/****************************************************************************
 * fs/vfs/fs_epoll.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/epoll.h>

#include <inttypes.h>
#include <stdint.h>
#include <poll.h>
#include <errno.h>
#include <sched.h>
#include <string.h>
#include <debug.h>

#include <nuttx/nuttx.h>
#include <nuttx/clock.h>
#include <nuttx/fs/fs.h>
#include <nuttx/kmalloc.h>
#include <nuttx/list.h>
#include <nuttx/mutex.h>
#include <nuttx/signal.h>
#include <nuttx/spinlock.h>
#include <nuttx/tls.h>

#include "inode/inode.h"
#include "fs_heap.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#ifndef CONFIG_EPOLL_NPOLLWAITERS
#  define CONFIG_EPOLL_NPOLLWAITERS 2
#endif

/****************************************************************************
 * Private Types
 ****************************************************************************/

struct epoll_node_s
{
  struct list_node         node;
  epoll_data_t             data;
  bool                     notified;
  struct pollfd            pfd;
  FAR struct file         *filep;
  FAR struct epoll_head_s *eph;
};

typedef struct epoll_node_s epoll_node_t;

struct epoll_head_s
{
  int                   size;
  int                   crefs;
  rmutex_t              lock;
  sem_t                 sem;
  struct list_node      setup;    /* The setup list, store all the setuped
                                   * epoll node.
                                   */
  struct list_node      teardown; /* The teardown list, store all the epoll
                                   * node notified after epoll_wait finish,
                                   * these epoll node should be setup again
                                   * to check the pending poll notification.
                                   */
  struct list_node      oneshot;  /* The oneshot list, store all the epoll
                                   * node notified after epoll_wait and with
                                   * EPOLLONESHOT events, these oneshot epoll
                                   * nodes can be reset by epoll_ctl (move
                                   * from oneshot list to the setup list).
                                   */
  struct list_node      free;     /* The free list, store all the freed epoll
                                   * node.
                                   */
  struct list_node      extend;   /* The extend list, store all the malloced
                                   * first node, used to free the malloced
                                   * memory in epoll_do_close().
                                   */
  spinlock_t            poll_lock;
  FAR struct pollfd    *fds[CONFIG_EPOLL_NPOLLWAITERS];
};

typedef struct epoll_head_s epoll_head_t;

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

static int epoll_do_open(FAR struct file *filep);
static int epoll_do_close(FAR struct file *filep);
static int epoll_do_poll(FAR struct file *filep,
                         FAR struct pollfd *fds, bool setup);
static int epoll_setup(FAR epoll_head_t *eph);
static int epoll_teardown(FAR epoll_head_t *eph, FAR struct epoll_event *evs,
                          int maxevents);
static void epoll_cleanup(FAR void *arg);

/****************************************************************************
 * Private Data
 ****************************************************************************/

static const struct file_operations g_epoll_ops =
{
  epoll_do_open,    /* open */
  epoll_do_close,   /* close */
  NULL,             /* read */
  NULL,             /* write */
  NULL,             /* seek */
  NULL,             /* ioctl */
  NULL,             /* mmap */
  NULL,             /* truncate */
  epoll_do_poll     /* poll */
};

static DEFINE_PER_CPU_BMP(struct inode, g_epoll_inode) =
{
  NULL,                   /* i_parent */
  NULL,                   /* i_peer */
  NULL,                   /* i_child */
  1,                      /* i_crefs */
  FSNODEFLAG_TYPE_DRIVER, /* i_flags */
  {
    &g_epoll_ops          /* u */
  }
};
#define g_epoll_inode this_cpu_var_bmp(g_epoll_inode)

/****************************************************************************
 * Private Functions
 ****************************************************************************/

static FAR epoll_head_t *epoll_head_from_fd(int fd, FAR struct file **filep)
{
  int ret;

