Background thread to remove expired multipart tempfiles

@@ -2,13 +2,41 @@
   (:require [clojure.java.io :as io])
   (:import java.io.File))
 
-(defn temp-file-store
-  "Stores multipart file parameters as a temporary file."
-  [item]
+(defmacro ^{:private true} do-every [delay & body]
+  `(future
+     (while true
+       (Thread/sleep (* ~delay 1000))
+       (try ~@body
+            (catch Exception ex#)))))
+
+(defn- expired? [file expiry-time]
+  (< (.lastModified file)
+     (- (System/currentTimeMillis)
+        (* expiry-time 1000))))
+
+(defn- remove-old-files [file-set expiry-time]
+  (doseq [file @file-set]
+    (when (expired? file expiry-time)
+      (.delete file)
+      (swap! file-set disj file))))
+
+(defn- make-temp-file [file-set]
   (let [temp-file (File/createTempFile "ring-multipart-" nil)]
+    (swap! file-set conj temp-file)
     (.deleteOnExit temp-file)
-    (with-open [out (io/output-stream temp-file)]
-      (io/copy (:stream item) out))
-    (-> (select-keys item [:filename :content-type])
-        (assoc :tempfile temp-file
-               :size (.length temp-file)))))
+    temp-file))
+
+(defn temp-file-store
+  "Stores multipart file parameters as a temporary file."
+  ([] (temp-file-store {:expire-in 3600}))
+  ([{:keys [expires-in]}]
+     (fn [item]
+       (let [file-set  (atom #{})
+             temp-file (make-temp-file file-set)]
+         (io/copy (:stream item) temp-file)
+         (when expires-in
+           (do-every expires-in
+             (remove-old-files file-set expires-in)))
+         (-> (select-keys item [:filename :content-type])
+             (assoc :tempfile temp-file
+                    :size (.length temp-file)))))))

@@ -4,12 +4,24 @@
         ring.middleware.multipart-params.temp-file))
 
 (deftest test-temp-file-store
-  (let [result (temp-file-store
+  (let [store  (temp-file-store)
+        result (store
                 {:filename "foo.txt"
                  :content-type "text/plain"
                  :stream (string-input-stream "foo")})]
     (is (= (:filename result) "foo.txt"))
     (is (= (:content-type result) "text/plain"))
     (is (= (:size result) 3))
     (is (instance? java.io.File (:tempfile result)))
+    (is (.exists (:tempfile result)))
     (is (= (slurp (:tempfile result)) "foo"))))
+
+(deftest test-temp-file-expiry
+  (let [store  (temp-file-store {:expires-in 2})
+        result (store
+                {:filename "foo.txt"
+                 :content-type "text/plain"
+                 :stream (string-input-stream "foo")})]
+    (is (.exists (:tempfile result)))
+    (Thread/sleep 2500)
+    (is (not (.exists (:tempfile result))))))