Add Bumblebee.cache_dir/0 for discovering cache location (#220)

lib/bumblebee.ex

@@ -932,4 +932,16 @@ defmodule Bumblebee do
           "expected repository to be either {:hf, repository_id}, {:hf, repository_id, options}" <>
             " or {:local, directory}, got: #{inspect(other)}"
   end
+
+  @doc """
+  Returns the directory where downloaded files are stored.
+  """
+  @spec cache_dir() :: String.t()
+  def cache_dir() do
+    if dir = System.get_env("BUMBLEBEE_CACHE_DIR") do
+      Path.expand(dir)
+    else
+      :filename.basedir(:user_cache, "bumblebee")
+    end
+  end
 end

lib/bumblebee/huggingface/hub.ex

@@ -36,7 +36,7 @@ defmodule Bumblebee.HuggingFace.Hub do
   """
   @spec cached_download(String.t(), keyword()) :: {:ok, String.t()} | {:error, String.t()}
   def cached_download(url, opts \\ []) do
-    cache_dir = opts[:cache_dir] || bumblebee_cache_dir()
+    cache_dir = opts[:cache_dir] || Bumblebee.cache_dir()
     offline = opts[:offline] || bumblebee_offline?()
     auth_token = opts[:auth_token]
 
@@ -154,14 +154,6 @@ defmodule Bumblebee.HuggingFace.Hub do
     File.write(path, json)
   end
 
-  defp bumblebee_cache_dir() do
-    if dir = System.get_env("BUMBLEBEE_CACHE_DIR") do
-      Path.expand(dir)
-    else
-      :filename.basedir(:user_cache, "bumblebee")
-    end
-  end
-
   defp bumblebee_offline?() do
     System.get_env("BUMBLEBEE_OFFLINE") in ~w(1 true)
   end