/*
 * 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.engine;

import org.apache.lucene.index.BinaryDocValues;
import org.apache.lucene.index.ByteVectorValues;
import org.apache.lucene.index.DocValuesType;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.FieldInfos;
import org.apache.lucene.index.Fields;
import org.apache.lucene.index.FloatVectorValues;
import org.apache.lucene.index.IndexOptions;
import org.apache.lucene.index.LeafMetaData;
import org.apache.lucene.index.LeafReader;
import org.apache.lucene.index.NumericDocValues;
import org.apache.lucene.index.PointValues;
import org.apache.lucene.index.SortedDocValues;
import org.apache.lucene.index.SortedNumericDocValues;
import org.apache.lucene.index.SortedSetDocValues;
import org.apache.lucene.index.StoredFieldVisitor;
import org.apache.lucene.index.StoredFields;
import org.apache.lucene.index.TermVectors;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.VectorEncoding;
import org.apache.lucene.index.VectorSimilarityFunction;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.util.Bits;
import org.apache.lucene.util.BytesRef;
import org.opensearch.common.util.set.Sets;
import org.opensearch.index.mapper.IdFieldMapper;
import org.opensearch.index.mapper.RoutingFieldMapper;
import org.opensearch.index.mapper.SourceFieldMapper;
import org.opensearch.index.mapper.Uid;
import org.opensearch.index.translog.Translog;

import java.io.IOException;
import java.util.Collections;
import java.util.Set;

/**
 * Internal class that mocks a single doc read from the transaction log as a leaf reader.
 *
 * @opensearch.internal
 */
public final class TranslogLeafReader extends LeafReader {

    private final Translog.Index operation;
    private static final FieldInfo FAKE_SOURCE_FIELD = new FieldInfo(
        SourceFieldMapper.NAME,
        1,
        false,
        false,
        false,
        IndexOptions.NONE,
        DocValuesType.NONE,
        -1,
        Collections.emptyMap(),
        0,
        0,
        0,
        0,
        VectorEncoding.FLOAT32,
        VectorSimilarityFunction.EUCLIDEAN,
        false
    );
    private static final FieldInfo FAKE_ROUTING_FIELD = new FieldInfo(
        RoutingFieldMapper.NAME,
        2,
        false,
        false,
        false,
        IndexOptions.NONE,
        DocValuesType.NONE,
        -1,
        Collections.emptyMap(),
        0,
        0,
        0,
        0,
        VectorEncoding.FLOAT32,
        VectorSimilarityFunction.EUCLIDEAN,
        false
    );
    private static final FieldInfo FAKE_ID_FIELD = new FieldInfo(
        IdFieldMapper.NAME,
        3,
        false,
        false,
        false,
        IndexOptions.NONE,
        DocValuesType.NONE,
        -1,
        Collections.emptyMap(),
        0,
        0,
        0,
        0,
        VectorEncoding.FLOAT32,
        VectorSimilarityFunction.EUCLIDEAN,
        false
    );
    public static Set<String> ALL_FIELD_NAMES = Sets.newHashSet(FAKE_SOURCE_FIELD.name, FAKE_ROUTING_FIELD.name, FAKE_ID_FIELD.name);

    TranslogLeafReader(Translog.Index operation) {
        this.operation = operation;
    }

    @Override
    public CacheHelper getCoreCacheHelper() {
        throw new UnsupportedOperationException();
    }

    @Override
    public Terms terms(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public NumericDocValues getNumericDocValues(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public BinaryDocValues getBinaryDocValues(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public SortedDocValues getSortedDocValues(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public SortedNumericDocValues getSortedNumericDocValues(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public SortedSetDocValues getSortedSetDocValues(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public NumericDocValues getNormValues(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public FieldInfos getFieldInfos() {
        throw new UnsupportedOperationException();
    }

    @Override
    public Bits getLiveDocs() {
        throw new UnsupportedOperationException();
    }

    @Override
    public PointValues getPointValues(String field) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void checkIntegrity() {

    }

    @Override
    public LeafMetaData getMetaData() {
        throw new UnsupportedOperationException();
    }

    @Override
    public Fields getTermVectors(int docID) {
        throw new UnsupportedOperationException();
    }

    @Override
    public TermVectors termVectors() throws IOException {
        throw new UnsupportedOperationException();
    }

    @Override
    public int numDocs() {
        return 1;
    }

    @Override
    public int maxDoc() {
        return 1;
    }

    @Override
    public void document(int docID, StoredFieldVisitor visitor) throws IOException {
        storedFields().document(docID, visitor);
    }

    @Override
    public StoredFields storedFields() throws IOException {
        return new StoredFields() {
            @Override
            public void document(int docID, StoredFieldVisitor visitor) throws IOException {
                if (docID != 0) {
                    throw new IllegalArgumentException("no such doc ID " + docID);
                }
                if (visitor.needsField(FAKE_SOURCE_FIELD) == StoredFieldVisitor.Status.YES) {
                    assert operation.source().toBytesRef().offset == 0;
                    assert operation.source().toBytesRef().length == operation.source().toBytesRef().bytes.length;
                    visitor.binaryField(FAKE_SOURCE_FIELD, operation.source().toBytesRef().bytes);
                }
                if (operation.routing() != null && visitor.needsField(FAKE_ROUTING_FIELD) == StoredFieldVisitor.Status.YES) {
                    visitor.stringField(FAKE_ROUTING_FIELD, operation.routing());
                }
                if (visitor.needsField(FAKE_ID_FIELD) == StoredFieldVisitor.Status.YES) {
                    BytesRef bytesRef = Uid.encodeId(operation.id());
                    final byte[] id = new byte[bytesRef.length];
                    System.arraycopy(bytesRef.bytes, bytesRef.offset, id, 0, bytesRef.length);
                    visitor.binaryField(FAKE_ID_FIELD, id);
                }
            }
        };
    }

    @Override
    protected void doClose() {

    }

    @Override
    public CacheHelper getReaderCacheHelper() {
        throw new UnsupportedOperationException();
    }

    @Override
    public FloatVectorValues getFloatVectorValues(String field) throws IOException {
        return getFloatVectorValues(field);
    }

    @Override
    public ByteVectorValues getByteVectorValues(String field) throws IOException {
        return getByteVectorValues(field);
    }

    @Override
    public TopDocs searchNearestVectors(String field, float[] target, int k, Bits acceptDocs, int visitedLimit) throws IOException {
        throw new UnsupportedOperationException();
    }

    @Override
    public TopDocs searchNearestVectors(String field, byte[] target, int k, Bits acceptDocs, int visitedLimit) throws IOException {
        throw new UnsupportedOperationException();
    }
}
