Make first WebUI random page stick

utils/hasher/hasher.go

@@ -1,6 +1,12 @@
 package hasher
 
-import "hash/maphash"
+import (
+	"hash/maphash"
+	"math"
+	"strconv"
+
+	"github.com/navidrome/navidrome/utils/random"
+)
 
 var instance = NewHasher()
 
@@ -8,37 +14,51 @@ func Reseed(id string) {
 	instance.Reseed(id)
 }
 
+func SetSeed(id string, seed string) {
+	instance.SetSeed(id, seed)
+}
+
 func HashFunc() func(id, str string) uint64 {
 	return instance.HashFunc()
 }
 
-type hasher struct {
-	seeds map[string]maphash.Seed
+type Hasher struct {
+	seeds    map[string]string
+	hashSeed maphash.Seed
 }
 
-func NewHasher() *hasher {
-	h := new(hasher)
-	h.seeds = make(map[string]maphash.Seed)
+func NewHasher() *Hasher {
+	h := new(Hasher)
+	h.seeds = make(map[string]string)
+	h.hashSeed = maphash.MakeSeed()
 	return h
 }
 
-// Reseed generates a new seed for the given id
-func (h *hasher) Reseed(id string) {
-	h.seeds[id] = maphash.MakeSeed()
+// SetSeed sets a seed for the given id
+func (h *Hasher) SetSeed(id string, seed string) {
+	h.seeds[id] = seed
+}
+
+// Reseed generates a new random seed for the given id
+func (h *Hasher) Reseed(id string) {
+	_ = h.reseed(id)
+}
+
+func (h *Hasher) reseed(id string) string {
+	seed := strconv.FormatInt(random.Int64(math.MaxInt64), 10)
+	h.seeds[id] = seed
+	return seed
 }
 
 // HashFunc returns a function that hashes a string using the seed for the given id
-func (h *hasher) HashFunc() func(id, str string) uint64 {
+func (h *Hasher) HashFunc() func(id, str string) uint64 {
 	return func(id, str string) uint64 {
-		var hash maphash.Hash
-		var seed maphash.Seed
+		var seed string
 		var ok bool
 		if seed, ok = h.seeds[id]; !ok {
-			seed = maphash.MakeSeed()
-			h.seeds[id] = seed
+			seed = h.reseed(id)
 		}
-		hash.SetSeed(seed)
-		_, _ = hash.WriteString(str)
-		return hash.Sum64()
+
+		return maphash.Bytes(h.hashSeed, []byte(seed+str))
 	}
 }

utils/hasher/hasher_test.go

@@ -40,4 +40,18 @@ var _ = Describe("HashFunc", func() {
 		Expect(sum).To(Equal(hashFunc("1", input)))
 		Expect(sum2).To(Equal(hashFunc("2", input)))
 	})
+
+	It("keeps the same hash for the same id and seed", func() {
+		id := "1"
+		hashFunc := hasher.HashFunc()
+		hasher.SetSeed(id, "original_seed")
+		sum := hashFunc(id, input)
+		Expect(sum).To(Equal(hashFunc(id, input)))
+
+		hasher.Reseed(id)
+		Expect(sum).NotTo(Equal(hashFunc(id, input)))
+
+		hasher.SetSeed(id, "original_seed")
+		Expect(sum).To(Equal(hashFunc(id, input)))
+	})
 })