import os

from .sessions import NullSessionInterface, RedisSessionInterface, \
    MemcachedSessionInterface, FileSystemSessionInterface, \
    MongoDBSessionInterface, SqlAlchemySessionInterface

__version__ = '0.5.0'


class Session(object):
    """This class is used to add Server-side Session to one or more Flask
    applications.

    There are two usage modes.  One is initialize the instance with a very
    specific Flask application::

        app = Flask(__name__)
        Session(app)

    The second possibility is to create the object once and configure the
    application later::

        sess = Session()

        def create_app():
            app = Flask(__name__)
            sess.init_app(app)
            return app

    By default Flask-Session will use :class:`NullSessionInterface`, you
    really should configurate your app to use a different SessionInterface.

    .. note::

        You can not use ``Session`` instance directly, what ``Session`` does
        is just change the :attr:`~flask.Flask.session_interface` attribute on
        your Flask applications.
    """

    def __init__(self, app=None):
        self.app = app
        if app is not None:
            self.init_app(app)

    def init_app(self, app):
        """This is used to set up session for your app object.

        :param app: the Flask app object with proper configuration.
        """
        app.session_interface = self._get_interface(app)

    def _get_interface(self, app):
        config = app.config.copy()
        config.setdefault('SESSION_TYPE', 'null')
        config.setdefault('SESSION_PERMANENT', True)
        config.setdefault('SESSION_USE_SIGNER', False)
        config.setdefault('SESSION_KEY_PREFIX', 'session:')
        config.setdefault('SESSION_REDIS', None)
        config.setdefault('SESSION_MEMCACHED', None)
        config.setdefault('SESSION_FILE_DIR',
                          os.path.join(os.getcwd(), 'flask_session'))
        config.setdefault('SESSION_FILE_THRESHOLD', 500)
        config.setdefault('SESSION_FILE_MODE', 384)
        config.setdefault('SESSION_MONGODB', None)
        config.setdefault('SESSION_MONGODB_DB', 'flask_session')
        config.setdefault('SESSION_MONGODB_COLLECT', 'sessions')
        config.setdefault('SESSION_SQLALCHEMY', None)
        config.setdefault('SESSION_SQLALCHEMY_TABLE', 'sessions')

        if config['SESSION_TYPE'] == 'redis':
            session_interface = RedisSessionInterface(
                config['SESSION_REDIS'], config['SESSION_KEY_PREFIX'],
                config['SESSION_USE_SIGNER'], config['SESSION_PERMANENT'])
        elif config['SESSION_TYPE'] == 'memcached':
            session_interface = MemcachedSessionInterface(
                config['SESSION_MEMCACHED'], config['SESSION_KEY_PREFIX'],
                config['SESSION_USE_SIGNER'], config['SESSION_PERMANENT'])
        elif config['SESSION_TYPE'] == 'filesystem':
            session_interface = FileSystemSessionInterface(
                config['SESSION_FILE_DIR'], config['SESSION_FILE_THRESHOLD'],
                config['SESSION_FILE_MODE'], config['SESSION_KEY_PREFIX'],
                config['SESSION_USE_SIGNER'], config['SESSION_PERMANENT'])
        elif config['SESSION_TYPE'] == 'mongodb':
            session_interface = MongoDBSessionInterface(
                config['SESSION_MONGODB'], config['SESSION_MONGODB_DB'],
                config['SESSION_MONGODB_COLLECT'],
                config['SESSION_KEY_PREFIX'], config['SESSION_USE_SIGNER'],
                config['SESSION_PERMANENT'])
        elif config['SESSION_TYPE'] == 'sqlalchemy':
            session_interface = SqlAlchemySessionInterface(
                app, config['SESSION_SQLALCHEMY'],
                config['SESSION_SQLALCHEMY_TABLE'],
                config['SESSION_KEY_PREFIX'], config['SESSION_USE_SIGNER'],
                config['SESSION_PERMANENT'])
        else:
            session_interface = NullSessionInterface()

        return session_interface