Package de.danielbechler.diff

Source Code of de.danielbechler.diff.ObjectMerger$MergingDifferenceVisitor

/*
* Copyright 2014 Daniel Bechler
*
* Licensed 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 de.danielbechler.diff;

import de.danielbechler.diff.node.DiffNode;
import de.danielbechler.diff.node.Visit;

/**
* Careful: This class has not yet been tested very thoroughly and serves more as an example for your own
* implementations.
*
* @author Daniel Bechler
*/
@SuppressWarnings("UnusedDeclaration")
public final class ObjectMerger
{
  private final ObjectDiffer objectDiffer;

  public ObjectMerger()
  {
    this.objectDiffer = ObjectDifferBuilder.buildDefault();
  }

  public ObjectMerger(final ObjectDiffer objectDiffer)
  {
    this.objectDiffer = objectDiffer;
  }

  @SuppressWarnings({"unchecked"})
  public <T> T merge(final T modified, final T base, final T head)
  {
    final DiffNode.Visitor visitor = new MergingDifferenceVisitor<T>(head, modified);
    final DiffNode difference = objectDiffer.compare(modified, base);
    difference.visit(visitor);
    return head;
  }

  private static final class MergingDifferenceVisitor<T> implements DiffNode.Visitor
  {
    private final T head;
    private final T modified;

    public MergingDifferenceVisitor(final T head, final T modified)
    {
      this.head = head;
      this.modified = modified;
    }

    public void node(final DiffNode node, final Visit visit)
    {
      if (node.getState() == DiffNode.State.ADDED)
      {
        node.canonicalSet(head, node.canonicalGet(modified));
      }
      else if (node.getState() == DiffNode.State.REMOVED)
      {
        node.canonicalUnset(head);
      }
      else if (node.getState() == DiffNode.State.CHANGED)
      {
        if (node.hasChildren())
        {
          node.visitChildren(this);
          visit.dontGoDeeper();
        }
        else
        {
          node.canonicalSet(head, node.canonicalGet(modified));
        }
      }
    }
  }
}
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