/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008, Digium, Inc.
 *
 * Russell Bryant <russell@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*!
 * \file
 * \author Russell Bryant <russell@digium.com>
 *
 * \brief pthread timing interface
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision$");

#include <math.h>
#include <sys/select.h>

#include "asterisk/module.h"
#include "asterisk/timing.h"
#include "asterisk/utils.h"
#include "asterisk/astobj2.h"
#include "asterisk/time.h"
#include "asterisk/lock.h"

static void *timing_funcs_handle;

static int pthread_timer_open(void);
static void pthread_timer_close(int handle);
static int pthread_timer_set_rate(int handle, unsigned int rate);
static void pthread_timer_ack(int handle, unsigned int quantity);
static int pthread_timer_enable_continuous(int handle);
static int pthread_timer_disable_continuous(int handle);
static enum ast_timer_event pthread_timer_get_event(int handle);
static unsigned int pthread_timer_get_max_rate(int handle);

static struct ast_timing_interface pthread_timing = {
	.name = "pthread",
	.priority = 0, /* use this as a last resort */
	.timer_open = pthread_timer_open,
	.timer_close = pthread_timer_close,
	.timer_set_rate = pthread_timer_set_rate,
	.timer_ack = pthread_timer_ack,
	.timer_enable_continuous = pthread_timer_enable_continuous,
	.timer_disable_continuous = pthread_timer_disable_continuous,
	.timer_get_event = pthread_timer_get_event,
	.timer_get_max_rate = pthread_timer_get_max_rate,
};

/* 1 tick / 10 ms */
#define MAX_RATE 100

static struct ao2_container *pthread_timers;
#define PTHREAD_TIMER_BUCKETS 563

enum {
	PIPE_READ =  0,
	PIPE_WRITE = 1
};

enum pthread_timer_state {
	TIMER_STATE_IDLE,
	TIMER_STATE_TICKING,
};

struct pthread_timer {
	int pipe[2];
	enum pthread_timer_state state;
	unsigned int rate;
	/*! Interval in ms for current rate */
	unsigned int interval;
	unsigned int tick_count;
	unsigned int pending_ticks;
	struct timeval start;
	unsigned int continuous:1;
};

static void pthread_timer_destructor(void *obj);
static struct pthread_timer *find_timer(int handle, int unlinkobj);
static void write_byte(struct pthread_timer *timer);
static void read_pipe(struct pthread_timer *timer, unsigned int num);

/*!
 * \brief Data for the timing thread
 */
static struct {
	pthread_t thread;
	ast_mutex_t lock;
	ast_cond_t cond;
	unsigned int stop:1;
} timing_thread;

static int pthread_timer_open(void)
{
	struct pthread_timer *timer;
	int fd;

	if (!(timer = ao2_alloc(sizeof(*timer), pthread_timer_destructor))) {
		errno = ENOMEM;
		return -1;
	}

	timer->pipe[PIPE_READ] = timer->pipe[PIPE_WRITE] = -1;
	timer->state = TIMER_STATE_IDLE;

	if (pipe(timer->pipe)) {
		ao2_ref(timer, -1);
		return -1;
	}

	ao2_lock(pthread_timers);
	if (!ao2_container_count(pthread_timers)) {
		ast_mutex_lock(&timing_thread.lock);
		ast_cond_signal(&timing_thread.cond);
		ast_mutex_unlock(&timing_thread.lock);
	}
	ao2_link(pthread_timers, timer);
	ao2_unlock(pthread_timers);

	fd = timer->pipe[PIPE_READ];

	ao2_ref(timer, -1);

	return fd;
}

static void pthread_timer_close(int handle)
{
	struct pthread_timer *timer;

	if (!(timer = find_timer(handle, 1))) {
		return;
	}

	ao2_ref(timer, -1);
}

static int pthread_timer_set_rate(int handle, unsigned int rate)
{
	struct pthread_timer *timer;

	if (!(timer = find_timer(handle, 0))) {
		errno = EINVAL;
		return -1;
	}

	if (rate > MAX_RATE) {
		ast_log(LOG_ERROR, "res_timing_pthread only supports timers at a "
				"max rate of %d / sec\n", MAX_RATE);
		errno = EINVAL;
		return -1;
	}

	ao2_lock(timer);

	if ((timer->rate = rate)) {
		timer->interval = roundf(1000.0 / ((float) rate));
		timer->start = ast_tvnow();
		timer->state = TIMER_STATE_TICKING;
	} else {
		timer->interval = 0;
		timer->start = ast_tv(0, 0);
		timer->state = TIMER_STATE_IDLE;
	}
	timer->tick_count = 0;

