pk.Option improvement

yggdrasil/user/user.go

@@ -1,10 +1,16 @@
 package user
 
 import (
+	"encoding/base64"
 	"encoding/json"
+	"encoding/pem"
+	"errors"
 	"fmt"
+	"io"
 	"net/http"
 	"time"
+
+	pk "github.com/Tnze/go-mc/net/packet"
 )
 
 var ServicesURL = "https://api.minecraftservices.com"
@@ -21,6 +27,22 @@ type KeyPairResp struct {
 	RefreshedAfter     time.Time `json:"refreshedAfter"`
 }
 
+func (k KeyPairResp) WriteTo(w io.Writer) (int64, error) {
+	block, _ := pem.Decode([]byte(k.KeyPair.PublicKey))
+	if block == nil {
+		return 0, errors.New("pem decode error: no data is found")
+	}
+	signature, err := base64.StdEncoding.DecodeString(k.PublicKeySignature)
+	if err != nil {
+		return 0, err
+	}
+	return pk.Tuple{
+		pk.Long(k.ExpiresAt.UnixMilli()),
+		pk.ByteArray(block.Bytes),
+		pk.ByteArray(signature),
+	}.WriteTo(w)
+}
+
 func GetOrFetchKeyPair(accessToken string) (KeyPairResp, error) {
 	return fetchKeyPair(accessToken) // TODO: cache
 }