/*
 * 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.
 */
package org.apache.lucene.classification;

import java.util.List;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.MockAnalyzer;
import org.apache.lucene.analysis.en.EnglishAnalyzer;
import org.apache.lucene.classification.utils.ConfusionMatrixGenerator;
import org.apache.lucene.index.LeafReader;
import org.apache.lucene.index.MultiTerms;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.similarities.BM25Similarity;
import org.apache.lucene.search.similarities.LMDirichletSimilarity;
import org.apache.lucene.util.BytesRef;
import org.junit.Test;

/** Testcase for {@link KNearestNeighborClassifier} */
public class TestKNearestNeighborClassifier extends ClassificationTestBase<BytesRef> {

  @Test
  public void testBasicUsage() throws Exception {
    LeafReader leafReader = null;
    try {
      MockAnalyzer analyzer = new MockAnalyzer(random());
      leafReader = getSampleIndex(analyzer);
      checkCorrectClassification(
          new KNearestNeighborClassifier(
              leafReader, null, analyzer, null, 1, 0, 0, categoryFieldName, textFieldName),
          TECHNOLOGY_INPUT,
          TECHNOLOGY_RESULT);
      checkCorrectClassification(
          new KNearestNeighborClassifier(
              leafReader,
              new LMDirichletSimilarity(),
              analyzer,
              null,
              1,
              0,
              0,
              categoryFieldName,
              textFieldName),
          TECHNOLOGY_INPUT,
          TECHNOLOGY_RESULT);
      ClassificationResult<BytesRef> resultDS =
          checkCorrectClassification(
              new KNearestNeighborClassifier(
                  leafReader,
                  new BM25Similarity(),
                  analyzer,
                  null,
                  3,
                  2,
                  1,
                  categoryFieldName,
                  textFieldName),
              TECHNOLOGY_INPUT,
              TECHNOLOGY_RESULT);
      ClassificationResult<BytesRef> resultLMS =
          checkCorrectClassification(
              new KNearestNeighborClassifier(
                  leafReader,
                  new LMDirichletSimilarity(),
                  analyzer,
                  null,
                  3,
                  2,
                  1,
                  categoryFieldName,
                  textFieldName),
              TECHNOLOGY_INPUT,
              TECHNOLOGY_RESULT);
      assertTrue(resultDS.getScore() != resultLMS.getScore());
    } finally {
      if (leafReader != null) {
        leafReader.close();
      }
    }
  }

  /**
   * This test is for the scenario where in the first topK results from the MLT query, we have the
   * same number of results per class. But the results for a class have a better ranking in
   * comparison with the results of the second class. So we would expect a greater score for the
   * best ranked class.
   *
   * @throws Exception if any error happens
   */
  @Test
  public void testRankedClasses() throws Exception {
    LeafReader leafReader = null;
    try {
      Analyzer analyzer = new EnglishAnalyzer();
      leafReader = getSampleIndex(analyzer);
      KNearestNeighborClassifier knnClassifier =
          new KNearestNeighborClassifier(
              leafReader, null, analyzer, null, 6, 1, 1, categoryFieldName, textFieldName);
      List<ClassificationResult<BytesRef>> classes =
          knnClassifier.getClasses(STRONG_TECHNOLOGY_INPUT);
      assertTrue(classes.get(0).getScore() > classes.get(1).getScore());
      checkCorrectClassification(knnClassifier, STRONG_TECHNOLOGY_INPUT, TECHNOLOGY_RESULT);
    } finally {
      if (leafReader != null) {
        leafReader.close();
      }
    }
  }

  /**
   * This test is for the scenario where in the first topK results from the MLT query, we have less
   * results for the expected class than the results for the bad class. But the results for the
   * expected class have a better score in comparison with the results of the second class. So we
   * would expect a greater score for the best ranked class.
   *
   * @throws Exception if any error happens
   */
  @Test
  public void testUnbalancedClasses() throws Exception {
    LeafReader leafReader = null;
    try {
      Analyzer analyzer = new EnglishAnalyzer();
      leafReader = getSampleIndex(analyzer);
      KNearestNeighborClassifier knnClassifier =
          new KNearestNeighborClassifier(
              leafReader, null, analyzer, null, 3, 1, 1, categoryFieldName, textFieldName);
      List<ClassificationResult<BytesRef>> classes =
          knnClassifier.getClasses(SUPER_STRONG_TECHNOLOGY_INPUT);
      assertTrue(classes.get(0).getScore() > classes.get(1).getScore());
      checkCorrectClassification(knnClassifier, SUPER_STRONG_TECHNOLOGY_INPUT, TECHNOLOGY_RESULT);
    } finally {
      if (leafReader != null) {
        leafReader.close();
      }
    }
  }

  @Test
  public void testBasicUsageWithQuery() throws Exception {
    LeafReader leafReader = null;
    try {
      MockAnalyzer analyzer = new MockAnalyzer(random());
      leafReader = getSampleIndex(analyzer);
      TermQuery query = new TermQuery(new Term(textFieldName, "it"));
      checkCorrectClassification(
          new KNearestNeighborClassifier(
              leafReader, null, analyzer, query, 1, 0, 0, categoryFieldName, textFieldName),
          TECHNOLOGY_INPUT,
          TECHNOLOGY_RESULT);
    } finally {
      if (leafReader != null) {
        leafReader.close();
      }
    }
  }

  @Test
  public void testPerformance() throws Exception {
    MockAnalyzer analyzer = new MockAnalyzer(random());
    int numDocs = atLeast(10);
    LeafReader leafReader = getRandomIndex(analyzer, numDocs);
    try {
      KNearestNeighborClassifier kNearestNeighborClassifier =
          new KNearestNeighborClassifier(
              leafReader, null, analyzer, null, 1, 1, 1, categoryFieldName, textFieldName);

      ConfusionMatrixGenerator.ConfusionMatrix confusionMatrix =
          ConfusionMatrixGenerator.getConfusionMatrix(
              leafReader, kNearestNeighborClassifier, categoryFieldName, textFieldName, -1);
      assertNotNull(confusionMatrix);

      double avgClassificationTime = confusionMatrix.getAvgClassificationTime();
      assertTrue(avgClassificationTime >= 0);

      double accuracy = confusionMatrix.getAccuracy();
      assertTrue(accuracy >= 0d);
      assertTrue(accuracy <= 1d);

      double recall = confusionMatrix.getRecall();
      assertTrue(recall >= 0d);
      assertTrue(recall <= 1d);

      double precision = confusionMatrix.getPrecision();
      assertTrue(precision >= 0d);
      assertTrue(precision <= 1d);

      Terms terms = MultiTerms.getTerms(leafReader, categoryFieldName);
      TermsEnum iterator = terms.iterator();
      BytesRef term;
      while ((term = iterator.next()) != null) {
        String s = term.utf8ToString();
        recall = confusionMatrix.getRecall(s);
        assertTrue(recall >= 0d);
        assertTrue(recall <= 1d);
        precision = confusionMatrix.getPrecision(s);
        assertTrue(precision >= 0d);
        assertTrue(precision <= 1d);
        double f1Measure = confusionMatrix.getF1Measure(s);
        assertTrue(f1Measure >= 0d);
        assertTrue(f1Measure <= 1d);
      }
    } finally {
      leafReader.close();
    }
  }
}