text: import re
  from datetime import datetime, date
  
  import django_filters
  from django import forms
  from django.contrib.contenttypes.models import ContentType
  from django.contrib.postgres.fields import ArrayField
  from django.core.validators import RegexValidator, ValidationError
  from django.db import models
  from django.urls import reverse
  from django.utils.html import escape
  from django.utils.safestring import mark_safe
  
  from extras.choices import *
  from extras.utils import FeatureQuery, extras_features
  from netbox.models import ChangeLoggedModel
  from utilities import filters
  from utilities.forms import (
      CSVChoiceField, CSVMultipleChoiceField, DatePicker, LaxURLField, StaticSelectMultiple, StaticSelect,
      add_blank_choice,
  )
  from utilities.querysets import RestrictedQuerySet
  from utilities.validators import validate_regex
  
  
  __all__ = (
      'CustomField',
      'CustomFieldManager',
  )
  
  
  class CustomFieldManager(models.Manager.from_queryset(RestrictedQuerySet)):
      use_in_migrations = True
  
      def get_for_model(self, model):
          """
          Return all CustomFields assigned to the given model.
          """
          content_type = ContentType.objects.get_for_model(model._meta.concrete_model)
          return self.get_queryset().filter(content_types=content_type)
  
  
  @extras_features('webhooks', 'export_templates')
  class CustomField(ChangeLoggedModel):
      content_types = models.ManyToManyField(
          to=ContentType,
          related_name='custom_fields',
          limit_choices_to=FeatureQuery('custom_fields'),
          help_text='The object(s) to which this field applies.'
      )
      type = models.CharField(
          max_length=50,
          choices=CustomFieldTypeChoices,
          default=CustomFieldTypeChoices.TYPE_TEXT
      )
      name = models.CharField(
          max_length=50,
          unique=True,
          help_text='Internal field name',
          validators=(
              RegexValidator(
                  regex=r'^[a-z0-9_]+$',
                  message="Only alphanumeric characters and underscores are allowed.",
                  flags=re.IGNORECASE
              ),
          )
      )
      label = models.CharField(
          max_length=50,
          blank=True,
          help_text='Name of the field as displayed to users (if not provided, '
                    'the field\'s name will be used)'
      )
      description = models.CharField(
          max_length=200,
          blank=True
      )
      required = models.BooleanField(
          default=False,
          help_text='If true, this field is required when creating new objects '
                    'or editing an existing object.'
      )
      filter_logic = models.CharField(
          max_length=50,
          choices=CustomFieldFilterLogicChoices,
          default=CustomFieldFilterLogicChoices.FILTER_LOOSE,
          help_text='Loose matches any instance of a given string; exact '
                    'matches the entire field.'
      )
      default = models.JSONField(
          blank=True,
          null=True,
          help_text='Default value for the field (must be a JSON value). Encapsulate '
                    'strings with double quotes (e.g. "Foo").'
      )
      weight = models.PositiveSmallIntegerField(
          default=100,
          help_text='Fields with higher weights appear lower in a form.'
      )
      validation_minimum = models.IntegerField(
          blank=True,
          null=True,
          verbose_name='Minimum value',
          help_text='Minimum allowed value (for numeric fields)'
      )
      validation_maximum = models.IntegerField(
          blank=True,
          null=True,
          verbose_name='Maximum value',
          help_text='Maximum allowed value (for numeric fields)'
      )
      validation_regex = models.CharField(
          blank=True,
          validators=[validate_regex],
          max_length=500,
          verbose_name='Validation regex',
          help_text='Regular expression to enforce on text field values. Use ^ and $ to force matching of entire string. '
                    'For example, <code>^[A-Z]{3}$</code> will limit values to exactly three uppercase letters.'
      )
      choices = ArrayField(
          base_field=models.CharField(max_length=100),
          blank=True,
          null=True,
          help_text='Comma-separated list of available choices (for selection fields)'
      )
  
      objects = CustomFieldManager()
  
      class Meta:
          ordering = ['weight', 'name']
  
      def __str__(self):
          return self.label or self.name.replace('_', ' ').capitalize()
  
      def get_absolute_url(self):
          return reverse('extras:customfield', args=[self.pk])
  
      def __init__(self, *args, **kwargs):
          super().__init__(*args, **kwargs)
  
          # Cache instance's original name so we can check later whether it has changed
          self._name = self.name
  
      def populate_initial_data(self, content_types):
          """
          Populate initial custom field data upon either a) the creation of a new CustomField, or
          b) the assignment of an existing CustomField to new object types.
          """
          for ct in content_types:
              model = ct.model_class()
              instances = model.objects.exclude(**{f'custom_field_data__contains': self.name})
              for instance in instances:
                  instance.custom_field_data[self.name] = self.default
              model.objects.bulk_update(instances, ['custom_field_data'], batch_size=100)
  
