assertThat(transformation.inverse().inverse()).isSameInstanceAs(transformation);
  }

  /**
   * Asserts that {@code transformation} behaves as expected for {@link
   * LinearTransformation#forNaN}.
   */
  static void assertLinearTransformationNaN(LinearTransformation transformation) {
    assertThat(transformation.isHorizontal()).isFalse();

/**
 * Standard transformer implementation for the Fess search engine.
 * This transformer handles document transformation and content extraction using
 * the standard Fess file transformation process with support for various content types.
 *
 * <p>It extends AbstractFessFileTransformer to provide file-specific transformation
 * capabilities while using the appropriate extractor for each document type.</p>
 */

    LinearTransformation transformation = LinearTransformation.mapping(x1, y1).withSlope(slope);
    assertThat(transformation.isVertical()).isFalse();
    assertThat(transformation.isHorizontal()).isFalse();
    assertThat(transformation.slope()).isWithin(ALLOWED_ERROR).of(slope);
    // Note that we cannot test the actual mapping of points, as the results will be unreliable due
    // to loss of precision with this value of the slope.
  }

    LinearTransformation transformation = LinearTransformation.mapping(x1, y1).withSlope(slope);
    assertThat(transformation.isVertical()).isFalse();
    assertThat(transformation.isHorizontal()).isFalse();
    assertThat(transformation.slope()).isWithin(ALLOWED_ERROR).of(slope);
    // Note that we cannot test the actual mapping of points, as the results will be unreliable due
    // to loss of precision with this value of the slope.
  }

    assertThat(transformation.inverse().inverse()).isSameInstanceAs(transformation);
  }

  /**
   * Asserts that {@code transformation} behaves as expected for {@link
   * LinearTransformation#forNaN}.
   */
  static void assertLinearTransformationNaN(LinearTransformation transformation) {
    assertThat(transformation.isHorizontal()).isFalse();

import jakarta.annotation.PostConstruct;

/**
 * File transformer implementation for the Fess search engine.
 * This transformer handles file-based document transformation and content extraction
 * using the Fess file transformation process with support for various file types.
 *
 * <p>It extends AbstractFessFileTransformer to provide specialized file processing

/**
 * Implementation of IndexUpdateCallback for handling document indexing operations.
 * This class manages the process of updating the search index with documents from
 * data stores, including bulk operations, document transformation, and error handling.
 */
public class IndexUpdateCallbackImpl implements IndexUpdateCallback {
    private static final Logger logger = LogManager.getLogger(IndexUpdateCallbackImpl.class);

    /**

import org.codelibs.fess.util.ComponentUtil;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInfo;

/**
 * Unit tests for {@link AbstractFessFileTransformer}.
 * Tests file transformation logic including content extraction and metadata handling.
 */
public class AbstractFessFileTransformerTest extends UnitFessTestCase {

    private TestableAbstractFessFileTransformer transformer;

    @Override

 * }
 *
 * <p>If you have some other mechanism for returning the predecessors of a node, or one that doesn't
 * return a {@code Iterable<? extends N>}, then you can use a lambda to perform a more general
 * transformation:
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, node -> ImmutableList.of(node.mother(), node.father()));
 * }
 *
 * <p>Graph algorithms that need additional capabilities (accessing both predecessors and

 * }
 *
 * <p>If you have some other mechanism for returning the successors of a node, or one that doesn't
 * return an {@code Iterable<? extends N>}, then you can use a lambda to perform a more general
 * transformation:
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, node -> ImmutableList.of(node.leftChild(), node.rightChild()));
 * }
 *
 * <p>Graph algorithms that need additional capabilities (accessing both predecessors and