import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * A bimap (or "bidirectional map") is a map that preserves the uniqueness of its values as well as
 * that of its keys. This constraint enables bimaps to support an "inverse view", which is another
 * bimap containing the same entries as this bimap but with reversed keys and values.
 *
 * <h3>Implementations</h3>
 *
 * <ul>

@NullMarked
public abstract class AbstractBiMapTester<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMapTester<K, V> {

  @Override
  protected BiMap<K, V> getMap() {
    return (BiMap<K, V>) super.getMap();
  }

  static <K extends @Nullable Object, V extends @Nullable Object> Entry<V, K> reverseEntry(
      Entry<K, V> entry) {
    return mapEntry(entry.getValue(), entry.getKey());
  }

    getMap().forcePut(null, v1());

    expectContents(mapEntry((K) null, v1()));

    assertFalse(getMap().containsValue(v0()));

    assertTrue(getMap().containsValue(v1()));
    assertTrue(getMap().inverse().containsKey(v1()));
    assertNull(getMap().inverse().get(v1()));
    assertEquals(v1(), getMap().get(null));
    assertEquals(1, getMap().size());
  }

  public void testClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();
    getMap().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeySetClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();
    getMap().keySet().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  public void testClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();
    getMap().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeySetClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();
    getMap().keySet().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  public void testKeySetIteratorRemove() {
    int initialSize = getNumElements();
    Iterator<K> iterator = getMap().keySet().iterator();
    iterator.next();
    iterator.remove();
    assertEquals(initialSize - 1, getMap().size());
    assertEquals(initialSize - 1, getMap().inverse().size());
  }

@NullMarked
public abstract class AbstractBiMapTester<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMapTester<K, V> {

  @Override
  protected BiMap<K, V> getMap() {
    return (BiMap<K, V>) super.getMap();
  }

  static <K extends @Nullable Object, V extends @Nullable Object> Entry<V, K> reverseEntry(
      Entry<K, V> entry) {
    return mapEntry(entry.getValue(), entry.getKey());
  }

public class BiMapInverseTester<K, V> extends AbstractBiMapTester<K, V> {

  public void testInverseSame() {
    assertSame(getMap(), getMap().inverse().inverse());
  }

  @CollectionFeature.Require(SERIALIZABLE)
  public void testInverseSerialization() {
    BiMapPair<K, V> pair = new BiMapPair<>(getMap());
    BiMapPair<K, V> copy = SerializableTester.reserialize(pair);
    assertEquals(pair.forward, copy.forward);

public class BiMapInverseTester<K, V> extends AbstractBiMapTester<K, V> {

  public void testInverseSame() {
    assertSame(getMap(), getMap().inverse().inverse());
  }

  @CollectionFeature.Require(SERIALIZABLE)
  public void testInverseSerialization() {
    BiMapPair<K, V> pair = new BiMapPair<>(getMap());
    BiMapPair<K, V> copy = SerializableTester.reserialize(pair);
    assertEquals(pair.forward, copy.forward);

    for (Entry<K, V> entry : getMap().entrySet()) {
      assertThrows(NullPointerException.class, () -> entry.setValue(null));
      expectUnchanged();
    }
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_VALUES})
  @CollectionSize.Require(absent = ZERO)
  public void testSetValueNullSupported() {
    for (Entry<K, V> entry : getMap().entrySet()) {
      if (entry.getKey().equals(k0())) {