Reload sheets in response to "CHANGED" events

Refs #53

It's happening!

src/cljs/wish/events.cljs

@@ -1,5 +1,5 @@
 (ns wish.events
-  (:require-macros [wish.util.log :refer [log]])
+  (:require-macros [wish.util.log :as log :refer [log]])
   (:require [clojure.string :as str]
             [re-frame.core :refer [dispatch reg-event-db reg-event-fx
                                    path
@@ -210,6 +210,7 @@
       ; delete the sheet source to trigger a reload
       [:db :sheet-sources sheet-id] nil)))
 
+
 ; ======= sheet-related ====================================
 
 (defn- reset-sheet-err
@@ -681,3 +682,16 @@
     (if-not (= current-ids interested-ids)
       (log "Drop un-interesting sesssion; was " interested-ids "; now " current-ids)
       {:push/connect session-id})))
+
+(reg-event-fx
+  :reload-changed!
+  [trim-v (inject-cofx ::inject/sub [:active-sheet-id])]
+  (fn [{:keys [active-sheet-id]} [changed-ids]]
+    (when (> (count changed-ids) 1)
+      ; TODO:
+      (log/todo "Support reloading data sources as well as sheets"))
+
+    (when (contains? changed-ids active-sheet-id)
+      ; trigger sheet data reload
+      {:load-sheet! active-sheet-id})))
+

src/cljs/wish/push.cljs

@@ -14,6 +14,7 @@
 
 (def ^:private push-url-base (str config/push-server "/" push-server-version "/push"))
 
+(def ^:private reload-changed-throttle-ms 750)
 
 ; ======= session creation ================================
 
@@ -51,10 +52,40 @@
   (let [id (keyword id)]
     (log/todo "Create watch for sheet " (keyword id))))
 
+;; "changed" handling
+
+(defonce ^:private pending-changes (atom {:timer nil
+                                          :ids #{}}))
+
+(defn- reload-changed []
+  (swap! pending-changes
+         (fn [{:keys [ids]}]
+           (>evt [:reload-changed! ids])
+
+           ; reset state:
+           {:timer nil :ids #{}})))
+
 (defmethod on-push! :changed
   [{{:keys [id]} :data}]
-  (let [id (keyword id)]
-    (log/todo "Sheet changed" (keyword id))))
+  (let [changed-id (keyword id)]
+    (log "Sheet changed" changed-id)
+    (swap! pending-changes
+           (fn [{:keys [timer ids] :as old}]
+             (if (contains? ids changed-id)
+               ; ignore the dup notification
+               old
+
+               ; cancel any old timer and start over
+               (do
+                 (when timer
+                   (js/clearTimeout timer))
+
+                 {:ids (conj ids changed-id)
+                  :timer (js/setTimeout
+                           reload-changed
+                           reload-changed-throttle-ms)}))))))
+
+;; fallback
 
 (defmethod on-push! :default
   [evt]
@@ -64,8 +95,15 @@
 ; ======= connect to a created session ====================
 
 ; NOTE event handler fns declared separately to improve hot-reload developer UX
-(defn- on-error [e]
-  (log/warn "Error with push session" e))
+(defn- on-error [evt]
+  ; TODO on fatal errors, we should create a new session, maybe?
+  ; An error is also emitted when the connection drops, but it
+  ; will attempt to auto-reconnect....
+  ; NOTE: readyState:
+  ;  0 - CONNECTING
+  ;  1 - OPEN
+  ;  2 - CLOSED
+  (log/warn "Error with push session; state=" (-> evt (.-target) (.-readyState))))
 
 (defn- on-message [evt]
   (let [data (-> (.-data evt)