1 files changed, 77 insertions, 0 deletions
diff --git a/lib/config.ex b/lib/config.ex
new file mode 100644
index 0000000..8778e5b
--- /dev/null
+++ b/lib/config.ex
@@ -0,0 +1,77 @@
+defmodule Mailchimp.Config do
+  use GenServer
+
+  defstruct api_key: nil, api_version: "3.0"
+
+  require Logger
+
+  # Public API
+
+  def start_link(%__MODULE__{}=config) do
+    Agent.start_link(fn -> config end, name: __MODULE__)
+  end
+
+  def start_link do
+    config = %__MODULE__{
+      api_key: get_api_key_from_config,
+      api_version: get_api_version_from_config
+    }
+
+    Agent.start_link(fn -> config end, name: __MODULE__)
+  end
+
+  def root_endpoint do
+    Agent.get(__MODULE__, fn %{api_key: api_key, api_version: api_version} ->
+      {:ok, shard} = get_shard(api_key)
+      "https://#{shard}.api.mailchimp.com/#{api_version}/"
+    end)
+  end
+
+  def api_key do
+    Agent.get(__MODULE__, fn %{api_key: api_key} -> api_key end)
+  end
+
+  def api_version do
+    Agent.get(__MODULE__, fn %{api_version: api_version} -> api_version end)
+  end
+
+  def update(config) when is_list(config) do
+    Agent.update(__MODULE__, fn current_config ->
+      Enum.reduce(config, current_config, fn({k,v}, acc) -> Map.put(acc, k, v) end)
+    end)
+  end
+
+  # Private methods
+
+  defp sanitize_api_key({:system, env_var}) do
+    sanitize_api_key System.get_env(env_var)
+  end
+
+  defp sanitize_api_key(api_key) do
+    api_key
+  end
+
+  defp get_api_key_from_config do
+    sanitize_api_key(Application.get_env(:mailchimp, :apikey)) || sanitize_api_key(Application.get_env(:mailchimp, :api_key))
+  end
+
+  defp get_api_version_from_config do
+    Application.get_env(:mailchimp, :api_version) || "3.0"
+  end
+
+  defp get_shard(api_key) do
+    shard = api_key
+            |> String.split(~r{-})
+            |> List.last
+
+    case shard do
+      nil ->
+        Logger.error "[mailchimp] This doesn't look like an API Key: #{api_key}"
+        Logger.error "[mailchimp] The API Key should have both a key and a server name, separated by a dash, like this: abcdefg8abcdefg6abcdefg4-us1"
+        :error
+
+      _ ->
+        {:ok, shard}
+    end
+  end
+end