/*
 * 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/stat.h>

#include "slack-timedate.h"

static void slack_method_call (GDBusConnection *connection, const gchar *sender, const gchar *object_path, const gchar *interface_name, const gchar *method_name, GVariant *parameters, GDBusMethodInvocation *invocation, gpointer user_data) {
	gchar *timezone, *response;
	gboolean user_interaction, relative, is_localtime, use_ntp;
	gint64 usec_utc;
    auto timedate1 = reinterpret_cast<dlackware::timedate::timedate1 *>(user_data);

	// Set time zone
    if (g_strcmp0(method_name, "SetTimezone") == 0)
    {
		g_variant_get(parameters, "(&sb)", &timezone, &user_interaction);
        std::error_code error_code;

		if (timedate1->set_timezone(timezone, error_code))
        {
            g_dbus_method_invocation_return_value(invocation, NULL);
        }
		else
        {
            g_dbus_method_invocation_return_error(invocation, G_IO_ERROR, G_IO_ERROR_FAILED,
				"Set time zone: %s",
                error_code ? error_code.message().c_str() : "Zone info is not a regular file");
        }
		g_free (timezone);
    }
    else if (g_strcmp0(method_name, "SetTime") == 0)
    {
		g_variant_get (parameters, "(xbb)", &usec_utc, &relative, &user_interaction);

		// Set time
		//if (!slack_set_time (usec_utc, slack_get_is_localtime ())) {
		if (slack_set_time(usec_utc, relative))
        {
            g_dbus_method_invocation_return_value(invocation, NULL);
        }
		else
        {
            g_dbus_method_invocation_return_error(invocation, G_IO_ERROR, G_IO_ERROR_FAILED,
                    "Failed to set system clock");
        }
    }
    else if (g_strcmp0(method_name, "SetNTP") == 0)
    {
		g_variant_get (parameters, "(bb)", &use_ntp, &user_interaction);

		// Enable NTP
        if (slack_set_ntp (use_ntp))
        {
            g_dbus_method_invocation_return_value (invocation, NULL);
        }
        else
        {
            g_dbus_method_invocation_return_error (invocation,
				G_IO_ERROR,
				G_IO_ERROR_FAILED,
				"Error enabling NTP");
        }
	}
    else if (g_strcmp0(method_name, "ListTimezones") == 0)
    {
        try
        {
            auto return_tuple = Glib::Variant<std::vector<Glib::ustring>>::create_tuple({
                    timedate1->list_timezones()
            });
            g_dbus_method_invocation_return_value(invocation, return_tuple.gobj());
        }
        catch (const std::exception& exception)
        {
            g_dbus_method_invocation_return_error(invocation, G_IO_ERROR, G_IO_ERROR_FAILED,
                    "List time zones: %s", exception.what());
        }
    }
}

static GVariant *slack_get_property (GDBusConnection *connection, const gchar *sender, const gchar *object_path, const gchar *interface_name, const gchar *prop_name, GError **slack_err, gpointer user_data) {
    auto timedate1 = reinterpret_cast<dlackware::timedate::timedate1 *>(user_data);

	if (g_strcmp0 ("Timezone", prop_name) == 0) {
		return Glib::Variant<Glib::ustring>::create(timedate1->timezone()).gobj_copy();
	} if (g_strcmp0 ("LocalRTC", prop_name) == 0) {
		return g_variant_new_boolean (slack_get_is_localtime ());
	} if (g_strcmp0 ("NTP", prop_name) == 0) {
		return g_variant_new_boolean (slack_get_ntp ());
	}
	return NULL;
}

static void on_timedate_acquired(const Glib::RefPtr<Gio::DBus::Connection>& connection,
        const Glib::ustring& name, gpointer user_data)
{
    Glib::RefPtr<Gio::DBus::NodeInfo> introspection_data;
    static const auto interface_vtable = Gio::DBus::InterfaceVTable(
        [user_data](const Glib::RefPtr<Gio::DBus::Connection>& connection,
            const Glib::ustring& sender,
            const Glib::ustring& obj_path,
            const Glib::ustring& interface_name,
            const Glib::ustring& method_name,
            const Glib::VariantContainerBase& parameters,
            const Glib::RefPtr<Gio::DBus::MethodInvocation>& invocation) {

