/*
 * Event Loop
 *
 * Copyright (c) 2011 David Herrmann <dh.herrmann@googlemail.com>
 * Copyright (c) 2011 University of Tuebingen
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files
 * (the "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * Event Loop
 * This provides a basic event loop similar to those provided by glib etc.
 * It uses linux specific features like signalfd so it may not be easy to port
 * it to other platforms.
 */

#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/signalfd.h>
#include <sys/time.h>
#include <sys/timerfd.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>
#include "eloop.h"
#include "log.h"
#include "misc.h"

#define LOG_SUBSYSTEM "eloop"

struct ev_signal_shared {
	struct ev_signal_shared *next;

	struct ev_fd *fd;
	int signum;
	struct kmscon_hook *hook;
};

struct ev_eloop {
	int efd;
	unsigned long ref;
	struct ev_fd *fd;

	struct ev_idle *idle_list;
	struct ev_idle *cur_idle;

	struct ev_signal_shared *sig_list;

	struct epoll_event *cur_fds;
	size_t cur_fds_cnt;
	bool exit;
};

struct ev_idle {
	unsigned long ref;
	struct ev_eloop *loop;
	struct ev_idle *next;
	struct ev_idle *prev;

	ev_idle_cb cb;
	void *data;
};

struct ev_fd {
	unsigned long ref;
	struct ev_eloop *loop;

	ev_fd_cb cb;
	void *data;
	int fd;
};

struct ev_timer {
	unsigned long ref;

	struct ev_fd *fd;
	ev_timer_cb cb;
	void *data;
};

int ev_eloop_new_eloop(struct ev_eloop *loop, struct ev_eloop **out)
{
	struct ev_eloop *el;
	int ret;

	if (!out || !loop)
		return -EINVAL;

	ret = ev_eloop_new(&el);
	if (ret)
		return ret;

	ret = ev_eloop_add_eloop(loop, el);
	if (ret) {
		ev_eloop_unref(el);
		return ret;
	}

	ev_eloop_unref(el);
	*out = el;
	return 0;
}

static void eloop_cb(struct ev_fd *fd, int mask, void *data)
{
	struct ev_eloop *eloop = data;

	if (mask & EV_READABLE)
		ev_eloop_dispatch(eloop, 0);
	if (mask & (EV_HUP | EV_ERR))
		log_warn("HUP/ERR on eloop source");
}

int ev_eloop_add_eloop(struct ev_eloop *loop, struct ev_eloop *add)
{
	int ret;

	if (!loop || !add)
		return -EINVAL;

	if (add->fd->loop)
		return -EALREADY;

	/* This adds the epoll-fd into the parent epoll-set. This works
	 * perfectly well with registered FDs, timers, etc. However, we use
	 * shared signals in this event-loop so if the parent and child have
	 * overlapping shared-signals, then the signal will be randomly
	 * delivered to either the parent-hook or child-hook but never both.
	 * TODO:
	 * We may fix this by linking the childs-sig_list into the parent's
	 * siglist but we didn't need this, yet, so ignore it here.
	 */

	ret = ev_eloop_add_fd(loop, add->fd, add->efd, EV_READABLE,
							eloop_cb, add);
	if (ret)
		return ret;

	ev_eloop_ref(add);
	return 0;
}

void ev_eloop_rm_eloop(struct ev_eloop *rm)
{
	if (!rm || !rm->fd->loop)
		return;

	ev_eloop_rm_fd(rm->fd);
	ev_eloop_unref(rm);
}

int ev_idle_new(struct ev_idle **out)
{
	struct ev_idle *idle;

	if (!out)
		return -EINVAL;

	idle = malloc(sizeof(*idle));
	if (!idle)
		return -ENOMEM;

	memset(idle, 0, sizeof(*idle));
	idle->ref = 1;

	*out = idle;
	return 0;
}

void ev_idle_ref(struct ev_idle *idle)
{
	if (!idle)
		return;

