are you implementing a SSE client?

I would write an ad-hoc stateful transducer

@UK0810AQ2 yes

(defn sse-chunk-xform
  "Returns a transducer that retains incomplete events (i.e. no trailing \n\n)"
  []
  (fn [rf]
    (let [incomplete (volatile! nil)]
      (fn
        ([] (rf))
        ([result] (rf result))
        ([result el]
         (cond
          (and (nil? @incomplete)
               (.endsWith el "\n\n"))
          (rf result el)

          (and @incomplete (.endsWith el "\n\n"))
          (do (rf result (str @incomplete el))
              (vreset! incomplete nil))

          :else
          (vswap! incomplete str el)))))))

@U050TNB9F in the front end or back end?

frontend

I started with https://github.com/oliyh/oxbow but I think the author may have only used it with small events where the chunks are usually complete

don't take it the wrong way, why torture yourself? the SSE specification is annoying. Let someone else solve the problem for you

Isn't there a SSE client in Javascript you can just use?

https://html.spec.whatwg.org/multipage/server-sent-events.html

you need an entire state machine

your initial state will have to me something like {:id "" :type "" :data ""}

you may get several messages before you emit, so you need to handle all the transitions

Fair comments, I originally just used EventSource which was working fine but I need HTTP header auth and so I have to go the js/fetch route. It’s a good idea to use a library for the parsing, not sure I really looked for one to do just that but I’ll take a look

Kind of a shame that the EventSource API is so tied to the networking layer when most of the complexity seems to be in the stream parsing

you can implement it yourself, but it's a pain

I mean after reading the spec it doesn’t seem that painful

We call that "famous last words"