	ao2_unlock(timer);

	ao2_ref(timer, -1);

	return 0;
}

static void pthread_timer_ack(int handle, unsigned int quantity)
{
	struct pthread_timer *timer;

	ast_assert(quantity > 0);

	if (!(timer = find_timer(handle, 0))) {
		return;
	}

	ao2_lock(timer);
	read_pipe(timer, quantity);
	ao2_unlock(timer);

	ao2_ref(timer, -1);
}

static int pthread_timer_enable_continuous(int handle)
{
	struct pthread_timer *timer;

	if (!(timer = find_timer(handle, 0))) {
		errno = EINVAL;
		return -1;
	}

	ao2_lock(timer);
	if (!timer->continuous) {
		timer->continuous = 1;
		write_byte(timer);
	}
	ao2_unlock(timer);

	ao2_ref(timer, -1);

	return 0;
}

static int pthread_timer_disable_continuous(int handle)
{
	struct pthread_timer *timer;

	if (!(timer = find_timer(handle, 0))) {
		errno = EINVAL;
		return -1;
	}

	ao2_lock(timer);
	if (timer->continuous) {
		timer->continuous = 0;
		read_pipe(timer, 1);
	}
	ao2_unlock(timer);

	ao2_ref(timer, -1);

	return 0;
}

static enum ast_timer_event pthread_timer_get_event(int handle)
{
	struct pthread_timer *timer;
	enum ast_timer_event res = AST_TIMING_EVENT_EXPIRED;

	if (!(timer = find_timer(handle, 0))) {
		return res;
	}

	ao2_lock(timer);
	if (timer->continuous && timer->pending_ticks == 1) {
		res = AST_TIMING_EVENT_CONTINUOUS;
	}
	ao2_unlock(timer);

	ao2_ref(timer, -1);

	return res;
}

static unsigned int pthread_timer_get_max_rate(int handle)
{
	return MAX_RATE;
}

static struct pthread_timer *find_timer(int handle, int unlinkobj)
{
	struct pthread_timer *timer;
	struct pthread_timer tmp_timer;
	int flags = OBJ_POINTER;

	tmp_timer.pipe[PIPE_READ] = handle;

	if (unlinkobj) {
		flags |= OBJ_UNLINK;
	}

	if (!(timer = ao2_find(pthread_timers, &tmp_timer, flags))) {
		ast_assert(timer != NULL);
		return NULL;
	}

	return timer;
}

static void pthread_timer_destructor(void *obj)
{
	struct pthread_timer *timer = obj;

	if (timer->pipe[PIPE_READ] > -1) {
		close(timer->pipe[PIPE_READ]);
		timer->pipe[PIPE_READ] = -1;
	}

	if (timer->pipe[PIPE_WRITE] > -1) {
		close(timer->pipe[PIPE_WRITE]);
		timer->pipe[PIPE_WRITE] = -1;
	}
}

/*!
 * \note only PIPE_READ is guaranteed valid
 */
static int pthread_timer_hash(const void *obj, const int flags)
{
	const struct pthread_timer *timer = obj;

	return timer->pipe[PIPE_READ];
}

/*!
 * \note only PIPE_READ is guaranteed valid
 */
static int pthread_timer_cmp(void *obj, void *arg, int flags)
{
	struct pthread_timer *timer1 = obj, *timer2 = arg;

	return (timer1->pipe[PIPE_READ] == timer2->pipe[PIPE_READ]) ? CMP_MATCH | CMP_STOP : 0;
}

/*!
 * \retval 0 no timer tick needed
 * \retval non-zero write to the timing pipe needed
 */
static int check_timer(struct pthread_timer *timer)
{
	struct timeval now;

	if (timer->state == TIMER_STATE_IDLE) {
		return 0;
	}

	now = ast_tvnow();

	if (timer->tick_count < (ast_tvdiff_ms(now, timer->start) / timer->interval)) {
		timer->tick_count++;
		if (!timer->tick_count) {
			/* Handle overflow. */
			timer->start = now;
		}
		return 1;
	}

	return 0;
}

/*!
 * \internal
 * \pre timer is locked
 */
static void read_pipe(struct pthread_timer *timer, unsigned int quantity)
{
	int rd_fd = timer->pipe[PIPE_READ];
	int pending_ticks = timer->pending_ticks;

	ast_assert(quantity);

	if (timer->continuous && pending_ticks) {
		pending_ticks--;
	}

	if (quantity > pending_ticks) {
		quantity = pending_ticks;
	}

	if (!quantity) {
		return;
	}

	do {
		unsigned char buf[1024];
		ssize_t res;
		fd_set rfds;
		struct timeval timeout = {
			.tv_sec = 0,
		};

