import shutil

from django.contrib.auth.models import User
from django.db import models
from django.db.models import QuerySet

from compensation.models import AbstractCompensation
from konova.models import AbstractDocument, generate_document_file_upload_path
from konova.settings import DEFAULT_SRID_RLP, LANIS_LINK_TEMPLATE, EMA_DOC_PATH
from user.models import UserActionLogEntry


class Ema(AbstractCompensation):
    """
    EMA = Ersatzzahlungsmaßnahme
    (compensation actions from payments)

    Until 2015 the EMA was the data object to keep track of any compensation, which has been funded by payments
    previously paid. In 2015 another organization got in charge of this, which led to the creation of the data object
    MAE (which is basically the same, just renamed in their system) to differ between the 'old' payment funded ones and
    the new. For historical reasons, we need to keep EMAs in our system, since there are still entries done to this day,
    which have been performed somewhere before 2015 and therefore needs to be entered.
    Further information:
    https://snu.rlp.de/de/foerderungen/massnahmen-aus-ersatzzahlungen/uebersicht-mae/

    EMA therefore holds data like a compensation: actions, before-/after-states, deadlines, ...

    """
    # Users having access on this object
    # Not needed in regular Compensation since their access is defined by the linked intervention's access
    users = models.ManyToManyField(
        User,
        help_text="Users having access (shared with)"
    )

    # Refers to "verzeichnen"
    recorded = models.OneToOneField(
        UserActionLogEntry,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        help_text="Holds data on user and timestamp of this action",
        related_name="+"
    )

    def __str__(self):
        return "{}".format(self.identifier)

    def save(self, *args, **kwargs):
        if self.identifier is None or len(self.identifier) == 0:
            # Create new identifier
            new_id = self._generate_new_identifier()
            while Ema.objects.filter(identifier=new_id).exists():
                new_id = self._generate_new_identifier()
            self.identifier = new_id
        super().save(*args, **kwargs)

    def get_LANIS_link(self) -> str:
        """ Generates a link for LANIS depending on the geometry

        Returns:

        """
        try:
            geom = self.geometry.geom.transform(DEFAULT_SRID_RLP, clone=True)
            x = geom.centroid.x
            y = geom.centroid.y
            zoom_lvl = 16
        except AttributeError:
            # If no geometry has been added, yet.
            x = 1
            y = 1
            zoom_lvl = 6
        return LANIS_LINK_TEMPLATE.format(
            zoom_lvl,
            x,
            y,
        )

    def quality_check(self) -> list:
        """ Quality check

        Returns:
            ret_msgs (list): Holds error messages
        """
        ret_msgs = []

        # ToDo: Add check methods!

        return ret_msgs

    def get_documents(self) -> QuerySet:
        """ Getter for all documents of an EMA

        Returns:
            docs (QuerySet): The queryset of all documents
        """
        docs = EmaDocument.objects.filter(
            instance=self
        )
        return docs


class EmaDocument(AbstractDocument):
    """
    Specializes document upload for ema with certain path
    """
    instance = models.ForeignKey(
        Ema,
        on_delete=models.CASCADE,
        related_name="documents",
    )
    file = models.FileField(
        upload_to=generate_document_file_upload_path,
        max_length=1000,
    )

    def delete(self, *args, **kwargs):
        """
        Custom delete functionality for EcoAccountDocuments.
        Removes the folder from the file system if there are no further documents for this entry.

        Args:
            *args ():
            **kwargs ():

        Returns:

        """
        ema_docs = self.instance.get_documents()

        folder_path = None
        if ema_docs.count() == 1:
            # The only file left for this EMA is the one which is currently processed and will be deleted
            # Make sure that the compensation folder itself is deleted as well, not only the file
            # Therefore take the folder path from the file path
            folder_path = self.file.path.split("/")[:-1]
            folder_path = "/".join(folder_path)

        # Remove the file itself
        super().delete(*args, **kwargs)

        # If a folder path has been set, we need to delete the whole folder!
        if folder_path is not None:
            try:
                shutil.rmtree(folder_path)
            except FileNotFoundError:
                # Folder seems to be missing already...
                pass