improve Content-Disposition header generation for non-ASCII characters.

backend/src/utils/http.rs

@@ -10,13 +10,44 @@ pub fn inline_content_disposition(filename: &str) -> Option<String> {
         .chars()
         .map(|ch| match ch {
             '"' | '\\' => '_',
+            c if !c.is_ascii() => '_',
             _ => ch,
         })
         .collect();
-    let encoded = utf8_percent_encode(&sanitized, NON_ALPHANUMERIC);
+    let encoded = utf8_percent_encode(filename, NON_ALPHANUMERIC);
 
     Some(format!(
         "inline; filename=\"{}\"; filename*=UTF-8''{}",
         sanitized, encoded
     ))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use reqwest::header::HeaderValue;
+
+    #[test]
+    fn test_inline_content_disposition_header_validity() {
+        // Test with a filename containing non-ASCII characters
+        let filename = "Täst.pdf";
+        let disposition = inline_content_disposition(filename).unwrap();
+        println!("Disposition: {}", disposition);
+        
+        // This should fail if the sanitized part contains non-ASCII characters
+        // and we try to create a HeaderValue from it.
+        let result = HeaderValue::from_str(&disposition);
+        
+        if let Ok(val) = result {
+             // Check if to_str succeeds (it should now!)
+             let to_str_res = val.to_str();
+             assert!(to_str_res.is_ok(), "HeaderValue::to_str should succeed for sanitized filename");
+             
+             let disposition_str = to_str_res.unwrap();
+             assert!(disposition_str.contains("filename=\"T_st.pdf\""), "Filename should be sanitized");
+             assert!(disposition_str.contains("filename*=UTF-8''T%C3%A4st%2Epdf"), "UTF-8 filename should be preserved");
+        } else {
+             panic!("HeaderValue rejected the string: {:?}", result.err());
+        }
+    }
+}