/*
 * Copyright (C) 2013-2024  Eugen Wissner <belka@caraus.de>
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#include <cstring>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <string>
#include <sys/timex.h>
#include "timedate.h"

static void slack_method_call(const Glib::RefPtr<Gio::DBus::Connection>& connection, const Glib::ustring& sender,
        const Glib::ustring& object_path, const Glib::ustring& interface_name, const Glib::ustring& method_name,
        const Glib::VariantContainerBase& parameters, const Glib::RefPtr<Gio::DBus::MethodInvocation>& invocation)
{
    // Set time zone
    if (method_name == "SetTimezone")
    {
        Glib::Variant<Glib::ustring> timezone;
        Glib::Variant<bool> user_interaction;

        parameters.get_child(timezone, 0);
        parameters.get_child(user_interaction, 1);
        try
        {
            dlackware::timedate::set_timezone(timezone.get(), user_interaction.get());
            invocation->return_value(Glib::VariantContainerBase());
        }
        catch (const std::filesystem::filesystem_error& filesystem_error)
        {
            invocation->return_error(Gio::DBus::Error{ Gio::DBus::Error::FAILED, filesystem_error.what() });
        }
    }
    else if (method_name == "SetTime")
    {
        Glib::Variant<gint64> usec_utc;
        Glib::Variant<bool> relative;
        Glib::Variant<bool> user_interaction;

        parameters.get_child(usec_utc, 0);
        parameters.get_child(relative, 1);
        parameters.get_child(user_interaction, 2);

        try
        {
            dlackware::timedate::set_time(usec_utc.get(), relative.get(), user_interaction.get());
            invocation->return_value(Glib::VariantContainerBase());
        }
        catch (const std::system_error& error)
        {
            invocation->return_error(Gio::DBus::Error{ Gio::DBus::Error::FAILED, error.what() });
        }
    }
    else if (method_name == "SetNTP")
    {
        Glib::Variant<bool> use_ntp;
        Glib::Variant<bool> user_interaction;

        parameters.get_child(use_ntp, 0);
        parameters.get_child(user_interaction, 1);

        // Enable NTP
        try
        {
            dlackware::timedate::set_ntp(use_ntp.get(), user_interaction.get());
            invocation->return_value(Glib::VariantContainerBase());
        }
        catch (const std::filesystem::filesystem_error& filesystem_error)
        {
            invocation->return_error(Gio::DBus::Error{ Gio::DBus::Error::FAILED, filesystem_error.what() });
        }
    }
    else if (method_name == "ListTimezones")
    {
        try
        {
            auto return_tuple = Glib::VariantContainerBase::create_tuple({
                    Glib::Variant<std::vector<Glib::ustring>>::create(dlackware::timedate::list_timezones())
            });
            invocation->return_value(return_tuple);
        }
        catch (const std::exception& exception)
        {
            Gio::DBus::Error error{ Gio::DBus::Error::FAILED, exception.what() };
            invocation->return_error(error);
        }
    }
}

static void slack_get_property(Glib::VariantBase& result, const Glib::RefPtr<Gio::DBus::Connection>& connection,
        const Glib::ustring& sender, const Glib::ustring& object_path, const Glib::ustring& interface_name,
        const Glib::ustring& prop_name)
{
    if (prop_name == "Timezone")
    {
        result = Glib::Variant<Glib::ustring>::create(dlackware::timedate::timezone());
    }
    else if (prop_name == "LocalRTC")
    {
        result = Glib::Variant<bool>::create(dlackware::timedate::local_rtc());
    }
    else if (prop_name == "NTP")
    {
        result = Glib::Variant<bool>::create(dlackware::timedate::ntp());
    }
    else if (prop_name == "CanNTP")
    {
        result = Glib::Variant<bool>::create(dlackware::timedate::can_ntp());
    }
    else if (prop_name == "NTPSynchronized")
    {
        result = Glib::Variant<bool>::create(dlackware::timedate::ntp_synchronized());
    }
    else if (prop_name == "TimeUSec")
    {
        result = Glib::Variant<std::uint64_t>::create(dlackware::timedate::time_usec());
    }
    else if (prop_name == "RTCTimeUSec")
    {
        result = Glib::Variant<std::uint64_t>::create(dlackware::timedate::rtc_time_usec());
    }
}

