/*
 * @notice
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 (C) 2022 Elasticsearch B.V.
 */
package org.elasticsearch.index.codec.postings;

import org.apache.lucene.codecs.Codec;
import org.apache.lucene.codecs.CompetitiveImpactAccumulator;
import org.apache.lucene.codecs.lucene90.blocktree.FieldReader;
import org.apache.lucene.codecs.lucene90.blocktree.Stats;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.Impact;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.store.ByteArrayDataInput;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.tests.analysis.MockAnalyzer;
import org.apache.lucene.tests.index.BasePostingsFormatTestCase;
import org.apache.lucene.tests.util.TestUtil;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class ES812PostingsFormatTests extends BasePostingsFormatTestCase {
    private final Codec codec = TestUtil.alwaysPostingsFormat(new ES812PostingsFormat());

    @Override
    protected Codec getCodec() {
        return codec;
    }

    /** Make sure the final sub-block(s) are not skipped. */
    public void testFinalBlock() throws Exception {
        Directory d = newDirectory();
        IndexWriter w = new IndexWriter(d, new IndexWriterConfig(new MockAnalyzer(random())));
        for (int i = 0; i < 25; i++) {
            Document doc = new Document();
            doc.add(newStringField("field", Character.toString((char) (97 + i)), Field.Store.NO));
            doc.add(newStringField("field", "z" + Character.toString((char) (97 + i)), Field.Store.NO));
            w.addDocument(doc);
        }
        w.forceMerge(1);

        DirectoryReader r = DirectoryReader.open(w);
        assertEquals(1, r.leaves().size());
        FieldReader field = (FieldReader) r.leaves().get(0).reader().terms("field");
        // We should see exactly two blocks: one root block (prefix empty string) and one block for z*
        // terms (prefix z):
        Stats stats = field.getStats();
        assertEquals(0, stats.floorBlockCount);
        assertEquals(2, stats.nonFloorBlockCount);
        r.close();
        w.close();
        d.close();
    }

    public void testImpactSerialization() throws IOException {
        // omit norms and omit freqs
        doTestImpactSerialization(Collections.singletonList(new Impact(1, 1L)));

        // omit freqs
        doTestImpactSerialization(Collections.singletonList(new Impact(1, 42L)));
        // omit freqs with very large norms
        doTestImpactSerialization(Collections.singletonList(new Impact(1, -100L)));

        // omit norms
        doTestImpactSerialization(Collections.singletonList(new Impact(30, 1L)));
        // omit norms with large freq
        doTestImpactSerialization(Collections.singletonList(new Impact(500, 1L)));

        // freqs and norms, basic
        doTestImpactSerialization(
            Arrays.asList(
                new Impact(1, 7L),
                new Impact(3, 9L),
                new Impact(7, 10L),
                new Impact(15, 11L),
                new Impact(20, 13L),
                new Impact(28, 14L)
            )
        );

        // freqs and norms, high values
        doTestImpactSerialization(
            Arrays.asList(
                new Impact(2, 2L),
                new Impact(10, 10L),
                new Impact(12, 50L),
                new Impact(50, -100L),
                new Impact(1000, -80L),
                new Impact(1005, -3L)
            )
        );
    }

    private void doTestImpactSerialization(List<Impact> impacts) throws IOException {
        CompetitiveImpactAccumulator acc = new CompetitiveImpactAccumulator();
        for (Impact impact : impacts) {
            acc.add(impact.freq, impact.norm);
        }
        try (Directory dir = newDirectory()) {
            try (IndexOutput out = dir.createOutput("foo", IOContext.DEFAULT)) {
                ES812SkipWriter.writeImpacts(acc, out);
            }
            try (IndexInput in = dir.openInput("foo", IOContext.DEFAULT)) {
                byte[] b = new byte[Math.toIntExact(in.length())];
                in.readBytes(b, 0, b.length);
                List<Impact> impacts2 = ES812ScoreSkipReader.readImpacts(
                    new ByteArrayDataInput(b),
                    new ES812ScoreSkipReader.MutableImpactList()
                );
                assertEquals(impacts, impacts2);
            }
        }
    }
}