import asyncio
import enum
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'


@asyncio.coroutine
def remember(request, response, identity, **kwargs):
    """Remember identity into response.

    The action is performed by identity_policy.remember()

    Usually the idenity is stored in user cookies homehow but may be
    pushed into custom header also.
    """
    assert isinstance(identity, str), identity
    assert identity
    identity_policy = request.app.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)
    yield from identity_policy.remember(request, response, identity, **kwargs)


@asyncio.coroutine
def forget(request, response):
    """Forget previously remembered identity.

    Usually it clears cookie or server-side storage to forget user
    session.
    """
    identity_policy = request.app.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)
    yield from identity_policy.forget(request, response)


@asyncio.coroutine
def authorized_userid(request):
    identity_policy = request.app.get(IDENTITY_KEY)
    autz_policy = request.app.get(AUTZ_KEY)
    if identity_policy is None or autz_policy is None:
        return None
    identity = yield from identity_policy.identify(request)
    if identity is None:
        return None  # non-registered user has None user_id
    user_id = yield from autz_policy.authorized_userid(identity)
    return user_id


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


@asyncio.coroutine
def is_anonymous(request):
    """Check if user is anonymous.

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


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

    User is considered authorized if authorized_userid
    returns some value.
    """
    @asyncio.coroutine
    @wraps(fn)
    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)

        userid = yield from authorized_userid(request)
        if userid is None:
            raise web.HTTPUnauthorized

        ret = yield from fn(*args, **kwargs)
        return ret

    return wrapped


def has_permission(
    permission,
    context=None,
):
    """Decorator that restrict 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):
        @asyncio.coroutine
        @wraps(fn)
        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)

            userid = yield from authorized_userid(request)
            if userid is None:
                raise web.HTTPUnauthorized

            allowed = yield from permits(request, permission, context)
            if not allowed:
                raise web.HTTPForbidden
            ret = yield from fn(*args, **kwargs)
            return ret

        return wrapped

    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