/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

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 com.google.security.zynamics.zylib.general.undo;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class UndoStack implements Iterable<IUndoable> {
  private final List<IUndoable> undoStack = new ArrayList<IUndoable>();

  private int undoPosition = 0;

  public void add(final IUndoable operation) {
    final int toRemove = undoStack.size() - undoPosition;

    for (int i = 0; i < toRemove; i++) {
      undoStack.remove(undoPosition);
    }

    undoStack.add(operation);

    undoPosition++;
  }

  public boolean canRedo() {
    return undoPosition < undoStack.size();
  }

  public boolean canUndo() {
    return undoPosition > 0;
  }

  @Override
  public Iterator<IUndoable> iterator() {
    return undoStack.iterator();
  }

  public void redo() {
    final IUndoable operationToUndo = undoStack.get(undoPosition);

    operationToUndo.revertToSnapshot();

    undoPosition++;
  }

  public void undo() {
    final IUndoable operationToUndo = undoStack.get(undoPosition - 1);

    operationToUndo.undo();

    undoPosition--;
  }
}