      def remove_stale_data(self, content_types):
          """
          Delete custom field data which is no longer relevant (either because the CustomField is
          no longer assigned to a model, or because it has been deleted).
          """
          for ct in content_types:
              model = ct.model_class()
              instances = model.objects.filter(**{f'custom_field_data__{self.name}__isnull': False})
              for instance in instances:
                  del(instance.custom_field_data[self.name])
              model.objects.bulk_update(instances, ['custom_field_data'], batch_size=100)
  
      def rename_object_data(self, old_name, new_name):
          """
          Called when a CustomField has been renamed. Updates all assigned object data.
          """
          for ct in self.content_types.all():
              model = ct.model_class()
              params = {f'custom_field_data__{old_name}__isnull': False}
              instances = model.objects.filter(**params)
              for instance in instances:
                  instance.custom_field_data[new_name] = instance.custom_field_data.pop(old_name)
              model.objects.bulk_update(instances, ['custom_field_data'], batch_size=100)
  
      def clean(self):
          super().clean()
  
          # Validate the field's default value (if any)
          if self.default is not None:
              try:
                  if self.type in (CustomFieldTypeChoices.TYPE_TEXT, CustomFieldTypeChoices.TYPE_LONGTEXT):
                      default_value = str(self.default)
                  else:
                      default_value = self.default
                  self.validate(default_value)
              except ValidationError as err:
                  raise ValidationError({
                      'default': f'Invalid default value "{self.default}": {err.message}'
                  })
  
          # Minimum/maximum values can be set only for numeric fields
          if self.validation_minimum is not None and self.type != CustomFieldTypeChoices.TYPE_INTEGER:
              raise ValidationError({
                  'validation_minimum': "A minimum value may be set only for numeric fields"
              })
          if self.validation_maximum is not None and self.type != CustomFieldTypeChoices.TYPE_INTEGER:
              raise ValidationError({
                  'validation_maximum': "A maximum value may be set only for numeric fields"
              })
  
          # Regex validation can be set only for text fields
          regex_types = (
              CustomFieldTypeChoices.TYPE_TEXT,
              CustomFieldTypeChoices.TYPE_LONGTEXT,
              CustomFieldTypeChoices.TYPE_URL,
          )
          if self.validation_regex and self.type not in regex_types:
              raise ValidationError({
                  'validation_regex': "Regular expression validation is supported only for text and URL fields"
              })
  
          # Choices can be set only on selection fields
          if self.choices and self.type not in (
                  CustomFieldTypeChoices.TYPE_SELECT,
                  CustomFieldTypeChoices.TYPE_MULTISELECT
          ):
              raise ValidationError({
                  'choices': "Choices may be set only for custom selection fields."
              })
  
          # A selection field must have at least two choices defined
          if self.type == CustomFieldTypeChoices.TYPE_SELECT and self.choices and len(self.choices) < 2:
              raise ValidationError({
                  'choices': "Selection fields must specify at least two choices."
              })
  
          # A selection field's default (if any) must be present in its available choices
          if self.type == CustomFieldTypeChoices.TYPE_SELECT and self.default and self.default not in self.choices:
              raise ValidationError({
                  'default': f"The specified default value ({self.default}) is not listed as an available choice."
              })
  
      def to_form_field(self, set_initial=True, enforce_required=True, for_csv_import=False):
          """
          Return a form field suitable for setting a CustomField's value for an object.
  
          set_initial: Set initial data for the field. This should be False when generating a field for bulk editing.
          enforce_required: Honor the value of CustomField.required. Set to False for filtering/bulk editing.
          for_csv_import: Return a form field suitable for bulk import of objects in CSV format.
          """
          initial = self.default if set_initial else None
          required = self.required if enforce_required else False
  
          # Integer
          if self.type == CustomFieldTypeChoices.TYPE_INTEGER:
              field = forms.IntegerField(
                  required=required,
                  initial=initial,
                  min_value=self.validation_minimum,
                  max_value=self.validation_maximum
              )
  
          # Boolean
          elif self.type == CustomFieldTypeChoices.TYPE_BOOLEAN:
              choices = (
                  (None, '---------'),
                  (True, 'True'),
                  (False, 'False'),
              )
              field = forms.NullBooleanField(
                  required=required, initial=initial, widget=StaticSelect(choices=choices)
              )
  
          # Date
          elif self.type == CustomFieldTypeChoices.TYPE_DATE:
              field = forms.DateField(required=required, initial=initial, widget=DatePicker())
  
          # Select
          elif self.type in (CustomFieldTypeChoices.TYPE_SELECT, CustomFieldTypeChoices.TYPE_MULTISELECT):
              choices = [(c, c) for c in self.choices]
              default_choice = self.default if self.default in self.choices else None
  
              if not required or default_choice is None:
                  choices = add_blank_choice(choices)
  
              # Set the initial value to the first available choice (if any)
              if set_initial and default_choice:
                  initial = default_choice
  
              if self.type == CustomFieldTypeChoices.TYPE_SELECT:
                  field_class = CSVChoiceField if for_csv_import else forms.ChoiceField
                  field = field_class(
                      choices=choices, required=required, initial=initial, widget=StaticSelect()
                  )
              else:
                  field_class = CSVMultipleChoiceField if for_csv_import else forms.MultipleChoiceField
                  field = field_class(
                      choices=choices, required=required, initial=initial, widget=StaticSelectMultiple()
                  )
  