  /* Push a cancellation point onto the stack.  This will be called if
   * the thread is canceled.
   */

  tls_cleanup_push(tls_get_info(), epoll_cleanup, filep);

  /* Get file pointer by file descriptor */

  ret = file_get(fd, filep);
  if (ret < 0)
    {
      tls_cleanup_pop(tls_get_info(), 0);
      set_errno(-ret);
      return NULL;
    }

  /* Check fd come from us */

  if ((*filep)->f_inode->u.i_ops != &g_epoll_ops)
    {
      file_put(*filep);
      tls_cleanup_pop(tls_get_info(), 0);
      set_errno(EBADF);
      return NULL;
    }

  return (*filep)->f_priv;
}

static void epoll_filep_close(FAR struct file *filep)
{
  file_put(filep);
  tls_cleanup_pop(tls_get_info(), 0);
}

static int epoll_do_open(FAR struct file *filep)
{
  FAR epoll_head_t *eph = filep->f_priv;
  int ret;

  ret = nxrmutex_lock(&eph->lock);
  if (ret < 0)
    {
      return ret;
    }

  eph->crefs++;
  nxrmutex_unlock(&eph->lock);
  return ret;
}

static int epoll_do_close(FAR struct file *filep)
{
  FAR epoll_head_t *eph = filep->f_priv;
  FAR epoll_node_t *epn;
  FAR epoll_node_t *tmp;
  int ret;

  ret = nxrmutex_lock(&eph->lock);
  if (ret < 0)
    {
      return ret;
    }

  if (--eph->crefs <= 0)
    {
      list_for_every_entry(&eph->setup, epn, epoll_node_t, node)
        {
          file_poll(epn->filep, &epn->pfd, false);
          file_put(epn->filep);
        }

      list_for_every_entry(&eph->teardown, epn, epoll_node_t, node)
        {
          file_put(epn->filep);
        }

      list_for_every_entry(&eph->oneshot, epn, epoll_node_t, node)
        {
          file_put(epn->filep);
        }

      list_for_every_entry_safe(&eph->extend, epn, tmp, epoll_node_t, node)
        {
          list_delete(&epn->node);
          fs_heap_free(epn);
        }

      nxrmutex_unlock(&eph->lock);
      nxrmutex_destroy(&eph->lock);
      fs_heap_free(eph);
    }
  else
    {
      nxrmutex_unlock(&eph->lock);
    }

  return ret;
}

/****************************************************************************
 * Name: epoll_notify
 ****************************************************************************/

static void epoll_notify(FAR epoll_head_t *eph, pollevent_t eventset)
{
  irqstate_t flags;

  flags = spin_lock_irqsave_nopreempt(&eph->poll_lock);
  poll_notify(eph->fds, CONFIG_EPOLL_NPOLLWAITERS, eventset);
  spin_unlock_irqrestore_nopreempt(&eph->poll_lock, flags);
}

static int epoll_do_poll(FAR struct file *filep,
                         FAR struct pollfd *fds, bool setup)
{
  FAR epoll_head_t *eph = filep->f_priv;
  irqstate_t flags;
  int ret = OK;
  int i;

  flags = spin_lock_irqsave(&eph->poll_lock);
  if (setup)
    {
      FAR epoll_node_t *epn;
      pollevent_t eventset = 0;

      for (i = 0; i < CONFIG_EPOLL_NPOLLWAITERS; i++)
        {
          if (eph->fds[i] == NULL)
            {
              eph->fds[i] = fds;
              fds->priv   = &eph->fds[i];
              break;
            }
        }

      if (i == CONFIG_EPOLL_NPOLLWAITERS)
        {
          fds->priv = NULL;
          ret       = -EBUSY;
          goto errout;
        }

      spin_unlock_irqrestore(&eph->poll_lock, flags);

      nxrmutex_lock(&eph->lock);

      list_for_every_entry(&eph->setup, epn, epoll_node_t, node)
        {
          /* Only check the notifed fd */

          if (!epn->notified)
            {
              continue;
            }

          if (epn->pfd.revents != 0)
            {
              eventset |= POLLIN;
            }
        }

      nxrmutex_unlock(&eph->lock);

      epoll_notify(eph, eventset);
    }
  else
    {
      /* This is a request to tear down the poll. */

