private static State Redo(State state, Command.AddCircle command)
{
return(new State(
state.Circles.Concat(new[] { command.Circle }).ToArray(),
command.Circle,
new[] { command }.Concat(state.UndoStack).ToArray(),
state.RedoStack.Except(new [] { command }).ToArray()
));
}
private static State Apply(State state, Command.AddCircle command)
{
return(new State(
state.Circles.Concat(new[] { command.Circle }).ToArray(),
command.Circle,
new[] { command }.Concat(state.UndoStack).ToArray(),
Enumerable.Empty <ICommand>()
));
}
private static State Undo(State state, Command.AddCircle command)
{
var circle = state.Circles.Where(c => c.Equals(command.Circle)).First();
return(new State(
state.Circles.Except(new[] { circle }).ToArray(),
null,
state.UndoStack.Except(new[] { command }).ToArray(),
new[] { command }.Concat(state.RedoStack).ToArray()
));
}