UndoList

LICENSE

The MIT License (MIT)

Copyright (c) 2014

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

UndoList.cs

using System.Collections;
using System.Collections.Generic;

namespace SchetsEditor
{
    public class UndoList<T> : IEnumerable
    {
        private enum ActionType
        {
            Add,
            Remove
        }

        private class UndoAction<U>
        {
            public ActionType Type { get; private set; }
            public U Value { get; private set; }

            public UndoAction(ActionType type, U value)
            {
                this.Type = type;
                this.Value = value;
            }
        }

        private List<T> list;
        private List<UndoAction<T>> undoActions = new List<UndoAction<T>>();
        private int pointer = -1;

        public int Count
        {
            get
            {
                return list.Count;
            }
        }

        public UndoList(List<T> list)
        {
            this.list = list;
        }

        private void addUndoAction(UndoAction<T> action)
        {
            if (pointer != -1)
                undoActions.RemoveRange(pointer + 1, undoActions.Count - pointer - 1);
            undoActions.Add(action);
            pointer = undoActions.Count - 1;
        }

        public bool Undo()
        {
            if (pointer == -1)
                return false;
            UndoAction<T> action = undoActions[pointer];
            pointer--;
            switch (action.Type)
            {
                case ActionType.Add:
                    list.RemoveAt(list.LastIndexOf(action.Value));
                    break;
                case ActionType.Remove:
                    list.Add(action.Value);
                    break;
            }
            return true;
        }

        public bool Redo()
        {
            if (pointer == undoActions.Count - 1)
                return false;
            pointer++;
            UndoAction<T> action = undoActions[pointer];
            switch (action.Type)
            {
                case ActionType.Add:
                    list.Add(action.Value);
                    break;
                case ActionType.Remove:
                    list.RemoveAt(list.LastIndexOf(action.Value));
                    break;
            }
            return true;
        }

        public IEnumerator GetEnumerator()
        {
            return list.GetEnumerator();
        }

        public void Add(T value)
        {
            list.Add(value);
            addUndoAction(new UndoAction<T>(ActionType.Add, value));
        }

        public void RemoveAt(int index)
        {
            addUndoAction(new UndoAction<T>(ActionType.Remove, list[index]));
            list.RemoveAt(index);
        }

        public void Clear()
        {
            foreach (T value in list)
                addUndoAction(new UndoAction<T>(ActionType.Remove, value));
            list.Clear();
        }

        public List<T> CopyList()
        {
            return new List<T>(list);
        }

        public T this[int index]
        {
            get
            {
                return list[index];
            }
            set
            {
                list[index] = value;
            }
        }
    }
}