content: /*
   *  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.causeway.commons.internal.binding;
  
  import java.lang.ref.WeakReference;
  
  import org.apache.causeway.commons.binding.Bindable;
  import org.apache.causeway.commons.binding.ChangeListener;
  import org.apache.causeway.commons.binding.Observable;
  import org.apache.causeway.commons.internal.exceptions._Exceptions;
  
  import lombok.Getter;
  import org.jspecify.annotations.NonNull;
  
  //@Log4j2
  abstract class InternalBidirectionalBinding<T>
  implements ChangeListener<T>, InternalUtil.WeakListener {
  
      public static <T> InternalBidirectionalBinding<T> bind(final Bindable<T> left, final Bindable<T> right) {
          checkParameters(left, right);
          var binding = new GenericBidirectionalBinding<T>(left, right);
          left.setValue(right.getValue());
          left.addListener(binding);
          right.addListener(binding);
          return binding;
      }
  
      public static <T> void unbind(final Bindable<T> left, final Bindable<T> right) {
          checkParameters(left, right);
          var binding = new UntypedBidirectionalBinding(left, right);
          left.removeListener(binding);
          right.removeListener(binding);
      }
  
      public static void unbind(final Object left, final Object right) {
          checkParameters(left, right);
          var binding = new UntypedBidirectionalBinding(left, right);
          if (left instanceof Observable) {
              ((Observable<?>) left).removeListener(binding);
          }
          if (right instanceof Observable) {
              ((Observable<?>) right).removeListener(binding);
          }
      }
  
      protected abstract Object getLeft();
  
      protected abstract Object getRight();
  
      @Override
      public int hashCode() {
          return cachedHash;
      }
  
      @Override
      public boolean isNoLongerReferenced() {
          return (getLeft() == null) || (getRight() == null);
      }
  
      @Override
      public boolean equals(final Object obj) {
          if (this == obj) {
              return true;
          }
  
          final Object left = getLeft();
          final Object right = getRight();
          if ((left == null) || (right == null)) {
              return false;
          }
  
          if (obj instanceof InternalBidirectionalBinding) {
              final InternalBidirectionalBinding<?> otherBinding = (InternalBidirectionalBinding<?>) obj;
              final Object otherLeft = otherBinding.getLeft();
              final Object otherRight = otherBinding.getRight();
              if ((otherLeft == null) || (otherRight == null)) {
                  return false;
              }
  
              if (left == otherLeft && right == otherRight) {
                  return true;
              }
              if (left == otherRight && right == otherLeft) {
                  return true;
              }
          }
          return false;
      }
  
      // -- HELPER
  
      private static void checkParameters(final @NonNull Object left, final @NonNull Object right) {
          if (left == right) {
              throw _Exceptions.illegalArgument("Cannot bind to self");
          }
      }
  
      private final int cachedHash;
  
      private InternalBidirectionalBinding(final Object left, final Object right) {
          cachedHash = left.hashCode() * right.hashCode();
      }
  
      private static class GenericBidirectionalBinding<T> extends InternalBidirectionalBinding<T> {
          private final WeakReference<Bindable<T>> leftRef;
          private final WeakReference<Bindable<T>> rightRef;
          private boolean updating = false;
  
          private GenericBidirectionalBinding(final Bindable<T> left, final Bindable<T> right) {
              super(left, right);
              leftRef = new WeakReference<Bindable<T>>(left);
              rightRef = new WeakReference<Bindable<T>>(right);
          }
  
          @Override
          protected Bindable<T> getLeft() {
              return leftRef.get();
          }
  
          @Override
          protected Bindable<T> getRight() {
              return rightRef.get();
          }
  
          @Override
          public void changed(final Observable<? extends T> observable, final T oldValue, final T newValue) {
              if (updating) {
                  return;
              }
              var left = getLeft();
              var right = getRight();
  
              if ((left == null) || (right == null)) {
                  if (left != null) {
                      left.removeListener(this);
                  }
                  if (right != null) {
                      right.removeListener(this);
                  }
                  return;
              }
  
              try {
                  updating = true;
                  if (left == observable) {
                      right.setValue(newValue);
                  } else {
                      left.setValue(newValue);
                  }
              } catch (RuntimeException e) {
                  try {
                      if (left == observable) {
                          left.setValue(oldValue);
                      } else {
                          right.setValue(oldValue);
                      }
                  } catch (Exception e2) {
                      e2.addSuppressed(e);
                      unbind(left, right);
                      throw _Exceptions.unrecoverable(e2,
                              "Bidirectional binding failed with an attempt to restore the "
                              + "Observable to the previous value. "
                              + "Removing the bidirectional binding from bindables %s and %s",
                              ""+left,
                              ""+right);
                  }
                  throw _Exceptions.unrecoverable(e,
                          "Bidirectional binding failed, setting to the previous value");
              } finally {
                  updating = false;
              }
  
          }
      }
  
      private static class UntypedBidirectionalBinding extends InternalBidirectionalBinding<Object> {
  
          @Getter private final Object left;
          @Getter private final Object right;
  
          public UntypedBidirectionalBinding(final Object left, final Object right) {
              super(left, right);
              this.left = left;
              this.right = right;
          }
  
          @Override
          public void changed(final Observable<? extends Object> sourceProperty, final Object oldValue, final Object newValue) {
              throw _Exceptions.unexpectedCodeReach();
          }
      }
  
  }
  