/*
 * 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
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package org.apache.lucene.search.similarities;

import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.store.ByteBuffersDirectory;
import org.apache.lucene.store.Directory;
import org.apache.lucene.tests.util.LuceneTestCase;

public class TestIndriDirichletMuConstructor extends LuceneTestCase {

  public void testExplicitDefaultMuScoresLikeDefaultConstructor() throws Exception {
    try (Directory dir = new ByteBuffersDirectory()) {
      try (IndexWriter w = new IndexWriter(dir, new IndexWriterConfig())) {
        Document doc = new Document();
        doc.add(new TextField("body", "a b", Field.Store.NO));
        w.addDocument(doc);
      }
      try (DirectoryReader reader = DirectoryReader.open(dir)) {
        IndexSearcher searcher = new IndexSearcher(reader);
        Query q = new TermQuery(new Term("body", "a"));
        searcher.setSimilarity(new IndriDirichletSimilarity());
        float defaultMu = searcher.explain(q, 0).getValue().floatValue();
        searcher.setSimilarity(new IndriDirichletSimilarity(2000f));
        float explicitMu = searcher.explain(q, 0).getValue().floatValue();
        // () means mu=2000: expected p(a|C)=cf/|C|=1/2 for both; (2000f) uses (cf+1)/(|C|+1)=2/3
        assertEquals(defaultMu, explicitMu, 0f);
      }
    }
  }
}