Improvements in error handling & descriptions

gemini/errors.go

@@ -20,21 +20,29 @@ func (e *GeminiError) Error() string {
 	return fmt.Sprintf("gemini error: code %d %s", e.Code, e.Msg)
 }
 
+// NewGeminiError creates a new GeminiError based on the status code and header.
+// Status codes are based on the Gemini protocol specification:
+// - 1x: Input required
+// - 2x: Success (not handled as errors)
+// - 3x: Redirect
+// - 4x: Temporary failure
+// - 5x: Permanent failure
+// - 6x: Client certificate required/rejected
 func NewGeminiError(code int, header string) error {
 	var msg string
 	switch {
 	case code >= 10 && code < 20:
-		msg = "needs input"
+		msg = fmt.Sprintf("input required: %s", header)
 	case code >= 30 && code < 40:
-		msg = "redirect"
+		msg = fmt.Sprintf("redirect: %s", header)
 	case code >= 40 && code < 50:
-		msg = "bad request"
+		msg = fmt.Sprintf("request failed: %s", header)
 	case code >= 50 && code < 60:
-		msg = "server error"
+		msg = fmt.Sprintf("server error: %s", header)
 	case code >= 60 && code < 70:
-		msg = "TLS error"
+		msg = fmt.Sprintf("TLS error: %s", header)
 	default:
-		msg = "unexpected Status code"
+		msg = fmt.Sprintf("unexpected status code %d: %s", code, header)
 	}
 	return &GeminiError{
 		Msg:    msg,
@@ -43,6 +51,7 @@ func NewGeminiError(code int, header string) error {
 	}
 }
 
+// IsGeminiError checks if the given error is a GeminiError.
 func IsGeminiError(err error) bool {
 	if err == nil {
 		return false