defmodule ExTus.Storage do
  @callback initiate_file(String.t) :: Tuple.type
  @callback put_file(map, String.t) :: Tuple.type
  @callback append_data(map, iodata) :: Tuple.type
  @callback complete_file(map) :: Tuple.type
  @callback abort_upload(map) :: Tuple.type
  @callback url(String.t) :: String.t
  @callback delete(String.t) :: Tuple.typ
  
  defmacro __using__(_) do
		quote do
			@behaviour ExTus.Storage
			
			def url(nil), do: nil
			def url(path), do: path
			def storage_dir(), do: ""
			def filename(file), do: file
			
			defoverridable [url: 1, storage_dir: 0, filename: 1]
		end
  end
	
	defmacro extends(module) do
	    module = Macro.expand(module, __CALLER__)
	    functions = module.__info__(:functions)
	    signatures = Enum.map functions, fn { name, arity } ->
	      args = if arity == 0 do
	               []
	             else
	               Enum.map 1 .. arity, fn(i) ->
	                 { String.to_atom(<< ?x, ?A + i - 1 >>), [], nil }
	               end
	             end
	      { name, [], args }
	    end
	    quote do
	      defdelegate unquote(signatures), to: unquote(module)
	      defoverridable unquote(functions)
	    end
	  end
end