add authentication method

internal/auth/service.go

@@ -0,0 +1,51 @@
+package auth
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+// Service provides authentication operations
+type Service struct {
+	jwtSecret []byte
+}
+
+// New creates a new auth service
+func New(secret string) *Service {
+	if secret == "" {
+		// Generate a random secret if not provided (not recommended for production)
+		secret = generateSecret()
+	}
+	return &Service{
+		jwtSecret: []byte(secret),
+	}
+}
+
+// HashPassword hashes a password using bcrypt
+func (s *Service) HashPassword(password string) (string, error) {
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return "", err
+	}
+	return string(hash), nil
+}
+
+// VerifyPassword verifies a password against a hash
+func (s *Service) VerifyPassword(hashedPassword, password string) bool {
+	err := bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(password))
+	return err == nil
+}
+
+// generateSecret generates a random secret for JWT signing
+func generateSecret() string {
+	b := make([]byte, 32)
+	rand.Read(b)
+	return base64.URLEncoding.EncodeToString(b)
+}
+
+// GetSecret returns the JWT secret
+func (s *Service) GetSecret() []byte {
+	return s.jwtSecret
+}