From 402212c808de4182902011b436233cd53caf7043 Mon Sep 17 00:00:00 2001
From: "alonso.torres" <alonso.torres@kaleidos.net>
Date: Wed, 25 May 2022 17:59:26 +0200
Subject: [PATCH] :bug: Fix problems with embed data cache

---
 frontend/src/app/util/cache.cljs | 29 +++++++++++++----
 frontend/src/app/util/http.cljs  | 54 +++++++++++++++++---------------
 2 files changed, 51 insertions(+), 32 deletions(-)

diff --git a/frontend/src/app/util/cache.cljs b/frontend/src/app/util/cache.cljs
index 53fa610cc..dc6d2b2c3 100644
--- a/frontend/src/app/util/cache.cljs
+++ b/frontend/src/app/util/cache.cljs
@@ -10,17 +10,34 @@
    [beicon.core :as rx]))
 
 (defonce cache (atom {}))
+(defonce pending (atom {}))
 
 (defn with-cache
   [{:keys [key max-age]} observable]
   (let [entry (get @cache key)
+        pending-entry (get @pending key)
+
         age   (when entry
                 (dt/diff (dt/now)
                          (:created-at entry)))]
-    (if (and (some? entry) (< age max-age))
+    (cond
+      (and (some? entry) (< age max-age))
       (rx/of (:data entry))
-      (->> observable
-           (rx/tap
-            (fn [data]
-              (let [entry {:created-at (dt/now) :data data}]
-                (swap! cache assoc key entry))))))))
+
+      (some? pending-entry)
+      pending-entry
+
+      :else
+      (let [subject (rx/subject)]
+        (swap! pending assoc key subject)
+        (->> observable
+             (rx/catch #(do (rx/error! subject %)
+                            (swap! pending dissoc key)
+                            (rx/throw %)))
+             (rx/tap
+              (fn [data]
+                (let [entry {:created-at (dt/now) :data data}]
+                  (swap! cache assoc key entry))
+                (rx/push! subject data)
+                (rx/end! subject)
+                (swap! pending dissoc key))))))))
diff --git a/frontend/src/app/util/http.cljs b/frontend/src/app/util/http.cljs
index 37c8cac35..adfb5aece 100644
--- a/frontend/src/app/util/http.cljs
+++ b/frontend/src/app/util/http.cljs
@@ -173,32 +173,34 @@
    (fetch-data-uri uri false))
 
   ([uri throw-err?]
-   (c/with-cache {:key uri :max-age (dt/duration {:hours 4})}
-     (let [request-stream
-           (send! {:method :get
-                   :uri uri
-                   :response-type :blob
-                   :omit-default-headers true})
+   (let [request-str
+         (->> (send! {:method :get
+                      :uri uri
+                      :response-type :blob
+                      :omit-default-headers true})
+              (rx/tap
+               (fn [resp]
+                 (when (or (< (:status resp) 200) (>= (:status resp) 300))
+                   (rx/throw (js/Error. "Error fetching data uri" #js {:cause (clj->js resp)})))))
 
-           request-stream
-           (if throw-err?
-             (rx/tap #(when-not (and (>= (:status %) 200) (< (:status %) 300))
-                        ;; HTTP ERRROR
-                        (throw (js/Error. "Error fetching data uri" #js {:cause (clj->js %)})))
-                     request-stream)
-             (rx/filter #(= 200 (:status %))
-                        request-stream))]
-       (->> request-stream
-            (rx/map :body)
-            (rx/mapcat wapi/read-file-as-data-url)
-            (rx/map #(hash-map uri %)))))))
+              (rx/map :body)
+              (rx/mapcat wapi/read-file-as-data-url)
+              (rx/map #(hash-map uri %))
+              (c/with-cache {:key uri :max-age (dt/duration {:hours 4})}))]
+
+     ;; We need to check `throw-err?` after the cache is resolved otherwise we cannot cache request
+     ;; with different values of throw-err. By default we throw always the exception and then we just
+     ;; ignore when `throw-err?` is `true`
+     (if (not throw-err?)
+       (->> request-str (rx/catch #(rx/empty)))
+       request-str))))
 
 (defn fetch-text [url]
-  (c/with-cache {:key url :max-age (dt/duration {:hours 4})}
-    (->> (send!
-          {:method :get
-           :mode :cors
-           :omit-default-headers true
-           :uri url
-           :response-type :text})
-         (rx/map :body))))
+  (->> (send!
+        {:method :get
+         :mode :cors
+         :omit-default-headers true
+         :uri url
+         :response-type :text})
+       (rx/map :body)
+       (c/with-cache {:key url :max-age (dt/duration {:hours 4})})))