/*
 * Copyright (C) 1997-2009 Andre Noll <maan@systemlinux.org>
 *
 * Licensed under the GPL v2. For licencing details see COPYING.
 */

/** \file daemon.c Some helpers for programs that detach from the console. */
#include "para.h"
#include "daemon.h"
#include <pwd.h>
#include <sys/types.h> /* getgrnam() */
#include <grp.h>

#include "string.h"
#include "color.h"

/** The internal state of the daemon. */
struct daemon {
	/** See \ref daemon_flags. */
	unsigned flags;
	/** Set by \ref daemon_set_logfile(). */
	char *logfile_name;
	/** Current loglevel, see \ref daemon_set_loglevel(). */
	int loglevel;

	/** Used by \ref server_uptime() and \ref uptime_str(). */
	time_t startuptime;
	/** The file pointer if the logfile is open. */
	FILE *logfile;
	/** Used by para_log() if \p DF_LOG_HOSTNAME is set. */
	char *hostname;
	/** Used for colored log messages. */
	char log_colors[NUM_LOGLEVELS][COLOR_MAXLEN];
};

static struct daemon the_daemon, *me = &the_daemon;

/**
 * Activate default log colors.
 *
 * This should be called early if color support is wanted.
 */
void daemon_set_default_log_colors(void)
{
	int i;
	static const char *default_log_colors[NUM_LOGLEVELS] = {
		[LL_DEBUG] = "normal",
		[LL_INFO] = "normal",
		[LL_NOTICE] = "normal",
		[LL_WARNING] = "yellow",
		[LL_ERROR] = "red",
		[LL_CRIT] = "magenta bold",
		[LL_EMERG] = "red bold",
	};
	for (i = 0; i < NUM_LOGLEVELS; i++) {
		int ret = color_parse(default_log_colors[i], me->log_colors[i]);
		assert(ret >= 0);
	}
}

/**
 * Set the color for one loglevel.
 *
 * \param arg The loglevel/color specifier.
 *
 * \a arg must be of the form "ll:[fg [bg]] [attr]".
 *
 * \return 1 On success, -1 on errors.
 */
int daemon_set_log_color(char const *arg)
{
	char *p = strchr(arg, ':');
	int ret, ll;

	if (!p)
		goto err;
	ret = get_loglevel_by_name(arg);
	if (ret < 0)
		goto err;
	ll = ret;
	p++;
	ret = color_parse(p, me->log_colors[ll]);
	if (ret < 0)
		goto err;
	return 1;
err:
	PARA_ERROR_LOG("%s: color syntax error\n", arg);
	return -1;

}

/**
 * Init or change the name of the log file.
 *
 * \param logfile_name The full path of the logfile.
 */
void daemon_set_logfile(char *logfile_name)
{
	free(me->logfile_name);
	me->logfile_name = NULL;
	if (logfile_name)
		me->logfile_name = para_strdup(logfile_name);
}

/**
 * Suppress log messages with severity lower than the given loglevel.
 *
 * \param loglevel The smallest level that should be logged.
 */
void daemon_set_loglevel(char *loglevel)
{
	int ret = get_loglevel_by_name(loglevel);

	assert(ret >= 0);
	me->loglevel = ret;
}

/**
 * Set one of the daemon config flags.
 *
 * \param flag The flag to set.
 *
 * \sa \ref daemon_flags.
 */
void daemon_set_flag(unsigned flag)
{
	me->flags |= flag;
}

/**
 * Clear one of the daemon config flags.
 *
 * \param flag The flag to clear.
 *
 * \sa \ref daemon_flags.
 */
void daemon_clear_flag(unsigned flag)
{
	me->flags &= ~flag;
}

static unsigned daemon_test_flag(unsigned flag)
{
	return me->flags & flag;
}

/**
 * Do the usual stuff to become a daemon.
 *
 * Fork, become session leader, dup fd 0, 1, 2 to /dev/null.
 *
 * \sa fork(2), setsid(2), dup(2).
 */
void daemonize(void)
{
	pid_t pid;
	int null;

	PARA_INFO_LOG("daemonizing\n");
	pid = fork();
	if (pid < 0)
		goto err;
	if (pid)
		exit(EXIT_SUCCESS); /* parent exits */
	/* become session leader */
	if (setsid() < 0)
		goto err;
	if (chdir("/") < 0)
		goto err;
	null = open("/dev/null", O_RDONLY);
	if (null < 0)
		goto err;
	if (dup2(null, STDIN_FILENO) < 0)
		goto err;
	if (dup2(null, STDOUT_FILENO) < 0)
		goto err;
	if (dup2(null, STDERR_FILENO) < 0)
		goto err;
	close(null);
	return;
err:
	PARA_EMERG_LOG("fatal: %s\n", strerror(errno));
	exit(EXIT_FAILURE);
}

/**
 * Close the log file of the daemon.
 */
void daemon_close_log(void)
{
	if (!me->logfile)
		return;
	PARA_INFO_LOG("closing logfile\n");
	fclose(me->logfile);
	me->logfile = NULL;
}

