forms.py

# This part of the code was adapted from pretalx (https://github.com/pretalx/pretalx)
# Copyright 2017-2019, Tobias Kunze
# Original Copyrights licensed under the Apache License, Version 2.0 http://www.apache.org/licenses/LICENSE-2.0
# Documentation was mainly added by us, other changes are marked in the code
import datetime
import json

from django import forms
from django.db import transaction
from django.db.models.signals import post_save
from django.utils.dateparse import parse_datetime
from django.utils.translation import gettext_lazy as _

from AKModel.availability.models import Availability
from AKModel.availability.serializers import AvailabilitySerializer
from AKModel.models import Event


class AvailabilitiesFormMixin(forms.Form):
    """
    Mixin for forms to add availabilities functionality to it
    Will handle the rendering and population of an availabilities field
    """
    availabilities = forms.CharField(
        label=_('Availability'),
        help_text=_(
            'Click and drag to mark the availability during the event, double-click to delete. '
            'Or use the start and end inputs to add entries to the calendar view.'  # Adapted help text
        ),
        widget=forms.TextInput(attrs={'class': 'availabilities-editor-data'}),
        required=False,
    )

    def _serialize(self, event, instance):
        """
        Serialize relevant availabilities into a JSON format to populate the text field in the form

        :param event: event the availabilities belong to (relevant for start and end times)
        :param instance: the entity availabilities in this form should belong to (e.g., an AK, or a Room)
        :return: JSON serializiation of the relevant availabilities
        :rtype: str
        """
        if instance:
            availabilities = AvailabilitySerializer(
                instance.availabilities.all(), many=True
            ).data
        else:
            availabilities = []

        return json.dumps(
            {
                'availabilities': availabilities,
                'event': {
                    # 'timezone': event.timezone,
                    'date_from': str(event.start),
                    'date_to': str(event.end),
                },
            }
        )

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # Load event information and populate availabilities text field
        self.event = self.initial.get('event')
        if isinstance(self.event, int):
            self.event = Event.objects.get(pk=self.event)
        initial = kwargs.pop('initial', {})
        initial['availabilities'] = self._serialize(self.event, kwargs['instance'])
        if not isinstance(self, forms.BaseModelForm):
            kwargs.pop('instance')
        kwargs['initial'] = initial

    def _parse_availabilities_json(self, jsonavailabilities):
        """
        Turn raw JSON availabilities into a list of model instances

        :param jsonavailabilities: raw json input
        :return: a list of availability objects corresponding to the raw input
        :rtype: List[Availability]
        """
        try:
            rawdata = json.loads(jsonavailabilities)
        except ValueError as exc:
            raise forms.ValidationError("Submitted availabilities are not valid json.") from exc
        if not isinstance(rawdata, dict):
            raise forms.ValidationError(
                "Submitted json does not comply with expected format, should be object."
            )
        availabilities = rawdata.get('availabilities')
        if not isinstance(availabilities, list):
            raise forms.ValidationError(
                "Submitted json does not comply with expected format, missing or malformed availabilities field"
            )
        return availabilities

    def _parse_datetime(self, strdate):
        """
        Parse input date string
        This will try to correct timezone information if needed

        :param strdate: string representing a timestamp
        :return: a timestamp object
        """
        tz = self.event.timezone  # adapt to our event model

        obj = parse_datetime(strdate)
        if not obj:
            raise TypeError
        if obj.tzinfo is None:
            # Adapt to new python timezone interface
            obj = obj.replace(tzinfo=tz)

        return obj

    def _validate_availability(self, rawavail):
        """
        Validate a raw availability instance input by making sure the relevant fields are present and can be parsed
        The cleaned up values that are produced to test the validity of the input are stored in-place in the input
        object for later usage in cleaning/parsing to availability objects

        :param rawavail: object to validate/clean
        """
        message = _("The submitted availability does not comply with the required format.")
        if not isinstance(rawavail, dict):
            raise forms.ValidationError(message)
        rawavail.pop('id', None)
        rawavail.pop('allDay', None)
        if not set(rawavail.keys()) == {'start', 'end'}:
            raise forms.ValidationError(message)

        try:
            rawavail['start'] = self._parse_datetime(rawavail['start'])
            rawavail['end'] = self._parse_datetime(rawavail['end'])
        # Adapt: Better error handling
        except (TypeError, ValueError) as exc:
            raise forms.ValidationError(
                _("The submitted availability contains an invalid date.")
            ) from exc

        timeframe_start = self.event.start  # adapt to our event model
        if rawavail['start'] < timeframe_start:
            rawavail['start'] = timeframe_start

        # add 1 day, not 24 hours, https://stackoverflow.com/a/25427822/2486196
        timeframe_end = self.event.end  # adapt to our event model
        timeframe_end = timeframe_end + datetime.timedelta(days=1)
        if rawavail['end'] > timeframe_end:
            # If the submitted availability ended outside the event timeframe, fix it silently
            rawavail['end'] = timeframe_end

    def clean_availabilities(self):
        """
        Turn raw availabilities into real availability objects
        :return:
        """
        data = self.cleaned_data.get('availabilities')
        required = (
                'availabilities' in self.fields and self.fields['availabilities'].required
        )
        if not data:
            if required:
                raise forms.ValidationError(_('Please fill in your availabilities!'))
            return None

        rawavailabilities = self._parse_availabilities_json(data)
        availabilities = []

        for rawavail in rawavailabilities:
            self._validate_availability(rawavail)
            availabilities.append(Availability(event_id=self.event.id, **rawavail))
        if not availabilities and required:
            raise forms.ValidationError(_('Please fill in your availabilities!'))
        return availabilities

    def _set_foreignkeys(self, instance, availabilities):
        """
        Set the reference to `instance` in each given availability.
        For example, set the availabilitiy.room_id to instance.id, in
        case instance of type Room.
        """
        reference_name = instance.availabilities.field.name + '_id'

        for avail in availabilities:
            setattr(avail, reference_name, instance.id)

    def _replace_availabilities(self, instance, availabilities: [Availability]):
        """
        Replace the existing list of availabilities belonging to an entity with a new, updated one

        This will trigger a post_save signal for usage in constraint violation checking

        :param instance: entity the availabilities belong to
        :param availabilities: list of new availabilities
        """
        with transaction.atomic():
            # TODO: do not recreate objects unnecessarily, give the client the IDs, so we can track modifications and
            #  leave unchanged objects alone
            instance.availabilities.all().delete()
            Availability.objects.bulk_create(availabilities)
            # Adaption:
            # Trigger post save signal manually to make sure constraints are updated accordingly
            # Doing this one time is sufficient, since this will nevertheless update all availability constraint
            # violations of the corresponding AK
            if len(availabilities) > 0:
                post_save.send(Availability, instance=availabilities[0], created=True)

    def save(self, *args, **kwargs):
        """
        Override the saving method of the (model) form
        """
        instance = super().save(*args, **kwargs)
        availabilities = self.cleaned_data.get('availabilities')

        if availabilities is not None:
            self._set_foreignkeys(instance, availabilities)
            self._replace_availabilities(instance, availabilities)

        return instance  # adapt to our forms