/*
 * 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.
 */

package org.elasticsearch.index.mapper;

import org.apache.lucene.document.Field;
import org.apache.lucene.document.NumericDocValuesField;
import org.apache.lucene.index.DocValuesType;
import org.apache.lucene.index.IndexOptions;
import org.apache.lucene.index.IndexableField;
import org.apache.lucene.search.Query;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.index.mapper.ParseContext.Document;
import org.elasticsearch.index.query.QueryShardContext;
import org.elasticsearch.index.query.QueryShardException;

import java.io.IOException;
import java.util.List;
import java.util.Map;

/** Mapper for the _version field. */
public class VersionFieldMapper extends MetadataFieldMapper {

    public static final String NAME = "_version";
    public static final String CONTENT_TYPE = "_version";

    public static class Defaults {

        public static final String NAME = VersionFieldMapper.NAME;
        public static final MappedFieldType FIELD_TYPE = new VersionFieldType();

        static {
            FIELD_TYPE.setName(NAME);
            FIELD_TYPE.setDocValuesType(DocValuesType.NUMERIC);
            FIELD_TYPE.setIndexOptions(IndexOptions.NONE);
            FIELD_TYPE.setHasDocValues(true);
            FIELD_TYPE.freeze();
        }
    }

    public static class TypeParser implements MetadataFieldMapper.TypeParser {
        @Override
        public MetadataFieldMapper.Builder<?, ?> parse(String name, Map<String, Object> node, ParserContext parserContext) throws MapperParsingException {
            throw new MapperParsingException(NAME + " is not configurable");
        }

        @Override
        public MetadataFieldMapper getDefault(MappedFieldType fieldType, ParserContext context) {
            final Settings indexSettings = context.mapperService().getIndexSettings().getSettings();
            return new VersionFieldMapper(indexSettings);
        }
    }

    static final class VersionFieldType extends MappedFieldType {

        VersionFieldType() {
        }

        protected VersionFieldType(VersionFieldType ref) {
            super(ref);
        }

        @Override
        public MappedFieldType clone() {
            return new VersionFieldType(this);
        }

        @Override
        public String typeName() {
            return CONTENT_TYPE;
        }

        @Override
        public Query termQuery(Object value, QueryShardContext context) {
            throw new QueryShardException(context, "The _version field is not searchable");
        }
    }

    private VersionFieldMapper(Settings indexSettings) {
        super(NAME, Defaults.FIELD_TYPE, Defaults.FIELD_TYPE, indexSettings);
    }

    @Override
    public void preParse(ParseContext context) throws IOException {
        super.parse(context);
    }

    @Override
    protected void parseCreateField(ParseContext context, List<IndexableField> fields) throws IOException {
        // see InternalEngine.updateVersion to see where the real version value is set
        final Field version = new NumericDocValuesField(NAME, -1L);
        context.version(version);
        fields.add(version);
    }

    @Override
    public Mapper parse(ParseContext context) throws IOException {
        // _version added in preparse
        return null;
    }

    @Override
    public void postParse(ParseContext context) throws IOException {
        // In the case of nested docs, let's fill nested docs with version=1 so that Lucene doesn't write a Bitset for documents
        // that don't have the field. This is consistent with the default value for efficiency.
        for (int i = 1; i < context.docs().size(); i++) {
            final Document doc = context.docs().get(i);
            doc.add(new NumericDocValuesField(NAME, 1L));
        }
    }

    @Override
    protected String contentType() {
        return CONTENT_TYPE;
    }

    @Override
    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
        return builder;
    }

    @Override
    protected void doMerge(Mapper mergeWith, boolean updateAllTypes) {
        // nothing to do
    }
}