      FAR struct pollfd **slot = (FAR struct pollfd **)fds->priv;

#ifdef CONFIG_DEBUG_FEATURES
      if (slot == NULL)
        {
          ret = -EIO;
          goto errout;
        }
#endif

      /* Remove all memory of the poll setup */

      *slot     = NULL;
      fds->priv = NULL;
      spin_unlock_irqrestore(&eph->poll_lock, flags);
    }

  return ret;

errout:
  spin_unlock_irqrestore(&eph->poll_lock, flags);
  return ret;
}

static int epoll_do_create(int size, int flags)
{
  FAR epoll_head_t *eph;
  FAR epoll_node_t *epn;
  int fd;
  int i;

  size = size <= 0 ? 1 : size;
  eph = fs_heap_zalloc(sizeof(epoll_head_t) + sizeof(epoll_node_t) * size);
  if (eph == NULL)
    {
      set_errno(ENOMEM);
      return ERROR;
    }

  eph->size = size;
  nxrmutex_init(&eph->lock);
  nxsem_init(&eph->sem, 0, 0);
  spin_lock_init(&eph->poll_lock);

  /* List initialize */

  epn = (FAR epoll_node_t *)(eph + 1);

  list_initialize(&eph->setup);
  list_initialize(&eph->teardown);
  list_initialize(&eph->oneshot);
  list_initialize(&eph->extend);
  list_initialize(&eph->free);
  for (i = 0; i < size; i++)
    {
      list_add_tail(&eph->free, &epn[i].node);
    }

  eph->crefs++;

  /* Alloc the file descriptor */

  fd = file_allocate_from_inode(&g_epoll_inode, flags, 0, eph, 0);
  if (fd < 0)
    {
      nxrmutex_destroy(&eph->lock);
      fs_heap_free(eph);
      set_errno(-fd);
      return ERROR;
    }

  return fd;
}

/****************************************************************************
 * Name: epoll_setup
 *
 * Description:
 *   Setup all the fd.
 *
 * Input Parameters:
 *   eph       - The epoll head pointer
 *
 * Returned Value:
 *   Positive on success, negative on fail
 *
 ****************************************************************************/

static int epoll_setup(FAR epoll_head_t *eph)
{
  FAR epoll_node_t *tepn;
  FAR epoll_node_t *epn;
  int ret;

  ret = nxrmutex_lock(&eph->lock);
  if (ret < 0)
    {
      return ret;
    }

  list_for_every_entry_safe(&eph->teardown, epn, tepn, epoll_node_t, node)
    {
      /* Setup again to check the notified pollfd last epoll_wait() to
       * cover the situation several poll event pending on one fd.
       */

      epn->notified    = false;
      epn->pfd.revents = 0;
      ret = file_poll(epn->filep, &epn->pfd, true);
      if (ret < 0)
        {
          ferr("epoll setup failed, filep=%p, events=%08" PRIx32 ", "
               "ret=%d\n", epn->filep, epn->pfd.events, ret);
          break;
        }

      list_delete(&epn->node);
      list_add_tail(&eph->setup, &epn->node);
    }

  nxrmutex_unlock(&eph->lock);
  return ret;
}

/****************************************************************************
 * Name: epoll_teardown
 *
 * Description:
 *   Teardown all the notifed fd and check the notified fd's event with user
 *   expected event.
 *
 * Input Parameters:
 *   eph       - The epoll head pointer
 *   evs       - The epoll events array
 *   maxevents - The epoll events array size
 *
 * Returned Value:
 *   Return the number of fd that notifed and the events is also user
 *   expected.
 *
 ****************************************************************************/

