// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.

#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/epoll.h>
#include <sys/timerfd.h>

#include "eventloop_platform.h"
#include "public/io.h"

struct tlsl_event_platform {
  int epoll_registered_fd;
  bool epoll_fd_owned;
};

struct tlsl_eventloop_platform {
  int epoll_fd;
};

int tlsl_platform_el_init(struct tlsl_eventloop *el) {
  TLSL_DEFINE_PLATFORM_EVENTLOOP_DATA(el, elp);

  if ((elp->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0)
    return -1;
  return 0;
}

void tlsl_platform_el_cleanup(struct tlsl_eventloop *el) {
  TLSL_DEFINE_PLATFORM_EVENTLOOP_DATA(el, elp);

  close(elp->epoll_fd);
}

void tlsl_platform_el_event_remove(struct tlsl_eventloop *el, struct tlsl_event *e) {
  TLSL_DEFINE_PLATFORM_EVENTLOOP_DATA(el, elp);
  TLSL_DEFINE_PLATFORM_EVENT_DATA(e, ep);

  epoll_ctl(elp->epoll_fd, EPOLL_CTL_DEL, ep->epoll_registered_fd, NULL);
}

void tlsl_platform_el_event_cleanup(struct tlsl_eventloop *el, struct tlsl_event *e) {
  TLSL_DEFINE_PLATFORM_EVENT_DATA(e, ep);

  (void)el;

  if (ep->epoll_fd_owned && (ep->epoll_registered_fd >= 0)) {
    close(ep->epoll_registered_fd);
    ep->epoll_registered_fd = -1;
  }
}

static int clear_timerfd(int fd) {
  uint64_t tfd_buf;
  ssize_t res;

  do {
    res = read(fd, &tfd_buf, sizeof(tfd_buf));
  } while ((res < 0) && (errno == EINTR));
  
  if (res < 0)
    return -1;

  return 0;
}

int tlsl_platform_el_event_clear(struct tlsl_eventloop *el, struct tlsl_event *e) {
  TLSL_DEFINE_PLATFORM_EVENT_DATA(e, ep);
  int res;

  (void)el;

  if ((e->id.source == TLSL_EVENT_SOURCE_TIMER) && (ep->epoll_registered_fd >= 0)) {
    if ((res = clear_timerfd(ep->epoll_registered_fd)))
      return res;
  }

  return 0;
}

int tlsl_platform_el_wait(
  struct tlsl_eventloop *el,
  tlsl_event_id_t *id_out,
  uint32_t *flags_out,
  int timeout_ms)
{
  TLSL_DEFINE_PLATFORM_EVENTLOOP_DATA(el, elp);
  struct epoll_event ev;
  struct tlsl_event *e;
  int res;

  if (timeout_ms < 0)
    timeout_ms = -1;
  
  do {
    res = epoll_pwait(elp->epoll_fd, &ev, 1, timeout_ms, NULL);
  } while ((res < 0) && (errno == EINTR));

  if (res <= 0) {
    if (!res)
      errno = ETIMEDOUT;
    return -1;
  }

  e = (struct tlsl_event *)ev.data.ptr;

  *id_out = e->id;
  *flags_out = 0;

  if (ev.events & EPOLLIN)
    *flags_out |= TLSL_EVENT_READABLE;
  if (ev.events & EPOLLOUT)
    *flags_out |= TLSL_EVENT_WRITABLE;

  return 0;
}

static int el_epoll_add(
  struct tlsl_eventloop *el,
  struct tlsl_event *e,
  int fd,
  enum tlsl_event_source source,
  uint32_t events,
  bool owned)
{
  TLSL_DEFINE_PLATFORM_EVENTLOOP_DATA(el, elp);
  TLSL_DEFINE_PLATFORM_EVENT_DATA(e, ep);
  struct epoll_event ev;

  memset(&ev, 0, sizeof(ev));
  ev.events = events;
  ev.data.fd = fd;
  ev.data.ptr = e;
  
  if (epoll_ctl(elp->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0)
    return -1;

  e->id.obj = (uintptr_t)fd;
  e->id.source = source;
  ep->epoll_registered_fd = fd;
  ep->epoll_fd_owned = owned;

  return 0;
}

int tlsl_platform_el_add_timer(
  struct tlsl_eventloop *el,
  struct tlsl_event *e,
  uint64_t millis,
  bool oneshot)
{
  FD_SCOPED(tfd);
  struct itimerspec spec;
  struct timespec ts;
  int res;

  ts.tv_sec = (long)(millis / 1000);
  ts.tv_nsec = (long)((millis % 1000) * 1000000);

  memset(&spec, 0, sizeof(spec));
  spec.it_value = ts;
  if (!oneshot)
    spec.it_interval = ts;

  if ((tfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC)) < 0)
    return -1;

  if (timerfd_settime(tfd, 0, &spec, NULL))
    return -1;

  if ((res = el_epoll_add(el, e, tfd, TLSL_EVENT_SOURCE_TIMER, EPOLLIN, true)))
    return res;

  FD_RELEASE(&tfd);
  return 0;
}

int tlsl_platform_el_add_fd(
  struct tlsl_eventloop *el,
  struct tlsl_event *e,
  int fd,
  uint32_t flags)
{
  uint32_t events;

  events = 0;
  if (flags & TLSL_EVENT_READABLE)
    events |= EPOLLIN;
  if (flags & TLSL_EVENT_WRITABLE)
    events |= EPOLLOUT;

  return el_epoll_add(el, e, fd, TLSL_EVENT_SOURCE_FD, events, false);
}