/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.index.fielddata.plain;

import org.apache.lucene.index.DocValues;
import org.apache.lucene.index.SortedSetDocValues;
import org.apache.lucene.util.Accountable;
import org.opensearch.index.fielddata.LeafOrdinalsFieldData;
import org.opensearch.index.fielddata.FieldData;
import org.opensearch.index.fielddata.ScriptDocValues;
import org.opensearch.index.fielddata.SortedBinaryDocValues;

import java.util.Collection;
import java.util.Collections;
import java.util.function.Function;

/**
 * Baseclass for ordinals docvalues
 *
 * @opensearch.internal
 */
public abstract class AbstractLeafOrdinalsFieldData implements LeafOrdinalsFieldData {

    public static final Function<SortedSetDocValues, ScriptDocValues<?>> DEFAULT_SCRIPT_FUNCTION = ((Function<
        SortedSetDocValues,
        SortedBinaryDocValues>) FieldData::toString).andThen(ScriptDocValues.Strings::new);

    private final Function<SortedSetDocValues, ScriptDocValues<?>> scriptFunction;

    protected AbstractLeafOrdinalsFieldData(Function<SortedSetDocValues, ScriptDocValues<?>> scriptFunction) {
        this.scriptFunction = scriptFunction;
    }

    @Override
    public final ScriptDocValues<?> getScriptValues() {
        return scriptFunction.apply(getOrdinalsValues());
    }

    @Override
    public final SortedBinaryDocValues getBytesValues() {
        return FieldData.toString(getOrdinalsValues());
    }

    public static LeafOrdinalsFieldData empty() {
        return new AbstractLeafOrdinalsFieldData(DEFAULT_SCRIPT_FUNCTION) {

            @Override
            public long ramBytesUsed() {
                return 0;
            }

            @Override
            public Collection<Accountable> getChildResources() {
                return Collections.emptyList();
            }

            @Override
            public void close() {}

            @Override
            public SortedSetDocValues getOrdinalsValues() {
                return DocValues.emptySortedSet();
            }
        };
    }
}