/*
  Copyright (c) 2012-2016, Matthias Schiffer <mschiffer@universe-factory.net>
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/**
   \file

   Portable polling API implementations
*/


#include "poll.h"
#include "async.h"
#include "peer.h"

#include <signal.h>


#ifdef USE_EPOLL

#include <sys/epoll.h>
#include <sys/syscall.h>

#endif

#ifdef USE_SELECT

#include <sys/select.h>

#endif


/** Returns the time to the next task or -1 */
static inline int task_timeout(void) {
	fastd_timeout_t timeout = fastd_task_queue_timeout();
	if (timeout == FASTD_TIMEOUT_INV)
		return -1;

	int diff_msec = timeout - ctx.now;
	if (diff_msec < 0)
		return 0;
	else
		return diff_msec;
}


/** Handles a file descriptor that was selected on */
static inline void handle_fd(fastd_poll_fd_t *fd, bool input, bool error) {
	switch (fd->type) {
	case POLL_TYPE_ASYNC:
		if (input)
			fastd_async_handle();
		break;

	case POLL_TYPE_STATUS:
		if (input)
			fastd_status_handle();
		break;

	case POLL_TYPE_IFACE:
	{
		fastd_iface_t *iface = container_of(fd, fastd_iface_t, fd);

		if (input)
			fastd_iface_handle(iface);

		break;
	}

	case POLL_TYPE_SOCKET:
	{
		fastd_socket_t *sock = container_of(fd, fastd_socket_t, fd);

		if (error) {
			if (sock->peer)
				fastd_peer_reset_socket(sock->peer);
			else
				fastd_socket_error(sock);

			return;
		}

		if (input)
			fastd_receive(sock);

		break;
	}

	default:
		exit_bug("unknown FD type");
	}

	if (error)
		exit_error("unexpected poll error");
}


#ifdef USE_EPOLL


#ifndef SYS_epoll_pwait
#define SYS_epoll_pwait __NR_epoll_pwait
#endif

/** Simplified epoll_pwait wrapper (as there are systems without or with broken epoll_pwait) */
static inline int epoll_wait_unblocked(int epfd, struct epoll_event *events, int maxevents, int timeout) {
	const uint8_t buf[_NSIG/8] = {};
	return syscall(SYS_epoll_pwait, epfd, events, maxevents, timeout, buf, sizeof(buf));
}


void fastd_poll_init(void) {
	ctx.epoll_fd = epoll_create(1);
	if (ctx.epoll_fd < 0)
		exit_errno("epoll_create1");
}

void fastd_poll_free(void) {
	if (close(ctx.epoll_fd))
		pr_warn_errno("closing EPOLL: close");
}


void fastd_poll_fd_register(fastd_poll_fd_t *fd) {
	if (fd->fd < 0)
		exit_bug("fastd_poll_fd_register: invalid FD");

	struct epoll_event event = {
		.events = EPOLLIN,
		.data.ptr = fd,
	};

	if (epoll_ctl(ctx.epoll_fd, EPOLL_CTL_ADD, fd->fd, &event) < 0)
		exit_errno("epoll_ctl");
}

bool fastd_poll_fd_close(fastd_poll_fd_t *fd) {
	if (epoll_ctl(ctx.epoll_fd, EPOLL_CTL_DEL, fd->fd, NULL) < 0)
		exit_errno("epoll_ctl");

	return (close(fd->fd) == 0);
}


void fastd_poll_handle(void) {
	int timeout = task_timeout();

	struct epoll_event events[16];
	int ret = epoll_wait_unblocked(ctx.epoll_fd, events, 16, timeout);
	if (ret < 0 && errno != EINTR)
		exit_errno("epoll_pwait");

	fastd_update_time();

	if (ret < 0)
		return;

	size_t i;
	for (i = 0; i < (size_t)ret; i++)
		handle_fd(events[i].data.ptr,
			  events[i].events & EPOLLIN,
			  events[i].events & (EPOLLERR|EPOLLHUP));
}

