/*
 * Copyright (C) 2019 Weber Yann
 * 
 * This file is part of PyFCGI.
 * 
 * PyFCGI is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * any later version.
 * 
 * PyFCGI 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 Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with PyFCGI.  If not, see <http://www.gnu.org/licenses/>.
 */
/**@defgroup stats PyFCGI statistics
 * @brief Information about statistics collection mechanism
 * @ingroup monitor_proc
 */
/**@file stats.h
 * @ingroup monitoring */
#ifndef _STATS__H___
#define _STATS__H___
#include "config.h"

#include <fcgiapp.h>

#include <stdarg.h>
#include <signal.h>
#include <string.h>

/**@brief Stats history size (900 = 900s = 15min) */
#define PYFCGI_STATS_SZ (900)
/**@brief Signal used to wake up stats server in order to collect stats*/
#define PYFCGI_STATS_SIGALRM 30

typedef struct pyfcgi_stats_s pyfcgi_stats_t;
typedef struct pyfcgi_stats_sample_s pyfcgi_stats_sample_t;
typedef struct pyfcgi_stats_shm_s pyfcgi_stats_shm_t;

#include "conf.h"
#include "logger.h"

/**@brief Stores data for stats on 15min (900s)
 * @ingroup stats
 */
struct pyfcgi_stats_sample_s
{
	/**@brief One sample per seconds */
	int samples[PYFCGI_STATS_SZ];
	/**@brief Current sample */
	int cur;
};

/**@brief Stores statistics informations
 * @ingroup stats
 */
struct pyfcgi_stats_s
{
	/**@brief Request per seconds on 15 minutes */
	pyfcgi_stats_sample_t reqs;
	/**@brief Worker count */
	pyfcgi_stats_sample_t wcount;
	/**@brief Load */
	pyfcgi_stats_sample_t load;

	/**@brief Repeating 1s timer sending SIGALRM */
	timer_t timerid;

	/**@brief Old SIGALRM handler */
	struct sigaction oldact;

	/**@brief Buffer to format the statistics before sending them */
	char *buff;
	size_t buff_ptr;
	size_t buff_len;
};

/**@brief Stores stats information on worker count & load average
 * @note Data are updated by @ref work_master_proc
 */
struct pyfcgi_stats_shm_s
{
	/**@brief Workers count */
	int nworker;
	/**@brief Load average */
	int pool_load;
};

/**@brief Starts collecting statistics
 *
 * Set an handler for SIGALRM and set a repeating alarm each seconds
 * @warning designed to be called from monitor server process
 * @return -1 on error else 0
 * @ingroup stats
 */
int pyfcgi_stats_init();

/**@brief SIGALRM signal handler
 * @param signum
 */
void pyfcgi_stats_collector(int signum);

/**@brief Format all stats in a buffer
 * @note uses the pyfcgi_stats.statsbuff buffer */
size_t pyfcgi_stats_format();

/**@brief Print in buffer using buff_ptr index
 *@note exit on mem alloc failure
 */
void pyfcgi_stats_buffprintf(const char *fmt, ...);

/**@brief Allocate the buffer with at least given space
 * @param sz the minimum buffer size
 * @note allocation size is rounded
 * @return 0 if OK else -1
 */
int pyfcgi_stats_reqbuff(size_t sz);

/**@brief Returns statistics about a 900s ringbuffer
 *
 * @param data a 900 ringbuffer stats samples
 * @param idx_nxt next data index in ring buffer (allow interrupt
 * detection : when *idx_nxt changes)
 * @param *last : last sample
 * @param avgs : average samples on 1, 5, 10 and 15 minutes
 * @return 0 if no error else -1 and set errno to EINTR
 */
int pyfcgi_stats_avg(const int data[PYFCGI_STATS_SZ], int* idx_nxt, int* last,
	double avgs[4]);
/**@brief Same than @ref pyfcgi_stats_avg but normalize average when
 * uptime is bellow 900
 * @see pyfcgi_stats_avg
 * @param data a 900 ringbuffer stats samples
 * @param idx_nxt next data index in ring buffer (allow interrupt
 * detection : when *idx_nxt changes)
 * @param *last : last sample
 * @param avgs : average samples on 1, 5, 10 and 15 minutes
 * @return 0 if no error else -1 and set errno to EINTR
 */
int pyfcgi_stats_avg_const(const int data[PYFCGI_STATS_SZ], int* idx_nxt, int* last,
	double avgs[4]);

/**@brief Returns the formated buffer
 * @todo make @ref pyfcgi_stats_format() implement this functionnality
 * to remove this function... */
const char *pyfcgi_stats_buff(const char **, size_t*);

/**@brief Fetch stats informations from dedicated SHM
 * @see pyfcgi_stats_shm_s
 */
int pyfcgi_stats_get_shm(pyfcgi_stats_shm_t*);

#endif