Django-Translatable-Fields/django_translatable_fields/fields.py

# -*- coding: utf-8 -*-
"""
Django Translatable Fields - Core Field Definitions

This module provides the core functionality for creating translatable database fields
that store translations as JSON and provide language-aware access similar to Odoo's
translate=True functionality.

Key Features:
- Automatic JSON storage of translations in database
- Language-aware field access based on Django's current language
- Admin interface integration with translation modal overlays
- Migration support for translate=True/False transitions
- Database-specific optimizations for search operations

Usage:
    from django_translatable_fields import CharField, TextField
    
    class MyModel(models.Model):
        name = CharField(max_length=200, translatable=True)
        description = TextField(translatable=True)

Author: Holger Sielaff <holger@backender.de>
Version: 0.1.0
"""

import json
from django.db import models
from django.core.exceptions import ValidationError
from django.utils.translation import get_language, gettext_lazy as _
import logging
import inspect


class TranslatableMixin:
    """
    Mixin that provides translatable functionality to any Django field.
    Stores translations as JSON and provides language-aware access.
    """

    def __init__(self, *args, **kwargs):
        self.translatable = kwargs.pop('translatable', False)
        super().__init__(*args, **kwargs)
        if self.translatable and hasattr(self, '_validators') and self.validators:
            self._original_validators = self.validators.copy()
            self.validators = []

    def contribute_to_class(self, cls, name, **kwargs):
        """Override to detect translatable changes and trigger migrations"""
        super().contribute_to_class(cls, name, **kwargs)

        # Store field info for migration detection
        if not hasattr(cls._meta, '_translatable_fields'):
            cls._meta._translatable_fields = {}

        cls._meta._translatable_fields[name] = {
            'translatable': self.translatable,
            'field_type': self.__class__.__name__
        }

    def deconstruct(self):
        """Include translatable parameter in field deconstruction for migrations"""
        name, path, args, kwargs = super().deconstruct()
        kwargs['translatable'] = self.translatable
        return name, path, args, kwargs

    def from_db_value(self, value, expression, connection):
        logging.debug(f"{self.__class__.__name__} from_db_value - received: {repr(value)}")

        if value is None:
            return value

        if not self.translatable:
            return value

        # Check if we're in admin context by looking at the call stack
        frames = inspect.getouterframes(inspect.currentframe())
        is_admin_context =  os.environ.get('DJANGO_ADMIN_OVERRIDE', False) == '1' or  any('admin' in frame.filename or 'forms' in frame.filename for frame in frames[:5])

        logging.debug(f"{self.__class__.__name__} from_db_value - admin context: {is_admin_context}")

        try:
            translations = json.loads(value) if isinstance(value, str) else value
            if not isinstance(translations, dict):
                return value

            logging.debug(f"{self.__class__.__name__} from_db_value - parsed translations: {translations}")

            # For admin/forms, return the full dict so widgets can access all translations
            if is_admin_context:
                logging.debug(
                    f"{self.__class__.__name__} from_db_value - returning full dict for admin: {translations}")
                return translations

            # For regular use, return the appropriate language
            current_lang = get_language()
            if current_lang and current_lang in translations:
                result = translations[current_lang]
                logging.debug(
                    f"{self.__class__.__name__} from_db_value - returning for language {current_lang}: {repr(result)}")
                return result

