diff --git a/src/aidbox_sdk/core.clj b/src/aidbox_sdk/core.clj
index f9f0aa5..8766088 100644
--- a/src/aidbox_sdk/core.clj
+++ b/src/aidbox_sdk/core.clj
@@ -1,9 +1,33 @@
 (ns aidbox-sdk.core
   (:gen-class)
   (:require
-   [clojure.tools.cli :as cli]
+   [clojure.java.io :as io]
    [aidbox-sdk.generator :as generator]))
 
+(defn url
+  "Safe version of as-url function"
+  [s]
+  (try
+    (io/as-url s)
+    (catch java.net.MalformedURLException _ nil)
+    (catch java.net.URISyntaxException _ nil)))
+
+(defn resource [path]
+  (or (url path)
+      (io/as-file path)))
+
 (defn -main [& args]
-  (let [[source target] (cli/parse-opts args nil)]
-    (generator/build-all! nil)))
+  (let [[input output] args]
+    (cond
+      (nil? input)
+      (binding [*out* *err*]
+        (println "Error: please provide an input argument"))
+
+      (nil? output)
+      (binding [*out* *err*]
+        (println "Error: please provide an output argument"))
+
+      :else
+      (generator/build-all!
+       (resource input)
+       (io/as-file output)))))
diff --git a/src/aidbox_sdk/generator.clj b/src/aidbox_sdk/generator.clj
index 8feb51a..188a7b1 100644
--- a/src/aidbox_sdk/generator.clj
+++ b/src/aidbox_sdk/generator.clj
@@ -693,7 +693,6 @@
 
 (defn get-directory-files [path]
   (->> path
-       io/file
        file-seq
        (remove #(.isDirectory %))))
 
@@ -722,21 +721,24 @@
        (map (fn [[_url same-url-schemas]]
               (apply merge same-url-schemas)))))
 
-(defn retrieve-schemas' [source]
-  (->>
-   (fetch-packages source)
-   (map parse-ndjson-gz)
-   (flatten)
-   (remove #(nil? (:package-meta %)))
-   (map (fn [schema]
-          (assoc schema :package (get-in schema [:package-meta :name]))))
-   (merge-duplicates)))
-
-(defn retrieve-search-params [source])
-
-(defn build-all! [source-dir target-dir]
-  (let [search-parameters-dir (io/file target-dir "search")
-        all-schemas           (retrieve-schemas' source-dir)
+(defmulti retrieve-schemas class)
+
+(defmethod retrieve-schemas java.io.File
+  [source]
+  (->> (fetch-packages source)
+       (map parse-ndjson-gz)
+       (flatten)
+       (remove #(nil? (:package-meta %)))
+       (map (fn [schema]
+              (assoc schema :package (get-in schema [:package-meta :name]))))
+       (merge-duplicates)))
+
+(defmethod retrieve-schemas java.net.URL
+  [source] (do "something"))
+
+(defn build-all! [input output]
+  (let [search-parameters-dir (io/file output "search")
+        all-schemas           (retrieve-schemas input)
         ;; search-params-schemas (retrieve-search-params source-dir)
         search-params-schemas all-schemas
         constraints           (->> all-schemas
@@ -744,7 +746,7 @@
                                              (constraint? %)
                                              (not (from-extension? %)))))]
 
-    (prepare-target-directory! target-dir)
+    (prepare-target-directory! output)
 
     ;; create base namespace (all FHIR datatypes) file
     (->> all-schemas
@@ -753,7 +755,7 @@
          (sort-by :base)
          (generate-base-namespace)
          (save-to-file!
-          (io/file target-dir "Base.cs")))
+          (io/file output "Base.cs")))
 
     ;; create spezialization files
     (doseq [item (->> all-schemas
@@ -766,7 +768,7 @@
                                      (update schema :base #(str % ", IResource"))))))))]
 
       (save-to-file!
-       (io/file target-dir (package->directory (:package item)) (str (:name item) ".cs"))
+       (io/file output (package->directory (:package item)) (str (:name item) ".cs"))
        (generate-resource-namespace item)))
 
     ;; create resource map file
@@ -784,7 +786,7 @@
                 :name (->pascal-case (url->resource-type (:url %)))))
          (generate-utils-namespace)
          (save-to-file!
-          (io/file target-dir "ResourceMap.cs")))
+          (io/file output "ResourceMap.cs")))
 
     ;; create search parameters classes
     (doseq [item (search-parameters-classes search-params-schemas
@@ -810,8 +812,8 @@
                                          (assoc schema
                                                 :url name'))})))]
       (save-to-file!
-       (io/file target-dir (package->directory (:package schema)) (str (->pascal-case (url->resource-type name)) ".cs"))
+       (io/file output (package->directory (:package schema)) (str (->pascal-case (url->resource-type name)) ".cs"))
        file-content))
 
     (doseq [file dotnettpl/files]
-      (spit (io/file target-dir (:name file)) (:content file)))))
+      (spit (io/file output (:name file)) (:content file)))))