from django.core.files.storage import Storage

class MultiStorage(Storage):
    ''' Django storage class that proxies multiple storage classes.

    Uses a name prefix to determine store e.g. 'images:foo/bar.jpg'
    '''

    def __init__(self, config=None):
        self.config = config or getattr(settings, 'BRING_YOUR_OWN_STORAGE', {})
        self._cache = {}

    def get_storage(self, name):
        if name not in self._cache:
            config = self.config[name]
            self._cache[name] = get_storage_class(config['storage'])(**config['settings'])
        return self._cache[name]

    def split(self, name):
        return name.split(":", 1)

    def _open(self, name, mode='rb'):
        storage, p = self.split(name)
        return self.get_storage(storage)._open(p, mode)

    def _proxy(self, method, name, *args, **kwargs):
        storage, p = self.split(name)
        sname = getattr(self.get_storage(storage), method)(name, *args, **kwargs)
        if sname is not None:
            return f"{storage}:{sname}"


    def _save(self, name, content, max_length=None):
        return self._proxy('save', name, content, max_length)

class BYOStorage(MultiStorage):
    ''' Database driven Bring-Your-Own-Storage

    Multiple storages can 
    '''

    def get_storage(self, name):
        if name not in self._cache:

            # use storage from config by default
            if name in self.config:
                return super(BYOStorage, self).get_storage(name)

            from .models import UserStorage
            obj = UserStorage.objects.get(name=name)
            self._cache[name] = obj.instance()
        return self._cache[name]