🏗️ Scan the classpath for resources with content-hashed filenames

Why:
- The UI must use public assets such as images, but their filenames are
  content-hashed to improve caching, so the UI doesn't know their exact
  filenames.
- The current solution scans the classpath for public assets on startup.
  This will be very fast at runtime, because it's just a hashmap lookup.
  But the disadvantage is that during development new and updated assets
  are not included automatically. Hopefully the assets are changed
  seldom enough for it to not become a problem, or the solution needs to
  be made more complicated.

project.clj

@@ -37,6 +37,7 @@
                  [org.flywaydb/flyway-core "10.9.1"]
                  [org.flywaydb/flyway-database-postgresql "10.9.1"]
                  [org.postgresql/postgresql "42.7.2"]
+                 [org.reflections/reflections "0.10.2"]
                  [prismatic/schema "1.4.1"]
                  [ring "1.11.0"]
                  [ring-logger "1.1.1"]

src/territory_bro/ui/html.clj

@@ -7,7 +7,9 @@
             [hiccup.util :as hiccup.util]
             [reitit.core :as reitit]
             [ring.util.http-response :as http-response]
-            [ring.util.response :as response]))
+            [ring.util.response :as response])
+  (:import (org.reflections Reflections)
+           (org.reflections.scanners Scanners)))
 
 (alter-var-root #'hiccup.util/*html-mode* (constantly :html)) ; change default from :xhtml to :html
 
@@ -76,3 +78,12 @@
       (assert (some? page-path))
       (binding [*page-path* page-path]
         (handler request)))))
+
+(def public-resources
+  (let [reflections (Reflections. "public" (into-array [Scanners/Resources]))]
+    (->> (.getResources reflections #".*")
+         (map (fn [resource-path]
+                (let [url (str/replace resource-path #"^public/" "/") ; resource path -> absolute URL
+                      wildcard-url (str/replace url #"-[0-9a-f]{8}\." "-*.")] ; mapping for content-hashed filenames
+                  [wildcard-url url])))
+         (into {}))))

territory-bro.iml

@@ -182,7 +182,7 @@
     <orderEntry type="library" name="Leiningen: org.eclipse.jetty/jetty-xml:11.0.18" level="project" />
     <orderEntry type="library" name="Leiningen: org.flywaydb/flyway-core:10.9.1" level="project" />
     <orderEntry type="library" name="Leiningen: org.flywaydb/flyway-database-postgresql:10.9.1" level="project" />
-    <orderEntry type="library" name="Leiningen: org.javassist/javassist:3.18.1-GA" level="project" />
+    <orderEntry type="library" name="Leiningen: org.javassist/javassist:3.28.0-GA" level="project" />
     <orderEntry type="library" name="Leiningen: org.jetbrains.kotlin/kotlin-stdlib-common:1.9.0" level="project" />
     <orderEntry type="library" name="Leiningen: org.jetbrains.kotlin/kotlin-stdlib-jdk7:1.9.23" level="project" />
     <orderEntry type="library" name="Leiningen: org.jetbrains.kotlin/kotlin-stdlib-jdk8:1.9.23" level="project" />
@@ -193,6 +193,7 @@
     <orderEntry type="library" name="Leiningen: org.nrepl/incomplete:0.1.0" level="project" />
     <orderEntry type="library" name="Leiningen: org.objenesis/objenesis:3.3" level="project" />
     <orderEntry type="library" name="Leiningen: org.postgresql/postgresql:42.7.2" level="project" />
+    <orderEntry type="library" name="Leiningen: org.reflections/reflections:0.10.2" level="project" />
     <orderEntry type="library" name="Leiningen: org.ring-clojure/ring-jakarta-servlet:1.11.0" level="project" />
     <orderEntry type="library" name="Leiningen: org.ring-clojure/ring-websocket-protocols:1.11.0" level="project" />
     <orderEntry type="library" name="Leiningen: org.slf4j/slf4j-api:2.0.12" level="project" />

test/territory_bro/ui/html_test.clj

@@ -3,7 +3,8 @@
 ;; The license text is at http://www.apache.org/licenses/LICENSE-2.0
 
 (ns territory-bro.ui.html-test
-  (:require [clojure.test :refer :all]
+  (:require [clojure.java.io :as io]
+            [clojure.test :refer :all]
             [hiccup2.core :as h]
             [territory-bro.ui.html :as html]))
 
@@ -77,3 +78,12 @@
 
   (testing "works for raw hiccup strings"
     (is (= "stuff" (html/visible-text (h/raw "<p>stuff</p>"))))))
+
+(deftest public-resources-test
+  (testing "regular files are mapped as-is"
+    (is (= "/index.html" (get html/public-resources "/index.html"))))
+
+  (testing "content-hashed files are mapped using a wildcard"
+    (let [path (get html/public-resources "/assets/crop-mark-*.svg")]
+      (is (some? path))
+      (is (some? (io/resource (str "public" path)))))))