)

// PreconditionFunc asserts that an incompatible change is not present within a patch.
type PreconditionFunc func(interface{}) bool

// RequireKeyUnchanged returns a precondition function that fails if the provided key
// is present in the patch (indicating that its value has changed).
func RequireKeyUnchanged(key string) PreconditionFunc {
	return func(patch interface{}) bool {
		patchMap, ok := patch.(map[string]interface{})
		if !ok {