Almost complete rewrite

deps.edn

@@ -0,0 +1,2 @@
+{:paths ["src" "resources"]
+ :deps {}}

resources/ring/js/refresh.js

@@ -1,19 +1,28 @@
-var pageLoadTime = new Date().getTime()
+var pageLoadTime = new Date().getTime();
 
-function reloadIfSourceChanged() {
-    var request = new XMLHttpRequest()
-    request.onreadystatechange = function() {
-        if (request.readyState == 4) {
-            if (request.responseText == 'true') {
-                window.location.reload()
-            }
-            else {
-                setTimeout(reloadIfSourceChanged, 200)
+
+async function reloadIfSourceChanged() {
+    try {
+        const response = await fetch('/__source_changed', {
+            method: 'GET',
+            headers: {
+                'Content-Type': 'application/json'
             }
+        });
+        const text = await response.text()
+        const sourceChanged = parseInt(text);
+
+        if (sourceChanged >= pageLoadTime) {
+            window.location.reload();
         }
+    } catch (error) {
+        console.error('Error:', error);
     }
-    request.open('GET', '/__source_changed?since=' + pageLoadTime, true)
-    request.send()
 }
 
-window.onload = reloadIfSourceChanged
+async function reloadIfSourceChangedJob() {
+    await reloadIfSourceChanged()
+    setTimeout(reloadIfSourceChangedJob, 200);
+}
+
+window.onload = reloadIfSourceChangedJob;

src/ring/middleware/refresh.clj

@@ -1,17 +1,21 @@
 (ns ring.middleware.refresh
-  (:refer-clojure :exclude [random-uuid])
-  (:use [compojure.core :only (routes GET)]
-        [watchtower.core :only (watcher rate on-change)]
-        ring.middleware.params)
   (:require [clojure.string :as str]
-            [clojure.java.io :as io])
-  (:import [java.util Date UUID]))
+            [clojure.java.io :as io]))
+
+(defn- dir-last-modified-ts [dir]
+  (when-let [files (file-seq (io/file dir))]
+    (apply max (map #(.lastModified %) files))))
+
+(defn- dirs-last-modified-ts [dir & dirs]
+  (->> (cons dir dirs)
+       (mapv dir-last-modified-ts)
+       (reduce max)))
 
 (defn- get-request? [request]
   (= (:request-method request) :get))
 
 (defn- html-content? [response]
-  (if-let [content-type (get-in response [:headers "Content-Type"])]
+  (when-let [content-type (get-in response [:headers "Content-Type"])]
     (re-find #"text/html" content-type)))
 
 (def ^:private refresh-script
@@ -33,45 +37,22 @@
   (as-str [_] nil))
 
 (defn- add-script [body script]
-  (if-let [body-str (as-str body)]
+  (when-let [body-str (as-str body)]
     (str/replace
      body-str
-     #"<head\s*(?:\s[^\/>]+)?>"
-     #(str % "<script type=\"text/javascript\">" script "</script>"))))
-
-(def ^:private last-modified
-  (atom (Date.)))
-
-(defn- watch-dirs! [dirs]
-  (watcher dirs
-   (rate 100)
-   (on-change
-    (fn [_] (reset! last-modified (Date.))))))
-
-(defn- random-uuid []
-  (str (UUID/randomUUID)))
+     #"</head>"
+     #(str "\n<script type=\"text/javascript\" async>\n" script "</script>\n" %))))
 
-(defn- watch-until [reference pred timeout-ms]
-  (let [result    (promise)
-        watch-key (random-uuid)]
-    (try
-      (add-watch reference
-                 watch-key
-                 (fn [_ _ _ value]
-                   (when (pred value)
-                     (deliver result true))))
-      (or (pred @reference)
-          (deref result timeout-ms false))
-      (finally
-       (remove-watch reference watch-key)))))
+(defn- source-changed-handler [_ dirs]
+  {:status 200
+   :headers {"Content-Type" "application/json"}
+   :body (str (apply dirs-last-modified-ts dirs))})
 
-(def ^:private source-changed-route
-  (GET "/__source_changed" [since]
-    (let [timestamp (Long. since)]
-      (str (watch-until
-            last-modified
-            #(> (.getTime %) timestamp)
-            60000)))))
+(defn- intercept-source-changed-route [handler dirs]
+  (fn [{:keys [uri] :as request}]
+  (if (= uri "/__source_changed")
+      (source-changed-handler request dirs)
+      (handler request))))
 
 (defn- wrap-with-script [handler script]
   (fn [request]
@@ -91,8 +72,6 @@
   ([handler]
      (wrap-refresh handler ["src" "resources"]))
   ([handler dirs]
-     (watch-dirs! dirs)
-     (wrap-params
-      (routes
-       source-changed-route
-       (wrap-with-script handler refresh-script)))))
+   (fn [request]
+     (let [wrapped (-> handler (intercept-source-changed-route dirs) (wrap-with-script refresh-script))]
+       (wrapped request)))))