	++idle->ref;
}

void ev_idle_unref(struct ev_idle *idle)
{
	if (!idle || !idle->ref || --idle->ref)
		return;

	free(idle);
}

int ev_eloop_new_idle(struct ev_eloop *loop, struct ev_idle **out,
			ev_idle_cb cb, void *data)
{
	struct ev_idle *idle;
	int ret;

	if (!out || !loop || !cb)
		return -EINVAL;

	ret = ev_idle_new(&idle);
	if (ret)
		return ret;

	ret = ev_eloop_add_idle(loop, idle, cb, data);
	if (ret) {
		ev_idle_unref(idle);
		return ret;
	}

	ev_idle_unref(idle);
	*out = idle;
	return 0;
}

int ev_eloop_add_idle(struct ev_eloop *loop, struct ev_idle *idle,
			ev_idle_cb cb, void *data)
{
	if (!loop || !idle || !cb)
		return -EINVAL;

	if (idle->next || idle->prev || idle->loop)
		return -EALREADY;

	idle->next = loop->idle_list;
	if (idle->next)
		idle->next->prev = idle;
	loop->idle_list = idle;

	idle->loop = loop;
	idle->cb = cb;
	idle->data = data;

	ev_idle_ref(idle);
	ev_eloop_ref(loop);

	return 0;
}

void ev_eloop_rm_idle(struct ev_idle *idle)
{
	struct ev_eloop *loop;

	if (!idle || !idle->loop)
		return;

	loop = idle->loop;

	/*
	 * If the loop is currently dispatching, we need to check whether we are
	 * the current element and correctly set it to the next element.
	 */
	if (loop->cur_idle == idle)
		loop->cur_idle = idle->next;

	if (idle->prev)
		idle->prev->next = idle->next;
	if (idle->next)
		idle->next->prev = idle->prev;
	if (loop->idle_list == idle)
		loop->idle_list = idle->next;

	idle->next = NULL;
	idle->prev = NULL;
	idle->loop = NULL;
	idle->cb = NULL;
	idle->data = NULL;

	ev_idle_unref(idle);
	ev_eloop_unref(loop);
}

int ev_fd_new(struct ev_fd **out)
{
	struct ev_fd *fd;

	if (!out)
		return -EINVAL;

	fd = malloc(sizeof(*fd));
	if (!fd)
		return -ENOMEM;

	memset(fd, 0, sizeof(*fd));
	fd->ref = 1;
	fd->fd = -1;

	*out = fd;
	return 0;
}

void ev_fd_ref(struct ev_fd *fd)
{
	if (!fd)
		return;

	++fd->ref;
}

void ev_fd_unref(struct ev_fd *fd)
{
	if (!fd || !fd->ref || --fd->ref)
		return;

	free(fd);
}

int ev_eloop_new_fd(struct ev_eloop *loop, struct ev_fd **out, int rfd,
			int mask, ev_fd_cb cb, void *data)
{
	struct ev_fd *fd;
	int ret;

	if (!out || !loop || !cb || rfd < 0)
		return -EINVAL;

	ret = ev_fd_new(&fd);
	if (ret)
		return ret;

	ret = ev_eloop_add_fd(loop, fd, rfd, mask, cb, data);
	if (ret) {
		ev_fd_unref(fd);
		return ret;
	}

	ev_fd_unref(fd);
	*out = fd;
	return 0;
}

int ev_eloop_add_fd(struct ev_eloop *loop, struct ev_fd *fd, int rfd,
			int mask, ev_fd_cb cb, void *data)
{
	struct epoll_event ep;

	if (!loop || !fd || !cb || rfd < 0)
		return -EINVAL;

	if (fd->loop)
		return -EALREADY;

	memset(&ep, 0, sizeof(ep));
	if (mask & EV_READABLE)
		ep.events |= EPOLLIN;
	if (mask & EV_WRITEABLE)
		ep.events |= EPOLLOUT;
	ep.data.ptr = fd;

	if (epoll_ctl(loop->efd, EPOLL_CTL_ADD, rfd, &ep) < 0)
		return -errno;

	fd->loop = loop;
	fd->cb = cb;
	fd->data = data;
	fd->fd = rfd;

	ev_fd_ref(fd);
	ev_eloop_ref(loop);

	return 0;
}

void ev_eloop_rm_fd(struct ev_fd *fd)
{
	struct ev_eloop *loop;
	size_t i;

	if (!fd || !fd->loop)
		return;

	loop = fd->loop;

	epoll_ctl(loop->efd, EPOLL_CTL_DEL, fd->fd, NULL);