            auto parameters_copy = parameters.gobj_copy();
            slack_method_call(connection->gobj(), sender.data(), obj_path.data(), interface_name.data(),
                    method_name.data(), parameters_copy, invocation->gobj(), user_data);
            g_free(parameters_copy);
        },
        [user_data](Glib::VariantBase& result,
            const Glib::RefPtr<Gio::DBus::Connection>& connection,
            const Glib::ustring& sender,
            const Glib::ustring& obj_path,
            const Glib::ustring& interface_name,
            const Glib::ustring& prop_name) {

            auto property_result = slack_get_property(connection->gobj(), sender.data(), obj_path.data(),
                    interface_name.data(), prop_name.data(), nullptr, user_data);
            result.init(property_result, true);
        }
    );

    try
    {
        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(), 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 on_timedate_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);
}

gboolean timeout_callback (Glib::RefPtr<Glib::MainLoop> loop2quit) {
	loop2quit->quit();
	return false;
}

int main(int argc, char **argv)
{
    Gio::init();
    auto timedate1 = std::make_unique<dlackware::timedate::timedate1>();

    guint owner_id = Gio::DBus::own_name(Gio::DBus::BUS_TYPE_SYSTEM, BUS_NAME,
            [&timedate1](const Glib::RefPtr<Gio::DBus::Connection>& connection, const Glib::ustring& name) {
                on_timedate_acquired(connection, name, timedate1.get());
            }, Gio::DBus::SlotNameAcquired(), &on_timedate_lost,
            Gio::DBus::BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT | Gio::DBus::BUS_NAME_OWNER_FLAGS_REPLACE);

    Glib::RefPtr<Glib::MainLoop> loop = Glib::MainLoop::create(false);

    Glib::signal_timeout().connect_seconds(sigc::bind(&timeout_callback, loop), DEFAULT_EXIT_SEC);
	loop->run();

    Gio::DBus::unown_name(owner_id);

	return EXIT_SUCCESS;
}

namespace dlackware::timedate
{
    void timedate1::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);
            }
        }
    }

    Glib::Variant<std::vector<Glib::ustring>> timedate1::list_timezones()
    {
        std::vector<Glib::ustring> result;

        list_timezones("", result);
        return Glib::Variant<std::vector<Glib::ustring>>::create(result);
    }

    Glib::ustring timedate1::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() + strlen(zoneinfo_database) + 1 };
    }

    bool timedate1::set_timezone(gchar *zone, std::error_code& ec)
    {
        ec.clear();
        auto zone_file = std::filesystem::path("/usr/share/zoneinfo") / zone;

        if (!std::filesystem::is_regular_file(zone_file, ec) || ec)
        {
            return false;
        }
        std::filesystem::path etc_localtime = "/etc/localtime";

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

        return !ec;
    }
}

gboolean slack_set_time(gint64 seconds_since_epoch, gboolean relative)
{
    timespec ts;

    if (relative)
    {
        if (clock_gettime(CLOCK_REALTIME, &ts) == -1)
        {
            return FALSE;
        }
        ts.tv_sec += static_cast<time_t>(seconds_since_epoch / USEC_PER_SEC);
        ts.tv_nsec += (seconds_since_epoch % USEC_PER_SEC) * NSEC_PER_USEC;

        if (ts.tv_nsec < 0)
        {
            --ts.tv_sec;
            ts.tv_nsec += USEC_PER_SEC;
        }
    }
    else
    {
        ts.tv_sec = static_cast<time_t>(seconds_since_epoch / USEC_PER_SEC);
        ts.tv_nsec = (seconds_since_epoch % USEC_PER_SEC) * NSEC_PER_USEC;
    }
    return clock_settime (CLOCK_REALTIME, &ts) == 0;
}

gboolean slack_get_is_localtime()
{
    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;
}

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

gboolean slack_set_ntp(gboolean xntp)
{
    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 (xntp)
    {
        rc_mode |= std::filesystem::perms::owner_exec
            | std::filesystem::perms::group_exec | std::filesystem::perms::others_exec;
        g_message("Please don't forget to configure the NTP daemon");

        /* It doesn't matter if fails.
         * The ntpdate command is considered obsolete, but "orthodox" ntpd -g
         * will fail if your system clock is off for more than half an hour. */
        g_spawn_command_line_async("/usr/sbin/ntpdate pool.ntp.org", NULL);
    }
    if (Glib::file_test("/etc/rc.d/rc.ntpd", Glib::FileTest::FILE_TEST_IS_REGULAR))
    {
        std::error_code ec;
        std::filesystem::permissions("/etc/rc.d/rc.ntpd", rc_mode, ec);
        return !ec;
    }
    else
    {
        g_error("The NTP daemon isn't installed");
        return false;
    }
}