custom storage module for OAuth2Ex in Elixir

repo_storage.ex

defmodule StorageUpload.RepoStorage do
  @moduledoc """
  This is a storage module built based on OAuth2Ex's file storage.

  The only difference here is that the token is fetched from the Repo
  in the app and stored in the Repo's data store.
  """

  alias StorageUpload.Repo
  alias StorageUpload.Setting

  defstruct module: __MODULE__, key: nil

  def save(token, storage) do
    map = Map.from_struct(token) |> Map.delete(:storage)
    if has_existing_token?(storage) do
      token = Repo.get_by!(Setting, key: storage.key)
      update_token(token, map, storage)
    else
      add_token(map, storage)
    end
  end

  def load(storage) do
    token = Repo.get_by!(Setting, key: storage.key).val
    |> OAuth2Ex.Token.merge_into_struct(%OAuth2Ex.Token{storage: storage})
  end

  def has_existing_token?(storage) do
    if token = Repo.get_by!(Setting, key: storage.key) do
      :true
    else
      :false
    end
  end

  def update_token(token, token_map, storage) do
    IO.inspect token_map
    IO.inspect token
    new_token = %{token | val: token_map}
    case Repo.update(new_token) do
      {:ok, token} ->
        token
      {_, error} ->
        raise %OAuth2Ex.Error{message: "Could not update token in Repo! Error: #{error}."}
    end
  end

  def add_token(token_map, storage) do
    changeset = %Setting{key: storage.key, val: token_map}
    case Repo.insert(changeset) do
      {:ok, token} ->
        token
      {_, error} ->
        raise %OAuth2Ex.Error{message: "Could not add token to Repo! Error: #{error}."}
    end
  end

end

usage.ex

config = OAuth2Ex.config(
      id:            System.get_env("GOOGLE_CLIENT_ID"),
      secret:        System.get_env("GOOGLE_CLIENT_SECRET"),
      authorize_url: "https://accounts.google.com/o/oauth2/auth",
      token_url:     "https://accounts.google.com/o/oauth2/token",
      scope:         "https://www.googleapis.com/auth/youtube",
      callback_url:  System.get_env("GOOGLE_CALLBACK"),
      token_store:   %StorageUpload.RepoStorage{key: "google_api_token"}
    )
    
# See: https://github.com/parroty/oauth2ex
# on how to use OAuth2Ex. It will work as it did with the default storage module, if you have your Repo, Model, setup.