"""A generic view for listing objects."""

from flask import request
from flask.views import MethodView
from owsresponse import response
from owsresponse.adaptors.flask import flaskify


class ListView(MethodView):
    """A generic view for listing objects."""

    def custom_order(self):
        """Override to specify a custom ordering."""
        pass

    def get(self):
        """Convert parameters and retrieve a page of results."""
        offset = max(request.args.get('offset', default=0, type=int), 0)
        limit = max(request.args.get('limit', default=100, type=int), 1)
        query = request.args.get('query')
        results = self.list_entry_schema.dump(
            self.get_page(
                offset=offset,
                limit=limit,
                query=query,
                custom_order=self.custom_order()
            ), many=True)
        count = self.model_class.count(query)
        return flaskify(
            response.Response({'items': results, 'total_count': count}))

    def get_page(self, offset, limit, query=None, custom_order=None):
        """Get a page of objects.

        Filters by the query, if provided.
        Orders by a custom order, if provided, or the default
        order, which is alphabetically by name.
        """
        return self.base_list_query() \
            .filter(*self.model_class.filter_for(query)) \
            .order_by(custom_order or self.model_class.default_order()) \
            .offset(offset) \
            .limit(limit) \
            .all()

    def base_list_query(self):
        """Override to customize pagination results."""
        return self.model_class.query