fix(types): cache address prefix for integrated detection

Co-Authored-By: Charon <charon@lethean.io>

types/address.go

@@ -31,6 +31,7 @@ type Address struct {
 	SpendPublicKey PublicKey
 	ViewPublicKey  PublicKey
 	Flags          uint8
+	prefix         uint64
 }
 
 // IsAuditable reports whether the address has the auditable flag set.
@@ -41,11 +42,7 @@ func (a *Address) IsAuditable() bool {
 // IsIntegrated reports whether the given prefix corresponds to an integrated
 // address type (standard integrated or auditable integrated).
 func (a *Address) IsIntegrated() bool {
-	// This method checks whether the address was decoded with an integrated
-	// prefix. Since we do not store the prefix in the Address struct, callers
-	// should use the prefix returned by DecodeAddress to determine this.
-	// This helper exists for convenience when the prefix is not available.
-	return false
+	return IsIntegratedPrefix(a.prefix)
 }
 
 // IsIntegratedPrefix reports whether the given prefix corresponds to an
@@ -62,6 +59,8 @@ func IsIntegratedPrefix(prefix uint64) bool {
 //
 // The checksum is the first 4 bytes of Keccak-256 over the preceding data.
 func (a *Address) Encode(prefix uint64) string {
+	a.prefix = prefix
+
 	// Build the raw data: prefix (varint) + keys + flags.
 	prefixBytes := encodeVarint(prefix)
 	raw := make([]byte, 0, len(prefixBytes)+32+32+1+4)
@@ -117,6 +116,7 @@ func DecodeAddress(s string) (*Address, uint64, error) {
 	copy(addr.SpendPublicKey[:], remaining[0:32])
 	copy(addr.ViewPublicKey[:], remaining[32:64])
 	addr.Flags = remaining[64]
+	addr.prefix = prefix
 
 	return addr, prefix, nil
 }

types/address_test.go

@@ -65,6 +65,10 @@ func TestAddressEncodeDecodeRoundTrip_Good(t *testing.T) {
 			if decoded.Flags != original.Flags {
 				t.Errorf("Flags mismatch: got 0x%02x, want 0x%02x", decoded.Flags, original.Flags)
 			}
+
+			if decoded.IsIntegrated() != IsIntegratedPrefix(tt.prefix) {
+				t.Errorf("IsIntegrated mismatch: got %v, want %v", decoded.IsIntegrated(), IsIntegratedPrefix(tt.prefix))
+			}
 		})
 	}
 }
@@ -103,6 +107,29 @@ func TestIsIntegratedPrefix_Good(t *testing.T) {
 	}
 }
 
+func TestAddressIsIntegrated_Good(t *testing.T) {
+	tests := []struct {
+		name   string
+		prefix uint64
+		want   bool
+	}{
+		{"standard", config.AddressPrefix, false},
+		{"integrated", config.IntegratedAddressPrefix, true},
+		{"auditable", config.AuditableAddressPrefix, false},
+		{"auditable_integrated", config.AuditableIntegratedAddressPrefix, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			addr := makeTestAddress(0)
+			addr.Encode(tt.prefix)
+			if got := addr.IsIntegrated(); got != tt.want {
+				t.Errorf("IsIntegrated: got %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
 func TestDecodeAddress_Bad(t *testing.T) {
 	tests := []struct {
 		name  string