/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.

 * 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.

 */

#include "uv.h"

#include "uv/tree.h"

#include "internal.h"

#include <stdint.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <assert.h>

#include <errno.h>

#include <sys/types.h>

#include <unistd.h>

struct watcher_list {

  RB_ENTRY(watcher_list) entry;

  QUEUE watchers;

  int iterating;

  char* path;

  int wd;

};

struct watcher_root {

  struct watcher_list* rbh_root;

};

#define CAST(p) ((struct watcher_root*)(p))

static int compare_watchers(const struct watcher_list* a,

                            const struct watcher_list* b) {

  if (a->wd < b->wd) return -1;

  if (a->wd > b->wd) return 1;

  return 0;

}

RB_GENERATE_STATIC(watcher_root, watcher_list, entry, compare_watchers)

static void uv__inotify_read(uv_loop_t* loop,

                             uv__io_t* w,

                             unsigned int revents);

static void maybe_free_watcher_list(struct watcher_list* w,

                                    uv_loop_t* loop);

static int new_inotify_fd(void) {

  int err;

  int fd;

  fd = uv__inotify_init1(UV__IN_NONBLOCK | UV__IN_CLOEXEC);

  if (fd != -1)

    return fd;

  if (errno != ENOSYS)

    return UV__ERR(errno);

  fd = uv__inotify_init();

  if (fd == -1)

    return UV__ERR(errno);

  err = uv__cloexec(fd, 1);

  if (err == 0)

    err = uv__nonblock(fd, 1);

  if (err) {

    uv__close(fd);

    return err;

  }

  return fd;

}

static int init_inotify(uv_loop_t* loop) {

  int err;

  if (loop->inotify_fd != -1)

    return 0;

  err = new_inotify_fd();

  if (err < 0)

    return err;

  loop->inotify_fd = err;

  uv__io_init(&loop->inotify_read_watcher, uv__inotify_read, loop->inotify_fd);

  uv__io_start(loop, &loop->inotify_read_watcher, POLLIN);

  return 0;

}

int uv__inotify_fork(uv_loop_t* loop, void* old_watchers) {

  /* Open the inotify_fd, and re-arm all the inotify watchers. */

  int err;

  struct watcher_list* tmp_watcher_list_iter;

  struct watcher_list* watcher_list;

  struct watcher_list tmp_watcher_list;

  QUEUE queue;

  QUEUE* q;

  uv_fs_event_t* handle;

  char* tmp_path;

  if (old_watchers != NULL) {

    /* We must restore the old watcher list to be able to close items

     * out of it.

     */

    loop->inotify_watchers = old_watchers;

    QUEUE_INIT(&tmp_watcher_list.watchers);

    /* Note that the queue we use is shared with the start and stop()

     * functions, making QUEUE_FOREACH unsafe to use. So we use the

     * QUEUE_MOVE trick to safely iterate. Also don't free the watcher

     * list until we're done iterating. c.f. uv__inotify_read.

     */

    RB_FOREACH_SAFE(watcher_list, watcher_root,

                    CAST(&old_watchers), tmp_watcher_list_iter) {

      watcher_list->iterating = 1;

      QUEUE_MOVE(&watcher_list->watchers, &queue);

      while (!QUEUE_EMPTY(&queue)) {

        q = QUEUE_HEAD(&queue);

        handle = QUEUE_DATA(q, uv_fs_event_t, watchers);

        /* It's critical to keep a copy of path here, because it

         * will be set to NULL by stop() and then deallocated by

         * maybe_free_watcher_list

         */

        tmp_path = uv__strdup(handle->path);

        assert(tmp_path != NULL);

        QUEUE_REMOVE(q);

        QUEUE_INSERT_TAIL(&watcher_list->watchers, q);

        uv_fs_event_stop(handle);

        QUEUE_INSERT_TAIL(&tmp_watcher_list.watchers, &handle->watchers);

        handle->path = tmp_path;

      }

      watcher_list->iterating = 0;

      maybe_free_watcher_list(watcher_list, loop);

    }

    QUEUE_MOVE(&tmp_watcher_list.watchers, &queue);

    while (!QUEUE_EMPTY(&queue)) {

        q = QUEUE_HEAD(&queue);

        QUEUE_REMOVE(q);

        handle = QUEUE_DATA(q, uv_fs_event_t, watchers);

        tmp_path = handle->path;

        handle->path = NULL;

        err = uv_fs_event_start(handle, handle->cb, tmp_path, 0);

        uv__free(tmp_path);

        if (err)

          return err;

    }

  }

  return 0;

}

static struct watcher_list* find_watcher(uv_loop_t* loop, int wd) {

  struct watcher_list w;

  w.wd = wd;

  return RB_FIND(watcher_root, CAST(&loop->inotify_watchers), &w);

}

static void maybe_free_watcher_list(struct watcher_list* w, uv_loop_t* loop) {

  /* if the watcher_list->watchers is being iterated over, we can't free it. */

  if ((!w->iterating) && QUEUE_EMPTY(&w->watchers)) {

    /* No watchers left for this path. Clean up. */

    RB_REMOVE(watcher_root, CAST(&loop->inotify_watchers), w);

    uv__inotify_rm_watch(loop->inotify_fd, w->wd);

    uv__free(w);

