new: output-template interpolates output values into config file

pkgs/output-template/output-template.fnl

@@ -0,0 +1,22 @@
+(local svc (require :anoia.svc))
+
+(fn substitute [text service opening closing]
+  (let [delim (.. opening "(.-)" closing)
+        myenv {
+               : string
+               :secret (fn [x] (service:output x))
+               :lua_quote #(string.format "%q" %1)
+               }]
+    (string.gsub text delim
+                 (fn [x]
+                   (assert ((load (.. "return " x) x :t myenv))
+                           (string.format "missing value for %q" x))))))
+
+(fn run []
+  (let [[service-dir opening closing] arg
+        service (assert (svc.open service-dir))
+        out  (substitute (: (io.input) :read "*a") service opening closing)]
+    (io.write out)))
+
+
+{ : run }