namespace dlackware::timedate
{
    constexpr const std::uint64_t usec_per_sec = 1000000ULL;
    constexpr const std::uint64_t nsec_per_usec = 1000ULL;

    timedate1::timedate1()
        : interface_vtable{ &slack_method_call, &slack_get_property }
    {
    }

    void timedate1::on_name_lost(const Glib::RefPtr<Gio::DBus::Connection>& connection, const Glib::ustring& name)
    {
        g_warning("Failed to acquire the service %s.\n", name.data());
        exit(1);
    }

    void timedate1::on_bus_acquired(const Glib::RefPtr<Gio::DBus::Connection>& connection, const Glib::ustring& name)
    {
        Glib::RefPtr<Gio::DBus::NodeInfo> introspection_data;
        try
        {
            auto introspection_xml = Glib::file_get_contents(
                    (std::filesystem::path(DATADIR_INTERFACES) / dlackware::timedate::bus_name).concat(".xml")
            );
            introspection_data = Gio::DBus::NodeInfo::create_for_xml(introspection_xml);
        }
        catch (Glib::Error& slack_err)
        {
            g_error("Failed to parse D-Bus introspection XML: %s\n", slack_err.what().data());
        }
        try
        {
            guint registration_id = connection->register_object(bus_path,
                    introspection_data->lookup_interface(), this->interface_vtable);
        }
        catch (Glib::Error& slack_err)
        {
            g_critical("Failed to register callbacks for the exported object with the D-Bus interface: %s\n",
                    slack_err.what().data());
        }
    }

    static void list_timezones(const std::string& prefix, std::vector<Glib::ustring>& accumulator)
    {
        auto zoneinfo_path = std::filesystem::path(zoneinfo_database) / prefix;

        for (auto zoneinfo_entry : std::filesystem::directory_iterator(zoneinfo_path))
        {
            auto new_prefix = prefix + zoneinfo_entry.path().filename().string();

            if (zoneinfo_entry.is_directory())
            {
                list_timezones(new_prefix + "/", accumulator);
            }
            else if (zoneinfo_entry.is_regular_file() && !zoneinfo_entry.path().has_extension()
                    && zoneinfo_entry.path().filename() != "leapseconds")
            {
                accumulator.emplace_back(new_prefix);
            }
        }
    }

    std::vector<Glib::ustring> list_timezones()
    {
        std::vector<Glib::ustring> result;

        list_timezones("", result);
        return result;
    }

    Glib::ustring timezone()
    {
        std::unique_ptr<gchar[], decltype(&g_free)> zone_copied_from(
                g_file_read_link("/etc/localtime", NULL), &g_free);

        if (zone_copied_from == nullptr)
        {
            return nullptr;
        }
        return Glib::ustring{ zone_copied_from.get() + zoneinfo_database.size() + 1 };
    }

    void set_timezone(const Glib::ustring& zone, bool)
    {
        auto zone_file = std::filesystem::path("/usr/share/zoneinfo") / zone.data();
        std::error_code ec{};

        if (!std::filesystem::is_regular_file(zone_file, ec))
        {
            throw std::filesystem::filesystem_error("Zone info is not a regular file", zone_file, ec);
        }
        std::filesystem::path etc_localtime = "/etc/localtime";

        std::filesystem::remove(etc_localtime);
        std::filesystem::create_symlink(zone_file, etc_localtime);
    }

    void set_ntp(bool use_ntp, bool)
    {
        std::filesystem::perms rc_mode = std::filesystem::perms::owner_read | std::filesystem::perms::owner_write
            | std::filesystem::perms::group_read | std::filesystem::perms::others_read;

        if (use_ntp)
        {
            rc_mode |= std::filesystem::perms::owner_exec
                | std::filesystem::perms::group_exec | std::filesystem::perms::others_exec;
        }
        std::error_code ec;
        const std::filesystem::path service_path{ "/etc/rc.d/rc.ntpd" };

