import time


class OAuth2Token(dict):
    def __init__(self, params):
        if params.get('expires_at'):
            params['expires_at'] = int(params['expires_at'])
        elif params.get('expires_in'):
            params['expires_at'] = int(time.time()) + \
                                   int(params['expires_in'])
        super(OAuth2Token, self).__init__(params)

    def is_expired(self):
        expires_at = self.get('expires_at')
        if not expires_at:
            return None
        return expires_at < time.time()

    @classmethod
    def from_dict(cls, token):
        if isinstance(token, dict) and not isinstance(token, cls):
            token = cls(token)
        return token