From 06d0fa5e05e6e350da782dc3b3e8fb1499522864 Mon Sep 17 00:00:00 2001
From: Florian Schroedl <flo.schroedl@gmail.com>
Date: Thu, 16 Apr 2026 19:09:08 +0200
Subject: [PATCH] =?UTF-8?q?feat:=20instant=20sync=20=E2=80=94=20push=20on?=
 =?UTF-8?q?=20write,=20pull=20on=20reconnect,=20render=20from=20cache?=
MIME-Version: 1.0
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- Add kick-ch to SyncedAtom: swap!/reset! trigger immediate push
  instead of waiting for the 15s sync loop interval
- SSE: pull on reconnect ("connected" message), not just on new events,
  so coming back online picks up missed server changes
- TodoMVC: render and bind events before IDB load completes; the watch
  re-renders automatically when cached data arrives
---
 example/todomvc/pocketbook/todomvc.cljs | 10 ++++------
 src/pocketbook/core.cljs                | 22 ++++++++++++++++------
 src/pocketbook/sync.cljs                |  6 +++---
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/example/todomvc/pocketbook/todomvc.cljs b/example/todomvc/pocketbook/todomvc.cljs
index 6a48eee..aa240e2 100644
--- a/example/todomvc/pocketbook/todomvc.cljs
+++ b/example/todomvc/pocketbook/todomvc.cljs
@@ -247,18 +247,16 @@
                    :interval 15000})]
       (reset! !conn conn)
       (reset! !todos todos)
-      ;; Wait for IDB load
-      (<! (pb/ready? todos))
-      ;; Initial render
+      ;; Render + bind immediately (empty or stale is fine)
       (render!)
       (bind-events!)
-      ;; Re-render on any data change
+      ;; Re-render on any data change (fires when IDB loads + server syncs)
       (add-watch todos :render (fn [_ _ _ _] (render!)))
-      ;; Re-render on filter change
       (add-watch !filter :render (fn [_ _ _ _] (render!)))
-      ;; Online/offline status updates
       (.addEventListener js/window "online" (fn [_] (render!)))
       (.addEventListener js/window "offline" (fn [_] (render!)))
+      ;; Wait for IDB — watch triggers render automatically
+      (<! (pb/ready? todos))
       (js/console.log "🔶 Pocketbook TodoMVC loaded —" (count @todos) "todos"))))
 
 (init)
diff --git a/src/pocketbook/core.cljs b/src/pocketbook/core.cljs
index 718a19c..a42b470 100644
--- a/src/pocketbook/core.cljs
+++ b/src/pocketbook/core.cljs
@@ -51,6 +51,7 @@
                      last-sync     ;; atom containing epoch ms
                      ready-ch      ;; channel, closed when initial load complete
                      stop-ch       ;; channel to signal stop
+                     kick-ch       ;; channel to trigger immediate push
                      cleanup-fn    ;; atom holding connectivity cleanup fn
                      sync-interval ;; ms
                      _meta]        ;; metadata atom
@@ -67,9 +68,11 @@
     (let [old @cache]
       (reset! cache new-val)
       ;; Track which docs changed/added/removed
-      (let [all-keys (into (set (keys old)) (keys new-val))]
+      (let [all-keys (into (set (keys old)) (keys new-val))
+            changed? (volatile! false)]
         (doseq [k all-keys]
           (when (not= (get old k) (get new-val k))
+            (vreset! changed? true)
             (swap! pending conj k)
             ;; Write to IDB
             (let [v (get new-val k)]
@@ -80,7 +83,10 @@
                    :updated (.now js/Date) :deleted true :synced false})
                 (idb/put-doc! (:db conn)
                   {:id k :value v :version (get @versions k 0)
-                   :updated (.now js/Date) :deleted false :synced false}))))))
+                   :updated (.now js/Date) :deleted false :synced false})))))
+        ;; Kick the sync loop to push immediately
+        (when @changed?
+          (put! kick-ch :kick)))
       new-val))
 
   ISwap
@@ -276,13 +282,16 @@
   "Start the background sync loop. Returns a stop function."
   [sa]
   (let [stop-ch  (.-stop_ch sa)
+        kick-ch  (.-kick_ch sa)
         interval (.-sync_interval sa)
         cleanups (atom [])]
-    ;; Periodic sync (fallback)
+    ;; Periodic sync (fallback) + immediate push on kick
     (go-loop []
-      (let [[_ ch] (alts! [stop-ch (timeout interval)])]
+      (let [[_ ch] (alts! [stop-ch kick-ch (timeout interval)])]
         (when-not (= ch stop-ch)
-          (<! (do-sync! sa))
+          (if (= ch kick-ch)
+            (<! (do-push! sa))   ;; kick = local write, just push
+            (<! (do-sync! sa)))  ;; timeout = full pull+push
           (recur))))
     ;; Online/offline handler
     (swap! cleanups conj
@@ -322,10 +331,11 @@
         last-sync   (atom 0)
         ready-ch    (chan 1)
         stop-ch     (chan 1)
+        kick-ch     (chan (async/sliding-buffer 1))
         cleanup-fn  (atom nil)
         meta-atom   (atom nil)
         sa          (SyncedAtom. group conn cache-atom versions pending
-                      server-opts last-sync ready-ch stop-ch
+                      server-opts last-sync ready-ch stop-ch kick-ch
                       cleanup-fn interval meta-atom)]
     ;; Load from IDB, then start sync
     (go
diff --git a/src/pocketbook/sync.cljs b/src/pocketbook/sync.cljs
index eadfd77..628bd6f 100644
--- a/src/pocketbook/sync.cljs
+++ b/src/pocketbook/sync.cljs
@@ -108,9 +108,9 @@
     (set! (.-onmessage es)
       (fn [e]
         (let [data (.-data e)]
-          ;; Skip initial "connected" message
-          (when (not= data "connected")
-            (on-change data)))))
+          ;; "connected" fires on initial connect AND every reconnect
+          ;; Always trigger a sync — picks up missed changes after reconnect
+          (on-change data))))
     (set! (.-onerror es)
       (fn [_e]
         ;; EventSource auto-reconnects; nothing to do