static int epoll_teardown(FAR epoll_head_t *eph, FAR struct epoll_event *evs,
                          int maxevents)
{
  FAR epoll_node_t *tepn;
  FAR epoll_node_t *epn;
  int i = 0;

  nxrmutex_lock(&eph->lock);

  list_for_every_entry_safe(&eph->setup, epn, tepn, epoll_node_t, node)
    {
      /* Only check the notifed fd */

      if (!epn->notified)
        {
          continue;
        }

      /* Teradown all the notified fd */

      file_poll(epn->filep, &epn->pfd, false);
      list_delete(&epn->node);

      if (epn->pfd.revents != 0 && i < maxevents)
        {
          evs[i].data     = epn->data;
          evs[i++].events = epn->pfd.revents;
          if ((epn->pfd.events & EPOLLONESHOT) != 0)
            {
              list_add_tail(&eph->oneshot, &epn->node);
            }
          else
            {
              list_add_tail(&eph->teardown, &epn->node);
            }
        }
      else
        {
          list_add_tail(&eph->teardown, &epn->node);
        }
    }

  nxrmutex_unlock(&eph->lock);
  return i;
}

/****************************************************************************
 * Name: epoll_cleanup
 *
 * Description:
 *   Cleanup the epoll operation.
 *
 ****************************************************************************/

static void epoll_cleanup(FAR void *arg)
{
  file_put(*(FAR struct file **)arg);
}

/****************************************************************************
 * Name: epoll_default_cb
 *
 * Description:
 *   The default epoll callback function, this function do the final step of
 *   poll notification.
 *
 * Input Parameters:
 *   fds - The fds
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

static void epoll_default_cb(FAR struct pollfd *fds)
{
  FAR epoll_node_t *epn = fds->arg;
  int semcount = 0;

  epn->notified = true;
  if (fds->revents != 0)
    {
      nxsem_get_value(&epn->eph->sem, &semcount);
      if (semcount < 1)
        {
          nxsem_post(&epn->eph->sem);
        }

      epoll_notify(epn->eph, POLLIN);
    }
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: epoll_create
 *
 * Description:
 *
 * Input Parameters:
 *
 * Returned Value:
 *
 ****************************************************************************/

int epoll_create(int size)
{
  return epoll_do_create(size, 0);
}

/****************************************************************************
 * Name: epoll_create1
 *
 * Description:
 *
 * Input Parameters:
 *
 * Returned Value:
 *
 ****************************************************************************/

int epoll_create1(int flags)
{
  return epoll_do_create(CONFIG_FS_NEPOLL_DESCRIPTORS, flags);
}

/****************************************************************************
 * Name: epoll_close
 *
 * Description:
 *
 * Input Parameters:
 *
 * Returned Value:
 *
 ****************************************************************************/

void epoll_close(int epfd)
{
  close(epfd);
}

/****************************************************************************
 * Name: epoll_ctl
 *
 * Description:
 *
 * Input Parameters:
 *
 * Returned Value:
 *
 ****************************************************************************/

int epoll_ctl(int epfd, int op, int fd, FAR struct epoll_event *ev)
{
  FAR struct list_node *extend;
  FAR struct file *filep = NULL;
  FAR epoll_head_t *eph;
  FAR epoll_node_t *epn;
  int ret;
  int i;

  eph = epoll_head_from_fd(epfd, &filep);
  if (eph == NULL)
    {
      set_errno(EBADF);
      return ERROR;
    }

  ret = nxrmutex_lock(&eph->lock);
  if (ret < 0)
    {
      goto err_without_lock;
    }

  switch (op)
    {
      case EPOLL_CTL_ADD:
        finfo("%p CTL ADD: fd=%d ev=%08" PRIx32 "\n", eph, fd, ev->events);

