/**
 * Multiple asynchronous read on file descriptors
 *
 * Copyright (C) 2015 Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>,
 *                    Martine Lenders <mlenders@inf.fu-berlin.de>
 *                    Kaspar Schleiser <kaspar@schleiser.de>
 *                    Ell-i open source co-operative
 *                    Takuo Yonezawa <Yonezawa-T2@mail.dnp.co.jp>
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 *
 * @ingroup cpu_native
 * @{
 * @file
 * @author  Takuo Yonezawa <Yonezawa-T2@mail.dnp.co.jp>
 */

#include <err.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>

#include "async_read.h"
#include "native_internal.h"

static int _next_index;
static struct pollfd _fds[ASYNC_READ_NUMOF];
static async_read_t pollers[ASYNC_READ_NUMOF];

static void _sigio_child(int fd);

static void _async_io_isr(void) {
    if (real_poll(_fds, _next_index, 0) > 0) {
        for (int i = 0; i < _next_index; i++) {
            /* handle if one of the events has happened */
            if (_fds[i].revents & _fds[i].events) {
                pollers[i].cb(_fds[i].fd, pollers[i].arg);
            }
        }
    }
}

void native_async_read_setup(void) {
    register_interrupt(SIGIO, _async_io_isr);
}

void native_async_read_cleanup(void) {
    unregister_interrupt(SIGIO);

    for (int i = 0; i < _next_index; i++) {
        real_close(_fds[i].fd);
        if (pollers[i].child_pid) {
            kill(pollers[i].child_pid, SIGKILL);
        }
    }
}

void native_async_read_continue(int fd) {
    for (int i = 0; i < _next_index; i++) {
        if (_fds[i].fd == fd && pollers[i].child_pid) {
            kill(pollers[i].child_pid, SIGCONT);
        }
    }
}

static void _add_handler(int fd, void *arg, native_async_read_callback_t handler) {
    _fds[_next_index].fd = fd;
    _fds[_next_index].events = POLLIN | POLLPRI;
    async_read_t *poll = &pollers[_next_index];

    poll->child_pid = 0;
    poll->cb = handler;
    poll->arg = arg;
    poll->fd = &_fds[_next_index];
}

void native_async_read_add_handler(int fd, void *arg, native_async_read_callback_t handler) {
    if (_next_index >= ASYNC_READ_NUMOF) {
        err(EXIT_FAILURE, "native_async_read_add_handler(): too many callbacks");
    }

    _add_handler(fd, arg, handler);

    /* configure fds to send signals on io */
    if (real_fcntl(fd, F_SETOWN, _native_pid) == -1) {
        err(EXIT_FAILURE, "native_async_read_add_handler(): fcntl(F_SETOWN)");
    }
    /* set file access mode to non-blocking */
    if (real_fcntl(fd, F_SETFL, O_NONBLOCK | O_ASYNC) == -1) {
        err(EXIT_FAILURE, "native_async_read_add_handler(): fcntl(F_SETFL)");
    }

    _next_index++;
}

void native_async_read_remove_handler(int fd)
{
    int res = real_fcntl(fd, F_GETFL);
    if (res < 0) {
        err(EXIT_FAILURE, "native_async_read_remove_handler(): fcntl(F_GETFL)");
    }
    unsigned flags = (unsigned)res & ~O_ASYNC;
    res = real_fcntl(fd, F_SETFL, flags);
    if (res < 0) {
        err(EXIT_FAILURE, "native_async_read_remove_handler(): fcntl(F_SETFL)");
    }

    unsigned i;
    for (i = 0; (i < (unsigned)_next_index) && (_fds[i].fd != fd); i++) { };
    if (i == (unsigned)_next_index) {
        return;
    }

    unregister_interrupt(SIGIO);
    for (; i < (unsigned)_next_index - 1; i++) {
        _fds[i] = _fds[i + 1];
    }
    _next_index--;
    register_interrupt(SIGIO, _async_io_isr);

    _fds[_next_index] = (struct pollfd){ 0 };
}

void native_async_read_add_int_handler(int fd, void *arg, native_async_read_callback_t handler) {
    if (_next_index >= ASYNC_READ_NUMOF) {
        err(EXIT_FAILURE, "native_async_read_add_int_handler(): too many callbacks");
    }

    _add_handler(fd, arg, handler);

    _sigio_child(_next_index);
    _next_index++;
}

static void _sigio_child(int index)
{
    struct pollfd fds = _fds[index];
    async_read_t *poll = &pollers[_next_index];
    pid_t parent = _native_pid;
    pid_t child;
    if ((child = real_fork()) == -1) {
        err(EXIT_FAILURE, "sigio_child: fork");
    }
    if (child > 0) {
        poll->child_pid = child;

        /* return in parent process */
        return;
    }

    sigset_t sigmask;

    sigemptyset(&sigmask);
    sigaddset(&sigmask, SIGCONT);
    sigprocmask(SIG_BLOCK, &sigmask, NULL);

    /* watch tap interface and signal parent process if data is
     * available */
    while (1) {
        if (real_poll(&fds, 1, -1) == 1) {
            kill(parent, SIGIO);
        }
        else {
            kill(parent, SIGKILL);
            err(EXIT_FAILURE, "osx_sigio_child: select");
        }

        /* If SIGCONT is sent before calling pause(), the process stops
         * forever, so using sigwait instead. */

        int sig;

        sigemptyset(&sigmask);
        sigaddset(&sigmask, SIGCONT);
        sigwait(&sigmask, &sig);
    }
}
/** @} */