/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.search;

import java.io.IOException;

/**
 * Manages loading information about nested documents for a single index segment
 */
public interface LeafNestedDocuments {

    /**
     * Advance to a specific doc, and return its NestedIdentity, or {@code null} if not a child
     */
    SearchHit.NestedIdentity advance(int doc) throws IOException;

    /**
     * The current doc
     */
    int doc();

    /**
     * The ultimate parent of the current doc
     */
    int rootDoc();

    /**
     * The NestedIdentity of the current doc
     */
    SearchHit.NestedIdentity nestedIdentity();

    /**
     * An implementation of LeafNestedDocuments for use when there are no nested field mappers
     */
    LeafNestedDocuments NO_NESTED_MAPPERS = new LeafNestedDocuments() {
        @Override
        public SearchHit.NestedIdentity advance(int doc) {
            return null;
        }

        @Override
        public int doc() {
            throw new UnsupportedOperationException();
        }

        @Override
        public int rootDoc() {
            throw new UnsupportedOperationException();
        }

        @Override
        public SearchHit.NestedIdentity nestedIdentity() {
            throw new UnsupportedOperationException();
        }
    };
}