// An Actor runs an action.
type Actor interface {
	Act(*Builder, context.Context, *Action) error
}

// An ActorFunc is an Actor that calls the function.
type ActorFunc func(*Builder, context.Context, *Action) error

func (f ActorFunc) Act(b *Builder, ctx context.Context, a *Action) error {
	return f(b, ctx, a)
}

// An Action represents a single action in the action graph.