          # URL
          elif self.type == CustomFieldTypeChoices.TYPE_URL:
              field = LaxURLField(required=required, initial=initial)
  
          # JSON
          elif self.type == CustomFieldTypeChoices.TYPE_JSON:
              field = forms.JSONField(required=required, initial=initial)
  
          # Text
          else:
              if self.type == CustomFieldTypeChoices.TYPE_LONGTEXT:
                  max_length = None
                  widget = forms.Textarea
              else:
                  max_length = 255
                  widget = None
              field = forms.CharField(max_length=max_length, required=required, initial=initial, widget=widget)
              if self.validation_regex:
                  field.validators = [
                      RegexValidator(
                          regex=self.validation_regex,
                          message=mark_safe(f"Values must match this regex: <code>{self.validation_regex}</code>")
                      )
                  ]
  
          field.model = self
          field.label = str(self)
          if self.description:
              field.help_text = escape(self.description)
  
          return field
  
      def to_filter(self, lookup_expr=None):
          """
          Return a django_filters Filter instance suitable for this field type.
  
          :param lookup_expr: Custom lookup expression (optional)
          """
          kwargs = {
              'field_name': f'custom_field_data__{self.name}'
          }
          if lookup_expr is not None:
              kwargs['lookup_expr'] = lookup_expr
  
          # Text/URL
          if self.type in (
                  CustomFieldTypeChoices.TYPE_TEXT,
                  CustomFieldTypeChoices.TYPE_LONGTEXT,
                  CustomFieldTypeChoices.TYPE_URL,
          ):
              filter_class = filters.MultiValueCharFilter
              if self.filter_logic == CustomFieldFilterLogicChoices.FILTER_LOOSE:
                  kwargs['lookup_expr'] = 'icontains'
  
          # Integer
          elif self.type == CustomFieldTypeChoices.TYPE_INTEGER:
              filter_class = filters.MultiValueNumberFilter
  
          # Boolean
          elif self.type == CustomFieldTypeChoices.TYPE_BOOLEAN:
              filter_class = django_filters.BooleanFilter
  
          # Date
          elif self.type == CustomFieldTypeChoices.TYPE_DATE:
              filter_class = filters.MultiValueDateFilter
  
          # Select
          elif self.type == CustomFieldTypeChoices.TYPE_SELECT:
              filter_class = filters.MultiValueCharFilter
  
          # Multiselect
          elif self.type == CustomFieldTypeChoices.TYPE_MULTISELECT:
              filter_class = filters.MultiValueCharFilter
              kwargs['lookup_expr'] = 'has_key'
  
          # Unsupported custom field type
          else:
              return None
  
          filter_instance = filter_class(**kwargs)
          filter_instance.custom_field = self
  
          return filter_instance
  
      def validate(self, value):
          """
          Validate a value according to the field's type validation rules.
          """
          if value not in [None, '']:
  
              # Validate text field
              if self.type in (CustomFieldTypeChoices.TYPE_TEXT, CustomFieldTypeChoices.TYPE_LONGTEXT):
                  if type(value) is not str:
                      raise ValidationError(f"Value must be a string.")
                  if self.validation_regex and not re.match(self.validation_regex, value):
                      raise ValidationError(f"Value must match regex '{self.validation_regex}'")
  
              # Validate integer
              if self.type == CustomFieldTypeChoices.TYPE_INTEGER:
                  if type(value) is not int:
                      raise ValidationError("Value must be an integer.")
                  if self.validation_minimum is not None and value < self.validation_minimum:
                      raise ValidationError(f"Value must be at least {self.validation_minimum}")
                  if self.validation_maximum is not None and value > self.validation_maximum:
                      raise ValidationError(f"Value must not exceed {self.validation_maximum}")
  
              # Validate boolean
              if self.type == CustomFieldTypeChoices.TYPE_BOOLEAN and value not in [True, False, 1, 0]:
                  raise ValidationError("Value must be true or false.")
  
              # Validate date
              if self.type == CustomFieldTypeChoices.TYPE_DATE:
                  if type(value) is not date:
                      try:
                          datetime.strptime(value, '%Y-%m-%d')
                      except ValueError:
                          raise ValidationError("Date values must be in the format YYYY-MM-DD.")
  
              # Validate selected choice
              if self.type == CustomFieldTypeChoices.TYPE_SELECT:
                  if value not in self.choices:
                      raise ValidationError(
                          f"Invalid choice ({value}). Available choices are: {', '.join(self.choices)}"
                      )
  
              # Validate all selected choices
              if self.type == CustomFieldTypeChoices.TYPE_MULTISELECT:
                  if not set(value).issubset(self.choices):
                      raise ValidationError(
                          f"Invalid choice(s) ({', '.join(value)}). Available choices are: {', '.join(self.choices)}"
                      )
  
          elif self.required:
              raise ValidationError("Required field cannot be empty.")
  