from os.path import exists
from importlib.machinery import SourceFileLoader
from django.apps import apps
from django.conf import settings


def transfer_objects(data_type):

    for app in apps.get_app_configs():
        if exists(f"{app.path}/transfer_data.py"):
            card_module = SourceFileLoader("transfer", f"{app.path}/transfer_data.py").load_module()
            if not hasattr(card_module, "data_types") \
                    or not isinstance(card_module.data_types, dict) \
                    or len(card_module.data_types) < 1:
                continue

            for module_data_type, transfer_funcs in card_module.data_types.items():
                if data_type == module_data_type:
                    for transfer_func in transfer_funcs:
                        print(f"========================== FUNCTION {transfer_func.__name__} ================================")
                        transfer_func()


def clean_old_records(model, conditions):
    error_file = open(f"{settings.PROJECT_ROOT}/apps/transfer/clear.error.txt", "w")
    non_existed_correct_city_ids = []

    try:
        old_records = model.objects.filter(**conditions)
    except Exception as e:
        error_file.write(f"Cannot find model objects: {e}")
        return

    for old_record in old_records:
        correct_record_qs = model.objects.exclude(id=old_record.id) \
                                         .exclude(**conditions) \
                                         .filter(name=old_record.name)
        if correct_record_qs.exists():
            correct_record = correct_record_qs.first()
            for rel_instance in old_record._related_instances:
                field_name = [related_field.name
                              for related_field in rel_instance._meta.fields
                              if related_field.related_model == correct_record._meta.model][0]
                # rebinding correct dependency instances
                if getattr(rel_instance, field_name) != correct_record:
                    setattr(rel_instance, field_name, correct_record)
                    rel_instance.save()
        else:
            non_existed_correct_city_ids.append(old_record.id)

    if non_existed_correct_city_ids:
        print(f"Non existed correct city ids: {non_existed_correct_city_ids}")
        return

    # delete old records
    counter = old_records.count()
    old_records.delete()
    print(f'Deleted {counter} objects.')