/*
 * @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) 2025 Elasticsearch B.V.
 */

package org.elasticsearch.index.codec.vectors;

import org.apache.lucene.document.IntPoint;
import org.apache.lucene.document.SortedNumericDocValuesField;
import org.apache.lucene.index.IndexWriter;
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.util.LuceneTestCase;
import org.apache.lucene.tests.util.TestUtil;
import org.apache.lucene.util.CollectionUtil;
import org.apache.lucene.util.Constants;

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

import static org.elasticsearch.index.codec.vectors.DocIdsWriter.DEFAULT_MAX_POINTS_IN_LEAF_NODE;

public class DocIdsWriterTests extends LuceneTestCase {

    public void testNoDocs() throws Exception {
        try (Directory dir = newDirectory()) {
            test(dir, new int[0]);
        }
    }

    public void testRandom() throws Exception {
        int numIters = atLeast(100);
        try (Directory dir = newDirectory()) {
            for (int iter = 0; iter < numIters; ++iter) {
                int count = random().nextBoolean() ? 1 + random().nextInt(5000) : DEFAULT_MAX_POINTS_IN_LEAF_NODE;
                int[] docIDs = new int[count];
                final int bpv = TestUtil.nextInt(random(), 1, 32);
                for (int i = 0; i < docIDs.length; ++i) {
                    docIDs[i] = TestUtil.nextInt(random(), 0, (1 << bpv) - 1);
                }
                test(dir, docIDs);
            }
        }
    }

    public void testSorted() throws Exception {
        int numIters = atLeast(100);
        try (Directory dir = newDirectory()) {
            for (int iter = 0; iter < numIters; ++iter) {
                int[] docIDs = new int[1 + random().nextInt(5000)];
                final int bpv = TestUtil.nextInt(random(), 1, 32);
                for (int i = 0; i < docIDs.length; ++i) {
                    docIDs[i] = TestUtil.nextInt(random(), 0, (1 << bpv) - 1);
                }
                Arrays.sort(docIDs);
                test(dir, docIDs);
            }
        }
    }

    public void testCluster() throws Exception {
        int numIters = atLeast(100);
        try (Directory dir = newDirectory()) {
            for (int iter = 0; iter < numIters; ++iter) {
                int count = random().nextBoolean() ? 1 + random().nextInt(5000) : DEFAULT_MAX_POINTS_IN_LEAF_NODE;
                int[] docIDs = new int[count];
                int min = random().nextInt(1000);
                final int bpv = TestUtil.nextInt(random(), 1, 16);
                for (int i = 0; i < docIDs.length; ++i) {
                    docIDs[i] = min + TestUtil.nextInt(random(), 0, (1 << bpv) - 1);
                }
                test(dir, docIDs);
            }
        }
    }

    public void testBitSet() throws Exception {
        int numIters = atLeast(100);
        try (Directory dir = newDirectory()) {
            for (int iter = 0; iter < numIters; ++iter) {
                int size = 1 + random().nextInt(5000);
                Set<Integer> set = CollectionUtil.newHashSet(size);
                int small = random().nextInt(1000);
                while (set.size() < size) {
                    set.add(small + random().nextInt(size * 16));
                }
                int[] docIDs = set.stream().mapToInt(t -> t).sorted().toArray();
                test(dir, docIDs);
            }
        }
    }

    public void testContinuousIds() throws Exception {
        int numIters = atLeast(100);
        try (Directory dir = newDirectory()) {
            for (int iter = 0; iter < numIters; ++iter) {
                int size = 1 + random().nextInt(5000);
                int[] docIDs = new int[size];
                int start = random().nextInt(1000000);
                for (int i = 0; i < docIDs.length; i++) {
                    docIDs[i] = start + i;
                }
                test(dir, docIDs);
            }
        }
    }

    private void test(Directory dir, int[] ints) throws Exception {
        final long len;
        // It is hard to get BPV24-encoded docs in TextLuceneXXPointsFormat, test bwc here as well.
        DocIdsWriter docIdsWriter = new DocIdsWriter();
        try (IndexOutput out = dir.createOutput("tmp", IOContext.DEFAULT)) {
            docIdsWriter.writeDocIds(i -> ints[i], ints.length, out);
            len = out.getFilePointer();
            if (random().nextBoolean()) {
                out.writeLong(0); // garbage
            }
        }
        try (IndexInput in = dir.openInput("tmp", IOContext.READONCE)) {
            int[] read = new int[ints.length];
            docIdsWriter.readInts(in, ints.length, read);
            assertArrayEquals(ints, read);
            assertEquals(len, in.getFilePointer());
        }
        dir.deleteFile("tmp");
    }

    // This simple test tickles a JVM C2 JIT crash on JDK's less than 21.0.1
    // Crashes only when run with HotSpot C2.
    // Regardless of whether C2 is enabled or not, the test should never fail.
    public void testCrash() throws IOException {
        assumeTrue("Requires HotSpot C2 compiler (won't work on client VM).", Constants.IS_HOTSPOT_VM && (Constants.IS_CLIENT_VM == false));
        int itrs = atLeast(100);
        for (int i = 0; i < itrs; i++) {
            try (Directory dir = newDirectory(); IndexWriter iw = new IndexWriter(dir, newIndexWriterConfig(null))) {
                for (int d = 0; d < 20_000; d++) {
                    iw.addDocument(List.of(new IntPoint("foo", 0), new SortedNumericDocValuesField("bar", 0)));
                }
            }
        }
    }
}