSandbox() {
        return CurrentModeValue == Mode::Sandbox;
    }

    void SetMode(Mode mode) {
        CurrentModeValue = mode;
    }

    const SystemPaths& Paths() {
        return PathsValue();
    }

    void SetPaths(SystemPaths paths) {
        PathsValue() = std::move(paths);
    }

    std::optional<std::string> GetEnv(std::string_view name) {
        const std::string key(name);
        const char* value = std::getenv(key.c_str());
        if (value == nullptr) return std::nullopt;
        return std::string(value);
    }

    std::map<std::string, std::string> Environment() {
        std::map<std::string, std::string> out;
        for (char** entry = environ; entry != nullptr && *entry != nullptr; ++entry) {
            const std::string_view text(*entry);
            const std::size_t equals = text.find('=');
            if (equals == std::string_view::npos) continue;
            out.emplace(std::string(text.substr(0, equals)), std::string(text.substr(equals + 1)));
        }
        return out;
    }

    std::string Home() {
        if (const std::optional<std::string> home = GetEnv("HOME"); home && !home->empty()) return *home;
        if (const passwd* entry = getpwuid(getuid()); entry != nullptr && entry->pw_dir != nullptr) return entry->pw_dir;
        return "/";
    }

    void RestoreHostXdg() {
        const std::string home = Home();
        const std::array<std::pair<std::string_view, std::string_view>, 4> defaults = { {
            { "CONFIG", ".config" },
            { "CACHE", ".cache" },
            { "DATA", ".local/share" },
            { "STATE", ".local/state" },
        } };
        for (const auto& [kind, relative] : defaults) {
            const std::string name = std::format("XDG_{}_HOME", kind);
            const std::optional<std::string> host = GetEnv(std::format("HOST_XDG_{}_HOME", kind));
            const std::string value = host && !host->empty() ? *host : Dyn::JoinPath(home, relative);
            setenv(name.c_str(), value.c_str(), 1);
        }
    }

    void RestoreShell() {
        const std::string shell = GetEnv("SHELL").value_or("");
        const bool usable = (shell.ends_with("/bash") || shell.ends_with("/zsh")) && access(shell.c_str(), X_OK) == 0;
        if (!usable && access("/bin/bash", X_OK) == 0) setenv("SHELL", "/bin/bash", 1);
    }

    fs::path SelfExe() {
        std::error_code error;
        const fs::path exe = fs::read_symlink("/proc/self/exe", error);
        return error ? fs::path() : exe;
    }

    double Now() {
        const auto since = std::chrono::system_clock::now().time_since_epoch();
        return std::chrono::duration<double>(since).count();
    }

    std::string LocalTime(std::string_view format, double epochSeconds) {
        const std::time_t seconds = static_cast<std::time_t>(std::floor(epochSeconds));
        std::tm local {};
        localtime_r(&seconds, &local);
        std::array<char, 128> buffer {};
        const std::string pattern(format);
        const std::size_t length = std::strftime(buffer.data(), buffer.size(), pattern.c_str(), &local);
        return std::string(buffer.data(), length);
    }

    std::string LocalTime(std::string_view format) {
        return LocalTime(format, Now());
    }

    std::string TodayIso() {
        return LocalTime("%Y-%m-%d");
    }

    std::optional<std::string> ReadFile(const fs::path& path) {
        std::ifstream in(path, std::ios::binary);
        if (!in) return std::nullopt;
        std::string bytes((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
        if (in.bad()) return std::nullopt;
        return bytes;
    }

    void WriteAtomic(const fs::path& path, std::string_view content, std::uint32_t mode) {
        if (path.has_parent_path()) fs::create_directories(path.parent_path());
        const fs::path temp = std::format("{}.{}.tmp", path.string(), PublishedPid());
        const std::int32_t fd = open(temp.c_str(), O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, static_cast<mode_t>(mode));
        if (fd < 0) throw std::runtime_error(std::format("{}: {}", Dyn::ErrnoText(errno), Dyn::Repr(temp.string())));
        std::size_t written = 0;
        while (written < content.size()) {
            const ssize_t step = write(fd, content.data() + written, content.size() - written);
            if (step < 0) {
                if (errno == EINTR) continue;
                const std::int32_t failure = errno;
                close(fd);
                unlink(temp.c_str());
                throw std::runtime_error(Dyn::ErrnoText(failure));
            }
            written += static_cast<std::size_t>(step);
        }
        close(fd);
        if (rename(temp.c_str(), path.c_str()) != 0) {
            const std::int32_t failure = errno;
            unlink(temp.c_str());
            throw std::runtime_error(std::format("{}: {} -> {}", Dyn::ErrnoText(failure), Dyn::Repr(temp.string()), Dyn::Repr(path.string())));
        }
    }

    void MakeDirs(const fs::path& path, std::uint32_t mode) {
        const fs::path name = path.filename().empty() && path.has_parent_path() ? path.parent_path() : path;
        const fs::path head = name.parent_path();
        std::error_code error;
        if (!head.empty() && head != name && !fs::exists(head, error)) {
            MakeDirs(head, 0777);
            if (name.filename() == ".") return;
        }
        if (mkdir(name.c_str(), static_cast<mode_t>(mode)) != 0) {
            const std::int32_t failure = errno;
            if (!fs::is_directory(name, error)) throw std::runtime_error(std::format("{}: {}", Dyn::ErrnoText(failure), Dyn::Repr(name.string())));
        }
    }

