from typing import Type, Generator, Set, Dict, List
from collections import defaultdict

from ._encyclopaedia_metallum import EncyclopaediaMetallum
from ._musify import Musify
from ._youtube import YouTube
from ._youtube_music import YoutubeMusic
from ._bandcamp import Bandcamp
from ._genius import Genius
from ._abstract import Page, INDEPENDENT_DB_OBJECTS


_registered_pages: Dict[Type[Page], Set[Page]] = defaultdict(set)


def get_pages(*page_types: List[Type[Page]]) -> Generator[Page, None, None]:
    if len(page_types) == 0:
        page_types = _registered_pages.keys()

    for page_type in page_types:
        yield from _registered_pages[page_type]


def register_page(page_type: Type[Page], **kwargs):
    if page_type in _registered_pages:
        return

    _registered_pages[page_type].add(page_type(**kwargs))


def deregister_page(page_type: Type[Page]):
    if page_type not in _registered_pages:
        return

    for p in _registered_pages[page_type]:
        p.__del__()
    del _registered_pages[page_type]

def scan_for_pages():
    # assuming the wanted pages are the leaf classes of the interface
    leaf_classes = []

    _class_list = [Page]
    while len(_class_list):
        _class = _class_list.pop()
        _class_subclasses = _class.__subclasses__()

        if len(_class_subclasses) == 0:
            if _class.REGISTER:
                leaf_classes.append(_class)
        else:
            _class_list.extend(_class_subclasses)

    print(leaf_classes)
    for leaf_class in leaf_classes:
        register_page(leaf_class)