""":module: watchdog.observers.inotify_buffer
:synopsis: A wrapper for ``Inotify``.
:author: thomas.amland@gmail.com (Thomas Amland)
:author: contact@tiger-222.fr (Mickaël Schoentgen)
:platforms: linux
"""

from __future__ import annotations

import logging

from watchdog.observers.inotify_c import Inotify, InotifyEvent
from watchdog.utils import BaseThread
from watchdog.utils.delayed_queue import DelayedQueue

logger = logging.getLogger(__name__)


class InotifyBuffer(BaseThread):
    """A wrapper for `Inotify` that holds events for `delay` seconds. During
    this time, IN_MOVED_FROM and IN_MOVED_TO events are paired.
    """

    delay = 0.5

    def __init__(self, path: bytes, *, recursive: bool = False, event_mask: int | None = None) -> None:
        super().__init__()
        # XXX: Remove quotes after Python 3.9 drop
        self._queue = DelayedQueue["InotifyEvent | tuple[InotifyEvent, InotifyEvent]"](self.delay)
        self._inotify = Inotify(path, recursive=recursive, event_mask=event_mask)
        self.start()

    def read_event(self) -> InotifyEvent | tuple[InotifyEvent, InotifyEvent] | None:
        """Returns a single event or a tuple of from/to events in case of a
        paired move event. If this buffer has been closed, immediately return
        None.
        """
        return self._queue.get()

    def on_thread_stop(self) -> None:
        self._inotify.close()
        self._queue.close()

    def close(self) -> None:
        self.stop()
        self.join()

    def _group_events(self, event_list: list[InotifyEvent]) -> list[InotifyEvent | tuple[InotifyEvent, InotifyEvent]]:
        """Group any matching move events"""
        grouped: list[InotifyEvent | tuple[InotifyEvent, InotifyEvent]] = []
        for inotify_event in event_list:
            logger.debug("in-event %s", inotify_event)

            def matching_from_event(event: InotifyEvent | tuple[InotifyEvent, InotifyEvent]) -> bool:
                return not isinstance(event, tuple) and event.is_moved_from and event.cookie == inotify_event.cookie

            if inotify_event.is_moved_to:
                # Check if move_from is already in the buffer
                for index, event in enumerate(grouped):
                    if matching_from_event(event):
                        grouped[index] = (event, inotify_event)  # type: ignore[assignment]
                        break
                else:
                    # Check if move_from is in delayqueue already
                    from_event = self._queue.remove(matching_from_event)
                    if from_event is not None:
                        grouped.append((from_event, inotify_event))  # type: ignore[arg-type]
                    else:
                        logger.debug("could not find matching move_from event")
                        grouped.append(inotify_event)
            else:
                grouped.append(inotify_event)
        return grouped

    def run(self) -> None:
        """Read event from `inotify` and add them to `queue`. When reading a
        IN_MOVE_TO event, remove the previous added matching IN_MOVE_FROM event
        and add them back to the queue as a tuple.
        """
        deleted_self = False
        while self.should_keep_running() and not deleted_self:
            inotify_events = self._inotify.read_events()
            grouped_events = self._group_events(inotify_events)
            for inotify_event in grouped_events:
                if not isinstance(inotify_event, tuple) and inotify_event.is_ignored:
                    if inotify_event.src_path == self._inotify.path:
                        # Watch was removed explicitly (inotify_rm_watch(2)) or automatically (file
                        # was deleted, or filesystem was unmounted), stop watching for events
                        deleted_self = True
                    continue

                # Only add delay for unmatched move_from events
                delay = not isinstance(inotify_event, tuple) and inotify_event.is_moved_from
                self._queue.put(inotify_event, delay=delay)

                if (
                    not isinstance(inotify_event, tuple)
                    and inotify_event.is_delete_self
                    and inotify_event.src_path == self._inotify.path
                ):
                    # Deleted the watched directory, stop watching for events
                    deleted_self = True