Initial commit: party-mix-app with prefetch cache, audio preload optimizations

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/backend/internal/handlers/middleware.go

@@ -0,0 +1,66 @@
+package handlers
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type jwtClaims struct {
+	UserID string `json:"user_id"`
+	jwt.RegisteredClaims
+}
+
+func generateToken(userID, secret string) (string, error) {
+	claims := jwtClaims{
+		UserID: userID,
+		RegisteredClaims: jwt.RegisteredClaims{
+			Subject: userID,
+		},
+	}
+	return jwt.NewWithClaims(jwt.SigningMethodHS256, claims).SignedString([]byte(secret))
+}
+
+func parseToken(tokenStr, secret string) (*jwtClaims, error) {
+	token, err := jwt.ParseWithClaims(tokenStr, &jwtClaims{}, func(t *jwt.Token) (interface{}, error) {
+		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
+			return nil, fmt.Errorf("unexpected signing method")
+		}
+		return []byte(secret), nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	claims, ok := token.Claims.(*jwtClaims)
+	if !ok || !token.Valid {
+		return nil, fmt.Errorf("invalid token")
+	}
+	return claims, nil
+}
+
+func AuthRequired(jwtSecret string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		header := c.GetHeader("Authorization")
+		tokenStr := strings.TrimPrefix(header, "Bearer ")
+		if tokenStr == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "unauthorized"})
+			return
+		}
+		claims, err := parseToken(tokenStr, jwtSecret)
+		if err != nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
+			return
+		}
+		c.Set("userID", claims.UserID)
+		c.Next()
+	}
+}
+
+func currentUserID(c *gin.Context) string {
+	id, _ := c.Get("userID")
+	s, _ := id.(string)
+	return s
+}