	/*
	 * If we are currently dispatching events, we need to remove ourself
	 * from the temporary event list.
	 */
	for (i = 0; i < loop->cur_fds_cnt; ++i) {
		if (fd == loop->cur_fds[i].data.ptr)
			loop->cur_fds[i].data.ptr = NULL;
	}

	fd->loop = NULL;
	fd->cb = NULL;
	fd->data = NULL;
	fd->fd = -1;
	ev_fd_unref(fd);
	ev_eloop_unref(loop);
}

int ev_eloop_update_fd(struct ev_fd *fd, int mask)
{
	struct epoll_event ep;

	if (!fd || !fd->loop)
		return -EINVAL;

	memset(&ep, 0, sizeof(ep));
	if (mask & EV_READABLE)
		ep.events |= EPOLLIN;
	if (mask & EV_WRITEABLE)
		ep.events |= EPOLLOUT;
	ep.data.ptr = fd;

	if (epoll_ctl(fd->loop->efd,  EPOLL_CTL_MOD, fd->fd, &ep))
		return -errno;

	return 0;
}

static void sig_child()
{
	pid_t pid;
	int status;

	while (1) {
		pid = waitpid(-1, &status, WNOHANG);
		if (pid == -1) {
			if (errno != ECHILD)
				log_warn("cannot wait on child: %m");
			break;
		} else if (pid == 0) {
			break;
		} else if (WIFEXITED(status)) {
			if (WEXITSTATUS(status) != 0)
				log_debug("child %d exited with status %d",
					pid, WEXITSTATUS(status));
			else
				log_debug("child %d exited successfully", pid);
		} else if (WIFSIGNALED(status)) {
			log_debug("child %d exited by signal %d", pid,
					WTERMSIG(status));
		}
	}
}

static void shared_signal_cb(struct ev_fd *fd, int mask, void *data)
{
	struct ev_signal_shared *sig = data;
	struct signalfd_siginfo info;
	int len;

	if (mask & EV_READABLE) {
		len = read(fd->fd, &info, sizeof(info));
		if (len != sizeof(info))
			log_warn("cannot read signalfd");
		else
			kmscon_hook_call(sig->hook, sig->fd->loop, &info);

		if (info.ssi_signo == SIGCHLD)
			sig_child();
	} else if (mask & (EV_HUP | EV_ERR)) {
		log_warn("HUP/ERR on signal source");
	}
}

static int signal_new(struct ev_signal_shared **out, struct ev_eloop *loop,
			int signum)
{
	sigset_t mask;
	int ret, fd;
	struct ev_signal_shared *sig;

	if (!out || !loop || signum < 0)
		return -EINVAL;

	sig = malloc(sizeof(*sig));
	if (!sig)
		return -ENOMEM;
	memset(sig, 0, sizeof(*sig));
	sig->signum = signum;

	ret = kmscon_hook_new(&sig->hook);
	if (ret)
		goto err_free;

	sigemptyset(&mask);
	sigaddset(&mask, signum);

	fd = signalfd(-1, &mask, SFD_CLOEXEC);
	if (fd < 0) {
		ret = -errno;
		goto err_hook;
	}

	ret = ev_eloop_new_fd(loop, &sig->fd, fd, EV_READABLE,
				shared_signal_cb, sig);
	if (ret)
		goto err_sig;

	pthread_sigmask(SIG_BLOCK, &mask, NULL);
	sig->next = loop->sig_list;
	loop->sig_list = sig;

	*out = sig;
	return 0;

err_sig:
	close(fd);
err_hook:
	kmscon_hook_free(sig->hook);
err_free:
	free(sig);
	return ret;
}

static void signal_free(struct ev_signal_shared *sig)
{
	int fd;

	if (!sig)
		return;

	fd = sig->fd->fd;
	ev_eloop_rm_fd(sig->fd);
	close(fd);
	kmscon_hook_free(sig->hook);
	free(sig);
	/* We do not unblock the signal here as there may be other subsystems
	 * which blocked this signal so we do not want to interfere. If you need
	 * a clean sigmask then do it yourself.
	 */
}

int ev_eloop_register_signal_cb(struct ev_eloop *loop, int signum,
				ev_signal_shared_cb cb, void *data)
{
	struct ev_signal_shared *sig;
	int ret;

	if (!loop || signum < 0 || !cb)
		return -EINVAL;

