import logging
import os

from pathlib import Path

import requests

from watchdog.events import PatternMatchingEventHandler
from watchdog.observers.polling import PollingObserver


class Watcher(PatternMatchingEventHandler):
    def __init__(self, watchdir: Path, notify_url: str):
        super().__init__(ignore_directories=True)
        self.watchdir = watchdir
        self.notify_url = notify_url
        self.watcher = PollingObserver()
        self.watcher.schedule(self, self.watchdir, recursive=True)
        self.logger = logging.getLogger('arec-watcher.Watcher')

    def start(self) -> None:
        self.logger.debug('Starting')
        self.logger.info("Montoring '%s' for new uploads, notifying to '%s'",
                         self.watchdir,
                         self.notify_url)
        self._pickup_existing()
        return self.watcher.start()

    def shutdown(self) -> None:
        self.logger.debug('Stopping')
        return self.watcher.stop()

    def is_datfile(self, path: Path) -> bool:
        return path.match('*.dat')

    def _pickup_existing(self):
        for subdir in self.watchdir.iterdir():
            if not subdir.is_dir():
                continue

            for child in subdir.iterdir():
                self._process(child)

    def _process(self, path: Path) -> None:
        if not self.is_datfile(path):
            return

        basedir = path.parent

        sentinel = basedir / 'arec-watcher-notified'
        if sentinel.exists():
            self.logger.debug('Ignored %s due to sentinel file present',
                              basedir)
            return

        self.logger.info('Picked up %s', basedir)

        # The arec upload fails to respect the parent's ACL,
        # so we have to fix the permissions here.
        self._make_group_writable(basedir)

        try:
            result = requests.post(self.notify_url,
                                   data={'upload_dir': basedir})
            result.raise_for_status()
            sentinel.touch(exist_ok=False)
            self.logger.info('Successfully notified %s about %s',
                             self.notify_url,
                             basedir)
        except requests.HTTPError as e:
            self.logger.error('Failed to notify %s about %s',
                              self.notify_url,
                              basedir,
                              exc_info=e)

    def on_created(self, event):
        self._process(Path(event.src_path))

    def on_moved(self, event):
        self._process(Path(event.dest_path))

    def _make_group_writable(self, path: Path):
        # Python doesn't have any good tools for recursive permissions,
        # so we lean on the OS.
        os.system(f'chmod -R g+w {path}')