		/* Make sure there is data to read */
		FD_ZERO(&rfds);
		FD_SET(rd_fd, &rfds);

		if (select(rd_fd + 1, &rfds, NULL, NULL, &timeout) != 1) {
			ast_debug(1, "Reading not available on timing pipe, "
					"quantity: %u\n", quantity);
			break;
		}

		res = read(rd_fd, buf,
			(quantity < sizeof(buf)) ? quantity : sizeof(buf));

		if (res == -1) {
			if (errno == EAGAIN) {
				continue;
			}
			ast_log(LOG_ERROR, "read failed on timing pipe: %s\n",
					strerror(errno));
			break;
		}

		quantity -= res;
		timer->pending_ticks -= res;
	} while (quantity);
}

/*!
 * \internal
 * \pre timer is locked
 */
static void write_byte(struct pthread_timer *timer)
{
	ssize_t res;
	unsigned char x = 42;

	do {
		res = write(timer->pipe[PIPE_WRITE], &x, 1);
	} while (res == -1 && errno == EAGAIN);

	if (res == -1) {
		ast_log(LOG_ERROR, "Error writing to timing pipe: %s\n",
				strerror(errno));
	} else {
		timer->pending_ticks++;
	}
}

static int run_timer(void *obj, void *arg, int flags)
{
	struct pthread_timer *timer = obj;

	if (timer->state == TIMER_STATE_IDLE) {
		return 0;
	}

	ao2_lock(timer);
	if (check_timer(timer)) {
		write_byte(timer);
	}
	ao2_unlock(timer);

	return 0;
}

static void *do_timing(void *arg)
{
	struct timeval next_wakeup = ast_tvnow();

	while (!timing_thread.stop) {
		struct timespec ts = { 0, };

		ao2_callback(pthread_timers, OBJ_NODATA, run_timer, NULL);

		next_wakeup = ast_tvadd(next_wakeup, ast_tv(0, 5000));

		ts.tv_sec = next_wakeup.tv_sec;
		ts.tv_nsec = next_wakeup.tv_usec * 1000;

		ast_mutex_lock(&timing_thread.lock);
		if (!timing_thread.stop) {
			if (ao2_container_count(pthread_timers)) {
				ast_cond_timedwait(&timing_thread.cond, &timing_thread.lock, &ts);
			} else {
				ast_cond_wait(&timing_thread.cond, &timing_thread.lock);
			}
		}
		ast_mutex_unlock(&timing_thread.lock);
	}

	return NULL;
}

static int init_timing_thread(void)
{
	ast_mutex_init(&timing_thread.lock);
	ast_cond_init(&timing_thread.cond, NULL);

	if (ast_pthread_create_background(&timing_thread.thread, NULL, do_timing, NULL)) {
		ast_log(LOG_ERROR, "Unable to start timing thread.\n");
		return -1;
	}

	return 0;
}

static int load_module(void)
{
	if (!(pthread_timers = ao2_container_alloc(PTHREAD_TIMER_BUCKETS,
		pthread_timer_hash, pthread_timer_cmp))) {
		return AST_MODULE_LOAD_DECLINE;
	}

	if (init_timing_thread()) {
		ao2_ref(pthread_timers, -1);
		pthread_timers = NULL;
		return AST_MODULE_LOAD_DECLINE;
	}

	return (timing_funcs_handle = ast_register_timing_interface(&pthread_timing)) ?
		AST_MODULE_LOAD_SUCCESS : AST_MODULE_LOAD_DECLINE;
}

static int unload_module(void)
{
	int res;

	ast_mutex_lock(&timing_thread.lock);
	timing_thread.stop = 1;
	ast_cond_signal(&timing_thread.cond);
	ast_mutex_unlock(&timing_thread.lock);
	pthread_join(timing_thread.thread, NULL);

	if (!(res = ast_unregister_timing_interface(timing_funcs_handle))) {
		ao2_ref(pthread_timers, -1);
		pthread_timers = NULL;
	}

	return res;
}
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "pthread Timing Interface",
		.load = load_module,
		.unload = unload_module,
		.load_pri = 10,
		);