	for (sig = loop->sig_list; sig; sig = sig->next) {
		if (sig->signum == signum)
			break;
	}

	if (!sig) {
		ret = signal_new(&sig, loop, signum);
		if (ret)
			return ret;
	}

	return kmscon_hook_add_cast(sig->hook, cb, data);
}

void ev_eloop_unregister_signal_cb(struct ev_eloop *loop, int signum,
					ev_signal_shared_cb cb, void *data)
{
	struct ev_signal_shared *sig;

	if (!loop)
		return;

	for (sig = loop->sig_list; sig; sig = sig->next) {
		if (sig->signum == signum) {
			kmscon_hook_rm_cast(sig->hook, cb, data);
			return;
		}
	}
}

int ev_timer_new(struct ev_timer **out)
{
	struct ev_timer *timer;
	int ret;

	if (!out)
		return -EINVAL;

	timer = malloc(sizeof(*timer));
	if (!timer)
		return -ENOMEM;

	memset(timer, 0, sizeof(*timer));
	timer->ref = 1;

	ret = ev_fd_new(&timer->fd);
	if (ret) {
		free(timer);
		return ret;
	}

	*out = timer;
	return 0;
}

void ev_timer_ref(struct ev_timer *timer)
{
	if (!timer)
		return;

	++timer->ref;
}

void ev_timer_unref(struct ev_timer *timer)
{
	if (!timer || !timer->ref || --timer->ref)
		return;

	ev_fd_unref(timer->fd);
	free(timer);
}

int ev_eloop_new_timer(struct ev_eloop *loop, struct ev_timer **out,
			const struct itimerspec *spec, ev_timer_cb cb,
			void *data)
{
	struct ev_timer *timer;
	int ret;

	if (!out || !loop || !spec || !cb)
		return -EINVAL;

	ret = ev_timer_new(&timer);
	if (ret)
		return ret;

	ret = ev_eloop_add_timer(loop, timer, spec, cb, data);
	if (ret) {
		ev_timer_unref(timer);
		return ret;
	}

	ev_timer_unref(timer);
	*out = timer;
	return 0;
}

static void timer_cb(struct ev_fd *fd, int mask, void *data)
{
	struct ev_timer *timer = data;
	uint64_t expirations;
	int len;

	if (mask & EV_READABLE) {
		len = read(fd->fd, &expirations, sizeof(expirations));
		if (len != sizeof(expirations))
			log_warn("cannot read timerfd");
		else
			timer->cb(timer, expirations, timer->data);
	} else if (mask & (EV_HUP | EV_ERR)) {
		log_warn("HUP/ERR on timer source");
	}
}

int ev_eloop_add_timer(struct ev_eloop *loop, struct ev_timer *timer,
			const struct itimerspec *spec, ev_timer_cb cb,
			void *data)
{
	int ret, fd;

	if (!loop || !timer || !spec || !cb)
		return -EINVAL;

	if (timer->fd->loop)
		return -EALREADY;

	fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
	if (fd < 0)
		return -errno;

	ret = timerfd_settime(fd, 0, spec, NULL);
	if (ret) {
		ret = -errno;
		log_warn("cannot set timerfd %d: %m", ret);
		goto err_fd;
	}

	ret = ev_eloop_add_fd(loop, timer->fd, fd, EV_READABLE,
				timer_cb, timer);
	if (ret)
		goto err_fd;

	timer->cb = cb;
	timer->data = data;
	ev_timer_ref(timer);

	return 0;

err_fd:
	close(fd);
	return ret;
}

void ev_eloop_rm_timer(struct ev_timer *timer)
{
	int fd;

	if (!timer || !timer->fd->loop)
		return;

	fd = timer->fd->fd;
	ev_eloop_rm_fd(timer->fd);
	close(fd);
	ev_timer_unref(timer);
}

int ev_eloop_update_timer(struct ev_timer *timer,
				const struct itimerspec *spec)
{
	int ret;

	if (!timer || !timer->fd->loop)
		return -EINVAL;

	ret = timerfd_settime(timer->fd->fd, 0, spec, NULL);
	if (ret) {
		ret = -errno;
		log_warn("cannot set timerfd %d: %m", ret);
		return ret;
	}

	return 0;
}

int ev_eloop_new(struct ev_eloop **out)
{
	struct ev_eloop *loop;
	int ret;

