Implement first archiver; pointless

lib/behaviors/archiver.ex

@@ -7,7 +7,7 @@ end
 
 defmodule Archiver do
   @doc """
-  Insertsd files into an archive
+  Inserts files into an archive
   """
-  @callback archive(String.t, [String.t]) :: {:ok, binary} | {:error, String.t}
+  @callback archive([String.t] | binary) :: {:ok, binary} | {:error, String.t}
 end

lib/zlb.ex

@@ -1,6 +1,7 @@
 defmodule Zlb do
   @behaviour Identification
   @behaviour Extractor
+  @behaviour Archiver
 
   @magic_number <<0x5A, 0x4C, 0x42, 0x00>>
 
@@ -36,4 +37,28 @@ defmodule Zlb do
           end).()
     end
   end
+
+  @doc """
+  This puts files into the Sting "zlb" format
+  Passing multiple files will combine them, but this format contains no directory so it should only be used when such result is acceptable.
+  For the above reason, this method will not handle directories.
+  """
+  @impl Archiver
+  def archive(file_names) when is_list(file_names) do
+    if Enum.all?(file_names, fn f -> File.exists?(f) and not File.dir?(f) end) do
+      file_names
+      |> Enum.map(&File.stream!/1)
+      |> Enum.join()
+      |> archive()
+    else
+      file_no_existe = Enum.find(file_names, fn f -> not File.exists?(f) end)
+      {:error, if(file_no_existe == nil, do: "Cannot handle directories", else: "#{file_no_existe} doesn't exist")}
+
+    end
+  end
+
+  @impl Archiver
+  def archive(file_data) when is_binary(file_data) do
+    {:ok, @magic_number <> <<byte_size(file_data)::little-integer-size(32)>> <> :zlib.compress(file_data) }
+  end
 end