/**
 * fopen() the logfile in append mode.
 *
 * \return Either succeeds or exits.
 */
void daemon_open_log_or_die(void)
{
	daemon_close_log();
	if (!me->logfile_name)
		return;
	me->logfile = fopen(me->logfile_name, "a");
	if (!me->logfile) {
		PARA_EMERG_LOG("can not open %s: %s\n", me->logfile_name,
			strerror(errno));
		exit(EXIT_FAILURE);
	}
	setlinebuf(me->logfile);
}

/**
 * Log the startup message containing the paraslash version.
 */
void log_welcome(const char *whoami)
{
	PARA_INFO_LOG("welcome to %s " PACKAGE_VERSION " ("BUILD_DATE")\n",
		whoami);
}

/**
 * Give up superuser privileges.
 *
 * \param username The user to switch to.
 * \param groupname The group to switch to.
 *
 * This function returns immediately if not invoked with EUID zero. Otherwise,
 * it tries to obtain the GID of \a groupname and the UID of \a username.  On
 * success, effective and real GID/UID and the saved set-group-ID/set-user-ID
 * are all set accordingly. On errors, an appropriate message is logged and
 * exit() is called to terminate the process.
 *
 * \sa getpwnam(3), getuid(2), setuid(2), getgrnam(2), setgid(2)
 */
void drop_privileges_or_die(const char *username, const char *groupname)
{
	struct passwd *p;
	char *tmp;

	if (geteuid())
		return;
	if (groupname) {
		struct group *g = getgrnam(groupname);
		if (!g) {
			PARA_EMERG_LOG("failed to get group %s: %s\n",
				groupname, strerror(errno));
			exit(EXIT_FAILURE);
		}
		if (setgid(g->gr_gid) < 0) {
			PARA_EMERG_LOG("failed to set group id %d: %s\n",
				(int)g->gr_gid, strerror(errno));
			exit(EXIT_FAILURE);
		}
	}
	if (!username) {
		PARA_EMERG_LOG("root privileges, but no user option given\n");
		exit(EXIT_FAILURE);
	}
	tmp = para_strdup(username);
	p = getpwnam(tmp);
	free(tmp);
	if (!p) {
		PARA_EMERG_LOG("%s: no such user\n", username);
		exit(EXIT_FAILURE);
	}
	PARA_INFO_LOG("dropping root privileges\n");
	if (setuid(p->pw_uid) < 0) {
		PARA_EMERG_LOG("failed to set effective user ID (%s)",
			strerror(errno));
		exit(EXIT_FAILURE);
	}
	PARA_DEBUG_LOG("uid: %d, euid: %d\n", (int)getuid(), (int)geteuid());
}

/**
 * Set/get the server uptime.
 *
 * \param set_or_get Chose one of the two modes.
 *
 * This should be called at startup time with \a set_or_get equal to \p
 * UPTIME_SET which sets the uptime to zero.  Subsequent calls with \a
 * set_or_get equal to \p UPTIME_GET return the uptime.

 * \return Zero if called with \a set_or_get equal to \p UPTIME_SET, the number
 * of seconds elapsed since the last reset otherwise.
 *
 * \sa time(2), difftime(3).
 */
time_t server_uptime(enum uptime set_or_get)
{
	time_t now;
	double diff;

	if (set_or_get == UPTIME_SET) {
		time(&me->startuptime);
		return 0;
	}
	time(&now);
	diff = difftime(now, me->startuptime);
	return (time_t) diff;
}

/**
 * Construct string containing uptime.
 *
 * \return A dynamically allocated string of the form "days:hours:minutes".
 *
 * \sa server_uptime.
 */
__malloc char *uptime_str(void)
{
	long t = server_uptime(UPTIME_GET);
	return make_message("%li:%02li:%02li", t / 86400,
		(t / 3600) % 24, (t / 60) % 60);
}

/**
 * The log function for para_server and para_audiod.
 *
 * \param ll The log level.
 * \param fmt The format string describing the log message.
 */
__printf_2_3 void para_log(int ll, const char* fmt,...)
{
	va_list argp;
	FILE *fp;
	struct tm *tm;
	time_t t1;
	char *color;

	ll = PARA_MIN(ll, NUM_LOGLEVELS - 1);
	ll = PARA_MAX(ll, LL_DEBUG);
	if (ll < me->loglevel)
		return;

	fp = me->logfile? me->logfile : stderr;
	color = daemon_test_flag(DF_COLOR_LOG)? me->log_colors[ll] : NULL;
	if (color)
		fprintf(fp, "%s", color);
	if (daemon_test_flag(DF_LOG_TIME)) { /* print date and time */
		char str[100];
		time(&t1);
		tm = localtime(&t1);
		strftime(str, sizeof(str), "%b %d %H:%M:%S", tm);
		fprintf(fp, "%s ", str);
	}
	if (daemon_test_flag(DF_LOG_HOSTNAME)) {
		if (!me->hostname)
			me->hostname = para_hostname();
		fprintf(fp, "%s ", me->hostname);
	}
	if (daemon_test_flag(DF_LOG_LL)) /* log loglevel */
		fprintf(fp, "(%d) ", ll);
	if (daemon_test_flag(DF_LOG_PID)) { /* log pid */
		pid_t mypid = getpid();
		fprintf(fp, "(%d) ", (int)mypid);
	}
	va_start(argp, fmt);
	vfprintf(fp, fmt, argp);
	va_end(argp);
	if (color)
		fprintf(fp, "%s", COLOR_RESET);
}