        if (std::filesystem::is_regular_file(service_path, ec))
        {
            std::filesystem::permissions("/etc/rc.d/rc.ntpd", rc_mode);
        }
        else
        {
            throw std::filesystem::filesystem_error("The NTP daemon isn't installed", service_path, ec);
        }
    }

    void set_time(std::int64_t seconds_since_epoch, bool relative, bool)
    {
        timespec ts;

        if (relative)
        {
            if (clock_gettime(CLOCK_REALTIME, &ts) == -1)
            {
                throw std::system_error(errno, std::generic_category());
            }
            ts.tv_sec += static_cast<time_t>(seconds_since_epoch / dlackware::timedate::usec_per_sec);
            ts.tv_nsec += (seconds_since_epoch % dlackware::timedate::usec_per_sec) * dlackware::timedate::nsec_per_usec;

            if (ts.tv_nsec < 0)
            {
                --ts.tv_sec;
                ts.tv_nsec += dlackware::timedate::usec_per_sec;
            }
        }
        else
        {
            ts.tv_sec = static_cast<time_t>(seconds_since_epoch / dlackware::timedate::usec_per_sec);
            ts.tv_nsec = (seconds_since_epoch % dlackware::timedate::usec_per_sec) * dlackware::timedate::nsec_per_usec;
        }
        if (clock_settime(CLOCK_REALTIME, &ts) == -1)
        {
            throw std::system_error(errno, std::generic_category());
        }
    }

    bool local_rtc()
    {
        std::ifstream fh{ "/etc/hardwareclock", std::ios::in };
        if (!fh.is_open())
        {
            return false;
        }
        std::array<char, 10> time_str; // "localtime" is longer than "UTC" and has 9 letters + \0

        while (fh.good())
        {
            fh.getline(time_str.data(), time_str.size());
            fh.clear(fh.rdstate() & (~std::ios_base::failbit));

            if (std::strncmp(time_str.data(), "localtime", time_str.size()) == 0)
            {
                return true;
            }
        }
        return false;
    }

    bool ntp()
    {
        return Glib::file_test("/etc/rc.d/rc.ntpd", Glib::FileTest::FILE_TEST_IS_EXECUTABLE);
    }

    bool can_ntp()
    {
        std::string standard_output;
        int wait_status{-1};

        try
        {
            Glib::spawn_sync("", std::vector<std::string>{ "s6-rc-db", "type", "ntpd" },
                    Glib::SpawnFlags::SPAWN_SEARCH_PATH | Glib::SpawnFlags::SPAWN_STDERR_TO_DEV_NULL,
                    {}, &standard_output, nullptr, &wait_status);
        }
        catch (const Glib::SpawnError& spawn_error)
        {
            return std::filesystem::exists("/etc/rc.d/rc.ntpd");
        }
        return wait_status == 0 && standard_output == "bundle\n";
    }

    bool ntp_synchronized()
    {
        timex buffer{ .modes = 0 };
        int ntp_result = adjtimex(&buffer);

        if (ntp_result == -1)
        {
            throw std::system_error(errno, std::generic_category());
        }
        return ntp_result != TIME_ERROR && (buffer.status & STA_UNSYNC) == 0;
    }

    std::uint64_t time_usec()
    {
        timespec spec;

        if (clock_gettime(CLOCK_REALTIME, &spec) == -1)
        {
            throw std::system_error(errno, std::generic_category());
        }
        time_t seconds = spec.tv_sec;
        tm time;

        if (local_rtc())
        {
            gmtime_r(&seconds, &time);
        }
        else
        {
            localtime_r(&seconds, &time);
        }
        return std::chrono::duration_cast<std::chrono::microseconds>(
                std::chrono::seconds(std::mktime(&time)) + std::chrono::nanoseconds(spec.tv_nsec)).count();
    }

    std::uint64_t rtc_time_usec()
    {
        return std::chrono::duration_cast<std::chrono::microseconds>(
                std::chrono::system_clock::now().time_since_epoch()).count();
    }
}