from urllib.parse import urlparse

from django.views.generic import View
from django.http import JsonResponse
from django.urls import reverse_lazy
from oauth2_provider.settings import oauth2_settings
from oauth2_provider.models import (
    AbstractGrant,
    Application,
)


class DiscoveryEndpoint(View):

    # Ref: https://openid.net/specs/openid-connect-discovery-1_0.html
    # The response is a set of Claims about the OpenID Provider's configuration,
    # including all necessary endpoints and public key location information.
    def get(self, request, *args, **kwargs):
        issuer_url = oauth2_settings.OIDC_ISS_ENDPOINT
        parsed_url = urlparse(oauth2_settings.OIDC_ISS_ENDPOINT)
        host = parsed_url.scheme + "://" + parsed_url.netloc

        scopes_class = oauth2_settings.SCOPES_BACKEND_CLASS
        scopes = scopes_class()
        scopes_supported = [scope for scope in scopes.get_available_scopes()]

        validator_class = oauth2_settings.OAUTH2_VALIDATOR_CLASS
        validator = validator_class()
        oidc_claims = list(set(validator.get_discovery_claims(request)))

        signing_algorithms = [Application.RS256_ALGORITHM, Application.HS256_ALGORITHM]

        return JsonResponse({
            'issuer': issuer_url,
            'authorization_endpoint': '{}{}'.format(host, reverse_lazy('oidc-auth')),
            'token_endpoint': '{}{}'.format(host, reverse_lazy('oidc-token')),
            'userinfo_endpoint': '{}{}'.format(host, reverse_lazy('oidc-userinfo')),
            'jwks_uri': '{}{}'.format(host, reverse_lazy('oidc-jwks')),
            'response_types_supported': oauth2_settings.OIDC_RESPONSE_TYPES_SUPPORTED,
            'subject_types_supported': oauth2_settings.OIDC_SUBJECT_TYPES_SUPPORTED,
            'id_token_signing_alg_values_supported': signing_algorithms,
            'token_endpoint_auth_methods_supported': oauth2_settings.OIDC_TOKEN_ENDPOINT_AUTH_METHODS_SUPPORTED,
            'scopes_supported': scopes_supported,
            'claims_supported': oidc_claims,
            'code_challenge_methods_supported': [key for key, _ in AbstractGrant.CODE_CHALLENGE_METHODS]
        })