Watch the configured files

    Example Config

    .. code-block:: yaml

        beacons:
          inotify:
            - files:
                /path/to/file/or/dir:
                  mask:
                    - open
                    - create
                    - close_write
                  recurse: True
                  auto_add: True
                  exclude:
                    - /path/to/file/or/dir/exclude1
                    - /path/to/file/or/dir/exclude2
                    - /path/to/file/or/dir/regex[a-m]*$:
                        regex: True
            - coalesce: True

    The mask list can contain the following events (the default mask is create,
    delete, and modify):

    * access            - File accessed
    * attrib            - File metadata changed
    * close_nowrite     - Unwritable file closed
    * close_write       - Writable file closed
    * create            - File created in watched directory
    * delete            - File deleted from watched directory
    * delete_self       - Watched file or directory deleted
    * modify            - File modified
    * moved_from        - File moved out of watched directory
    * moved_to          - File moved into watched directory
    * move_self         - Watched file moved
    * open              - File opened

    The mask can also contain the following options:

    * dont_follow       - Don't dereference symbolic links
    * excl_unlink       - Omit events for children after they have been unlinked
    * oneshot           - Remove watch after one event
    * onlydir           - Operate only if name is directory

    recurse:
      Recursively watch files in the directory
    auto_add:
      Automatically start watching files that are created in the watched directory
    exclude:
      Exclude directories or files from triggering events in the watched directory.
      Can use regex if regex is set to True
    coalesce:
      If this coalescing option is enabled, events are filtered based on
      their unicity, only unique events are enqueued, doublons are discarded.
      An event is unique when the combination of its fields (wd, mask,
      cookie, name) is unique among events of a same batch. After a batch of
      events is processed any events are accepted again.
      This option is top-level (at the same level as the path) and therefore
      affects all paths that are being watched. This is due to this option
      being at the Notifier level in pyinotify.

def beacon(config):
    '''
    Watch the configured files

    Example Config

    .. code-block:: yaml

        beacons:
          inotify:
            - files:
                /path/to/file/or/dir:
                  mask:
                    - open
                    - create
                    - close_write
                  recurse: True
                  auto_add: True
                  exclude:
                    - /path/to/file/or/dir/exclude1
                    - /path/to/file/or/dir/exclude2
                    - /path/to/file/or/dir/regex[a-m]*$:
                        regex: True
            - coalesce: True

    The mask list can contain the following events (the default mask is create,
    delete, and modify):

    * access            - File accessed
    * attrib            - File metadata changed
    * close_nowrite     - Unwritable file closed
    * close_write       - Writable file closed
    * create            - File created in watched directory
    * delete            - File deleted from watched directory
    * delete_self       - Watched file or directory deleted
    * modify            - File modified
    * moved_from        - File moved out of watched directory
    * moved_to          - File moved into watched directory
    * move_self         - Watched file moved
    * open              - File opened

    The mask can also contain the following options:

    * dont_follow       - Don't dereference symbolic links
    * excl_unlink       - Omit events for children after they have been unlinked
    * oneshot           - Remove watch after one event
    * onlydir           - Operate only if name is directory

    recurse:
      Recursively watch files in the directory
    auto_add:
      Automatically start watching files that are created in the watched directory
    exclude:
      Exclude directories or files from triggering events in the watched directory.
      Can use regex if regex is set to True
    coalesce:
      If this coalescing option is enabled, events are filtered based on
      their unicity, only unique events are enqueued, doublons are discarded.
      An event is unique when the combination of its fields (wd, mask,
      cookie, name) is unique among events of a same batch. After a batch of
      events is processed any events are accepted again.
      This option is top-level (at the same level as the path) and therefore
      affects all paths that are being watched. This is due to this option
      being at the Notifier level in pyinotify.
    '''
    _config = {}
    list(map(_config.update, config))

    ret = []
    notifier = _get_notifier(_config)
    wm = notifier._watch_manager

    # Read in existing events
    if notifier.check_events(1):
        notifier.read_events()
        notifier.process_events()
        queue = __context__['inotify.queue']
        while queue:
            event = queue.popleft()

            _append = True
            # Find the matching path in config
            path = event.path
            while path != '/':
                if path in _config.get('files', {}):
                    break
                path = os.path.dirname(path)

            excludes = _config['files'][path].get('exclude', '')

            if excludes and isinstance(excludes, list):
                for exclude in excludes:
                    if isinstance(exclude, dict):
                        _exclude = next(iter(exclude))
                        if exclude[_exclude].get('regex', False):
                            try:
                                if re.search(_exclude, event.pathname):
                                    _append = False
                            except Exception:
                                log.warning('Failed to compile regex: %s',
                                            _exclude)
                        else:
                            exclude = _exclude
                    elif '*' in exclude:
                        if fnmatch.fnmatch(event.pathname, exclude):
                            _append = False
                    else:
                        if event.pathname.startswith(exclude):
                            _append = False

            if _append:
                sub = {'tag': event.path,
                       'path': event.pathname,
                       'change': event.maskname}
                ret.append(sub)
            else:
                log.info('Excluding %s from event for %s', event.pathname, path)

    # Get paths currently being watched
    current = set()
    for wd in wm.watches:
        current.add(wm.watches[wd].path)

    # Update existing watches and add new ones
    # TODO: make the config handle more options
    for path in _config.get('files', ()):

        if isinstance(_config['files'][path], dict):
            mask = _config['files'][path].get('mask', DEFAULT_MASK)
            if isinstance(mask, list):
                r_mask = 0
                for sub in mask:
                    r_mask |= _get_mask(sub)
            elif isinstance(mask, salt.ext.six.binary_type):
                r_mask = _get_mask(mask)
            else:
                r_mask = mask
            mask = r_mask
            rec = _config['files'][path].get('recurse', False)
            auto_add = _config['files'][path].get('auto_add', False)
        else:
            mask = DEFAULT_MASK
            rec = False
            auto_add = False

        if path in current:
            for wd in wm.watches:
                if path == wm.watches[wd].path:
                    update = False
                    if wm.watches[wd].mask != mask:
                        update = True
                    if wm.watches[wd].auto_add != auto_add:
                        update = True
                    if update:
                        wm.update_watch(wd, mask=mask, rec=rec, auto_add=auto_add)
        elif os.path.exists(path):
            excludes = _config['files'][path].get('exclude', '')
            excl = None
            if isinstance(excludes, list):
                excl = []
                for exclude in excludes:
                    if isinstance(exclude, dict):
                        excl.append(list(exclude)[0])
                    else:
                        excl.append(exclude)
                excl = pyinotify.ExcludeFilter(excl)

            wm.add_watch(path, mask, rec=rec, auto_add=auto_add, exclude_filter=excl)

    # Return event data
    return ret