# Source code for aiohttp_security.api

    import enum
    import warnings
    from aiohttp import web
    from aiohttp_security.abc import (AbstractIdentityPolicy,
                                      AbstractAuthorizationPolicy)
    from functools import wraps

    IDENTITY_KEY = 'aiohttp_security_identity_policy'
    AUTZ_KEY = 'aiohttp_security_autz_policy'

    async def remember(request, response, identity, **kwargs):
        """Remember identity into response.

        The action is performed by identity_policy.remember()

        Usually the identity is stored in user cookies somehow but may be
        pushed into custom header also.
        """
        assert isinstance(identity, str), identity
        assert identity
        identity_policy = request.config_dict.get(IDENTITY_KEY)
        if identity_policy is None:
            text = ("Security subsystem is not initialized, "
                    "call aiohttp_security.setup(...) first")
            # in order to see meaningful exception message both: on console
            # output and rendered page we add same message to *reason* and
            # *text* arguments.
            raise web.HTTPInternalServerError(reason=text, text=text)
        await identity_policy.remember(request, response, identity, **kwargs)

    async def forget(request, response):
        """Forget previously remembered identity.

        Usually it clears cookie or server-side storage to forget user
        session.
        """
        identity_policy = request.config_dict.get(IDENTITY_KEY)
        if identity_policy is None:
            text = ("Security subsystem is not initialized, "
                    "call aiohttp_security.setup(...) first")
            # in order to see meaningful exception message both: on console
            # output and rendered page we add same message to *reason* and
            # *text* arguments.
            raise web.HTTPInternalServerError(reason=text, text=text)
        await identity_policy.forget(request, response)

    async def authorized_userid(request):
        identity_policy = request.config_dict.get(IDENTITY_KEY)
        autz_policy = request.config_dict.get(AUTZ_KEY)
        if identity_policy is None or autz_policy is None:
            return None
        identity = await identity_policy.identify(request)
        if identity is None:
            return None  # non-registered user has None user_id
        user_id = await autz_policy.authorized_userid(identity)
        return user_id

    async def permits(request, permission, context=None):
        assert isinstance(permission, (str, enum.Enum)), permission
        assert permission
        identity_policy = request.config_dict.get(IDENTITY_KEY)
        autz_policy = request.config_dict.get(AUTZ_KEY)
        if identity_policy is None or autz_policy is None:
            return True
        identity = await identity_policy.identify(request)
        # non-registered user still may has some permissions
        access = await autz_policy.permits(identity, permission, context)
        return access

    async def is_anonymous(request):
        """Check if user is anonymous.

        User is considered anonymous if there is not identity
        in request.
        """
        identity_policy = request.config_dict.get(IDENTITY_KEY)
        if identity_policy is None:
            return True
        identity = await identity_policy.identify(request)
        if identity is None:
            return True
        return False

    async def check_authorized(request):
        """Checker that raises HTTPUnauthorized for anonymous users.
        """
        userid = await authorized_userid(request)
        if userid is None:
            raise web.HTTPUnauthorized()
        return userid

    def login_required(fn):
        """Decorator that restrict access only for authorized users.

        User is considered authorized if authorized_userid
        returns some value.
        """
        @wraps(fn)
        async def wrapped(*args, **kwargs):
            request = args[-1]
            if not isinstance(request, web.BaseRequest):
                msg = ("Incorrect decorator usage. "
                       "Expecting `def handler(request)` "
                       "or `def handler(self, request)`.")
                raise RuntimeError(msg)

            await check_authorized(request)
            return await fn(*args, **kwargs)

        warnings.warn("login_required decorator is deprecated, "
                      "use check_authorized instead",
                      DeprecationWarning)
        return wrapped

    async def check_permission(request, permission, context=None):
        """Checker that passes only to authoraised users with given permission.

        If user is not authorized - raises HTTPUnauthorized,
        if user is authorized and does not have permission -
        raises HTTPForbidden.
        """

        await check_authorized(request)
        allowed = await permits(request, permission, context)
        if not allowed:
            raise web.HTTPForbidden()

    def has_permission(
        permission,
        context=None,
    ):
        """Decorator that restricts access only for authorized users
        with correct permissions.

        If user is not authorized - raises HTTPUnauthorized,
        if user is authorized and does not have permission -
        raises HTTPForbidden.
        """
        def wrapper(fn):
            @wraps(fn)
            async def wrapped(*args, **kwargs):
                request = args[-1]
                if not isinstance(request, web.BaseRequest):
                    msg = ("Incorrect decorator usage. "
                           "Expecting `def handler(request)` "
                           "or `def handler(self, request)`.")
                    raise RuntimeError(msg)

                await check_permission(request, permission, context)
                return await fn(*args, **kwargs)

            return wrapped

        warnings.warn("has_permission decorator is deprecated, "
                      "use check_permission instead",
                      DeprecationWarning)
        return wrapper

    def setup(app, identity_policy, autz_policy):
        assert isinstance(identity_policy, AbstractIdentityPolicy), identity_policy
        assert isinstance(autz_policy, AbstractAuthorizationPolicy), autz_policy

        app[IDENTITY_KEY] = identity_policy
        app[AUTZ_KEY] = autz_policy