from django.core.management.base import BaseCommand
from django.apps import apps
from django.db.models import Q, CharField, TextField

"""Completely written by https://gemini.google.com/ 2.5
"""

def get_all_project_models():
    """
    Returns a list of all concrete model.Model classes in the Django project.
    It ignores abstract models and models from third-party apps that aren't
    part of the project's own apps.
    """
    # You can customize this list to include/exclude specific apps
    # For example: installed_apps = settings.INSTALLED_APPS
    all_models = []
    # This gathers all models from all installed apps.
    for app_config in apps.get_app_configs():
        all_models.extend(list(app_config.get_models()))
    return all_models


def find_empty_or_null_fields(model_class):
    """
    Takes a model class and checks every field.

    Returns a list of field names for which all database entries
    are either NULL or an empty string.
    """
    completely_empty_fields = []
    
    # Get the total number of records for this model.
    total_records = model_class.objects.count()

    # If there are no records, all fields are technically "empty".
    # We return an empty list to avoid reporting every field from an empty table.
    if total_records == 0:
        return []

    # Iterate over all concrete fields of the model.
    for field in model_class._meta.get_fields():
        # We only want to check actual database columns, not relations.
        if not hasattr(field, 'column'):
            continue

        field_name = field.name
        
        # Build a query to find records that have a meaningful value.
        # This is more efficient than counting all null/empty records.
        # We exclude records that are NULL.
        query_has_value = model_class.objects.exclude(Q(**{f'{field_name}__isnull': True}))
        
        # For text-based fields, we also exclude empty strings.
        if isinstance(field, (CharField, TextField)):
            query_has_value = query_has_value.exclude(Q(**{f'{field_name}': ''}))

        # If the query for records WITH a value returns FALSE (no such records exist),
        # it means all records for this field are empty or null.
        if not query_has_value.exists():
            completely_empty_fields.append(field_name)

    return completely_empty_fields


class Command(BaseCommand):
    help = "Scans all project models to find fields where all entries are empty or null."

    def handle(self, *args, **options):
        self.stdout.write(self.style.SUCCESS("🚀 Starting scan for empty or null fields across all models..."))
        
        all_models = get_all_project_models()
        found_any = False

        for model in all_models:
            total_records = model.objects.count()
            model_name = f"{model._meta.app_label}.{model._meta.object_name}"
            self.stdout.write(f"\n🔍 Checking model: {self.style.HTTP_INFO(model_name)} ({total_records} instances found)")

            empty_fields = find_empty_or_null_fields(model)

            if empty_fields:
                found_any = True
                for field_name in empty_fields:
                    self.stdout.write(
                        self.style.WARNING(f"  -> Field '{field_name}' is completely empty or null.")
                    )
            else:
                self.stdout.write(self.style.SUCCESS("  ✅ All fields contain data."))

        if not found_any:
            self.stdout.write(self.style.SUCCESS("\n🎉 Scan complete. No fields were found to be universally empty or null."))


"""

### How to Run the Command

After saving the file, you can run your new command from your project's root directory (where `manage.py` is located):

bash
uv run manage.py find_empty_fields


### Example Output

The output in your terminal will look something like this:

```
🚀 Starting scan for empty or null fields across all models...

🔍 Checking model: auth.Group
  ✅ All fields contain data.

🔍 Checking model: auth.User
  -> Field 'last_name' is completely empty or null.
  -> Field 'first_name' is completely empty or null.

🔍 Checking model: products.Product
  -> Field 'notes' is completely empty or null.
  -> Field 'discount_code' is completely empty or null.

🔍 Checking model: products.Category
  ✅ All fields contain data.
"""