⚡ Add thumbnail/imposter queue

frontend/src/app/util/queue.cljs

@@ -0,0 +1,101 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC
+
+(ns app.util.queue
+  (:require [app.common.logging :as l]
+            [app.common.math :as mth]
+            [app.util.time :as t]))
+
+(l/set-level! :info)
+
+(declare process)
+(declare dequeue)
+
+(defrecord Queue [f items timeout time threshold max-iterations])
+
+(defn create
+  [f threshold]
+  (Queue. f
+          #js []
+          nil
+          0
+          threshold
+          ##Inf))
+
+(defn- measure-fn
+  [f & args]
+  (let [tp       (t/tpoint-ms)
+        _        (apply f args)
+        duration (tp)]
+    (l/dbg :hint "queue::measure-fn" :duration duration)
+    duration))
+
+(defn- next-process-time
+  [queue]
+  (let [time      (unchecked-get queue "time")
+        threshold (unchecked-get queue "threshold")
+        max-time  5000
+        min-time  1000
+        calc-time (mth/min (mth/max (* (- time threshold) 10) min-time) max-time)]
+    (l/dbg :hint "queue::next-process-time" :time time :threshold threshold :calc-time calc-time :max-time max-time :min-time min-time)
+    calc-time))
+
+(defn- has-requested-process?
+  [queue]
+  (not (nil? (unchecked-get queue "timeout"))))
+
+(defn- request-process
+  [queue time]
+  (l/dbg :hint "queue::request-process" :time time)
+  (unchecked-set queue "timeout" (js/setTimeout (fn [] (process queue)) time)))
+
+;; NOTE: Right now there are no cases where we need to cancel a process
+;;       but if we do, we can use this function
+#_(defn- cancel-process
+  [queue]
+  (l/dbg :hint "queue::cancel-process")
+  (let [timeout (unchecked-get queue "timeout")]
+    (when (some? timeout)
+      (js/clearTimeout timeout))
+    (unchecked-set queue "timeout" nil)))
+
+(defn- process
+  [queue]
+  (unchecked-set queue "timeout" nil)
+  (unchecked-set queue "time" 0)
+  (let [threshold      (unchecked-get queue "threshold")
+        max-iterations (unchecked-get queue "max-iterations")
+        f              (unchecked-get queue "f")]
+    (loop [item (dequeue queue)
+           iterations 0]
+      (l/dbg :hint "queue::process" :item item)
+      (when (some? item)
+        (let [duration (measure-fn f item)
+              time     (unchecked-get queue "time")
+              time     (unchecked-set queue "time" (+ time duration))]
+          (if (or (> time threshold) (>= iterations max-iterations))
+            (request-process queue (next-process-time queue))
+            (recur (dequeue queue) (inc iterations))))))))
+
+(defn- dequeue
+  [queue]
+  (let [items (unchecked-get queue "items")]
+    (.shift items)))
+
+(defn enqueue
+  [queue item]
+  (assert (instance? Queue queue))
+  (let [items (unchecked-get queue "items")]
+    (.push items item)
+    (when-not (has-requested-process? queue)
+      (request-process queue (next-process-time queue)))))
+
+(defn enqueue-unique
+  [queue item f]
+  (assert (instance? Queue queue))
+  (let [items (unchecked-get queue "items")]
+    (when-not (.findLast items f)
+      (enqueue queue item))))