"""
Author: Michel Peltriaux
Organization: Struktur- und Genehmigungsdirektion Nord, Rhineland-Palatinate, Germany
Contact: michel.peltriaux@sgdnord.rlp.de
Created on: 16.12.21

"""
from django.db import models, transaction

from konova.models import UuidModel


class AdministrativeSpatialReference(models.Model):
    key = models.CharField(
        max_length=255,
        help_text="Represents Kreisschlüssel",
        null=True,
        blank=True
    )
    name = models.CharField(
        max_length=1000,
        help_text="Kreis",
        null=True,
        blank=True,
    )

    class Meta:
        abstract = True

    def __str__(self):
        return f"{self.name} ({self.key})"

    @property
    def table_str(self):
        return f"{self.name} ({self.key})"


class District(UuidModel, AdministrativeSpatialReference):
    """ The model District refers to "Kreis"

    """

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=[
                    "key",
                    "name",
                ],
                name="Unique district constraint"
            )
        ]


class Municipal(UuidModel, AdministrativeSpatialReference):
    """ The model Municipal refers to "Gemeinde"

    """
    district = models.ForeignKey(
        District,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
    )

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=[
                    "key",
                    "name",
                    "district",
                ],
                name="Unique municipal constraint"
            )
        ]


class ParcelGroup(UuidModel, AdministrativeSpatialReference):
    """ The model ParcelGroup refers to "Gemarkung", which is defined as a loose group of parcels

    """
    municipal = models.ForeignKey(
        Municipal,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
    )

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=[
                    "key",
                    "name",
                    "municipal",
                ],
                name="Unique parcel group constraint"
            )
        ]


class Parcel(UuidModel):
    """ The Parcel model holds administrative data on covered properties.

    Due to the unique but relevant naming of the administrative data, we have to use these namings as field
    names in german. Any try to translate them to English result in strange or insufficient translations.

    All fields have to be CharFields as well, since there are e.g. Flurstücksnummer holding e.g. '123____' which
    can not be realized using numerical fields.

    To avoid conflicts due to german Umlaute, the field names are shortened and vocals are dropped.

    """
    geometries = models.ManyToManyField("konova.Geometry", blank=True, related_name="parcels", through='ParcelIntersection')
    district = models.ForeignKey("konova.District", on_delete=models.SET_NULL, null=True, blank=True, related_name="parcels")
    municipal = models.ForeignKey("konova.Municipal", on_delete=models.SET_NULL, null=True, blank=True, related_name="parcels")
    parcel_group = models.ForeignKey(
        "konova.ParcelGroup",
        on_delete=models.SET_NULL,
        help_text="Gemarkung",
        null=True,
        blank=True,
        related_name="parcels"
    )
    flr = models.IntegerField(
        help_text="Flur",
        null=True,
        blank=True,
    )
    flrstck_nnr = models.IntegerField(
        help_text="Flurstücksnenner",
        null=True,
        blank=True,
    )
    flrstck_zhlr = models.IntegerField(
        help_text="Flurstückszähler",
        null=True,
        blank=True,
    )
    updated_on = models.DateTimeField(auto_now_add=True)

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=[
                    "district",
                    "municipal",
                    "parcel_group",
                    "flr",
                    "flrstck_nnr",
                    "flrstck_zhlr",
                ],
                name="Unique parcel constraint"
            )
        ]

    def __str__(self):
        return f"{self.parcel_group} | {self.flr} | {self.flrstck_zhlr} | {self.flrstck_nnr}"

    @classmethod
    def make_unique(cls, **kwargs):
        """ Checks for duplicates of a Parcel, choose a (now) unique one,
        repairs relations for ParcelIntersection and removes duplicates.

        Args:
            **kwargs ():

        Returns:
            unique_true (Parcel): The new unique 'true one'
        """
        parcel_objs = Parcel.objects.filter(**kwargs)

        if not parcel_objs.exists():
            return None

        # Get one of the found parcels and use it as new 'true one'
        unique_parcel = parcel_objs.first()
        # separate it from the rest
        parcel_objs = parcel_objs.exclude(id=unique_parcel.id)

        if not parcel_objs.exists():
            # There are no duplicates - all good, just return
            return unique_parcel

        # Fetch existing intersections, which still point on the duplicated parcels
        intersection_objs = ParcelIntersection.objects.filter(
            parcel__in=parcel_objs
        )

        # Change each intersection, so they point on the 'true one' parcel from now on
        for intersection in intersection_objs:
            intersection.parcel = unique_parcel
            intersection.save()

        # Remove the duplicated parcels
        parcel_objs.delete()

        return unique_parcel


class ParcelIntersection(UuidModel):
    """
    ParcelIntersection is an intermediary model, which is used to add extras to the
    M2M relation between Parcel and Geometry.
    """
    parcel = models.ForeignKey(Parcel, on_delete=models.CASCADE)
    geometry = models.ForeignKey("konova.Geometry", on_delete=models.CASCADE)