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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Tango.Editors
{
/// <summary>
/// Represents an undo/redo states provider base class.
/// </summary>
/// <seealso cref="Tango.Editors.IUndoRedoStatesProvider" />
public abstract class UndoRedoStatesProviderBase : IUndoRedoStatesProvider
{
private IUndoRedoState _uncommittedState; //Holds the current undo state about to be committed.
/// <summary>
/// Occurs when an Undo/Redo state was executed.
/// </summary>
public event EventHandler<UndoRedoStateExecutedEventArgs> StateExecuted;
/// <summary>
/// Gets the undo states.
/// </summary>
public Stack<IUndoRedoState> UndoStates { get; protected set; }
/// <summary>
/// Gets the redo states.
/// </summary>
public Stack<IUndoRedoState> RedoStates { get; protected set; }
/// <summary>
/// Gets a value indicating whether this instance can undo.
/// </summary>
public bool CanUndo
{
get
{
return UndoStates.Count > 0;
}
}
/// <summary>
/// Gets a value indicating whether this instance can redo.
/// </summary>
public bool CanRedo
{
get
{
return RedoStates.Count > 0;
}
}
/// <summary>
/// Initializes a new instance of the <see cref="UndoRedoStatesProviderBase"/> class.
/// </summary>
public UndoRedoStatesProviderBase()
{
UndoStates = new Stack<IUndoRedoState>();
RedoStates = new Stack<IUndoRedoState>();
}
/// <summary>
/// Prepares the state of the undo.
/// </summary>
public virtual void PrepareUndoState()
{
RedoStates.Clear();
_uncommittedState = CreateUndoRedoState();
}
/// <summary>
/// Commits the state created by <see cref="PrepareUndoState" />.
/// </summary>
public void CommitUndoState()
{
if (_uncommittedState != null)
{
UndoStates.Push(_uncommittedState);
_uncommittedState = null;
}
}
/// <summary>
/// Creates the a new undo/redo state.
/// </summary>
/// <returns></returns>
public abstract IUndoRedoState CreateUndoRedoState();
/// <summary>
/// Executes the an undo/redo state.
/// </summary>
/// <param name="state">The state.</param>
public abstract void ExecuteState(IUndoRedoState state);
/// <summary>
/// Performs an undo operation.
/// </summary>
public virtual void Undo()
{
if (UndoStates.Count > 0)
{
var state = UndoStates.Pop();
var redoState = CreateUndoRedoState();
ExecuteState(state);
OnStateExecuted(new UndoRedoStateExecutedEventArgs() { Mode = UndoRedoStateMode.Undo, State = state });
RedoStates.Push(redoState);
}
}
/// <summary>
/// Performs a redo operation.
/// </summary>
public virtual void Redo()
{
if (RedoStates.Count > 0)
{
var state = RedoStates.Pop();
var undoState = CreateUndoRedoState();
ExecuteState(state);
OnStateExecuted(new UndoRedoStateExecutedEventArgs() { Mode = UndoRedoStateMode.Redo, State = state });
UndoStates.Push(undoState);
}
}
/// <summary>
/// Raises the <see cref="E:StateExecuted" /> event.
/// </summary>
/// <param name="e">The <see cref="UndoRedoStateExecutedEventArgs"/> instance containing the event data.</param>
public virtual void OnStateExecuted(UndoRedoStateExecutedEventArgs e)
{
if (StateExecuted != null) StateExecuted(this, e);
}
/// <summary>
/// Resets undo and redo states.
/// </summary>
public void Reset()
{
UndoStates.Clear();
RedoStates.Clear();
}
}
}
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