	if (!out)
		return -EINVAL;

	loop = malloc(sizeof(*loop));
	if (!loop)
		return -ENOMEM;

	memset(loop, 0, sizeof(*loop));
	loop->ref = 1;

	loop->efd = epoll_create1(EPOLL_CLOEXEC);
	if (loop->efd < 0) {
		ret = -errno;
		goto err_free;
	}

	ret = ev_fd_new(&loop->fd);
	if (ret)
		goto err_close;

	log_debug("new eloop object %p", loop);
	*out = loop;
	return 0;

err_close:
	close(loop->efd);
err_free:
	free(loop);
	return ret;
}

void ev_eloop_ref(struct ev_eloop *loop)
{
	if (!loop)
		return;

	++loop->ref;
}

void ev_eloop_unref(struct ev_eloop *loop)
{
	struct ev_signal_shared *sig;

	if (!loop || !loop->ref || --loop->ref)
		return;

	log_debug("free eloop object %p", loop);

	while ((sig = loop->sig_list)) {
		loop->sig_list = sig->next;
		signal_free(sig);
	}

	ev_fd_unref(loop->fd);
	close(loop->efd);
	free(loop);
}

int ev_eloop_dispatch(struct ev_eloop *loop, int timeout)
{
	struct epoll_event ep[32];
	struct ev_fd *fd;
	int i, count, mask;

	if (!loop || loop->exit)
		return -EINVAL;

	/* dispatch idle events */
	loop->cur_idle = loop->idle_list;
	while (loop->cur_idle) {
		loop->cur_idle->cb(loop->cur_idle, loop->cur_idle->data);
		if (loop->cur_idle)
			loop->cur_idle = loop->cur_idle->next;
	}

	/* dispatch fd events */
	count = epoll_wait(loop->efd, ep, 32, timeout);
	if (count < 0) {
		if (errno == EINTR) {
			count = 0;
		} else {
			log_warn("epoll_wait dispatching failed: %m");
			return -errno;
		}
	}

	loop->cur_fds = ep;
	loop->cur_fds_cnt = count;

	for (i = 0; i < count; ++i) {
		fd = ep[i].data.ptr;
		if (!fd || !fd->cb)
			continue;

		mask = 0;
		if (ep[i].events & EPOLLIN)
			mask |= EV_READABLE;
		if (ep[i].events & EPOLLOUT)
			mask |= EV_WRITEABLE;
		if (ep[i].events & EPOLLERR)
			mask |= EV_ERR;
		if (ep[i].events & EPOLLHUP) {
			mask |= EV_HUP;
			epoll_ctl(loop->efd, EPOLL_CTL_DEL, fd->fd, NULL);
		}

		fd->cb(fd, mask, fd->data);
	}

	loop->cur_fds = NULL;
	loop->cur_fds_cnt = 0;

	return 0;
}

/* ev_eloop_dispatch() performs one idle-roundtrip. This function performs as
 * many idle-roundtrips as needed to run \timeout milliseconds.
 * If \timeout is 0, this is equal to ev_eloop_dispath(), if \timeout is <0,
 * this runs until \loop->exit becomes true.
 */
int ev_eloop_run(struct ev_eloop *loop, int timeout)
{
	int ret;
	struct timeval tv, start;
	int64_t off, msec;

	if (!loop)
		return -EINVAL;
	loop->exit = false;

	log_debug("run for %d msecs", timeout);
	gettimeofday(&start, NULL);

	while (!loop->exit) {
		ret = ev_eloop_dispatch(loop, timeout);
		if (ret)
			return ret;

		if (!timeout) {
			break;
		} else if (timeout > 0) {
			gettimeofday(&tv, NULL);
			off = tv.tv_sec - start.tv_sec;
			msec = (int64_t)tv.tv_usec - (int64_t)start.tv_usec;
			if (msec < 0) {
				off -= 1;
				msec = 1000000 + msec;
			}
			off *= 1000;
			off += msec / 1000;
			if (off >= timeout)
				break;
		}
	}

	return 0;
}

void ev_eloop_exit(struct ev_eloop *loop)
{
	if (!loop)
		return;

	log_debug("exiting %p", loop);

	loop->exit = true;
	if (loop->fd->loop)
		ev_eloop_exit(loop->fd->loop);
}