diff --git a/parsers/src/message.rs b/parsers/src/message.rs index 40c45e4..16dbddf 100644 --- a/parsers/src/message.rs +++ b/parsers/src/message.rs @@ -204,6 +204,40 @@ impl Message { pub fn get_best_subject(&self, preferred_langs: Vec<&str>) -> Option<(Lang, &Subject)> { Message::get_best::(&self.subjects, preferred_langs) } + + /// Try to extract the given payload type from the message's payloads. + /// + /// Returns the first matching payload element as parsed struct or its + /// parse error. If no element matches, `Ok(None)` is returned. If an + /// element matches, but fails to parse, it is nontheless removed from + /// the message. + /// + /// Elements which do not match the given type are not removed. + pub fn extract_payload>( + &mut self, + ) -> Result, Error> { + let mut buf = Vec::with_capacity(self.payloads.len()); + let mut iter = self.payloads.drain(..); + let mut result = Ok(None); + for item in &mut iter { + match T::try_from(item) { + Ok(v) => { + result = Ok(Some(v)); + break; + } + Err(Error::TypeMismatch(_, _, residual)) => { + buf.push(residual); + } + Err(other) => { + result = Err(other); + break; + } + } + } + buf.extend(iter); + std::mem::swap(&mut buf, &mut self.payloads); + result + } } impl TryFrom for Message { @@ -460,4 +494,27 @@ mod tests { let elem2 = message.into(); assert_eq!(elem1, elem2); } + + #[test] + fn test_extract_payload() { + use super::super::attention::Attention; + use super::super::pubsub::event::PubSubEvent; + + #[cfg(not(feature = "component"))] + let elem: Element = "".parse().unwrap(); + #[cfg(feature = "component")] + let elem: Element = "".parse().unwrap(); + let mut message = Message::try_from(elem).unwrap(); + assert_eq!(message.payloads.len(), 1); + match message.extract_payload::() { + Ok(None) => (), + other => panic!("unexpected result: {:?}", other), + }; + assert_eq!(message.payloads.len(), 1); + match message.extract_payload::() { + Ok(Some(_)) => (), + other => panic!("unexpected result: {:?}", other), + }; + assert_eq!(message.payloads.len(), 0); + } }