"It's a good sort of brake but it doesn't work yet"

Trying to list resource names from jar file...

project.clj

@@ -1,6 +1,8 @@
 (defproject mw-ui "0.1.6-SNAPSHOT"
   :description "Web-based user interface for MicroWorld"
   :dependencies [[org.clojure/clojure "1.10.3"]
+                 [clj-time "0.15.2"] ;; this is a hack. Something in libnoir requires 
+                                     ;; JodaTime, but doesn't request it. clj-time does.
                  [mw-engine "0.1.6-SNAPSHOT"]
                  [mw-parser "0.1.6-SNAPSHOT"]
                  [lib-noir "0.9.9"]

src/mw_ui/routes/home.clj

@@ -1,7 +1,7 @@
 (ns ^{:doc "Routes which serve the main pages of the application."
       :author "Simon Brooke"}
   mw-ui.routes.home
-  (:require [clojure.java/io :refer [file]]
+  (:require [clojure.java.io :refer [file]]
             [clojure.walk :refer [keywordize-keys]]
             [compojure.core :refer [defroutes GET POST]]
             [hiccup.core :refer [html]]

src/mw_ui/routes/params.clj

@@ -35,9 +35,9 @@
 
 (defn- send-params []
   {:title "Choose your world"
-   :heightmaps (util/list-resources "/img/heightmaps" #"([0-9a-z-_]+).png")
+   :heightmaps (util/list-resources "/img/heightmaps" #"/?([0-9a-z-_]+).png")
    :pause (or (session/get :pause) 5)
-   :rulesets (util/list-resources "/rulesets" #"([0-9a-z-_]+).txt")
+   :rulesets (util/list-resources "/rulesets" #"/?([0-9a-z-_]+).txt")
    })
 
 

src/mw_ui/util.clj

@@ -1,10 +1,12 @@
 (ns ^{:doc "Utility functions used by other namespaces in this package."
       :author "Simon Brooke"}
-  mw-ui.util
+ mw-ui.util
   (:require [clojure.java.io :refer [file]]
+            [clojure.string :refer [starts-with?]]
+            [markdown.core :as md]
             [noir.io :as io]
             [noir.session :as session]
-            [markdown.core :as md]))
+            [taoensso.timbre :as timbre]))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;
@@ -29,25 +31,56 @@
 ;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+(def running-from-filesystem (atom true))
+
+(def compile-time-resources
+  "The resources which were visible at compile time. If we are running from
+   a JAR file, it is highly likely that these are all the resources available
+   at run time."
+  (let [n (count (io/resource-path))]
+    (remove nil?
+            (map #(let [s (str %)]
+                    (when (> (count s) n)
+                      (subs s 56)))
+                 (file-seq (file (io/resource-path)))))))
+
 
 (defn md->html
   "reads a markdown file from public/md and returns an HTML string"
   [filename]
   (->>
-    (io/slurp-resource filename)
-    (md/md-to-html-string)))
+   (io/slurp-resource filename)
+   (md/md-to-html-string)))
+
+
+(defn cache-seq-match
+  "Do the same processing that list-resources does on names fetched from
+   the file system, except on the resource list cached at compile time."
+  [path pattern]
+  (let [n (count path)]
+    (remove nil?
+            (map #(when (> (count %) n)
+                    (let [name (subs % n)]
+                      (first (rest (re-matches pattern name)))))
+                 (filter #(starts-with? % path) 
+                         compile-time-resources)))))
 
-;; TODO: The reason we can't list files in a jar file, and what to do about it,
-;; is here. Too tired to fix this tonight.
-;; https://stackoverflow.com/questions/46488466/clojure-list-subfolders-in-resources-in-uberjar
 
 (defn list-resources
   "List resource files matching `pattern` in `directory`."
   [directory pattern]
   (let
-    [path (str (io/resource-path) directory)]
+   [path (str (io/resource-path) directory)]
     (session/put! :list-resources-path path)
-    (sort
-      (remove nil?
-            (map #(first (rest (re-matches pattern (.getName %))))
-                 (file-seq (file path)))))))
+    (try
+      (sort
+       (remove nil?
+               (if @running-from-filesystem
+                 (map #(first (rest (re-matches pattern (.getName %))))
+                      (file-seq (file path)))
+                 (cache-seq-match directory pattern))))
+      (catch Exception any
+        (timbre/log (str "Not running from filesystem?"
+                         (.getName (.getClass any))))
+        (reset! running-from-filesystem false)
+        (cache-seq-match directory pattern)))))