private static State Apply(State state, Command.ChangeDiameter command)
{
return(new State(
state.Circles,
command.Circle,
new[] { command }.Concat(state.UndoStack).ToArray(),
Enumerable.Empty <ICommand>()
));
}
private static State Redo(State state, Command.ChangeDiameter command)
{
var circle = state.Circles.Where(c => c.Equals(command.Circle)).First();
circle.Diameter = command.Diameter;
return(new State(
state.Circles,
command.Circle,
new[] { command }.Concat(state.UndoStack).ToArray(),
state.RedoStack.Except(new[] { command }).ToArray()
));
}
private static State Undo(State state, Command.ChangeDiameter command)
{
var previousDiameter = state.UndoStack
.OfType <Command.ChangeDiameter>()
.Where(c => !c.Equals(command) && c.Circle.Equals(command.Circle))
.Select(c => (int?)c.Diameter)
.FirstOrDefault() ?? Logic.InitialDiameter;
var circle = state.Circles
.Where(c => c.Equals(command.Circle))
.First();
circle.Diameter = previousDiameter;
return(new State(
state.Circles,
command.Circle,
state.UndoStack.Except(new[] { command }).ToArray(),
new[] { command }.Concat(state.RedoStack).ToArray()
));
}