Add JWT authentication for admin dashboard login

internal/auth/jwt.go

@@ -1,2 +1,58 @@
 package auth
 
+import (
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type JwtTokenGenerator struct {
+	Key  string
+	Issuer string
+	Audience string
+}
+
+func NewJwtTokenGenerator(key string, issuer string, audience string) *JwtTokenGenerator {
+	return &JwtTokenGenerator{
+		Key: key,
+		Issuer: issuer,
+		Audience: audience,
+	}
+}
+
+func (j *JwtTokenGenerator) GenerateToken(claims map[string]interface{}) (string, error) {
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
+		"exp": time.Now().AddDate(0, 0, 3).Unix(),
+		"iat": time.Now().Unix(),
+		"iss": j.Issuer,
+		"aud": j.Audience,
+	})
+	for k, v := range claims {
+		token.Claims.(jwt.MapClaims)[k] = v
+	}
+
+	return token.SignedString([]byte(j.Key))
+}
+
+// Gin middleware
+func (j *JwtTokenGenerator) GinMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		token, err := c.Request.Cookie("token")
+		if err != nil {
+			c.AbortWithStatusJSON(401, gin.H{"error": "Unauthorized"})
+			return
+		}
+		_, err = jwt.Parse(token.Value, func(t *jwt.Token) (interface{}, error) {
+			if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
+				return nil, jwt.ErrSignatureInvalid
+			}
+			return []byte(j.Key), nil
+		})
+		if err != nil {
+			c.AbortWithStatusJSON(401, gin.H{"error": "Unauthorized"})
+			return
+		}
+		c.Next()
+	}
+}