"""passbook SAML IDP Views"""
from typing import Optional

from django.contrib.auth.mixins import LoginRequiredMixin
from django.core.exceptions import PermissionDenied
from django.core.validators import URLValidator
from django.http import HttpRequest, HttpResponse
from django.shortcuts import get_object_or_404, redirect, render, reverse
from django.utils.decorators import method_decorator
from django.utils.http import urlencode
from django.views import View
from django.views.decorators.csrf import csrf_exempt
from signxml.util import strip_pem_header
from structlog import get_logger

from passbook.audit.models import Event, EventAction
from passbook.core.models import Application, Provider
from passbook.flows.models import in_memory_stage
from passbook.flows.planner import (
    PLAN_CONTEXT_APPLICATION,
    PLAN_CONTEXT_SSO,
    FlowPlanner,
)
from passbook.flows.stage import StageView
from passbook.flows.views import SESSION_KEY_PLAN
from passbook.lib.utils.template import render_to_string
from passbook.lib.utils.urls import redirect_with_qs
from passbook.lib.views import bad_request_message
from passbook.policies.mixins import PolicyAccessMixin
from passbook.providers.saml.exceptions import CannotHandleAssertion
from passbook.providers.saml.models import SAMLBindings, SAMLProvider
from passbook.providers.saml.processors.types import SAMLResponseParams
from passbook.stages.consent.stage import PLAN_CONTEXT_CONSENT_TEMPLATE

LOGGER = get_logger()
URL_VALIDATOR = URLValidator(schemes=("http", "https"))
SESSION_KEY_SAML_REQUEST = "SAMLRequest"
SESSION_KEY_SAML_RESPONSE = "SAMLResponse"
SESSION_KEY_RELAY_STATE = "RelayState"
SESSION_KEY_PARAMS = "SAMLParams"


class SAMLSSOView(LoginRequiredMixin, PolicyAccessMixin, View):
    """"SAML SSO Base View, which plans a flow and injects our final stage.
    Calls get/post handler."""

    application: Application
    provider: SAMLProvider

    def dispatch(
        self, request: HttpRequest, *args, application_slug: str, **kwargs
    ) -> HttpResponse:
        self.application = get_object_or_404(Application, slug=application_slug)
        self.provider: SAMLProvider = get_object_or_404(
            SAMLProvider, pk=self.application.provider_id
        )
        if not self.user_has_access(self.application):
            raise PermissionDenied()
        # Call the method handler, which checks the SAML Request
        method_response = super().dispatch(request, *args, application_slug, **kwargs)
        if method_response:
            return method_response
        # Regardless, we start the planner and return to it
        planner = FlowPlanner(self.provider.authorization_flow)
        planner.allow_empty_flows = True
        plan = planner.plan(
            self.request,
            {
                PLAN_CONTEXT_SSO: True,
                PLAN_CONTEXT_APPLICATION: self.application,
                PLAN_CONTEXT_CONSENT_TEMPLATE: "providers/saml/consent.html",
            },
        )
        plan.append(in_memory_stage(SAMLFlowFinalView))
        self.request.session[SESSION_KEY_PLAN] = plan
        return redirect_with_qs(
            "passbook_flows:flow-executor-shell",
            self.request.GET,
            flow_slug=self.provider.authorization_flow.slug,
        )


class SAMLSSOBindingRedirectView(SAMLSSOView):
    """SAML Handler for SSO/Redirect bindings, which are sent via GET"""

    # pylint: disable=unused-argument
    def get(  # lgtm [py/similar-function]
        self, request: HttpRequest, application_slug: str
    ) -> Optional[HttpResponse]:
        """Handle REDIRECT bindings"""
        # Store these values now, because Django's login cycle won't preserve them.
        if SESSION_KEY_SAML_REQUEST not in request.GET:
            LOGGER.info("handle_saml_request: SAML payload missing")
            return bad_request_message(
                self.request, "The SAML request payload is missing."
            )

        self.request.session[SESSION_KEY_SAML_REQUEST] = request.GET[
            SESSION_KEY_SAML_REQUEST
        ]
        self.request.session[SESSION_KEY_RELAY_STATE] = request.GET.get(
            SESSION_KEY_RELAY_STATE, ""
        )

        try:
            self.provider.processor.can_handle(self.request)
            params = self.provider.processor.generate_response()
            self.request.session[SESSION_KEY_PARAMS] = params
        except CannotHandleAssertion as exc:
            LOGGER.info(exc)
            return bad_request_message(self.request, str(exc))
        return None


@method_decorator(csrf_exempt, name="dispatch")
class SAMLSSOBindingPOSTView(SAMLSSOView):
    """SAML Handler for SSO/POST bindings"""

