Separate auth failures and development settings

src/TaxBaik.Web/Endpoints/Auth/LoginEndpoint.cs

@@ -39,18 +39,20 @@ public class LoginEndpoint : Endpoint<LoginRequest, TokenPairResponse>
             ThrowError("로그인 정보가 필요합니다.");
         }
 
-        var tokenPair = await _authService.AuthenticateAndGenerateTokenPairAsync(request.Username, request.Password);
+        var authResult = await _authService.AuthenticateAndGenerateTokenPairAsync(request.Username, request.Password);
-        if (tokenPair == null)
+        if (!authResult.IsSuccess || authResult.TokenPair is null)
         {
-            ThrowError("아이디 또는 비밀번호가 올바르지 않습니다.");
+            ThrowError(authResult.FailureReason == AuthFailureReason.DatabaseUnavailable
+                ? "로그인 서비스를 일시적으로 사용할 수 없습니다."
+                : "아이디 또는 비밀번호가 올바르지 않습니다.");
         }
 
         await SendAsync(new TokenPairResponse
         {
-            Token = tokenPair!.AccessToken,
+            Token = authResult.TokenPair!.AccessToken,
-            AccessToken = tokenPair.AccessToken,
+            AccessToken = authResult.TokenPair.AccessToken,
-            RefreshToken = tokenPair.RefreshToken,
+            RefreshToken = authResult.TokenPair.RefreshToken,
-            ExpiresIn = tokenPair.ExpiresIn
+            ExpiresIn = authResult.TokenPair.ExpiresIn
         }, 200, cancellation: ct);
     }
 }

src/TaxBaik.Web/Pages/Admin/Login.cshtml.cs

@@ -49,10 +49,14 @@ public class LoginModel(AuthService authService) : PageModel
             return Page();
         }
 
-        var tokenPair = await authService.AuthenticateAndGenerateTokenPairAsync(Username, Password);
+        var authResult = await authService.AuthenticateAndGenerateTokenPairAsync(Username, Password);
-        if (tokenPair is null)
+        if (!authResult.IsSuccess || authResult.TokenPair is null)
         {
-            ErrorMessage = "아이디 또는 비밀번호가 올바르지 않습니다.";
+            ErrorMessage = authResult.FailureReason switch
+            {
+                AuthFailureReason.DatabaseUnavailable => "로그인 서비스를 일시적으로 사용할 수 없습니다. 잠시 후 다시 시도하세요.",
+                _ => "아이디 또는 비밀번호가 올바르지 않습니다."
+            };
             return Page();
         }
 
@@ -60,10 +64,10 @@ public class LoginModel(AuthService authService) : PageModel
         RedirectUrl = NormalizeRedirectUrl(ReturnUrl);
         TokenPair = new TokenPairResponse
         {
-            AccessToken = tokenPair.AccessToken,
+            AccessToken = authResult.TokenPair.AccessToken,
-            RefreshToken = tokenPair.RefreshToken,
+            RefreshToken = authResult.TokenPair.RefreshToken,
-            ExpiresIn = tokenPair.ExpiresIn,
+            ExpiresIn = authResult.TokenPair.ExpiresIn,
-            Token = tokenPair.AccessToken
+            Token = authResult.TokenPair.AccessToken
         };
 
         return Page();

src/TaxBaik.Web/Services/AuthService.cs

@@ -34,10 +34,10 @@ public class AuthService
         _passwordResetToken = configuration["Admin:PasswordResetToken"];
     }
 
-    public async Task<AuthTokenPair?> AuthenticateAndGenerateTokenPairAsync(string username, string password)
+    public async Task<AuthResult> AuthenticateAndGenerateTokenPairAsync(string username, string password)
     {
         if (string.IsNullOrWhiteSpace(username) || string.IsNullOrWhiteSpace(password))
-            return null;
+            return AuthResult.InvalidCredentials();
 
         AdminUser? user;
         try
@@ -49,17 +49,22 @@ public class AuthService
             if (IsLocalE2ETestCredentials(username, password))
             {
                 _logger.LogWarning(ex, "개발 환경에서 DB 없이 로컬 E2E 관리자 로그인 허용: {Username}", username);
-                return GenerateTokenPair(new AdminUser
+                return AuthResult.Success(GenerateTokenPair(new AdminUser
                 {
                     Id = 0,
                     Username = username,
                     PasswordHash = string.Empty,
                     CreatedAt = DateTime.UtcNow
-                });
+                }));
             }
 
             _logger.LogWarning(ex, "개발 환경에서 관리자 로그인 DB 조회 실패: {Username}", username);
-            return null;
+            return AuthResult.DatabaseUnavailable();
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "관리자 로그인 중 예상치 못한 오류: {Username}", username);
+            return AuthResult.DatabaseUnavailable();
         }
 
         if (user == null)
@@ -68,35 +73,35 @@ public class AuthService
             if (_environment.IsDevelopment() && IsLocalE2ETestCredentials(username, password))
             {
                 _logger.LogWarning("개발 환경에서 시드 계정 없이 로컬 E2E 관리자 로그인 허용: {Username}", username);
-                return GenerateTokenPair(new AdminUser
+                return AuthResult.Success(GenerateTokenPair(new AdminUser
                 {
                     Id = 0,
                     Username = username,
                     PasswordHash = string.Empty,
                     CreatedAt = DateTime.UtcNow
-                });
+                }));
             }
 
-            return null;
+            return AuthResult.InvalidCredentials();
         }
 
         if (string.IsNullOrWhiteSpace(user.PasswordHash))
         {
             _logger.LogError("로그인 실패: 사용자 '{Username}'의 PasswordHash가 비어 있습니다.", username);
-            return null;
+            return AuthResult.DatabaseUnavailable();
         }
 
         if (!BCrypt.Net.BCrypt.Verify(password, user.PasswordHash))
         {
             _logger.LogWarning("로그인 시도: 잘못된 비밀번호 '{Username}'", username);
             // 실패한 로그인은 알림하지 않음 (로그만 남김)
-            return null;
+            return AuthResult.InvalidCredentials();
         }
 
         _logger.LogInformation("로그인 성공: {Username}", username);
         // 로그인 알림은 제거 (로그만 남김)
         await _adminUserRepository.UpdateLastLoginAtAsync(user.Id);
-        return GenerateTokenPair(user);
+        return AuthResult.Success(GenerateTokenPair(user));
     }
 
     public async Task<AuthTokenPair?> RefreshAccessTokenAsync(string refreshToken)
@@ -271,3 +276,26 @@ public class AuthTokenPair(string accessToken, string refreshToken, int expiresI
     public string RefreshToken { get; } = refreshToken;
     public int ExpiresIn { get; } = expiresIn;
 }
+
+public enum AuthFailureReason
+{
+    InvalidCredentials,
+    DatabaseUnavailable
+}
+
+public sealed class AuthResult
+{
+    private AuthResult(AuthTokenPair? tokenPair, AuthFailureReason? failureReason)
+    {
+        TokenPair = tokenPair;
+        FailureReason = failureReason;
+    }
+
+    public AuthTokenPair? TokenPair { get; }
+    public AuthFailureReason? FailureReason { get; }
+    public bool IsSuccess => TokenPair is not null;
+
+    public static AuthResult Success(AuthTokenPair tokenPair) => new(tokenPair, null);
+    public static AuthResult InvalidCredentials() => new(null, AuthFailureReason.InvalidCredentials);
+    public static AuthResult DatabaseUnavailable() => new(null, AuthFailureReason.DatabaseUnavailable);
+}