class Database:
__slots__ = ['_path', '_signal', '_db']
Event = namedtuple('Event', ['type', 'feed', 'link'])
def __init__(self, path: str):
self._path = path
self._signal = Signal()
self._db = self._load_db()
def __getitem__(self, key):
return self._db[key]
def feeds(self):
return self._db.keys()
def channels(self):
return (ch for chs in self._db.values() for ch in chs.values())
def channels_of_feed(self, feed: str, links: bool = True):
origin = self._db[feed].keys if links else self._db[feed].values
return (ch for ch in origin())
def add_feed(self, link: str):
self._db[link] = {}
self.flush()
def add_channel(self, link: str, last_id: int, feed: str):
self._db[feed][link] = Channel(link, last_id, feed)
self.flush()
self._publish(self.Event('add', feed, link))
def remove_channel(self, link: str, feed: str):
del self._db[feed][link]
self.flush()
self._publish(self.Event('remove', feed, link))
def remove_feed(self, feed: str):
for link in self._db[feed].keys():
self._publish(self.Event('remove', feed, link))
del self._db[feed]
self.flush()
def feed_nonempty(self, feed: str):
return bool(self._db[feed].keys())
def feed_exists(self, link: str):
return link in self._db.keys()
def channel_exists(self, link: str, feed: str = None):
return link in self._db[feed].keys() if feed else any(
link in chs.keys() for chs in self._db.values())
def flush(self):
with open(self._path, 'w') as db:
json.dump(self._db, db)
def subscribe(self, receiver: Callable[[Database.Event], None]):
self._signal.connect(receiver)
def _publish(self, event: Database.Event):
self._signal(event)
def _load_db(self) -> Dict[str, Dict[str, Channel]]:
try:
with open(self._path) as db:
_db = json.load(db)
for channels in _db.values():
for link in channels.keys():
channels[link] = Channel(*channels[link])
return _db
except FileNotFoundError:
return {}
