// SPDX-License-Identifier: BSD-2-Clause
// author: Max Kellermann <max.kellermann@gmail.com>

#include "Util.hxx"
#include "system/Error.hxx"

#ifdef __linux__
#include <sched.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <dbus/dbus.h>
#include <string.h>
#include <sys/types.h>
#include <errno.h>
#include "lib/fmt/RuntimeError.hxx"
#elif defined(_WIN32)
#include <windows.h>
#endif


#ifdef __linux__
const char* RTKIT_SERVICE_NAME = "org.freedesktop.RealtimeKit1";
const char* RTKIT_OBJECT_PATH = "/org/freedesktop/RealtimeKit1";

// static int
// rtkit_get_max_realtime_priority(DBusConnection &connection)
// {
//   // TODO: Implement this function
//   DBusError error;
// }

// static void
// rtkit_make_realtime(DBusConnection &connection, pid_t thread, int priority)
// {
//   // TODO: Implement this function

// }
#endif

// TODO: minimize and drop
#ifdef __linux__

#define RTKIT_SERVICE_NAME "org.freedesktop.RealtimeKit1"
#define RTKIT_OBJECT_PATH "/org/freedesktop/RealtimeKit1"

static pid_t _gettid(void) {
        return (pid_t) syscall(SYS_gettid);
}

static int translate_error(const char *name) {
        if (strcmp(name, DBUS_ERROR_NO_MEMORY) == 0)
                return -ENOMEM;
        if (strcmp(name, DBUS_ERROR_SERVICE_UNKNOWN) == 0 ||
            strcmp(name, DBUS_ERROR_NAME_HAS_NO_OWNER) == 0)
                return -ENOENT;
        if (strcmp(name, DBUS_ERROR_ACCESS_DENIED) == 0 ||
            strcmp(name, DBUS_ERROR_AUTH_FAILED) == 0)
                return -EACCES;

        return -EIO;
}

static long long rtkit_get_int_property(DBusConnection *connection, const char* propname, long long* propval) {
        DBusMessage *m = NULL, *r = NULL;
        DBusMessageIter iter, subiter;
        dbus_int64_t i64;
        dbus_int32_t i32;
        DBusError error;
        int current_type;
        long long ret;
        const char * interfacestr = "org.freedesktop.RealtimeKit1";

        dbus_error_init(&error);

        if (!(m = dbus_message_new_method_call(
                              RTKIT_SERVICE_NAME,
                              RTKIT_OBJECT_PATH,
                              "org.freedesktop.DBus.Properties",
                              "Get"))) {
                ret = -ENOMEM;
                goto finish;
        }

        if (!dbus_message_append_args(
                            m,
                            DBUS_TYPE_STRING, &interfacestr,
                            DBUS_TYPE_STRING, &propname,
                            DBUS_TYPE_INVALID)) {
                ret = -ENOMEM;
                goto finish;
        }

        if (!(r = dbus_connection_send_with_reply_and_block(connection, m, -1, &error))) {
                ret = translate_error(error.name);
                goto finish;
        }

        if (dbus_set_error_from_message(&error, r)) {
                ret = translate_error(error.name);
                goto finish;
        }

        ret = -EBADMSG;
        dbus_message_iter_init(r, &iter);
        while ((current_type = dbus_message_iter_get_arg_type (&iter)) != DBUS_TYPE_INVALID) {

                if (current_type == DBUS_TYPE_VARIANT) {
                        dbus_message_iter_recurse(&iter, &subiter);

                        while ((current_type = dbus_message_iter_get_arg_type (&subiter)) != DBUS_TYPE_INVALID) {

                                if (current_type == DBUS_TYPE_INT32) {
                                        dbus_message_iter_get_basic(&subiter, &i32);
                                        *propval = i32;
                                        ret = 0;
                                }

                                if (current_type == DBUS_TYPE_INT64) {
                                        dbus_message_iter_get_basic(&subiter, &i64);
                                        *propval = i64;
                                        ret = 0;
                                }

