feat: user metadata middleware

cmd/server/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"app/internal/core/cfg"
+	"app/internal/core/middleware"
 	"app/internal/pkg"
 	gossiper "github.com/pieceowater-dev/lotof.lib.gossiper/v2"
 	"google.golang.org/grpc"
@@ -10,7 +11,7 @@ import (
 )
 
 func init() {
-	// EXAMPLE, todo: make global CURRENT SCHEMA pass + switching, then store and manage schemas in HUB
+	// EXAMPLE, todo: make schema switching, then store and manage schemas in HUB
 	encryptedTenants := []gossiper.EncryptedTenant{
 		{
 			Namespace:   "someSchema",
@@ -43,7 +44,13 @@ func main() {
 	appCfg := cfg.Inst()
 	appRouter := pkg.NewRouter()
 
-	grpcServer := grpc.NewServer()
+	grpcServer := grpc.NewServer(
+		grpc.UnaryInterceptor(
+			middleware.GrpcMiddleware(
+				middleware.NewMetadataMiddleware(),
+			).MiddlewareMethod(),
+		),
+	)
 	reflection.Register(grpcServer)
 
 	serverManager := gossiper.NewServerManager()

internal/core/middleware/middleware.go

@@ -0,0 +1,7 @@
+package middleware
+
+import "google.golang.org/grpc"
+
+type GrpcMiddleware interface {
+	MiddlewareMethod() grpc.UnaryServerInterceptor
+}

internal/core/middleware/userdata.middleware.go

@@ -0,0 +1,70 @@
+package middleware
+
+import (
+	"context"
+	"fmt"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
+	"log"
+)
+
+type contextKey string
+
+type UserMetadata struct {
+	UserID    string
+	Namespace string
+}
+
+func GetUserMetadata(ctx context.Context) (*UserMetadata, bool) {
+	userMetadata, ok := ctx.Value(contextKey("userMetadata")).(*UserMetadata)
+	return userMetadata, ok
+}
+
+type GrpcMetadata struct {
+	contextUserMetadataKey contextKey
+}
+
+func NewMetadataMiddleware() *GrpcMetadata {
+	return &GrpcMetadata{
+		contextUserMetadataKey: "userMetadata",
+	}
+}
+
+func (md *GrpcMetadata) MiddlewareMethod() grpc.UnaryServerInterceptor {
+	return func(
+		ctx context.Context,
+		req any,
+		info *grpc.UnaryServerInfo,
+		handler grpc.UnaryHandler,
+	) (any, error) {
+		userMetadata, err := md.getUserMetadataFromContext(ctx)
+		if err != nil {
+			log.Printf("Failed to extract metadata: %v", err)
+			return nil, status.Errorf(codes.Unauthenticated, "missing metadata")
+		}
+		ctx = md.withUserMetadata(ctx, userMetadata)
+		return handler(ctx, req)
+	}
+}
+
+func (md *GrpcMetadata) getUserMetadataFromContext(ctx context.Context) (*UserMetadata, error) {
+	incoming, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return nil, fmt.Errorf("no metadata found in context")
+	}
+	userIDs := incoming.Get("userid")
+	namespaces := incoming.Get("namespace")
+	if len(userIDs) == 0 || len(namespaces) == 0 {
+		return nil, fmt.Errorf("missing metadata keys: userid or namespace")
+	}
+	return &UserMetadata{
+		UserID:    userIDs[0],
+		Namespace: namespaces[0],
+	}, nil
+}
+
+func (md *GrpcMetadata) withUserMetadata(ctx context.Context, userMetadata *UserMetadata) context.Context {
+	return context.WithValue(ctx, md.contextUserMetadataKey, userMetadata)
+}