        /* Check repetition */

        list_for_every_entry(&eph->setup, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                ret = -EEXIST;
                goto err;
              }
          }

        list_for_every_entry(&eph->teardown, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                ret = -EEXIST;
                goto err;
              }
          }

        list_for_every_entry(&eph->oneshot, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                ret = -EEXIST;
                goto err;
              }
          }

        if (list_is_empty(&eph->free))
          {
            /* Malloc new epoll node, insert the first list_node to the
             * extend list and insert the remaining epoll nodes to the free
             * list.
             */

            extend = fs_heap_zalloc(sizeof(*extend) +
                                2 * sizeof(epoll_node_t) * eph->size);
            if (extend == NULL)
              {
                ret = -ENOMEM;
                goto err;
              }

            eph->size *= 2;
            list_add_tail(&eph->extend, extend);
            epn = (FAR epoll_node_t *)(extend + 1);
            for (i = 0; i < eph->size; i++)
              {
                list_add_tail(&eph->free, &epn[i].node);
              }
          }

        epn = container_of(list_remove_head(&eph->free), epoll_node_t, node);
        epn->eph         = eph;
        epn->data        = ev->data;
        epn->notified    = false;
        epn->pfd.events  = ev->events | POLLALWAYS;
        epn->pfd.fd      = fd;
        epn->pfd.arg     = epn;
        epn->pfd.cb      = epoll_default_cb;
        epn->pfd.revents = 0;

        ret = file_get(fd, &epn->filep);
        if (ret < 0)
          {
            list_add_tail(&eph->free, &epn->node);
            goto err;
          }

        ret = file_poll(epn->filep, &epn->pfd, true);
        if (ret < 0)
          {
            file_put(epn->filep);
            list_add_tail(&eph->free, &epn->node);
            goto err;
          }

        list_add_tail(&eph->setup, &epn->node);
        break;

      case EPOLL_CTL_DEL:
        finfo("%p CTL DEL: fd=%d\n", eph, fd);
        list_for_every_entry(&eph->setup, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                file_poll(epn->filep, &epn->pfd, false);
                file_put(epn->filep);
                list_delete(&epn->node);
                list_add_tail(&eph->free, &epn->node);
                goto out;
              }
          }

        list_for_every_entry(&eph->teardown, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                file_put(epn->filep);
                list_delete(&epn->node);
                list_add_tail(&eph->free, &epn->node);
                goto out;
              }
          }

        list_for_every_entry(&eph->oneshot, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                file_put(epn->filep);
                list_delete(&epn->node);
                list_add_tail(&eph->free, &epn->node);
                goto out;
              }
          }

        break;

      case EPOLL_CTL_MOD:
        finfo("%p CTL MOD: fd=%d ev=%08" PRIx32 "\n", eph, fd, ev->events);
        list_for_every_entry(&eph->setup, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                if (epn->pfd.events != (ev->events | POLLALWAYS))
                  {
                    file_poll(epn->filep, &epn->pfd, false);

                    epn->notified    = false;
                    epn->data        = ev->data;
                    epn->pfd.events  = ev->events | POLLALWAYS;
                    epn->pfd.revents = 0;

                    ret = file_poll(epn->filep, &epn->pfd, true);
                    if (ret < 0)
                      {
                        goto err;
                      }
                  }

                goto out;
              }
          }

        list_for_every_entry(&eph->teardown, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                if (epn->pfd.events != (ev->events | POLLALWAYS))
                  {
                    epn->notified    = false;
                    epn->data        = ev->data;
                    epn->pfd.events  = ev->events | POLLALWAYS;
                    epn->pfd.revents = 0;

                    ret = file_poll(epn->filep, &epn->pfd, true);
                    if (ret < 0)
                      {
                        goto err;
                      }

                    list_delete(&epn->node);
                    list_add_tail(&eph->setup, &epn->node);
                  }

