Behaviour for anything that can hand an access token to Magpie.Client.

A client stores a provider as a {module, arg} pair — the arg is opaque to Magpie and is passed back to every callback, so it can be a token string, a GenServer name, a keyword list, an account id, whatever your implementation needs:

Magpie.Client.new(token_provider: {MyApp.DropboxTokens, "user-42"})

Magpie ships two implementations: Magpie.Auth.StaticToken (used behind the scenes by Magpie.Client.new("ACCESS_TOKEN")) and Magpie.Auth.TokenServer (refreshes automatically).

Example

defmodule MyApp.DropboxTokens do
  @behaviour Magpie.Auth.TokenProvider

  @impl true
  def fetch_token(user_id) do
    {:ok, MyApp.Repo.get!(MyApp.DropboxAccount, user_id).access_token}
  end

  @impl true
  def refresh_token(user_id) do
    account = MyApp.Repo.get!(MyApp.DropboxAccount, user_id)

    with {:ok, token} <- Magpie.Auth.refresh(app_key(), account.refresh_token, app_secret: app_secret()) do
      MyApp.Accounts.store_token!(account, token)
      {:ok, token.access_token}
    end
  end
end