import asyncio
import functools
import inspect
import typing

from starlette.exceptions import HTTPException
from starlette.requests import HTTPConnection, Request
from starlette.responses import RedirectResponse, Response
from starlette.websockets import WebSocket


def has_required_scope(conn: HTTPConnection, scopes: typing.Sequence[str]) -> bool:
    for scope in scopes:
        if scope not in conn.auth.scopes:
            return False
    return True


def requires(
    scopes: typing.Union[str, typing.Sequence[str]],
    status_code: int = 403,
    redirect: str = None,
) -> typing.Callable:
    scopes_list = [scopes] if isinstance(scopes, str) else list(scopes)

    def decorator(func: typing.Callable) -> typing.Callable:
        type = None
        sig = inspect.signature(func)
        for idx, parameter in enumerate(sig.parameters.values()):
            if parameter.name == "request" or parameter.name == "websocket":
                type = parameter.name
                break
        else:
            raise Exception(
                f'No "request" or "websocket" argument on function "{func}"'
            )

        if type == "websocket":
            # Handle websocket functions. (Always async)
            @functools.wraps(func)
            async def websocket_wrapper(
                *args: typing.Any, **kwargs: typing.Any
            ) -> None:
                websocket = kwargs.get("websocket", args[idx])
                assert isinstance(websocket, WebSocket)

                if not has_required_scope(websocket, scopes_list):
                    await websocket.close()
                else:
                    await func(*args, **kwargs)

            return websocket_wrapper

        elif asyncio.iscoroutinefunction(func):
            # Handle async request/response functions.
            @functools.wraps(func)
            async def async_wrapper(
                *args: typing.Any, **kwargs: typing.Any
            ) -> Response:
                request = kwargs.get("request", args[idx])
                assert isinstance(request, Request)

                if not has_required_scope(request, scopes_list):
                    if redirect is not None:
                        return RedirectResponse(
                            url=request.url_for(redirect), status_code=303
                        )
                    raise HTTPException(status_code=status_code)
                return await func(*args, **kwargs)

            return async_wrapper

        else:
            # Handle sync request/response functions.
            @functools.wraps(func)
            def sync_wrapper(*args: typing.Any, **kwargs: typing.Any) -> Response:
                request = kwargs.get("request", args[idx])
                assert isinstance(request, Request)

                if not has_required_scope(request, scopes_list):
                    if redirect is not None:
                        return RedirectResponse(
                            url=request.url_for(redirect), status_code=303
                        )
                    raise HTTPException(status_code=status_code)
                return func(*args, **kwargs)

            return sync_wrapper

    return decorator


class AuthenticationError(Exception):
    pass


class AuthenticationBackend:
    async def authenticate(
        self, conn: HTTPConnection
    ) -> typing.Optional[typing.Tuple["AuthCredentials", "BaseUser"]]:
        raise NotImplementedError()  # pragma: no cover


class AuthCredentials:
    def __init__(self, scopes: typing.Sequence[str] = None):
        self.scopes = [] if scopes is None else list(scopes)


class BaseUser:
    @property
    def is_authenticated(self) -> bool:
        raise NotImplementedError()  # pragma: no cover

    @property
    def display_name(self) -> str:
        raise NotImplementedError()  # pragma: no cover

    @property
    def identity(self) -> str:
        raise NotImplementedError()  # pragma: no cover


class SimpleUser(BaseUser):
    def __init__(self, username: str) -> None:
        self.username = username

    @property
    def is_authenticated(self) -> bool:
        return True

    @property
    def display_name(self) -> str:
        return self.username


class UnauthenticatedUser(BaseUser):
    @property
    def is_authenticated(self) -> bool:
        return False

    @property
    def display_name(self) -> str:
        return ""