package utils

import (
	"fmt"
	"github.com/davecgh/go-spew/spew"
	"hash"
	"hash/fnv"
	"k8s.io/apimachinery/pkg/util/rand"
)

// ComputeHash computes hash value of a interface
func ComputeHash(obj interface{}) string {
	hasher := fnv.New32a()
	deepHashObject(hasher, obj)
	return rand.SafeEncodeString(fmt.Sprint(hasher.Sum32()))
}

// deepHashObject writes specified object to hash using the spew library
// which follows pointers and prints actual values of the nested objects
// ensuring the hash does not change when a pointer changes.
// **Notice**
// we don't want to import k8s.io/kubernetes as a module, but this is a very small function
// so just copy it from k8s.io/kubernetes@v1.14.0/pkg/util/hash/hash.go
// **Notice End**
func deepHashObject(hasher hash.Hash, objectToWrite interface{}) {
	hasher.Reset()
	printer := spew.ConfigState{
		Indent:         " ",
		SortKeys:       true,
		DisableMethods: true,
		SpewKeys:       true,
	}
	printer.Fprintf(hasher, "%#v", objectToWrite)
}