example.clj

(defn render-handler
  "A default http-kit ring handler for rendering views over a long-lived SSE connection with datastar.

    - `render-fn` is an arity-1 function of req that returns a string of HTML sent to the client with D*'s merge-fragment

   Opts are:
    - `init-tab-state-fn` is an arity-1 pure-function of state and returns the initialized state.
                          On a first-connect/refresh the state will be nil, but on an SSE reconnect the state will be whatever
                          the state was before the disconnect.

  This handler is a basic implementation, if you outgrow it, copy and paste it into your codebase to extend it."
  ([render-fn]
   (render-handler render-fn nil))
  ([render-fn {:keys [init-tab-state-fn]}]
   (let [init-tab-state-fn (or init-tab-state-fn #(identity %2))]
     (fn [req]
       (let [ctx             (datastar/long-lived-render-setup req render-fn)
             first-tab-state (tab-state/init-tab-state! req (:hifi.datastar/<render ctx) #(init-tab-state-fn req %))
             req             (assoc req :hifi.datastar/tab-state first-tab-state)]
         (hk-gen/->sse-response req
                                {:headers            {}
                                 hk-gen/on-open      (fn [sse-gen]
                                                       (datastar/long-lived-render-on-open ctx req sse-gen))
                                 hk-gen/on-close     (fn [_ _]
                                                       (datastar/long-lived-render-on-close ctx))
                                 d*com/write-profile (datastar/brotli-write-profile)}))))))