    FileLock::FileLock(const fs::path& lockPath) {
        std::error_code error;
        if (lockPath.has_parent_path()) fs::create_directories(lockPath.parent_path(), error);
        fd = open(lockPath.c_str(), O_WRONLY | O_CREAT | O_APPEND | O_CLOEXEC, 0666);
        if (fd < 0) {
            problem = std::format("{}: {}", Dyn::ErrnoText(errno), Dyn::Repr(lockPath.string()));
            return;
        }
        while (flock(fd, LOCK_EX) != 0) {
            if (errno == EINTR) continue;
            problem = Dyn::ErrnoText(errno);
            close(fd);
            fd = -1;
            return;
        }
    }

    FileLock::~FileLock() {
        if (fd >= 0) {
            flock(fd, LOCK_UN);
            close(fd);
        }
    }

    bool FileLock::Held() const {
        return fd >= 0;
    }

    const std::string& FileLock::Problem() const {
        return problem;
    }

    Json LockedUpdate(const fs::path& path, const std::function<bool(Json&)>& change, const Json& fallback,
                      std::uint32_t mode, const std::function<void(const std::string&)>& warn) {
        const FileLock lock(std::format("{}.lock", path.string()));
        if (!lock.Held() && warn) {
            warn(std::format("{}: no lock ({}) - best-effort write", path.filename().string(), lock.Problem()));
        }
        Json data;
        try {
            if (const std::optional<std::string> text = ReadFile(path)) data = ParseLoose(*text);
        } catch (const std::exception&) {
            data = Json();
        }
        if (!data.is_object()) data = fallback.is_object() ? fallback : Json::object();
        if (change(data)) {
            try {
                WriteAtomic(path, DumpFile(data), mode);
            } catch (const std::exception& e) {
                if (warn) warn(std::format("{}: not saved ({})", path.filename().string(), e.what()));
            }
        }
        return data;
    }

    std::optional<std::int64_t> ProcStart(std::int64_t pid) {
        const std::optional<std::string> stat = ReadFile(Paths().proc / std::to_string(pid) / "stat");
        if (!stat) return std::nullopt;
        const std::size_t close = stat->rfind(')');
        if (close == std::string::npos) return std::nullopt;
        const std::vector<std::string> rest = Dyn::Split(std::string_view(*stat).substr(close + 1));
        if (rest.size() < 20) return std::nullopt;
        if (rest[0] == "Z" || rest[0] == "X") return std::nullopt;
        return ToInt(rest[19]);
    }

    std::string BootId() {
        const std::optional<std::string> text = ReadFile(Paths().proc / "sys" / "kernel" / "random" / "boot_id");
        if (!text) return "";
        return Dyn::Slice(Dyn::Strip(*text), 0, 8);
    }

    std::map<std::string, std::int64_t> MemInfo(const fs::path& path) {
        std::map<std::string, std::int64_t> out;
        const std::optional<std::string> text = ReadFile(path);
        if (!text) return out;
        for (const std::string& line : Dyn::SplitLines(*text)) {
            const std::size_t colon = line.find(':');
            if (colon == std::string::npos) continue;
            const std::vector<std::string> parts = Dyn::Split(std::string_view(line).substr(colon + 1));
            if (parts.empty()) continue;
            const std::optional<std::int64_t> value = ToInt(parts[0]);
            if (!value) continue;
            out[line.substr(0, colon)] = parts.size() > 1 && parts[1] == "kB" ? *value / 1024 : *value;
        }
        return out;
    }

    std::map<std::int64_t, std::vector<std::int64_t>> PpidMap() {
        std::map<std::int64_t, std::vector<std::int64_t>> out;
        std::error_code error;
        for (const fs::directory_entry& entry : fs::directory_iterator("/proc", error)) {
            const std::string name = entry.path().filename().string();
            const std::optional<std::int64_t> pid = ToInt(name);
            if (!pid) continue;
            const std::optional<std::string> stat = ReadFile(entry.path() / "stat");
            if (!stat) continue;
            const std::size_t close = stat->rfind(')');
            if (close == std::string::npos) continue;
            const std::vector<std::string> rest = Dyn::Split(std::string_view(*stat).substr(close + 1));
            if (rest.size() < 2) continue;
            if (const std::optional<std::int64_t> ppid = ToInt(rest[1])) out[*ppid].push_back(*pid);
        }
        return out;
    }

