using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Tango.PPC.Jobs.UndoRedoCommands
{
    public sealed class UndoRedoManager
    {
        private Stack<IUndoRedoCommand> _UndoCommands;
        private Stack<IUndoRedoCommand> _RedoCommands;
        private bool _isBusy;

        private UndoRedoManager()
        {
            _UndoCommands = new Stack<IUndoRedoCommand>();
            _RedoCommands = new Stack<IUndoRedoCommand>();
            _isBusy = false;
        }
        private static readonly Lazy<UndoRedoManager> lazy = new Lazy<UndoRedoManager>(() => new UndoRedoManager());
        public static UndoRedoManager Instance
        {
            get
            {
                return lazy.Value;
            }
        }

        public void InsertAndExecuteCommand(IUndoRedoCommand command)
        {
            _UndoCommands.Push(command);
            command.Execute();
        }

        
        public void Redo()
        {
            if (!_isBusy)
            {
                _isBusy = true;

                if (_RedoCommands.Count != 0)
                {
                    IUndoRedoCommand command = _RedoCommands.Pop();
                    command.Execute();
                    _UndoCommands.Push(command);
                }
                _isBusy = false;
            }
        }

        public void Undo()
        {
            if (!_isBusy)
            {
                _isBusy = true;
                if (_UndoCommands.Count != 0)
                {
                    IUndoRedoCommand command = _UndoCommands.Pop();
                    command.UnExecute();
                    _RedoCommands.Push(command);
                }
                _isBusy = false;
            }
        }

        public bool IsEnableUndoOperation()
        {
            return _UndoCommands.Count() > 0;
        }

        public bool IsEnableRedoOperation()
        {
            return _RedoCommands.Count() > 0;
        }

        public void ClearAll()
        {
            _UndoCommands.Clear();
            _RedoCommands.Clear();
        }
    }
}