using System.Collections.Generic;
using Microsoft.VisualBasic.CompilerServices;

namespace Pilz.Collections.SimpleHistory
{
    public class HistoryStack
    {
        private Stack<HistoryPoint> stackPast = new Stack<HistoryPoint>();
        private Stack<HistoryPoint> stackFuture = new Stack<HistoryPoint>();

        /// <summary>
        /// Gets the count of history points.
        /// </summary>
        /// <returns></returns>
        public bool ChangesCount
        {
            get
            {
                return Conversions.ToBoolean(stackPast.Count);
            }
        }

        /// <summary>
        /// Checks if the History has past changes.
        /// </summary>
        /// <returns></returns>
        public bool HasChanges()
        {
            return stackPast.Count > 0;
        }

        /// <summary>
        /// Patch Object States and call Undo Actions.
        /// </summary>
        public HistoryPoint Undo()
        {
            HistoryPoint ret;
            if (stackPast.Count > 0)
            {
                var hp = stackPast.Pop();
                hp.Undo();
                stackFuture.Push(hp);
                ret = hp;
            }
            else
            {
                ret = null;
            }

            return ret;
        }

        /// <summary>
        /// Patch Object States and call Redo Actions.
        /// </summary>
        public HistoryPoint Redo()
        {
            HistoryPoint ret;
            if (stackFuture.Count > 0)
            {
                var hp = stackFuture.Pop();
                hp.Redo();
                stackPast.Push(hp);
                ret = hp;
            }
            else
            {
                ret = null;
            }

            return ret;
        }

        /// <summary>
        /// Clear the History.
        /// </summary>
        public void Clear()
        {
            stackPast.Clear();
            stackFuture.Clear();
        }

        /// <summary>
        /// Store a History Point.
        /// </summary>
        /// <param name="point">The History Point to add to the past changes.</param>
        /// <param name="newName">The name to set for the History Point.</param>
        public void Store(HistoryPoint point, string newName)
        {
            point.Name = newName;
            Store(point);
        }

        /// <summary>
        /// Store a History Point.
        /// </summary>
        /// <param name="point">The History Point to add to the past changes.</param>
        public void Store(HistoryPoint point)
        {
            stackPast.Push(point);
            stackFuture.Clear();
        }
    }
}