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   *  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
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   *
   *    https://www.apache.org/licenses/LICENSE-2.0
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   *  Unless required by applicable law or agreed to in writing,
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  package org.apache.cayenne;
  
  import org.apache.cayenne.graph.ArcCreateOperation;
  import org.apache.cayenne.graph.ArcDeleteOperation;
  import org.apache.cayenne.graph.CompoundDiff;
  import org.apache.cayenne.graph.GraphDiff;
  import org.apache.cayenne.graph.NodeDiff;
  
  import java.io.ObjectStreamException;
  import java.io.Serializable;
  import java.util.AbstractList;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  /**
   * Stores graph operations in the order they were performed, optionally allowing to set
   * named markers.
   * 
   * @since 1.2
   */
  class ObjectContextChangeLog {
  
      List<GraphDiff> diffs;
      Map<String, Integer> markers;
  
      ObjectContextChangeLog() {
          reset();
      }
  
      void unregisterNode(Object nodeId) {
          Iterator<?> it = diffs.iterator();
          while (it.hasNext()) {
              Object next = it.next();
  
              if (next instanceof NodeDiff) {
  
                  if (nodeId.equals(((NodeDiff) next).getNodeId())) {
                      it.remove();
                  }
                  else if (next instanceof ArcCreateOperation) {
                      if (nodeId.equals(((ArcCreateOperation) next).getTargetNodeId())) {
                          it.remove();
                      }
                  }
                  else if (next instanceof ArcDeleteOperation) {
                      if (nodeId.equals(((ArcDeleteOperation) next).getTargetNodeId())) {
                          it.remove();
                      }
                  }
              }
          }
      }
  
      void setMarker(String markerTag) {
          markers.put(markerTag, diffs.size());
      }
  
      void removeMarker(String markerTag) {
          markers.remove(markerTag);
      }
  
      /**
       * Returns a combined GraphDiff for all recorded operations.
       */
      GraphDiff getDiffs() {
          return new CompoundDiff(immutableList(0, diffs.size()));
      }
  
      GraphDiff getDiffsAfterMarker(String markerTag) {
          Integer pos = markers.get(markerTag);
          int marker = (pos == null) ? -1 : pos.intValue();
          if (marker < 0) {
              throw new IllegalStateException("No marked position for tag '"
                      + markerTag
                      + "'");
          }
  
          return new CompoundDiff(immutableList(marker, diffs.size()));
      }
  
      boolean hasMarker(String markerTag) {
          return markers.containsKey(markerTag);
      }
  
      /**
       * "Forgets" all stored operations.
       */
      void reset() {
          // must create a new list instead of clearing an existing one, as the original
          // list may have been exposed via events or "getDiffs", and trimming it is
          // undesirable.
          this.diffs = new ArrayList<>();
          this.markers = new HashMap<>();
      }
  
      int size() {
          return diffs.size();
      }
  
      int sizeAfterMarker(String markerTag) {
          Integer pos = markers.get(markerTag);
          int marker = (pos == null) ? -1 : pos.intValue();
          if (marker < 0) {
              throw new IllegalStateException("No marked position for tag '"
                      + markerTag
                      + "'");
          }
  
          return diffs.size() - marker;
      }
  
      /**
       * Adds an operation to the list.
       */
      void addOperation(GraphDiff diff) {
          diffs.add(diff);
      }
  
      /**
       * Returns a sublist of the diffs list that shouldn't change when OperationRecorder is
       * cleared or new operations are added.
       */
      private List<GraphDiff> immutableList(int fromIndex, int toIndex) {
          if (toIndex - fromIndex == 0) {
              return Collections.emptyList();
          }
  
          // Assuming that internal diffs list can only grow and can never be trimmed,
          // return sublist will never change - something that callers are expecting
          return Collections.unmodifiableList(new SubList(diffs, fromIndex, toIndex));
      }
  
      // moded Sublist from JDK that doesn't check for co-modification, as the underlying
      // list is guaranteed to only grow and never shrink or be replaced.
      static class SubList extends AbstractList<GraphDiff> implements Serializable {
  
          private List<GraphDiff> list;
          private int offset;
          private int size;
  
          SubList(List<GraphDiff> list, int fromIndex, int toIndex) {
              if (fromIndex < 0) {
                  throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
              }
              if (toIndex > list.size()) {
                  throw new IndexOutOfBoundsException("toIndex = " + toIndex);
              }
              if (fromIndex > toIndex) {
                  throw new IllegalArgumentException("fromIndex("
                          + fromIndex
                          + ") > toIndex("
                          + toIndex
                          + ")");
              }
              this.list = list;
              offset = fromIndex;
              size = toIndex - fromIndex;
          }
  
          @Override
          public GraphDiff get(int index) {
              rangeCheck(index);
              return list.get(index + offset);
          }
  
          @Override
          public int size() {
              return size;
          }
  
          private void rangeCheck(int index) {
              if (index < 0 || index >= size) {
                  throw new IndexOutOfBoundsException("Index: " + index + ",Size: " + size);
              }
          }
  
          // serialization method...
          private Object writeReplace() throws ObjectStreamException {
              return new ArrayList<>(list.subList(offset, offset + size));
          }
      }
  }
  