Refactor error code functions and add enhanced status code tests

Renamed `getErrorCode` function to `errorCode` for consistency. Added new tests for the `enhancedStatusCode` function to validate its behavior with various error scenarios.

senderror_test.go

@@ -255,7 +255,7 @@ func TestSendError_ErrorCode(t *testing.T) {
 			errlist: []error{ErrNoRcptAddresses},
 			rcpt:    []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
 			Reason:  ErrAmbiguous,
-			errcode: getErrorCode(ErrNoRcptAddresses),
+			errcode: errorCode(ErrNoRcptAddresses),
 		}
 		if err.ErrorCode() != 0 {
 			t.Errorf("expected error code: %d, got: %d", 0, err.ErrorCode())
@@ -266,7 +266,7 @@ func TestSendError_ErrorCode(t *testing.T) {
 			errlist: []error{ErrNoRcptAddresses},
 			rcpt:    []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
 			Reason:  ErrAmbiguous,
-			errcode: getErrorCode(errors.New("535 5.7.8 Error: authentication failed")),
+			errcode: errorCode(errors.New("535 5.7.8 Error: authentication failed")),
 		}
 		if err.ErrorCode() != 535 {
 			t.Errorf("expected error code: %d, got: %d", 535, err.ErrorCode())
@@ -277,7 +277,7 @@ func TestSendError_ErrorCode(t *testing.T) {
 			errlist: []error{ErrNoRcptAddresses},
 			rcpt:    []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
 			Reason:  ErrAmbiguous,
-			errcode: getErrorCode(errors.New("441 4.1.0 Server currently unavailable")),
+			errcode: errorCode(errors.New("441 4.1.0 Server currently unavailable")),
 		}
 		if err.ErrorCode() != 441 {
 			t.Errorf("expected error code: %d, got: %d", 441, err.ErrorCode())
@@ -291,45 +291,78 @@ func TestSendError_ErrorCode(t *testing.T) {
 	})
 }
 
-func TestSendError_getErrorCode(t *testing.T) {
+func TestSendError_errorCode(t *testing.T) {
-	t.Run("getErrorCode with a go-mail error should return 0", func(t *testing.T) {
+	t.Run("errorCode with a go-mail error should return 0", func(t *testing.T) {
-		code := getErrorCode(ErrNoRcptAddresses)
+		code := errorCode(ErrNoRcptAddresses)
 		if code != 0 {
 			t.Errorf("expected error code: %d, got: %d", 0, code)
 		}
 	})
-	t.Run("getErrorCode with permanent error", func(t *testing.T) {
+	t.Run("errorCode with permanent error", func(t *testing.T) {
-		code := getErrorCode(errors.New("535 5.7.8 Error: authentication failed"))
+		code := errorCode(errors.New("535 5.7.8 Error: authentication failed"))
 		if code != 535 {
 			t.Errorf("expected error code: %d, got: %d", 535, code)
 		}
 	})
-	t.Run("getErrorCode with temporary error", func(t *testing.T) {
+	t.Run("errorCode with temporary error", func(t *testing.T) {
-		code := getErrorCode(errors.New("443 4.1.0 Server currently unavailable"))
+		code := errorCode(errors.New("443 4.1.0 Server currently unavailable"))
 		if code != 443 {
 			t.Errorf("expected error code: %d, got: %d", 443, code)
 		}
 	})
-	t.Run("getErrorCode with wrapper error", func(t *testing.T) {
+	t.Run("errorCode with wrapper error", func(t *testing.T) {
-		code := getErrorCode(fmt.Errorf("an error occured: %w", errors.New("443 4.1.0 Server currently unavailable")))
+		code := errorCode(fmt.Errorf("an error occured: %w", errors.New("443 4.1.0 Server currently unavailable")))
 		if code != 443 {
 			t.Errorf("expected error code: %d, got: %d", 443, code)
 		}
 	})
-	t.Run("getErrorCode with non-4xx and non-5xx error", func(t *testing.T) {
+	t.Run("errorCode with non-4xx and non-5xx error", func(t *testing.T) {
-		code := getErrorCode(errors.New("220 2.1.0 This is not an error"))
+		code := errorCode(errors.New("220 2.1.0 This is not an error"))
 		if code != 0 {
 			t.Errorf("expected error code: %d, got: %d", 0, code)
 		}
 	})
-	t.Run("getErrorCode with non 3-digit code", func(t *testing.T) {
+	t.Run("errorCode with non 3-digit code", func(t *testing.T) {
-		code := getErrorCode(errors.New("4xx 4.1.0 The status code is invalid"))
+		code := errorCode(errors.New("4xx 4.1.0 The status code is invalid"))
 		if code != 0 {
 			t.Errorf("expected error code: %d, got: %d", 0, code)
 		}
 	})
 }
 
+func TestSendError_enhancedStatusCode(t *testing.T) {
+	t.Run("enhancedStatusCode with nil error should return empty string", func(t *testing.T) {
+		code := enhancedStatusCode(nil, true)
+		if code != "" {
+			t.Errorf("expected empty enhanced status code, got: %s", code)
+		}
+	})
+	t.Run("enhancedStatusCode with error but no support should return empty string", func(t *testing.T) {
+		code := enhancedStatusCode(errors.New("553 5.5.3 something went wrong"), false)
+		if code != "" {
+			t.Errorf("expected empty enhanced status code, got: %s", code)
+		}
+	})
+	t.Run("enhancedStatusCode with error and support", func(t *testing.T) {
+		code := enhancedStatusCode(errors.New("553 5.5.3 something went wrong"), true)
+		if code != "5.5.3" {
+			t.Errorf("expected enhanced status code: %s, got: %s", "5.5.3", code)
+		}
+	})
+	t.Run("enhancedStatusCode with wrapped error and support", func(t *testing.T) {
+		code := enhancedStatusCode(fmt.Errorf("this error is wrapped: %w", errors.New("553 5.5.3 something went wrong")), true)
+		if code != "5.5.3" {
+			t.Errorf("expected enhanced status code: %s, got: %s", "5.5.3", code)
+		}
+	})
+	t.Run("enhancedStatusCode with 3xx error", func(t *testing.T) {
+		code := enhancedStatusCode(errors.New("300 3.0.0 i don't know what i'm doing"), true)
+		if code != "" {
+			t.Errorf("expected enhanced status code to be empty, got: %s", code)
+		}
+	})
+}
+
 // returnSendError is a helper method to retunr a SendError with a specific reason
 func returnSendError(r SendErrReason, t bool) error {
 	message := NewMsg()