# -*- coding: utf-8 -*-
'''
Watch files and translate the changes into salt events

:depends:   - pyinotify Python module >= 0.9.5

:Caution:   Using generic mask options like open, access, ignored, and
            closed_nowrite with reactors can easily cause the reactor
            to loop on itself. To mitigate this behavior, consider
            setting the `disable_during_state_run` flag to `True` in
            the beacon configuration.

:note: The `inotify` beacon only works on OSes that have `inotify` kernel support.
       Currently this excludes FreeBSD, macOS, and Windows.

'''
# Import Python libs
from __future__ import absolute_import
import collections
import fnmatch
import os
import re

# Import salt libs
import salt.ext.six

# Import third party libs
try:
    import pyinotify
    HAS_PYINOTIFY = True
    DEFAULT_MASK = pyinotify.IN_CREATE | pyinotify.IN_DELETE | pyinotify.IN_MODIFY
    MASKS = {}
    for var in dir(pyinotify):
        if var.startswith('IN_'):
            key = var[3:].lower()
            MASKS[key] = getattr(pyinotify, var)
except ImportError:
    HAS_PYINOTIFY = False
    DEFAULT_MASK = None

__virtualname__ = 'inotify'

import logging
log = logging.getLogger(__name__)


def __virtual__():
    if HAS_PYINOTIFY:
        return __virtualname__
    return False


def _get_mask(mask):
    '''
    Return the int that represents the mask
    '''
    return MASKS.get(mask, 0)


def _enqueue(revent):
    '''
    Enqueue the event
    '''
    __context__['inotify.queue'].append(revent)


def _get_notifier(config):
    '''
    Check the context for the notifier and construct it if not present
    '''
    if 'inotify.notifier' not in __context__:
        __context__['inotify.queue'] = collections.deque()
        wm = pyinotify.WatchManager()
        __context__['inotify.notifier'] = pyinotify.Notifier(wm, _enqueue)
        if ('coalesce' in config and
                isinstance(config['coalesce'], bool) and
                config['coalesce']):
            __context__['inotify.notifier'].coalesce_events()
    return __context__['inotify.notifier']


def __validate__(config):
    '''
    Validate the beacon configuration
    '''

    VALID_MASK = [
        'access',
        'attrib',
        'close_nowrite',
        'close_write',
        'create',
        'delete',
        'delete_self',
        'excl_unlink',
        'ignored',
        'modify',
        'moved_from',
        'moved_to',
        'move_self',
        'oneshot',
        'onlydir',
        'open',
        'unmount'
    ]

    # Configuration for inotify beacon should be a dict of dicts
    log.debug('config {0}'.format(config))
    if not isinstance(config, dict):
        return False, 'Configuration for inotify beacon must be a dictionary.'
    else:
        for config_item in config:
            if not isinstance(config[config_item], dict):
                return False, ('Configuration for inotify beacon must '
                               'be a dictionary of dictionaries.')
            else:
                if not any(j in ['mask', 'recurse', 'auto_add'] for j in config[config_item]):
                    return False, ('Configuration for inotify beacon must '
                                   'contain mask, recurse or auto_add items.')

            if 'auto_add' in config[config_item]:
                if not isinstance(config[config_item]['auto_add'], bool):
                    return False, ('Configuration for inotify beacon '
                                   'auto_add must be boolean.')

            if 'recurse' in config[config_item]:
                if not isinstance(config[config_item]['recurse'], bool):
                    return False, ('Configuration for inotify beacon '
                                   'recurse must be boolean.')

            if 'mask' in config[config_item]:
                if not isinstance(config[config_item]['mask'], list):
                    return False, ('Configuration for inotify beacon '
                                   'mask must be list.')
                for mask in config[config_item]['mask']:
                    if mask not in VALID_MASK:
                        return False, ('Configuration for inotify beacon '
                                       'invalid mask option {0}.'.format(mask))
    return True, 'Valid beacon configuration'


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

    Example Config

    .. code-block:: yaml

        beacons:
          inotify:
            /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.
    '''
    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:
                    break
                path = os.path.dirname(path)

            excludes = config[path].get('exclude', '')
            if excludes and isinstance(excludes, list):
                for exclude in excludes:
                    if isinstance(exclude, dict):
                        if exclude.values()[0].get('regex', False):
                            try:
                                if re.search(exclude.keys()[0], event.pathname):
                                    _append = False
                            except Exception:
                                log.warning('Failed to compile regex: {0}'.format(exclude.keys()[0]))
                        else:
                            exclude = exclude.keys()[0]
                    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 {0} from event for {1}'.format(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:
        if isinstance(config[path], dict):
            mask = config[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[path].get('recurse', False)
            auto_add = config[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[path].get('exclude', '')
            excl = None
            if isinstance(excludes, list):
                excl = []
                for exclude in excludes:
                    if isinstance(exclude, dict):
                        excl.append(exclude.keys()[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


def close(config):
    if 'inotify.notifier' in __context__:
        __context__['inotify.notifier'].stop()
        del __context__['inotify.notifier']