    # pylint: disable=unused-argument
    def post(
        self, request: HttpRequest, application_slug: str
    ) -> Optional[HttpResponse]:
        """Handle POST bindings"""
        # Store these values now, because Django's login cycle won't preserve them.
        if SESSION_KEY_SAML_REQUEST not in request.POST:
            LOGGER.info("handle_saml_request: SAML payload missing")
            return bad_request_message(
                self.request, "The SAML request payload is missing."
            )

        self.request.session[SESSION_KEY_SAML_REQUEST] = request.POST[
            SESSION_KEY_SAML_REQUEST
        ]
        self.request.session[SESSION_KEY_RELAY_STATE] = request.POST.get(
            SESSION_KEY_RELAY_STATE, ""
        )

        try:
            self.provider.processor.can_handle(self.request)
            params = self.provider.processor.generate_response()
            self.request.session[SESSION_KEY_PARAMS] = params
        except CannotHandleAssertion as exc:
            LOGGER.info(exc)
            return bad_request_message(self.request, str(exc))
        return None


class SAMLSSOBindingInitView(SAMLSSOView):
    """SAML Handler for for IdP Initiated login flows"""

    # pylint: disable=unused-argument
    def get(
        self, request: HttpRequest, application_slug: str
    ) -> Optional[HttpResponse]:
        """Create saml params from scratch"""
        LOGGER.debug(
            "handle_saml_no_request: No SAML Request, using IdP-initiated flow."
        )
        self.provider.processor.is_idp_initiated = True
        self.provider.processor.init_deep_link(self.request)
        params = self.provider.processor.generate_response()
        self.request.session[SESSION_KEY_PARAMS] = params


# This View doesn't have a URL on purpose, as its called by the FlowExecutor
class SAMLFlowFinalView(StageView):
    """View used by FlowExecutor after all stages have passed. Logs the authorization,
    and redirects to the SP (if REDIRECT is configured) or shows and auto-submit for
    (if POST is configured)."""

    def get(self, request: HttpRequest, *args, **kwargs) -> HttpResponse:
        application: Application = self.executor.plan.context[PLAN_CONTEXT_APPLICATION]
        provider: SAMLProvider = get_object_or_404(
            SAMLProvider, pk=application.provider_id
        )
        # Log Application Authorization
        Event.new(
            EventAction.AUTHORIZE_APPLICATION,
            authorized_application=application,
            flow=self.executor.plan.flow_pk,
        ).from_http(self.request)
        self.request.session.pop(SESSION_KEY_SAML_REQUEST, None)
        self.request.session.pop(SESSION_KEY_SAML_RESPONSE, None)
        self.request.session.pop(SESSION_KEY_RELAY_STATE, None)
        if SESSION_KEY_PARAMS not in self.request.session:
            return self.executor.stage_invalid()
        response: SAMLResponseParams = self.request.session.pop(SESSION_KEY_PARAMS)

        if provider.sp_binding == SAMLBindings.POST:
            return render(
                self.request,
                "providers/saml/autosubmit_form.html",
                {
                    "url": response.acs_url,
                    "application": application,
                    "attrs": {
                        "ACSUrl": response.acs_url,
                        SESSION_KEY_SAML_RESPONSE: response.saml_response,
                        SESSION_KEY_RELAY_STATE: response.relay_state,
                    },
                },
            )
        if provider.sp_binding == SAMLBindings.REDIRECT:
            querystring = urlencode(
                {
                    SESSION_KEY_SAML_RESPONSE: response.saml_response,
                    SESSION_KEY_RELAY_STATE: response.relay_state,
                }
            )
            return redirect(f"{response.acs_url}?{querystring}")
        return bad_request_message(request, "Invalid sp_binding specified")


class DescriptorDownloadView(View):
    """Replies with the XML Metadata IDSSODescriptor."""

    @staticmethod
    def get_metadata(request: HttpRequest, provider: SAMLProvider) -> str:
        """Return rendered XML Metadata"""
        entity_id = provider.issuer
        saml_sso_binding_post = request.build_absolute_uri(
            reverse(
                "passbook_providers_saml:sso-post",
                kwargs={"application_slug": provider.application.slug},
            )
        )
        saml_sso_binding_redirect = request.build_absolute_uri(
            reverse(
                "passbook_providers_saml:sso-redirect",
                kwargs={"application_slug": provider.application.slug},
            )
        )
        subject_format = provider.processor.subject_format
        ctx = {
            "saml_sso_binding_post": saml_sso_binding_post,
            "saml_sso_binding_redirect": saml_sso_binding_redirect,
            "entity_id": entity_id,
            "subject_format": subject_format,
        }
        if provider.signing_kp:
            ctx["cert_public_key"] = strip_pem_header(
                provider.signing_kp.certificate_data.replace("\r", "")
            ).replace("\n", "")
        return render_to_string("providers/saml/xml/metadata.xml", ctx)

    def get(self, request: HttpRequest, application_slug: str) -> HttpResponse:
        """Replies with the XML Metadata IDSSODescriptor."""
        application = get_object_or_404(Application, slug=application_slug)
        provider: SAMLProvider = get_object_or_404(
            SAMLProvider, pk=application.provider_id
        )
        try:
            metadata = DescriptorDownloadView.get_metadata(request, provider)
        except Provider.application.RelatedObjectDoesNotExist:  # pylint: disable=no-member
            return bad_request_message(
                request, "Provider is not assigned to an application."
            )
        else:
            response = HttpResponse(metadata, content_type="application/xml")
            response[
                "Content-Disposition"
            ] = f'attachment; filename="{provider.name}_passbook_meta.xml"'
            return response