"""OAuth2 client utilities."""
from datetime import datetime, timedelta
from urllib.parse import urljoin, urlparse

import requests
from flask import request, current_app as app

from pymonad.either import Left, Right, Either

from authlib.jose import jwt
from authlib.jose import KeySet, JsonWebKey
from authlib.jose.errors import BadSignatureError
from authlib.integrations.requests_client import OAuth2Session

from uploader import session
import uploader.monadic_requests as mrequests

SCOPE = ("profile group role resource register-client user masquerade "
         "introspect migrate-data")


def authserver_uri():
    """Return URI to authorisation server."""
    return app.config["AUTH_SERVER_URL"]


def oauth2_clientid():
    """Return the client id."""
    return app.config["OAUTH2_CLIENT_ID"]


def oauth2_clientsecret():
    """Return the client secret."""
    return app.config["OAUTH2_CLIENT_SECRET"]


def __make_token_validator__(keys: KeySet):
    """Make a token validator function."""
    def __validator__(token: str):
        for key in keys.keys:
            try:
                jwt.decode(token["access_token"], key)
                return Right(token)
            except BadSignatureError:
                pass

        return Left("INVALID-TOKEN")

    return __validator__


def __validate_token__(sess_info):
    """Validate that the token is really from the auth server."""
    info = sess_info
    info["user"]["token"] = info["user"]["token"].then(__make_token_validator__(
        KeySet([JsonWebKey.import_key(key) for key in info.get(
            "auth_server_jwks", {}).get(
                "jwks", {"keys": []})["keys"]])))
    return session.save_session_info(info)


def __update_auth_server_jwks__(sess_info):
    """Updates the JWKs every 2 hours or so."""
    jwks = sess_info.get("auth_server_jwks")
    if bool(jwks):
        last_updated = jwks.get("last-updated")
        now = datetime.now().timestamp()
        if bool(last_updated) and (now - last_updated) < timedelta(hours=2).seconds:
            return __validate_token__({**sess_info, "auth_server_jwks": jwks})

    jwksuri = urljoin(authserver_uri(), "auth/public-jwks")
    return __validate_token__({
        **sess_info,
        "auth_server_jwks": {
            "jwks": KeySet([
                JsonWebKey.import_key(key)
                for key in requests.get(jwksuri).json()["jwks"]]).as_dict(),
            "last-updated": datetime.now().timestamp()
        }
    })


def oauth2_client():
    """Build the OAuth2 client for use fetching data."""
    def __update_token__(token, refresh_token=None, access_token=None):# pylint: disable=[unused-argument]
        """Update the token when refreshed."""
        session.set_user_token(token)

    def __client__(token) -> OAuth2Session:
        client = OAuth2Session(
            oauth2_clientid(),
            oauth2_clientsecret(),
            scope=SCOPE,
            token_endpoint=urljoin(authserver_uri(), "/auth/token"),
            token_endpoint_auth_method="client_secret_post",
            token=token,
            update_token=__update_token__)
        return client

    __update_auth_server_jwks__(session.session_info())
    return session.user_token().either(
        lambda _notok: __client__(None),
        __client__)


def user_logged_in():
    """Check whether the user has logged in."""
    suser = session.session_info()["user"]
    return suser["logged_in"] and suser["token"].is_right()


def authserver_authorise_uri():
    req_baseurl = urlparse(request.base_url, scheme=request.scheme)
    host_uri = f"{req_baseurl.scheme}://{req_baseurl.netloc}/"
    return urljoin(
        authserver_uri(),
        "auth/authorise?response_type=code"
        f"&client_id={oauth2_clientid()}"
        f"&redirect_uri={urljoin(host_uri, 'oauth2/code')}")


def __no_token__(_err) -> Left:
    """Handle situation where request is attempted with no token."""
    resp = requests.models.Response()
    resp._content = json.dumps({
        "error": "AuthenticationError",
        "error-description": ("You need to authenticate to access requested "
                              "information.")}).encode("utf-8")
    resp.status_code = 400
    return Left(resp)


def oauth2_get(url, **kwargs) -> Either:
    """Do a get request to the authentication/authorisation server."""
    def __get__(token) -> Either:
        _uri = urljoin(authserver_uri(), url)
        try:
            resp = oauth2_client().get(
                _uri,
                **{
                    **kwargs,
                    "headers": {
                        **kwargs.get("headers", {}),
                        "Content-Type": "application/json"
                    }
                })
            if resp.status_code in mrequests.SUCCESS_CODES:
                return Right(resp.json())
            return Left(resp)
        except Exception as exc:
            app.logger.error("Error retriving data from auth server: (GET %s)",
                             _uri,
                             exc_info=True)
            return Left(exc)
    return session.user_token().either(__no_token__, __get__)


def oauth2_post(url, data=None, json=None, **kwargs):
    """Do a POST request to the authentication/authorisation server."""
    def __post__(token) -> Either:
        _uri = urljoin(authserver_uri(), url)
        _headers = ({
                        **kwargs.get("headers", {}),
                        "Content-Type": "application/json"
                    }
                    if bool(json) else kwargs.get("headers", {}))
        try:
            request_data = {
                **(data or {}),
                **(json or {}),
                "client_id": oauth2_clientid(),
                "client_secret": oauth2_clientsecret()
            }
            resp = oauth2_client().post(
                _uri,
                data=(request_data if bool(data) else None),
                json=(request_data if bool(json) else None),
                **{**kwargs, "headers": _headers})
            if resp.status_code in mrequests.SUCCESS_CODES:
                return Right(resp.json())
            return Left(resp)
        except Exception as exc:
            app.logger.error("Error retriving data from auth server: (POST %s)",
                             _uri,
                             exc_info=True)
            return Left(exc)
    return session.user_token().either(__no_token__, __post__)