Add Discogs module

lib/discogs/api.ex

@@ -0,0 +1,45 @@
+defmodule Discogs.API do
+  @moduledoc """
+  Interface to the Discogs API.
+  """
+
+  require Logger
+
+  def get_artist(id, config) do
+    config
+    |> new_request()
+    |> Req.merge(url: "/artists/#{id}")
+    |> get_request()
+  end
+
+  defp new_request(config) do
+    Req.new(
+      base_url: "https://api.discogs.com",
+      max_retries: 1,
+      user_agent: config.user_agent,
+      auth: "Discogs token=#{config.personal_access_token}"
+    )
+    |> Req.Request.merge_options(config.req_options)
+    |> Req.Request.append_request_steps(log_attempt: &log_attempt/1)
+  end
+
+  defp get_request(request) do
+    case Req.get(request) do
+      {:ok, response} when response.status == 200 ->
+        {:ok, response.body}
+
+      # all non-success responses can be treated as errors
+      {:ok, response} ->
+        {:error, response.body}
+
+      error ->
+        error
+    end
+  end
+
+  defp log_attempt(request) do
+    url = URI.to_string(request.url)
+    Logger.debug("Fetching data from #{url}")
+    request
+  end
+end

lib/discogs/config.ex

@@ -0,0 +1,39 @@
+defmodule Discogs.Config do
+  @type t :: %__MODULE__{
+          personal_access_token: String.t(),
+          user_agent: String.t(),
+          req_options: Keyword.t()
+        }
+
+  @enforce_keys [:personal_access_token]
+  defstruct personal_access_token: "",
+            user_agent: "change me",
+            req_options: []
+
+  @schema NimbleOptions.new!(
+            personal_access_token: [
+              type: :string,
+              required: true
+            ],
+            user_agent: [
+              type: :string,
+              required: false,
+              default: "change me"
+            ],
+            req_options: [
+              type: :keyword_list,
+              required: false,
+              default: []
+            ]
+          )
+
+  @doc NimbleOptions.docs(@schema)
+  @spec resolve(Application.app()) :: t | no_return
+  def resolve(otp_app) do
+    app_config =
+      Application.get_env(otp_app, Discogs)
+      |> NimbleOptions.validate!(@schema)
+
+    struct(__MODULE__, app_config)
+  end
+end