#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright (C) 2011 Yesudeep Mangalapilly <yesudeep@gmail.com>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


"""
:module: watchdog.observers.polling
:synopsis: Polling emitter implementation.
:author: Yesudeep Mangalapilly <yesudeep@gmail.com>

Classes
-------
.. autoclass:: PollingEmitter
   :members:
   :show-inheritance:
"""


from __future__ import with_statement

import time
import threading

from watchdog.utils.dirsnapshot import DirectorySnapshot, DirectorySnapshotDiff
from watchdog.observers.api import \
    EventEmitter, \
    BaseObserver, \
    DEFAULT_OBSERVER_TIMEOUT, \
    DEFAULT_EMITTER_TIMEOUT
from watchdog.events import \
    DirMovedEvent, \
    DirDeletedEvent, \
    DirCreatedEvent, \
    DirModifiedEvent, \
    FileMovedEvent, \
    FileDeletedEvent, \
    FileCreatedEvent, \
    FileModifiedEvent


class PollingEmitter(EventEmitter):
    """
    Platform-independent emitter that polls a directory to detect file
    system changes.
    """
    def __init__(self, event_queue, watch, timeout=DEFAULT_EMITTER_TIMEOUT):
        EventEmitter.__init__(self, event_queue, watch, timeout)
        self._snapshot = DirectorySnapshot(watch.path, watch.is_recursive)
        self._lock = threading.Lock()

    def on_thread_exit(self):
        self._snapshot = None


    def queue_events(self, timeout):
        with self._lock:
            # We don't want to hit the disk continuously.
            # timeout behaves like an interval for polling emitters.
            time.sleep(timeout)

            # Get event diff between fresh snapshot and previous snapshot.
            # Update snapshot.
            new_snapshot = DirectorySnapshot(self.watch.path, self.watch.is_recursive)
            events = DirectorySnapshotDiff(self._snapshot, new_snapshot)
            self._snapshot = new_snapshot

            # Files.
            for src_path in events.files_deleted:
                self.queue_event(FileDeletedEvent(src_path))
            for src_path in events.files_modified:
                self.queue_event(FileModifiedEvent(src_path))
            for src_path in events.files_created:
                self.queue_event(FileCreatedEvent(src_path))
            for src_path, dest_path in events.files_moved:
                self.queue_event(FileMovedEvent(src_path, dest_path))

            # Directories.
            for src_path in events.dirs_deleted:
                self.queue_event(DirDeletedEvent(src_path))
            for src_path in events.dirs_modified:
                self.queue_event(DirModifiedEvent(src_path))
            for src_path in events.dirs_created:
                self.queue_event(DirCreatedEvent(src_path))
            for src_path, dest_path in events.dirs_moved:
                self.queue_event(DirMovedEvent(src_path, dest_path))



class PollingObserver(BaseObserver):
    """
    Observer thread that schedules watching directories and dispatches
    calls to event handlers.
    """
    def __init__(self, timeout=DEFAULT_OBSERVER_TIMEOUT):
        BaseObserver.__init__(self, emitter_class=PollingEmitter, timeout=timeout)