                goto out;
              }
          }

        list_for_every_entry(&eph->oneshot, epn, epoll_node_t, node)
          {
            if (epn->pfd.fd == fd)
              {
                epn->notified    = false;
                epn->data        = ev->data;
                epn->pfd.events  = ev->events | POLLALWAYS;
                epn->pfd.revents = 0;

                ret = file_poll(epn->filep, &epn->pfd, true);
                if (ret < 0)
                  {
                    goto err;
                  }

                list_delete(&epn->node);
                list_add_tail(&eph->setup, &epn->node);
                break;
              }
          }

        break;

      default:
        ret = -EINVAL;
        goto err;
    }

out:
  nxrmutex_unlock(&eph->lock);
  epoll_filep_close(filep);
  return OK;
err:
  nxrmutex_unlock(&eph->lock);
err_without_lock:
  epoll_filep_close(filep);
  set_errno(-ret);
  return ERROR;
}

/****************************************************************************
 * Name: epoll_pwait
 ****************************************************************************/

int epoll_pwait(int epfd, FAR struct epoll_event *evs,
                int maxevents, int timeout, FAR const sigset_t *sigmask)
{
  FAR struct file *filep = NULL;
  FAR epoll_head_t *eph;
  sigset_t oldsigmask;
  int ret;

  eph = epoll_head_from_fd(epfd, &filep);
  if (eph == NULL)
    {
      goto out;
    }

retry:
  ret = epoll_setup(eph);
  if (ret < 0)
    {
      goto err;
    }

  /* Wait the poll ready */

  nxsig_procmask(SIG_SETMASK, sigmask, &oldsigmask);

  if (timeout == 0)
    {
      ret = -ETIMEDOUT;
    }
  else if (timeout > 0)
    {
      ret = nxsem_tickwait(&eph->sem, MSEC2TICK(timeout));
    }
  else
    {
      ret = nxsem_wait(&eph->sem);
    }

  nxsig_procmask(SIG_SETMASK, &oldsigmask, NULL);
  if (ret < 0 && ret != -ETIMEDOUT)
    {
      goto err;
    }
  else /* ret >= 0 or ret == -ETIMEDOUT */
    {
      int num = epoll_teardown(eph, evs, maxevents);
      if (num == 0 && ret >= 0)
        {
          goto retry;
        }

      ret = num;
    }

  epoll_filep_close(filep);

  return ret;

err:
  epoll_filep_close(filep);
  set_errno(-ret);
out:
  ferr("epoll wait failed:%d, timeout:%d\n", errno, timeout);
  return ERROR;
}

/****************************************************************************
 * Name: epoll_wait
 *
 * Description:
 *
 * Input Parameters:
 *
 * Returned Value:
 *
 ****************************************************************************/

int epoll_wait(int epfd, FAR struct epoll_event *evs,
               int maxevents, int timeout)
{
  FAR struct file *filep = NULL;
  FAR epoll_head_t *eph;
  int ret;

  eph = epoll_head_from_fd(epfd, &filep);
  if (eph == NULL)
    {
      goto out;
    }

retry:
  ret = epoll_setup(eph);
  if (ret < 0)
    {
      goto err;
    }

  /* Wait the poll ready */

  if (timeout == 0)
    {
      ret = -ETIMEDOUT;
    }
  else if (timeout > 0)
    {
      ret = nxsem_tickwait(&eph->sem, MSEC2TICK(timeout));
    }
  else
    {
      ret = nxsem_wait(&eph->sem);
    }

  if (ret < 0 && ret != -ETIMEDOUT)
    {
      goto err;
    }
  else /* ret >= 0 or ret == -ETIMEDOUT */
    {
      int num = epoll_teardown(eph, evs, maxevents);
      if (num == 0 && ret >= 0)
        {
          goto retry;
        }

      ret = num;
    }

  epoll_filep_close(filep);

  return ret;

err:
  epoll_filep_close(filep);
  set_errno(-ret);
out:
  ferr("epoll wait failed:%d, timeout:%d\n", errno, timeout);
  return ERROR;
}