            # Fallback to default language or first available
            if 'en' in translations:
                result = translations['en']
                logging.debug(f"{self.__class__.__name__} from_db_value - returning english fallback: {repr(result)}")
                return result
            elif translations:
                result = next(iter(translations.values()))
                logging.debug(f"{self.__class__.__name__} from_db_value - returning first available: {repr(result)}")
                return result

            logging.debug(f"{self.__class__.__name__} from_db_value - returning empty string")
            return ''
        except (json.JSONDecodeError, TypeError):
            logging.debug(f"{self.__class__.__name__} from_db_value - JSON decode error, returning raw value")
            return value

    def to_python(self, value):
        if value is None:
            return value

        if not self.translatable:
            return super().to_python(value)

        if isinstance(value, dict):
            return value

        try:
            return json.loads(value) if isinstance(value, str) else value
        except (json.JSONDecodeError, TypeError):
            return value

    def get_prep_value(self, value):
        if not self.translatable:
            return super().get_prep_value(value)

        if value is None:
            return value

        # If it's already a JSON string from database, don't double encode
        if isinstance(value, str):
            try:
                # Try to parse it - if it parses, it's already JSON
                parsed = json.loads(value)
                if isinstance(parsed, dict):
                    return value  # Return as-is, it's already proper JSON
            except (json.JSONDecodeError, TypeError):
                pass
            # If parsing fails, treat as regular string for current language
            current_lang = get_language() or 'en'
            return json.dumps({current_lang: str(value)})

        if isinstance(value, dict):
            # Filter out empty values and ensure all values are strings
            clean_dict = {k: str(v) for k, v in value.items() if v and str(v).strip()}
            return json.dumps(clean_dict) if clean_dict else None

        # Fallback for other types
        current_lang = get_language() or 'en'
        return json.dumps({current_lang: str(value)})

    def validate(self, value, model_instance):
        if not self.translatable or not value or not isinstance(value, (str, dict)):
            super().validate(value, model_instance)

        # Validate each translation individually
        for lang_code, translation in value.items():
            if not isinstance(lang_code, str) or not isinstance(translation, str):
                raise ValidationError(_('Invalid translation format'))

            # Validate each translation string with appropriate validators
            if translation.strip():  # Only validate non-empty values
                try:
                    # Run field-specific validation for each translation
                    self._validate_translation(translation, lang_code)
                except ValidationError as e:
                    # Re-raise with language context
                    raise ValidationError(f"Invalid value for language '{lang_code}': {e.message}")

    def _validate_translation(self, value, lang_code):
        """Validate a single translation value with field-specific validators"""
        for validator in getattr(self, '_original_validators', []):
            validator(value)

    def formfield(self, **kwargs):
        # Only apply translatable widgets to text-like fields
        if self.translatable and isinstance(self,
                                            (models.CharField, models.TextField, models.SlugField, models.EmailField,
                                             models.URLField)):
            # Use specific form fields for fields with validators
            if isinstance(self, models.EmailField):
                from .forms import TranslatableEmailFormField
                defaults = {'form_class': TranslatableEmailFormField}
            elif isinstance(self, models.SlugField):
                from .forms import TranslatableSlugFormField
                defaults = {'form_class': TranslatableSlugFormField}
            elif isinstance(self, models.URLField):
                from .forms import TranslatableURLFormField
                defaults = {'form_class': TranslatableURLFormField}
            else:
                # For CharField and TextField, use the unified form field
                from .forms import TranslatableUnifiedFormField

                # Determine if this is char-like based on max_length or field type
                is_charfield = (
                                       hasattr(self, 'max_length') and self.max_length is not None
                               ) or isinstance(self, models.CharField)

                defaults = {
                    'form_class': TranslatableUnifiedFormField,
                    'is_charfield': is_charfield,
                    'max_length': getattr(self, 'max_length', None),
                }

            defaults.update(kwargs)
            return super().formfield(**defaults)
        return super().formfield(**kwargs)


class CharField(TranslatableMixin, models.CharField):
    """ A translatable Char Field"""
    pass


class TextField(TranslatableMixin, models.TextField):
    """ A translatable Text Field """
    pass


class EmailField(TranslatableMixin, models.EmailField):
    """Translatable email field"""
    pass


class URLField(TranslatableMixin, models.URLField):
    """Translatable URL field"""
    pass


class SlugField(TranslatableMixin, models.SlugField):
    """Translatable slug field"""
    pass