deepcopy.go

package lib

import (
	"reflect"
	"time"

	"k8s.io/apimachinery/pkg/api/resource"
)

// DeepCopy creates a deep copy of whatever is passed to it and returns the copy
// in an interface{}. The returned value will need to be asserted to the
// correct type.
func DeepCopy(src interface{}) interface{} {
	if src == nil {
		return nil
	}

	// Make the interface a reflect.Value
	original := reflect.ValueOf(src)

	// Make a copy of the same type as the original.
	cpy := reflect.New(original.Type()).Elem()

	// Recursively copy the original.
	copyRecursive(original, cpy)

	// Return the copy as an interface.
	return cpy.Interface()
}

// copyRecursive does the actual copying of the interface. It currently has
// limited support for what it can handle. Add as needed.
func copyRecursive(original, cpy reflect.Value) {
	// handle according to original's Kind
	//nolint:exhaustive // rest of cases are handled in default, so it's not exhaustive
	switch original.Kind() {
	case reflect.Ptr:
		// Get the actual value being pointed to.
		originalValue := original.Elem()

		// if  it isn't valid, return.
		if !originalValue.IsValid() {
			return
		}

		cpy.Set(reflect.New(originalValue.Type()))
		copyRecursive(originalValue, cpy.Elem())

	case reflect.Interface:
		// If this is a nil, don't do anything
		if original.IsNil() {
			return
		}
		// Get the value for the interface, not the pointer.
		originalValue := original.Elem()

		// Get the value by calling Elem().
		copyValue := reflect.New(originalValue.Type()).Elem()
		copyRecursive(originalValue, copyValue)
		cpy.Set(copyValue)

	case reflect.Struct:
		t, ok := original.Interface().(time.Time)
		if ok {
			cpy.Set(reflect.ValueOf(t))
			return
		}

		r, ok := original.Interface().(resource.Quantity)
		if ok {
			cpy.Set(reflect.ValueOf(r))
			return
		}
		// Go through each field of the struct and copy it.
		for i := 0; i < original.NumField(); i++ {
			if original.Type().Field(i).PkgPath != "" {
				continue
			}

			copyRecursive(original.Field(i), cpy.Field(i))
		}

	case reflect.Slice:
		if original.IsNil() {
			return
		}
		// Make a new slice and copy each element.
		cpy.Set(reflect.MakeSlice(original.Type(), original.Len(), original.Cap()))

		for i := 0; i < original.Len(); i++ {
			copyRecursive(original.Index(i), cpy.Index(i))
		}

	case reflect.Map:
		if original.IsNil() {
			return
		}

		cpy.Set(reflect.MakeMap(original.Type()))

		for _, key := range original.MapKeys() {
			originalValue := original.MapIndex(key)
			copyValue := reflect.New(originalValue.Type()).Elem()
			copyRecursive(originalValue, copyValue)

			copyKey := DeepCopy(key.Interface())
			cpy.SetMapIndex(reflect.ValueOf(copyKey), copyValue)
		}

	default:
		cpy.Set(original)
	}
}