defmodule Ueberauth.Strategy.IcyNet do
  @moduledoc """
  Provides an Ueberauth strategy for authenticating with Icy Network.

  ### Setup

  Obtain a Client ID and Secret from Icy Network.

  Include the provider in your configuration for Ueberauth

      config :ueberauth, Ueberauth,
        providers: [
          icynet: { Ueberauth.Strategy.IcyNet, [] }
        ]

  Then include the configuration for icynet.

      config :ueberauth, Ueberauth.Strategy.IcyNet.OAuth,
        client_id: System.get_env("ICYNET_CLIENT_ID"),
        client_secret: System.get_env("ICYNET_CLIENT_SECRET")

  If you haven't already, create a pipeline and setup routes for your callback handler

      pipeline :auth do
        Ueberauth.plug "/auth"
      end

      scope "/auth" do
        pipe_through [:browser, :auth]

        get "/:provider/callback", AuthController, :callback
      end


  Create an endpoint for the callback where you will handle the `Ueberauth.Auth` struct

      defmodule MyApp.AuthController do
        use MyApp.Web, :controller

        def callback_phase(%{ assigns: %{ ueberauth_failure: fails } } = conn, _params) do
          # do things with the failure
        end

        def callback_phase(%{ assigns: %{ ueberauth_auth: auth } } = conn, params) do
          # do things with the auth
        end
      end

  You can edit the behaviour of the Strategy by including some options when you register your provider.

  To set the `uid_field`

      config :ueberauth, Ueberauth,
        providers: [
          icynet: { Ueberauth.Strategy.IcyNet, [uid_field: :email] }
        ]

  Default is `:id`

  To set the default 'scopes' (permissions):

      config :ueberauth, Ueberauth,
        providers: [
          icynet: { Ueberauth.Strategy.IcyNet, [default_scope: "email,image"] }
        ]

  Default is empty ("") which "Grants read-only access to public information (includes public user profile info, public repository info, and gists)"
  """
  use Ueberauth.Strategy,
    uid_field: :id,
    default_scope: "",
    oauth2_module: Ueberauth.Strategy.IcyNet.OAuth

  alias Ueberauth.Auth.Info
  alias Ueberauth.Auth.Credentials
  alias Ueberauth.Auth.Extra

  @doc """
  Handles the initial redirect to the icynet authentication page.

  To customize the scope (permissions) that are requested by icynet include them as part of your url:

      "/auth/icynet?scope=email,image,privilege"

  You can also include a `state` param that icynet will return to you.
  """
  def handle_request!(conn) do
    scopes = conn.params["scope"] || option(conn, :default_scope)

    opts = [redirect_uri: callback_url(conn), scope: scopes]

    opts =
      if conn.params["state"], do: Keyword.put(opts, :state, conn.params["state"]), else: opts

    module = option(conn, :oauth2_module)
    redirect!(conn, apply(module, :authorize_url!, [opts]))
  end

  @doc """
  Handles the callback from IcyNet. When there is a failure from IcyNet the failure is included in the
  `ueberauth_failure` struct. Otherwise the information returned from IcyNet is returned in the `Ueberauth.Auth` struct.
  """
  def handle_callback!(%Plug.Conn{params: %{"code" => code}} = conn) do
    module = option(conn, :oauth2_module)
    token = apply(module, :get_token!, [[code: code]])

    if token.access_token == nil do
      set_errors!(conn, [
        error(token.other_params["error"], token.other_params["error_description"])
      ])
    else
      fetch_user(conn, token)
    end
  end

  @doc false
  def handle_callback!(conn) do
    set_errors!(conn, [error("missing_code", "No code received")])
  end

  @doc """
  Cleans up the private area of the connection used for passing the raw IcyNet response around during the callback.
  """
  def handle_cleanup!(conn) do
    conn
    |> put_private(:icynet_user, nil)
    |> put_private(:icynet_token, nil)
  end

  @doc """
  Fetches the uid field from the IcyNet response. This defaults to the option `uid_field` which in-turn defaults to `id`
  """
  def uid(conn) do
    uid_field =
      conn
      |> option(:uid_field)
      |> to_string

    conn.private.icynet_user[uid_field]
  end

  @doc """
  Includes the credentials from the IcyNet response.
  """
  def credentials(conn) do
    token = conn.private.icynet_token

    %Credentials{
      token: token.access_token,
      refresh_token: token.refresh_token,
      expires_at: nil,
      token_type: token.token_type,
      expires: false
    }
  end

  @doc """
  Fetches the fields to populate the info section of the `Ueberauth.Auth` struct.
  """
  def info(conn) do
    user = conn.private.icynet_user

    %Info{
      name: user["display_name"],
      nickname: user["username"],
      email: user["email"],
      image: user["image"],
    }
  end

  @doc """
  Stores the raw information (including the token) obtained from the IcyNet callback.
  """
  def extra(conn) do
    %Extra{
      raw_info: %{
        token: conn.private.icynet_token,
        user: conn.private.icynet_user
      }
    }
  end

  defp fetch_user(conn, token) do
    conn = put_private(conn, :icynet_token, token)
    case Ueberauth.Strategy.IcyNet.OAuth.get(token, "/oauth2/user") do
      {:ok, %OAuth2.Response{status_code: 401, body: _body}} ->
        set_errors!(conn, [error("token", "unauthorized")])

      {:ok, %OAuth2.Response{status_code: status_code, body: user}}
      when status_code in 200..399 ->
        put_private(conn, :icynet_user, user)

      {:error, %OAuth2.Error{reason: reason}} ->
        set_errors!(conn, [error("OAuth2", reason)])
    end
  end

  defp option(conn, key) do
    Keyword.get(options(conn), key, Keyword.get(default_options(), key))
  end
end