default_app_config = 'autocomplete.apps.AutocompleteConfig'

from django.db import models
from django.core.exceptions import ImproperlyConfigured
from django.forms.widgets import Widget
from django.template.loader import render_to_string


class ModelAutocomplete:
    """Base class for model-based autocomplete."""
    model = None  # Model class to use for autocomplete
    search_attrs = []  # List of model attributes to search
    minimum_search_length = 2  # Minimum length of search string
    max_results = 10  # Maximum number of results to return

    def __init__(self):
        if not self.model:
            raise ImproperlyConfigured("ModelAutocomplete requires a model class")
        if not self.search_attrs:
            raise ImproperlyConfigured("ModelAutocomplete requires search_attrs")

    def get_search_results(self, search):
        """Return search results for a given search string."""
        raise NotImplementedError("Subclasses must implement get_search_results()")

    def format_result(self, obj):
        """Format a single result object."""
        raise NotImplementedError("Subclasses must implement format_result()")


class AutocompleteWidget(Widget):
    """Widget for autocomplete fields."""
    template_name = 'autocomplete/widget.html'

    def __init__(self, ac_class, attrs=None):
        super().__init__(attrs)
        if not issubclass(ac_class, ModelAutocomplete):
            raise ImproperlyConfigured("ac_class must be a subclass of ModelAutocomplete")
        self.ac_class = ac_class

    def get_context(self, name, value, attrs):
        context = super().get_context(name, value, attrs)
        # Add ac_name for URL resolution
        context['ac_name'] = self.ac_class.__name__.lower()
        return context

    def render(self, name, value, attrs=None, renderer=None):
        context = self.get_context(name, value, attrs)
        return render_to_string(self.template_name, context)