  }

}

static void uv__inotify_read(uv_loop_t* loop,

                             uv__io_t* dummy,

                             unsigned int events) {

  const struct uv__inotify_event* e;

  struct watcher_list* w;

  uv_fs_event_t* h;

  QUEUE queue;

  QUEUE* q;

  const char* path;

  ssize_t size;

  const char *p;

  /* needs to be large enough for sizeof(inotify_event) + strlen(path) */

  char buf[4096];

  while (1) {

    do

      size = read(loop->inotify_fd, buf, sizeof(buf));

    while (size == -1 && errno == EINTR);

    if (size == -1) {

      assert(errno == EAGAIN || errno == EWOULDBLOCK);

      break;

    }

    assert(size > 0); /* pre-2.6.21 thing, size=0 == read buffer too small */

    /* Now we have one or more inotify_event structs. */

    for (p = buf; p < buf + size; p += sizeof(*e) + e->len) {

      e = (const struct uv__inotify_event*)p;

      events = 0;

      if (e->mask & (UV__IN_ATTRIB|UV__IN_MODIFY))

        events |= UV_CHANGE;

      if (e->mask & ~(UV__IN_ATTRIB|UV__IN_MODIFY))

        events |= UV_RENAME;

      w = find_watcher(loop, e->wd);

      if (w == NULL)

        continue; /* Stale event, no watchers left. */

      /* inotify does not return the filename when monitoring a single file

       * for modifications. Repurpose the filename for API compatibility.

       * I'm not convinced this is a good thing, maybe it should go.

       */

      path = e->len ? (const char*) (e + 1) : uv__basename_r(w->path);

      /* We're about to iterate over the queue and call user's callbacks.

       * What can go wrong?

       * A callback could call uv_fs_event_stop()

       * and the queue can change under our feet.

       * So, we use QUEUE_MOVE() trick to safely iterate over the queue.

       * And we don't free the watcher_list until we're done iterating.

       *

       * First,

       * tell uv_fs_event_stop() (that could be called from a user's callback)

       * not to free watcher_list.

       */

      w->iterating = 1;

      QUEUE_MOVE(&w->watchers, &queue);

      while (!QUEUE_EMPTY(&queue)) {

        q = QUEUE_HEAD(&queue);

        h = QUEUE_DATA(q, uv_fs_event_t, watchers);

        QUEUE_REMOVE(q);

        QUEUE_INSERT_TAIL(&w->watchers, q);

        h->cb(h, path, events, 0);

      }

      /* done iterating, time to (maybe) free empty watcher_list */

      w->iterating = 0;

      maybe_free_watcher_list(w, loop);

    }

  }

}

int uv_fs_event_init(uv_loop_t* loop, uv_fs_event_t* handle) {

  uv__handle_init(loop, (uv_handle_t*)handle, UV_FS_EVENT);

  return 0;

}

int uv_fs_event_start(uv_fs_event_t* handle,

                      uv_fs_event_cb cb,

                      const char* path,

                      unsigned int flags) {

  struct watcher_list* w;

  int events;

  int err;

  int wd;

  if (uv__is_active(handle))

    return UV_EINVAL;

  err = init_inotify(handle->loop);

  if (err)

    return err;

  events = UV__IN_ATTRIB

         | UV__IN_CREATE

         | UV__IN_MODIFY

         | UV__IN_DELETE

         | UV__IN_DELETE_SELF

         | UV__IN_MOVE_SELF

         | UV__IN_MOVED_FROM

         | UV__IN_MOVED_TO;

  wd = uv__inotify_add_watch(handle->loop->inotify_fd, path, events);

  if (wd == -1)

    return UV__ERR(errno);

  w = find_watcher(handle->loop, wd);

  if (w)

    goto no_insert;

  w = uv__malloc(sizeof(*w) + strlen(path) + 1);

  if (w == NULL)

    return UV_ENOMEM;

  w->wd = wd;

  w->path = strcpy((char*)(w + 1), path);

  QUEUE_INIT(&w->watchers);

  w->iterating = 0;

  RB_INSERT(watcher_root, CAST(&handle->loop->inotify_watchers), w);

no_insert:

  uv__handle_start(handle);

  QUEUE_INSERT_TAIL(&w->watchers, &handle->watchers);

  handle->path = w->path;

  handle->cb = cb;

  handle->wd = wd;

  return 0;

}

int uv_fs_event_stop(uv_fs_event_t* handle) {

  struct watcher_list* w;

  if (!uv__is_active(handle))

    return 0;

  w = find_watcher(handle->loop, handle->wd);

  assert(w != NULL);

  handle->wd = -1;

  handle->path = NULL;

  uv__handle_stop(handle);

  QUEUE_REMOVE(&handle->watchers);

  maybe_free_watcher_list(w, handle->loop);

  return 0;

}

void uv__fs_event_close(uv_fs_event_t* handle) {

  uv_fs_event_stop(handle);

}