    std::vector<std::int64_t> Tree(std::int64_t pid, const std::map<std::int64_t, std::vector<std::int64_t>>& kids) {
        std::vector<std::int64_t> out;
        std::vector<std::int64_t> todo { pid };
        std::set<std::int64_t> seen;
        while (!todo.empty()) {
            const std::int64_t next = todo.back();
            todo.pop_back();
            if (!seen.insert(next).second) continue;
            out.push_back(next);
            if (const auto found = kids.find(next); found != kids.end()) todo.insert(todo.end(), found->second.begin(), found->second.end());
        }
        return out;
    }

    double PssMb(std::span<const std::int64_t> pids) {
        std::int64_t kb = 0;
        for (const std::int64_t pid : pids) {
            const std::optional<std::string> text = ReadFile(std::format("/proc/{}/smaps_rollup", pid));
            if (!text) continue;
            for (const std::string& line : Dyn::SplitLines(*text)) {
                if (!line.starts_with("Pss:")) continue;
                const std::vector<std::string> parts = Dyn::Split(line);
                if (parts.size() > 1) {
                    if (const std::optional<std::int64_t> value = ToInt(parts[1])) kb += *value;
                }
                break;
            }
        }
        return static_cast<double>(kb) / 1024;
    }

    std::string Identity::Key() const {
        return std::format("{}:{}", pid, start);
    }

    std::optional<Identity> Self() {
        if (!InSandbox()) {
            const std::int64_t pid = getpid();
            return Identity { .pid = pid, .start = ProcStart(pid).value_or(0) };
        }
        const std::optional<std::string> info = ReadFile(Paths().flatpakInfo);
        const std::optional<std::string> instance = info ? KeyFileValue(*info, "Instance", "instance-id") : std::nullopt;
        if (!instance) return std::nullopt;
        const fs::path bwrapinfo = Paths().runtimeDir / ".flatpak" / *instance / "bwrapinfo.json";
        // flatpak writes the file once bwrap reports the child's pid, which
        // can be a moment after the application is already running.
        for (std::int32_t attempt = 0; attempt < 20; ++attempt) {
            if (const std::optional<std::string> text = ReadFile(bwrapinfo)) {
                try {
                    const Json parsed = Json::parse(*text);
                    if (parsed.contains("child-pid") && parsed["child-pid"].is_number_integer()) {
                        const std::optional<std::int64_t> start = ProcStart(1);
                        if (start) return Identity { .pid = parsed["child-pid"].get<std::int64_t>(), .start = *start };
                    }
                } catch (const std::exception&) {
                }
            }
            std::this_thread::sleep_for(std::chrono::milliseconds(100));
        }
        return std::nullopt;
    }

    std::int64_t PublishedPid() {
        static const std::int64_t pid = [] {
            if (const std::optional<Identity> self = Self()) return self->pid;
            return static_cast<std::int64_t>(getpid());
        }();
        return pid;
    }

    fs::path LifetimeLockFile(const fs::path& dir, std::int64_t pid, std::int64_t start) {
        return dir / std::format("{}-{}.lock", pid, start);
    }

    LifetimeLock::LifetimeLock(const fs::path& dir, const Identity& identity) : file(LifetimeLockFile(dir, identity.pid, identity.start)) {
        fs::create_directories(dir);
        if (ProbeLifetimeLock(dir, identity.pid, identity.start) == true) {
            throw std::runtime_error(std::format("another driver already runs as {} (its lock {} is held): start each driver with its own `flatpak run`", identity.Key(), file.string()));
        }
        const fs::path temp = dir / std::format(".{}-{}.{}.tmp", identity.pid, identity.start, TokenHex(4));
        fd = open(temp.c_str(), O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0644);
        if (fd < 0) throw std::runtime_error(std::format("{}: {}", temp.string(), Dyn::ErrnoText(errno)));
        if (flock(fd, LOCK_EX | LOCK_NB) != 0 || rename(temp.c_str(), file.c_str()) != 0) {
            const std::int32_t failure = errno;
            close(fd);
            fd = -1;
            unlink(temp.c_str());
            throw std::runtime_error(std::format("{}: {}", file.string(), Dyn::ErrnoText(failure)));
        }
    }

    LifetimeLock::~LifetimeLock() {
        if (fd < 0) return;
        // Unlinked while still held: a prober that opens the file after this
        // finds none, which every rule reads as "this driver is gone or never
        // took a lock" and the board's own leave() has already removed it.
        unlink(file.c_str());
        flock(fd, LOCK_UN);
        close(fd);
    }

    const fs::path& LifetimeLock::File() const {
        return file;
    }

    std::optional<bool> ProbeLifetimeLock(const fs::path& dir, std::int64_t pid, std::int64_t start) {
        const fs::path file = LifetimeLockFile(dir, pid, start);
        const std::int32_t fd = open(file.c_str(), O_RDONLY | O_CLOEXEC);
        if (fd < 0) return std::nullopt;
        // Shared: two probers looking at one dead driver both see it dead,
        // where an exclusive probe would show each the other's lock.
        const bool free = flock(fd, LOCK_SH | LOCK_NB) == 0;
        if (free) flock(fd, LOCK_UN);
        close(fd);
        return !free;
    }
}