"""
Author: Michel Peltriaux
Organization: Struktur- und Genehmigungsdirektion Nord, Rhineland-Palatinate, Germany
Contact: michel.peltriaux@sgdnord.rlp.de
Created on: 21.01.22

"""
import json

from django.db.models import QuerySet
from django.http import JsonResponse, HttpRequest
from django.views import View
from django.views.decorators.csrf import csrf_exempt

from api.models import APIUserToken
from api.settings import KSP_TOKEN_HEADER_IDENTIFIER, KSP_USER_HEADER_IDENTIFIER
from compensation.models import EcoAccount
from ema.models import Ema
from intervention.models import Intervention
from konova.utils.message_templates import DATA_UNSHARED
from konova.utils.user_checks import is_default_group_only
from user.models import User


class AbstractAPIView(View):
    """ Base class for API views

    The API must follow the GeoJSON Specification RFC 7946
    https://geojson.org/
    https://datatracker.ietf.org/doc/html/rfc7946

    """
    user = None
    serializer = None
    rpp = 5  # Results per page default
    page_number = 1  # Page number default

    class Meta:
        abstract = True

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.response_body_base = {
            "rpp": None,
            "p": None,
            "next": None,
            "results": None
        }

    @csrf_exempt
    def dispatch(self, request, *args, **kwargs):
        try:
            # Fetch the proper user from the given request header token
            ksp_token = request.headers.get(KSP_TOKEN_HEADER_IDENTIFIER, None)
            ksp_user = request.headers.get(KSP_USER_HEADER_IDENTIFIER, None)
            self.user = APIUserToken.get_user_from_token(ksp_token, ksp_user)
            request.user = self.user
            if not self.user.is_default_user():
                raise PermissionError("Default permissions required")
        except PermissionError as e:
            return self._return_error_response(e, 403)
        return super().dispatch(request, *args, **kwargs)

    def _return_error_response(self, error, status_code=500):
        """ Returns an error as JsonReponse

        Args:
            error (): The error/exception
            status_code (): The desired status code

        Returns:

        """
        content = [error.__str__()]
        if hasattr(error, "messages"):
            content = error.messages
        return JsonResponse(
            {
                "errors": content
            },
            status=status_code
        )

    def _return_response(self, request: HttpRequest, data):
        """ Returns all important data into a response object

        Args:
            request (HttpRequest): The incoming request
            data (dict): The serialized data

        Returns:
            response (JsonResponse): The response to be returned
        """
        response = self.response_body_base
        next_page = self.page_number + 1
        next_page = next_page if next_page in self.serializer.paginator.page_range else None
        if next_page is not None:
            next_url = request.build_absolute_uri(
                request.path + f"?rpp={self.rpp}&p={next_page}"
            )
        else:
            next_url = None
        response["rpp"] = self.rpp
        response["p"] = self.page_number
        response["next"] = next_url
        response["results"] = data
        return JsonResponse(response)


class InterventionCheckAPIView(AbstractAPIView):

    def get(self, request: HttpRequest, id):
        """ Takes the GET request

        Args:
            request (HttpRequest): The incoming request
            id (str): The intervention's id

        Returns:
            response (JsonResponse)
        """
        if not self.user.is_zb_user():
            return self._return_error_response("Permission not granted", 403)
        try:
            obj = Intervention.objects.get(
                id=id,
                users__in=[self.user]
            )
        except Exception as e:
            return self._return_error_response(e)

        all_valid, check_details = self.run_quality_checks(obj)

        if all_valid:
            log_entry = obj.set_checked(self.user)
            obj.log.add(log_entry)

        data = {
            "success": all_valid,
            "details": check_details
        }
        return JsonResponse(data)

    def run_quality_checks(self, obj: Intervention) -> (bool, dict):
        """ Performs a check for intervention and related compensations

        Args:
            obj (Intervention): The intervention

        Returns:
            all_valid (boold): Whether an error occured or not
            check_details (dict): A dict containg details on which elements have errors
        """
        # Run quality check for Intervention
        all_valid = True
        intervention_checker = obj.quality_check()
        all_valid = intervention_checker.valid and all_valid

        # Run quality checks for linked compensations
        comps = obj.compensations.all()
        comp_checkers = []
        for comp in comps:
            comp_checker = comp.quality_check()
            comp_checkers.append(comp_checker)
            all_valid = comp_checker.valid and all_valid

        check_details = {
            "intervention": {
                "id": obj.id,
                "errors": intervention_checker.messages
            },
            "compensations": [
                {
                    "id": comp_checker.obj.id,
                    "errors": comp_checker.messages
                }
                for comp_checker in comp_checkers
            ]
        }
        return all_valid, check_details


class AbstractModelShareAPIView(AbstractAPIView):
    model = None

    class Meta:
        abstract = True

    def get(self, request: HttpRequest, id):
        """ Performs the GET request handling

        Args:
            request (HttpRequest): The incoming request
            id (str): The object's id

        Returns:

        """
        try:
            users = self._get_shared_users_of_object(id)
        except Exception as e:
            return self._return_error_response(e)

        data = {
            "users": [
                user.username for user in users
            ]
        }

        return JsonResponse(data)

    def put(self, request: HttpRequest, id):
        """ Performs the PUT request handling

        Args:
            request (HttpRequest): The incoming request
            id (str): The object's id

        Returns:

        """

        try:
            success = self._process_put_body(request.body, id)
        except Exception as e:
            return self._return_error_response(e)
        data = {
            "success": success,
        }
        return JsonResponse(data)

    def _check_user_has_shared_access(self, obj):
        """ Raises a PermissionError if user has no shared access

        Args:
            obj (BaseObject): The object

        Returns:

        """
        is_shared = obj.is_shared_with(self.user)
        if not is_shared:
            raise PermissionError(DATA_UNSHARED)

    def _get_shared_users_of_object(self, id) -> QuerySet:
        """ Check permissions and get the users

        Args:
            id (str): The object's id

        Returns:
            users (QuerySet)
        """
        obj = self.model.objects.get(
            id=id
        )
        self._check_user_has_shared_access(obj)
        users = obj.shared_users
        return users

    def _process_put_body(self, body: bytes, id: str):
        """ Reads the body data, performs validity checks and sets the new users

        Args:
            body (bytes): The request.body
            id (str): The object's id

        Returns:
            success (bool)
        """
        obj = self.model.objects.get(id=id)
        self._check_user_has_shared_access(obj)

        new_users = json.loads(body.decode("utf-8"))
        new_users = new_users.get("users", [])
        if len(new_users) == 0:
            raise ValueError("Shared user list must not be empty!")

        # Eliminate duplicates
        new_users = list(dict.fromkeys(new_users))

        # Make sure each of these names exist as a user
        new_users_objs = []
        for user in new_users:
            new_users_objs.append(User.objects.get(username=user))

        if is_default_group_only(self.user):
            # Default only users are not allowed to remove other users from having access. They can only add new ones!
            new_users_to_be_added = User.objects.filter(
                username__in=new_users
            ).exclude(
                id__in=obj.shared_users
            )
            new_users_objs = obj.shared_users.union(new_users_to_be_added)
        obj.share_with_list(new_users_objs)
        return True


class InterventionAPIShareView(AbstractModelShareAPIView):
    model = Intervention


class EcoAccountAPIShareView(AbstractModelShareAPIView):
    model = EcoAccount


class EmaAPIShareView(AbstractModelShareAPIView):
    model = Ema