#else

void fastd_poll_init(void) {
}

void fastd_poll_free(void) {
	VECTOR_FREE(ctx.fds);
	VECTOR_FREE(ctx.pollfds);
}


void fastd_poll_fd_register(fastd_poll_fd_t *fd) {
	if (fd->fd < 0)
		exit_bug("fastd_poll_fd_register: invalid FD");

	while (VECTOR_LEN(ctx.fds) <= (size_t)fd->fd)
		VECTOR_ADD(ctx.fds, NULL);

	VECTOR_INDEX(ctx.fds, fd->fd) = fd;

	VECTOR_RESIZE(ctx.pollfds, 0);
}

bool fastd_poll_fd_close(fastd_poll_fd_t *fd) {
	if (fd->fd < 0 || (size_t)fd->fd >= VECTOR_LEN(ctx.fds))
		exit_bug("fastd_poll_fd_close: invalid FD");

	VECTOR_INDEX(ctx.fds, fd->fd) = NULL;

	VECTOR_RESIZE(ctx.pollfds, 0);

	return (close(fd->fd) == 0);
}


void fastd_poll_handle(void) {
	size_t i;

	int timeout = task_timeout();

	if (!VECTOR_LEN(ctx.pollfds)) {
		for (i = 0; i < VECTOR_LEN(ctx.fds); i++) {
			fastd_poll_fd_t *fd = VECTOR_INDEX(ctx.fds, i);
			if (!fd)
				continue;

			struct pollfd pollfd = {
				.fd = fd->fd,
				.events = POLLIN,
				.revents = 0,
			};
			VECTOR_ADD(ctx.pollfds, pollfd);
		}
	}

	sigset_t set, oldset;
	sigemptyset(&set);
	pthread_sigmask(SIG_SETMASK, &set, &oldset);

	int ret = 0;

#ifdef USE_SELECT
	/* Inefficient implementation for OSX... */
	fd_set readfds;
	FD_ZERO(&readfds);
	int maxfd = -1;

	for (i = 0; i < VECTOR_LEN(ctx.pollfds); i++) {
		struct pollfd *pollfd = &VECTOR_INDEX(ctx.pollfds, i);
		if (pollfd->fd >= 0) {
			FD_SET(pollfd->fd, &readfds);

			if (pollfd->fd > maxfd)
				maxfd = pollfd->fd;
		}
	}

	fd_set errfds = readfds;

	if (maxfd >= 0) {
		struct timeval tv = {}, *tvp = NULL;
		if (timeout >= 0) {
			tvp = &tv;
			tv.tv_sec = timeout/1000;
			tv.tv_usec = (timeout%1000)*1000;
		}
		ret = select(maxfd+1, &readfds, NULL, &errfds, tvp);
		if (ret < 0 && errno != EINTR)
			exit_errno("select");
	}

	if (ret > 0) {
		ret = 0;

		for (i = 0; i < VECTOR_LEN(ctx.pollfds); i++) {
			struct pollfd *pollfd = &VECTOR_INDEX(ctx.pollfds, i);
			pollfd->revents = 0;

			if (pollfd->fd < 0)
				continue;

			if (FD_ISSET(pollfd->fd, &readfds))
				pollfd->revents |= POLLIN;
			if (FD_ISSET(pollfd->fd, &errfds))
				pollfd->revents |= POLLERR;

			if (pollfd->revents)
				ret++;
		}
	}

#else
	ret = poll(VECTOR_DATA(ctx.pollfds), VECTOR_LEN(ctx.pollfds), timeout);
	if (ret < 0 && errno != EINTR)
		exit_errno("poll");
#endif

	pthread_sigmask(SIG_SETMASK, &oldset, NULL);
	fastd_update_time();

	if (ret <= 0)
		return;

	for (i = 0; i < VECTOR_LEN(ctx.pollfds) && ret > 0; i++) {
		struct pollfd *pollfd = &VECTOR_INDEX(ctx.pollfds, i);

		if (pollfd->revents)
			ret--;

		handle_fd(VECTOR_INDEX(ctx.fds, pollfd->fd), pollfd->revents & POLLIN, pollfd->revents & (POLLERR|POLLHUP|POLLNVAL));
	}
}

#endif