Field Management

def create_translation_field(model, field_name, lang, empty_value):
    """
    Create a translation field for a specific language.
    
    Parameters:
    - model: Model class containing the original field
    - field_name: Name of the original field to translate
    - lang: Language code for this translation field
    - empty_value: How to handle empty values ('', 'both', None, NONE)
    
    Returns:
    - TranslationField instance
    
    Raises:
    - ImproperlyConfigured: If field type is not supported
    """

def field_factory(baseclass):
    """
    Create a translation field class based on Django field type.
    
    Parameters:
    - baseclass: Django field class to base translation field on
    
    Returns:
    - TranslationField subclass
    """

from modeltranslation.fields import create_translation_field
from myapp.models import Article

# Create French translation field for title
title_fr_field = create_translation_field(
    model=Article,
    field_name='title', 
    lang='fr',
    empty_value=''
)

class TranslationField:
    """
    Base class for translation fields that proxy to original fields.
    
    Attributes:
    - translated_field: Original field being translated
    - language: Language code for this translation
    - empty_value: Empty value handling strategy
    """
    
    def __init__(self, translated_field, language, empty_value):
        """
        Initialize translation field.
        
        Parameters:
        - translated_field: Original Django field
        - language: Language code (e.g., 'en', 'fr')
        - empty_value: Empty value handling
        """
    
    def contribute_to_class(self, cls, name):
        """Add this field to the model class."""
    
    def formfield(self, **kwargs):
        """Create form field for this translation field."""

class TranslationFieldDescriptor:
    """
    Descriptor for accessing translation fields with language awareness.
    Handles fallback logic and value resolution.
    """
    
    def __init__(self, field):
        """
        Initialize descriptor for translation field.
        
        Parameters:
        - field: TranslationField instance
        """
    
    def __get__(self, instance, owner):
        """Get field value with language-aware fallback."""
    
    def __set__(self, instance, value):
        """Set field value for current language."""

class TranslatedRelationIdDescriptor:
    """Descriptor for translated foreign key ID fields."""

class TranslatedManyToManyDescriptor:
    """Descriptor for translated many-to-many relationships."""

SUPPORTED_FIELDS: tuple = (
    # Text fields
    fields.CharField,
    fields.TextField,
    fields.json.JSONField,
    
    # Numeric fields  
    fields.IntegerField,
    fields.FloatField,
    fields.DecimalField,
    
    # Boolean fields
    fields.BooleanField,
    fields.NullBooleanField,
    
    # Date/time fields
    fields.DateField,
    fields.DateTimeField,
    fields.TimeField,
    
    # File fields
    fields.files.FileField,
    fields.files.ImageField,
    
    # Network fields
    fields.IPAddressField,
    fields.GenericIPAddressField,
    
    # Relationship fields
    fields.related.ForeignKey,
    fields.related.ManyToManyField,
)
"""Tuple of Django field types supported for translation."""

# In Django settings.py
MODELTRANSLATION_CUSTOM_FIELDS = ('MyCustomField', 'AnotherField')

# Now MyCustomField can be used in translation
@register(MyModel)
class MyModelTranslationOptions(TranslationOptions):
    fields = ('my_custom_field',)  # Works if MyCustomField is in CUSTOM_FIELDS

class NONE:
    """
    Sentinel class for undefined translation values.
    Used when fallback value is not yet known and needs computation.
    """

@register(Article)
class ArticleTranslationOptions(TranslationOptions):
    fields = ('title', 'content', 'summary')
    empty_values = {
        'title': '',        # Only empty string is considered empty
        'content': 'both',  # Both None and empty string are empty
        'summary': None,    # Only None is considered empty
    }

# Original field
class Article(models.Model):
    title = models.CharField(max_length=255, help_text="Article title")
    content = models.TextField(blank=True, null=True)

# After registration, translation fields inherit attributes:
# title_en = CharField(max_length=255, help_text="Article title (English)")
# title_fr = CharField(max_length=255, help_text="Article title (French)")
# content_en = TextField(blank=True, null=True)  
# content_fr = TextField(blank=True, null=True)

# For ForeignKey fields
class TranslatedRelationIdDescriptor:
    """
    Handles translated foreign key relationships.
    Manages the _id suffix and related object access.
    """

# For ManyToManyField fields  
class TranslatedManyToManyDescriptor:
    """
    Handles translated many-to-many relationships.
    Creates intermediate models for each language.
    """

class Article(models.Model):
    title = models.CharField(max_length=255)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    tags = models.ManyToManyField(Tag)

@register(Article)
class ArticleTranslationOptions(TranslationOptions):
    fields = ('title', 'category', 'tags')

# Creates fields:
# title_en, title_fr, title_de
# category_en, category_fr, category_de (ForeignKey fields)
# tags_en, tags_fr, tags_de (ManyToMany fields with intermediate models)

class CustomTranslationField(TranslationField):
    def validate(self, value, model_instance):
        """Custom validation for translation field."""
        super().validate(value, model_instance)
        
        # Add custom validation logic
        if value and len(value) < 5:
            raise ValidationError("Translation must be at least 5 characters")
    
    def clean(self, value, model_instance):
        """Clean and prepare field value."""
        value = super().clean(value, model_instance)
        
        # Add custom cleaning logic
        if isinstance(value, str):
            value = value.strip()
            
        return value

from modeltranslation.fields import create_translation_field

def add_translation_field(model, field_name, language):
    """Dynamically add translation field to model."""
    trans_field = create_translation_field(
        model=model,
        field_name=field_name,
        lang=language,
        empty_value=''
    )
    
    localized_name = f"{field_name}_{language}"
    trans_field.contribute_to_class(model, localized_name)
    
    return trans_field

class CustomTranslationDescriptor:
    def __init__(self, field_name, language):
        self.field_name = field_name
        self.language = language
        
    def __get__(self, instance, owner):
        if instance is None:
            return self
            
        # Custom logic for getting translated value
        return getattr(instance, f"{self.field_name}_{self.language}", None)
        
    def __set__(self, instance, value):
        # Custom logic for setting translated value
        setattr(instance, f"{self.field_name}_{self.language}", value)

# Migration support for adding translation fields
from django.db import migrations
from modeltranslation.fields import TranslationField

class Migration(migrations.Migration):
    operations = [
        migrations.AddField(
            model_name='article',
            name='title_fr',
            field=TranslationField(original_field='title', language='fr'),
        ),
    ]

class OptimizedTranslationDescriptor:
    def __init__(self, field):
        self.field = field
        self._cache_key = f"_{field.name}_cache"
    
    def __get__(self, instance, owner):
        if instance is None:
            return self
            
        # Use caching to improve performance
        cache_key = self._cache_key
        if hasattr(instance, cache_key):
            return getattr(instance, cache_key)
            
        value = self._get_translated_value(instance)
        setattr(instance, cache_key, value)
        return value