from __future__ import annotations

import datetime
import json
import typing
from base64 import b64decode, b64encode

import itsdangerous
from itsdangerous.exc import BadSignature
from starlette.datastructures import MutableHeaders, Secret
from starlette.requests import HTTPConnection
from starlette.types import ASGIApp, Message, Receive, Scope, Send

from .. import config

if typing.TYPE_CHECKING:
    from ..auth import AuthSessionData


class SessionMiddleware:
    def __init__(
        self,
        app: ASGIApp,
        secret_key: str | Secret = config.Config.SECRET_KEY,
        session_cookie: str = "session",
        max_age: int | None = config.Config.SESSION_EXPIRES,
        path: str = "/",
        same_site: typing.Literal["lax", "strict", "none"] = "strict",
        https_only: bool = False,
        domain: str | None = None,
    ) -> None:
        self.app = app
        self.signer = itsdangerous.TimestampSigner(str(secret_key))
        self.session_cookie = session_cookie
        self.max_age = max_age
        self.path = path
        self.security_flags = "httponly; samesite=" + same_site
        if https_only:  # Secure flag can be used with HTTPS only
            self.security_flags += "; secure"
        if domain is not None:
            self.security_flags += f"; domain={domain}"

    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
        if scope["type"] not in ("http", "websocket"):  # pragma: no cover
            await self.app(scope, receive, send)
            return

        connection = HTTPConnection(scope)
        initial_session_was_empty = True

        if self.session_cookie in connection.cookies:
            data = connection.cookies[self.session_cookie].encode("utf-8")
            try:
                data_bytes, timestamp = self.signer.unsign(
                    data, max_age=self.max_age, return_timestamp=True
                )
                data_decoded = b64decode(data_bytes)
                json_data: AuthSessionData = json.loads(data_decoded)
                reauthenticate_after = timestamp + datetime.timedelta(
                    seconds=config.Config.SESSION_REVALIDATE_AFTER
                )
                if datetime.datetime.now(datetime.timezone.utc) > reauthenticate_after:
                    json_data["is_authenticated"] = (
                        False  # Force reauthentication if session needs revalidated
                    )
                scope["session"] = json_data
                initial_session_was_empty = False
            except BadSignature:
                scope["session"] = {}
        else:
            scope["session"] = {}

        async def send_wrapper(message: Message) -> None:
            if message["type"] == "http.response.start":
                if scope["session"]:
                    # We have session data to persist.
                    data = b64encode(json.dumps(scope["session"]).encode("utf-8"))
                    data = self.signer.sign(data)
                    headers = MutableHeaders(scope=message)
                    header_value = "{session_cookie}={data}; path={path}; {max_age}{security_flags}".format(  # noqa E501
                        session_cookie=self.session_cookie,
                        data=data.decode("utf-8"),
                        path=self.path,
                        max_age=f"Max-Age={self.max_age}; " if self.max_age else "",
                        security_flags=self.security_flags,
                    )
                    headers.append("Set-Cookie", header_value)
                elif not initial_session_was_empty:
                    # The session has been cleared.
                    headers = MutableHeaders(scope=message)
                    header_value = "{session_cookie}={data}; path={path}; {expires}{security_flags}".format(  # noqa E501
                        session_cookie=self.session_cookie,
                        data="null",
                        path=self.path,
                        expires="expires=Thu, 01 Jan 1970 00:00:00 GMT; ",
                        security_flags=self.security_flags,
                    )
                    headers.append("Set-Cookie", header_value)
            await send(message)

        await self.app(scope, receive, send_wrapper)
