1 files changed, 57 insertions, 0 deletions
diff --git a/internal/api/auth/auth.go b/internal/api/auth/auth.go
new file mode 100644
index 0000000..b382beb
--- /dev/null
+++ b/internal/api/auth/auth.go
@@ -0,0 +1,57 @@
+package auth
+
+import (
+	"errors"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+var jwtKey = []byte(os.Getenv("JWT_SECRET"))
+
+type Claims struct {
+	UserID int `json:"user_id"`
+	jwt.RegisteredClaims
+}
+
+func GenerateJWT(userID int) (string, error) {
+	expirationTime := time.Now().Add(5 * time.Hour)
+	claims := &Claims{
+		UserID: userID,
+		RegisteredClaims: jwt.RegisteredClaims{
+			ExpiresAt: jwt.NewNumericDate(expirationTime),
+		},
+	}
+
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+	tokenString, err := token.SignedString(jwtKey)
+	if err != nil {
+		return "", err
+	}
+	return tokenString, nil
+}
+
+func ValidateJWT(tokenString string) (*Claims, error) {
+	claims := &Claims{}
+	// A token has a form `Bearer ...`
+	tokenParts := strings.Split(tokenString, " ")
+	if len(tokenParts) != 2 {
+		return nil, errors.New("not valid JWT")
+	}
+
+	token, err := jwt.ParseWithClaims(tokenParts[1], claims, func(token *jwt.Token) (interface{}, error) {
+		return jwtKey, nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	if !token.Valid {
+		return nil, err
+	}
+
+	return claims, nil
+}