Added typemap and type sanitizing

lib/ffi.ex

@@ -1,14 +1,34 @@
 defmodule FFI do
   @on_load :init
 
+  @typemap %{
+    void: 0,
+    string: 1,
+    int: 2
+  }
+
   def init do
-    :erlang.load_nif("./ffi_nif", 0)
+    :ok = :erlang.load_nif("./ffi_nif", 0)
   end
 
-  def call({library, name, arguments, return_type}, params),
-    do: nif_call(library, name, arguments, return_type, params)
+  def call({library, function, arguments, return_type}, values) do
+    nif_call(String.to_atom(library),
+              function,
+              Enum.map(arguments, &map_type/1),
+              map_type(return_type),
+              clean_values(values))
+  end
 
-  def nif_call(library, name, arguments, return_type, params) do
+  def nif_call(library, function, arguments, return_type, values) do
     :badarg
   end
+
+  defp map_type(type), do: @typemap[type]
+
+  defp clean_values(values) do
+    Enum.map values, fn
+      str when is_bitstring(str) -> to_char_list(str)
+      other -> other
+    end
+  end
 end