                                dbus_message_iter_next (&subiter);
                        }
                }
                dbus_message_iter_next (&iter);
        }

finish:

        if (m)
                dbus_message_unref(m);

        if (r)
                dbus_message_unref(r);

        dbus_error_free(&error);

        return ret;
}

static int rtkit_get_max_realtime_priority(DBusConnection *connection) {
        long long retval;
        int err;

        err = rtkit_get_int_property(connection, "MaxRealtimePriority", &retval);
        return err < 0 ? err : retval;
}

static int rtkit_make_realtime(DBusConnection *connection, pid_t thread, int priority) {
        DBusMessage *m = NULL, *r = NULL;
        dbus_uint64_t u64;
        dbus_uint32_t u32;
        DBusError error;
        int ret;

        dbus_error_init(&error);

        if (thread == 0)
                thread = _gettid();

        if (!(m = dbus_message_new_method_call(
                              RTKIT_SERVICE_NAME,
                              RTKIT_OBJECT_PATH,
                              "org.freedesktop.RealtimeKit1",
                              "MakeThreadRealtime"))) {
                ret = -ENOMEM;
                goto finish;
        }

        u64 = (dbus_uint64_t) thread;
        u32 = (dbus_uint32_t) priority;

        if (!dbus_message_append_args(
                            m,
                            DBUS_TYPE_UINT64, &u64,
                            DBUS_TYPE_UINT32, &u32,
                            DBUS_TYPE_INVALID)) {
                ret = -ENOMEM;
                goto finish;
        }

        if (!(r = dbus_connection_send_with_reply_and_block(connection, m, -1, &error))) {
                ret = translate_error(error.name);
                goto finish;
        }


        if (dbus_set_error_from_message(&error, r)) {
                ret = translate_error(error.name);
                goto finish;
        }

        ret = 0;

finish:

        if (m)
                dbus_message_unref(m);

        if (r)
                dbus_message_unref(r);

        dbus_error_free(&error);

        return ret;
}

#endif

#ifdef __linux__

#ifndef ANDROID

static int
linux_ioprio_set(int which, int who, int ioprio) noexcept
{
	return syscall(__NR_ioprio_set, which, who, ioprio);
}

static void
ioprio_set_idle() noexcept
{
	static constexpr int _IOPRIO_WHO_PROCESS = 1;
	static constexpr int _IOPRIO_CLASS_IDLE = 3;
	static constexpr int _IOPRIO_CLASS_SHIFT = 13;
	static constexpr int _IOPRIO_IDLE =
		(_IOPRIO_CLASS_IDLE << _IOPRIO_CLASS_SHIFT) | 7;

	linux_ioprio_set(_IOPRIO_WHO_PROCESS, 0, _IOPRIO_IDLE);
}

#endif /* !ANDROID */

/**
 * Wrapper for the "sched_setscheduler" system call.  We don't use the
 * one from the C library because Musl has an intentionally broken
 * implementation.
 */
static int
linux_sched_setscheduler(pid_t pid, int sched,
			 const struct sched_param *param) noexcept
{
	return syscall(__NR_sched_setscheduler, pid, sched, param);
}

#endif

void
SetThreadIdlePriority() noexcept
{
#ifdef __linux__
#ifdef SCHED_IDLE
	static struct sched_param sched_param;
	linux_sched_setscheduler(0, SCHED_IDLE, &sched_param);
#endif

#ifndef ANDROID
	/* this system call is forbidden via seccomp on Android 8 and
	   leads to crash (SIGSYS) */
	ioprio_set_idle();
#endif

#elif defined(_WIN32)
	SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_IDLE);
#endif
}

void
SetThreadRealtime()
{
#ifdef __linux__
	struct sched_param sched_param;
	sched_param.sched_priority = 20;

	int policy = SCHED_FIFO;
#ifdef SCHED_RESET_ON_FORK
	policy |= SCHED_RESET_ON_FORK;
#endif

	int res = linux_sched_setscheduler(0, policy, &sched_param);

	if (res < 0 && errno == EPERM) {
		DBusError error;
		DBusConnection *system_bus;

		dbus_error_init(&error);

		system_bus = dbus_bus_get(DBUS_BUS_SYSTEM, &error);
		if (dbus_error_is_set(&error)) {
			throw FmtRuntimeError("could not connect to dbus: %s", error.message);
		}
		dbus_error_free(&error);

		int max_realtime_priority;
		if ((max_realtime_priority = rtkit_get_max_realtime_priority(system_bus)) < 0) {
			dbus_connection_unref(system_bus);
			throw MakeErrno("could not retrieve maximum realtime priority allowed");
		}

		if (max_realtime_priority < sched_param.sched_priority) {
			sched_param.sched_priority = max_realtime_priority;
			/* dbus_connection_unref(system_bus); */
			/* throw MakeErrno("maximum realtime priority is below 40"); */
		}

		if (rtkit_make_realtime(system_bus, 0, sched_param.sched_priority) < 0) {
			dbus_connection_unref(system_bus);
			throw MakeErrno("failed to request realtime scheduling");
		}

		dbus_connection_unref(system_bus);
		res = 0;
	}

	// if (res < 0) {
	// 	throw MakeErrno("sched_setscheduler failed");
	// }
#endif	// __linux__
}