"""
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.

"""

import collections
import fnmatch
import logging
import os
import re

import salt.utils.beacons

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"

log = logging.getLogger(__name__)


def __virtual__():
    if HAS_PYINOTIFY:
        return __virtualname__
    err_msg = "pyinotify library is missing."
    log.error("Unable to load inotify beacon: %s", err_msg)
    return False, err_msg


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
    """
    beacon_name = config.get("_beacon_name", "inotify")
    notifier = "{}.notifier".format(beacon_name)
    if notifier not in __context__:
        __context__["inotify.queue"] = collections.deque()
        wm = pyinotify.WatchManager()
        __context__[notifier] = pyinotify.Notifier(wm, _enqueue)
        if (
            "coalesce" in config
            and isinstance(config["coalesce"], bool)
            and config["coalesce"]
        ):
            __context__[notifier].coalesce_events()
    return __context__[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
    if not isinstance(config, list):
        return False, "Configuration for inotify beacon must be a list."
    else:
        config = salt.utils.beacons.list_to_dict(config)

        if "files" not in config:
            return False, "Configuration for inotify beacon must include files."
        else:
            if not isinstance(config["files"], dict):
                return (
                    False,
                    "Configuration for inotify beacon invalid, files must be a dict.",
                )

            for path in config.get("files"):

                if not isinstance(config["files"][path], dict):
                    return (
                        False,
                        "Configuration for inotify beacon must be a list of"
                        " dictionaries.",
                    )
                else:
                    if not any(
                        j in ["mask", "recurse", "auto_add"]
                        for j in config["files"][path]
                    ):
                        return (
                            False,
                            "Configuration for inotify beacon must contain mask,"
                            " recurse or auto_add items.",
                        )

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

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

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


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.
    """

    whitelist = ["_beacon_name"]
    config = salt.utils.beacons.remove_hidden_options(config, whitelist)

    config = salt.utils.beacons.list_to_dict(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"].get(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:  # pylint: disable=broad-except
                                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, bytes):
                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


def close(config):
    config = salt.utils.beacons.list_to_dict(config)
    beacon_name = config.get("_beacon_name", "inotify")
    notifier = "{}.notifier".format(beacon_name)
    if notifier in __context__:
        __context__[notifier].stop()
        del __context__[notifier]
