From e3410d5f2fef00558cadce5afb1d69d7260fa831 Mon Sep 17 00:00:00 2001
From: Weihua Lu <luwh364@gmail.com>
Date: Tue, 20 Jul 2021 14:32:18 +0800
Subject: [PATCH] core async debounce

---
 src/main/frontend/extensions/zotero.cljs     | 22 +++++++++++---------
 src/main/frontend/extensions/zotero/api.cljs | 21 ++++++++++++++++++-
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/src/main/frontend/extensions/zotero.cljs b/src/main/frontend/extensions/zotero.cljs
index 0b314ebc96..e9dd63a8ae 100644
--- a/src/main/frontend/extensions/zotero.cljs
+++ b/src/main/frontend/extensions/zotero.cljs
@@ -1,5 +1,5 @@
 (ns frontend.extensions.zotero
-  (:require [cljs.core.async :refer [<! go]]
+  (:require [cljs.core.async :refer [<! >! go chan]]
             [clojure.string :as str]
             [frontend.extensions.zotero.api :as api]
             [frontend.extensions.zotero.handler :as zotero-handler]
@@ -38,18 +38,18 @@
     (let [[term set-term!]                   (rum/use-state "")
           [search-result set-search-result!] (rum/use-state [])
           [search-error set-search-error!]   (rum/use-state nil)
-          [is-searching set-is-searching!]   (rum/use-state false)]
+          [is-searching set-is-searching!]   (rum/use-state false)
+          term-chan                          (chan)
+          debounce-chan                      (api/debounce term-chan 500)]
 
 
       (rum/use-effect!
        (fn []
-         (let [do-search (fn [] (when-not (str/blank? term)
-                                  (go
-                                    (let [result (<! (api/query-items "journalArticle" term))]
-                                      (set-search-result! result)))))
-               do-search (util/debounce 200 do-search)]
-
-           (do-search)))
+         (go
+           (let [term   (<! debounce-chan)]
+             (when-not (str/blank? term)
+               (set-search-result!
+                (<! (api/query-items "journalArticle" term)))))))
        [term])
 
 
@@ -59,7 +59,9 @@
        [:input.p-2.border.block.w-full.mb-3
         {:autoFocus   true
          :placeholder "Search for your Zotero journal article (title, author, text, anything)"
-         :value       term :on-change (fn [e] (set-term! (util/evalue e)))}]
+         :value       term :on-change (fn [e]
+                                        (set-term! (util/evalue e))
+                                        (go (>! term-chan (util/evalue e))))}]
 
        [:div
         (map
diff --git a/src/main/frontend/extensions/zotero/api.cljs b/src/main/frontend/extensions/zotero/api.cljs
index 3eacb8f864..a7d8a77a2b 100644
--- a/src/main/frontend/extensions/zotero/api.cljs
+++ b/src/main/frontend/extensions/zotero/api.cljs
@@ -1,6 +1,7 @@
 (ns frontend.extensions.zotero.api
   (:require [cljs-http.client :as http]
-            [cljs.core.async :refer [go <!]]
+            [cljs.core.async
+             :refer [go <! >! go-loop timeout close! chan alt!]]
             [camel-snake-kebab.core :as csk]
             [camel-snake-kebab.extras :as cske]
             [frontend.util :as util]))
@@ -14,6 +15,24 @@
              :type        :user
              :type-id     8234867})
 
+;; taken from https://github.com/metosin/metosin-common/blob/master/src/cljc/metosin/core/async/debounce.cljc
+(defn debounce
+  "Creates a channel which will change put a new value to the output channel
+   after timeout has passed. Each value change resets the timeout. If value
+   changes more frequently only the latest value is put out.
+   When input channel closes, the output channel is closed."
+  [in ms]
+  (let [out (chan)]
+    (go-loop [last-val nil]
+      (let [val   (if (nil? last-val) (<! in) last-val)
+            timer (timeout ms)]
+        (alt!
+          in ([v] (if v
+                    (recur v)
+                    (close! out)))
+          timer ([_] (do (>! out val) (recur nil))))))
+    out))
+
 ;; "/users/475425/collections?v=3"
 (defn get*
   ([config api]