/**
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * Set of functions to gather system information for the jack setup wizard.
 *
 * TODO: Test for rt prio availability
 *
 * @author Florian Faber, faber@faberman.de
 *
 **/

/** maximum number of groups a user can be a member of **/
#define MAX_GROUPS 100

#include <fcntl.h>

#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <grp.h>

#include <sched.h>
#include <string.h>

#include <sys/time.h>
#include <sys/resource.h>

#include <stdio.h>
#include <errno.h>

#include "systemtest.h"

/**
 * This function checks for the existence of known frequency scaling mechanisms
 * in this system by testing for the availability of scaling governors/
 *
 * @returns 0 if the system has no frequency scaling capabilities non-0 otherwise.
 **/
int system_has_frequencyscaling ()
{
	int fd;

	fd = open ("/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors", O_RDONLY);

	if (-1 == fd) {
		return 0;
	}

	(void)close (fd);

	return 1;
}


static int read_string (char* filename, char* buf, size_t buflen)
{
	int fd;
	ssize_t r = -1;

	memset (buf, 0, buflen);

	fd = open (filename, O_RDONLY);
	if (-1 < fd) {
		r = read (fd, buf, buflen - 1);
		(void)close (fd);

		if (-1 == r) {
			fprintf (stderr, "Error while reading \"%s\": %s\n", filename, strerror (errno));
			exit (EXIT_FAILURE);
		}
	}

	return (int)r;
}


static int read_int (char* filename, int* value)
{
	char buf[20];

	if (0 < read_string (filename, buf, 20)) {
		return 1 == sscanf (buf, "%d", value);
	}

	return 0;
}


/**
 * This function determines wether any CPU core uses a variable clock speed if frequency
 * scaling is available. If the governor for all cores is either "powersave" or
 * "performance", the CPU frequency can be assumed to be static. This is also the case
 * if scaling_min_freq and scaling_max_freq are set to the same value.
 *
 * @returns 0 if system doesn't use frequency scaling at the moment, non-0 otherwise
 **/
int system_uses_frequencyscaling ()
{
	int cpu = 0, done = 0, min, max;
	char filename[256], buf[256];

	while (!done) {
		(void)snprintf (filename, 256, "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor", cpu);
		if (0 < read_string (filename, buf, 256)) {
			if ((0 != strncmp ("performance", buf, 11)) &&
			    (0 != strncmp ("powersafe", buf, 9))) {
				// So it's neither the "performance" nor the "powersafe" governor
				(void)snprintf (filename, 256, "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_min_freq", cpu);
				if (read_int (filename, &min)) {
					(void)snprintf (filename, 256, "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_max_freq", cpu);
					if (read_int (filename, &max)) {
						if (min != max) {
							// wrong governor AND different frequency limits -> scaling
							return 1;
						}
					}
				}
			}
		} else {
			// couldn't open file -> no more cores
			done = 1;
		}
		cpu++;
	}

	// couldn't find anything that points to scaling
	return 0;
}


static gid_t get_group_by_name (const char* name)
{
	struct group* grp;
	gid_t res = 0;

	while ((0 == res) && (NULL != (grp = getgrent ()))) {
		if (0 == strcmp (name, grp->gr_name)) {
			res = grp->gr_gid;
		}
	}

	endgrent ();

	return res;
}

/***
 * Checks for a definition in /etc/security/limits.conf that looks
 * as if it allows RT scheduling priority.
 *
 * @returns 1 if there appears to be such a line
 **/
int system_has_rtprio_limits_conf ()
{
	const char* limits = "/etc/security/limits.conf";
	char cmd[100];

	snprintf (cmd, sizeof(cmd), "grep -q 'rtprio *[0-9][0-9]*' %s", limits);
	if (system (cmd) == 0) {
		return 1;
	}
	return 0;
}


/**
 * Checks for the existence of the 'audio' group on this system
 *
 * @returns 0 is there is no 'audio' group, the group id otherwise
 **/
int system_has_audiogroup ()
{
	return get_group_by_name ("audio") || get_group_by_name ("jackuser");
}


/**
 * Tests wether the owner of this process is in the 'audio' group.
 *
 * @returns 0 if the owner of this process is not in the audio group, non-0 otherwise
 **/
int system_user_in_audiogroup ()
{
	gid_t* list = (gid_t*)malloc (MAX_GROUPS * sizeof(gid_t));
	int num_groups, i = 0, found = 0;
	unsigned int gid;

	if (NULL == list) {
		perror ("Cannot allocate group list structure");
		exit (EXIT_FAILURE);
	}

	gid = get_group_by_name ("audio");
	if (0 == gid) {
		fprintf (stderr, "No audio group found\n");
		exit (EXIT_FAILURE);
	}

	num_groups = getgroups (MAX_GROUPS, list);

	while (i < num_groups) {
		if (list[i] == gid) {
			found = 1;
			i = num_groups;
		}

		i++;
	}

	free (list);

	return found;
}


/**
 * Determines wether the owner of this process can enable rt priority.
 *
 * @returns 0 if this process can not be switched to rt prio, non-0 otherwise
 **/
int system_user_can_rtprio ()
{
	int min_prio;
	struct sched_param schparam;

	memset (&schparam, 0, sizeof(struct sched_param));

	if (-1 == (min_prio = sched_get_priority_min (SCHED_FIFO))) {
		perror ("sched_get_priority");
		exit (EXIT_FAILURE);
	}
	schparam.sched_priority = min_prio;

	if (0 == sched_setscheduler (0, SCHED_FIFO, &schparam)) {
		// TODO: restore previous state
		schparam.sched_priority = 0;
		if (0 != sched_setscheduler (0, SCHED_OTHER, &schparam)) {
			perror ("sched_setscheduler");
			exit (EXIT_FAILURE);
		}
		return 1;
	}

	return 0;
}


long long unsigned int system_memlock_amount ()
{
	struct rlimit limits;

	if (-1 == getrlimit (RLIMIT_MEMLOCK, &limits)) {
		perror ("getrlimit on RLIMIT_MEMLOCK");
		exit (EXIT_FAILURE);
	}

	return limits.rlim_max;
}


/**
 * Checks wether the memlock limit is unlimited
 *
 * @returns - 0 if the memlock limit is limited, non-0 otherwise
 **/
int system_memlock_is_unlimited ()
{
	return (RLIM_INFINITY == system_memlock_amount ()) ? 1 : 0;
}


long long unsigned int system_available_physical_mem ()
{
	char buf[256];
	long long unsigned int res = 0;

	if (0 < read_string ("/proc/meminfo", buf, sizeof(buf))) {
		if (strncmp (buf, "MemTotal:", 9) == 0) {
			if (sscanf (buf, "%*s %llu", &res) != 1) {
				perror ("parse error in /proc/meminfo");
			}
		}
	} else {
		perror ("read from /proc/meminfo");
	}

	return res * 1024;
}


/**
 * Gets the version of the currently running kernel. The string
 * returned has to be freed by the caller.
 *
 * @returns String with the full version of the kernel
 **/
char* system_kernel_version ()
{
	return NULL;
}



char* system_get_username ()
{
	char* res = NULL;
	char* name = NULL;

	if ((name = getlogin ())) {
		res = strdup (name);
	}

	return res;
}
