defmodule ShopifexWeb.AuthController do
  @moduledoc """
  You can use this module inside of another controller to handle initial iFrame load and shop installation

  Example:

  ```elixir
  defmodule MyAppWeb.AuthController do
    use MyAppWeb, :controller
    use ShopifexWeb.AuthController

    # Thats it! Validation, installation are now handled for you :)
  end
  ```
  """
  @type shop :: %{access_token: String.t(), scope: String.t(), url: String.t()}

  @doc """
  An optional callback called after the installation is completed, the shop is
  persisted in the database and webhooks are registered. By default, this function
  redirects the user to the app within their Shopify admin panel.

  ## Example

      @impl true
      def after_install(conn, shop) do
        # send yourself an e-mail about shop installation

        # follow default behaviour.
        super(conn, shop)
      end
  """
  @callback after_install(Plug.Conn.t(), shop()) :: Plug.Conn.t()

  @doc """
  An optional callback which is called after the shop data has been retrieved from
  Shopify API. This function should persist the shop data and return a shop record.

  ## Example

      @impl true
      def insert_shop(conn) do
        # make sure there is only one store in the database because we don't have
        # a unique index on the url column for some reason.

        case Shopifex.Shops.get_shop_by_url(shop_url) do
          nil -> super(shop)
          shop -> shop
        end
      end
  """
  @callback insert_shop(shop()) :: shop()

  @optional_callbacks after_install: 2, insert_shop: 1

  defmacro __using__(_opts) do
    quote do
      @behaviour ShopifexWeb.AuthController

      require Logger

      def auth(conn, _) do
        path_prefix = Application.get_env(:shopifex, :path_prefix, "")

        conn
        |> redirect(to: path_prefix <> "/?token=" <> Guardian.Plug.current_token(conn))
      end

      def initialize_installation(conn, %{"shop" => shop_url}) do
        if Regex.match?(~r/^.*\.myshopify\.com/, shop_url) do
          # check if store is in the system already:
          case Shopifex.Shops.get_shop_by_url(shop_url) do
            nil ->
              Logger.info("Initiating shop installation for #{shop_url}")

              install_url =
                "https://#{shop_url}/admin/oauth/authorize?client_id=#{
                  Application.fetch_env!(:shopifex, :api_key)
                }&scope=#{Application.fetch_env!(:shopifex, :scopes)}&redirect_uri=#{
                  Application.fetch_env!(:shopifex, :redirect_uri)
                }"

              conn
              |> redirect(external: install_url)

            shop ->
              Logger.info("Initiating shop reinstallation for #{shop_url}")

              reinstall_url =
                "https://#{shop_url}/admin/oauth/request_grant?client_id=#{
                  Application.fetch_env!(:shopifex, :api_key)
                }&scope=#{Application.fetch_env!(:shopifex, :scopes)}&redirect_uri=#{
                  Application.fetch_env!(:shopifex, :reinstall_uri)
                }"

              conn
              |> redirect(external: reinstall_url)
          end
        else
          conn
          |> put_view(ShopifexWeb.AuthView)
          |> put_layout({ShopifexWeb.LayoutView, "app.html"})
          |> put_flash(:error, "Invalid shop URL")
          |> render("select-store.html")
        end
      end

      @impl ShopifexWeb.AuthController
      def after_install(conn, shop) do
        redirect(conn,
          external:
            "https://#{shop.url}/admin/apps/#{Application.fetch_env!(:shopifex, :api_key)}"
        )
      end

      @impl ShopifexWeb.AuthController
      def insert_shop(shop) do
        Shopifex.Shops.create_shop(shop)
      end

      def install(conn, %{"code" => code, "shop" => shop_url}) do
        url = "https://#{shop_url}/admin/oauth/access_token"

        case(
          HTTPoison.post(
            url,
            Jason.encode!(%{
              client_id: Application.fetch_env!(:shopifex, :api_key),
              client_secret: Application.fetch_env!(:shopifex, :secret),
              code: code
            }),
            "Content-Type": "application/json",
            Accept: "application/json"
          )
        ) do
          {:ok, response} ->
            shop =
              Jason.decode!(response.body, keys: :atoms)
              |> Map.put(:url, shop_url)
              |> insert_shop()

            Shopifex.Shops.configure_webhooks(shop)

            after_install(conn, shop)

          error ->
            raise(Shopifex.InstallError, message: "Installation failed for shop #{shop_url}")
        end
      end

      def update(conn, %{"code" => code, "shop" => shop_url}) do
        url = "https://#{shop_url}/admin/oauth/access_token"

        case(
          HTTPoison.post(
            url,
            Jason.encode!(%{
              client_id: Application.fetch_env!(:shopifex, :api_key),
              client_secret: Application.fetch_env!(:shopifex, :secret),
              code: code
            }),
            "Content-Type": "application/json",
            Accept: "application/json"
          )
        ) do
          {:ok, response} ->
            params = Jason.decode!(response.body, keys: :atoms)

            shop =
              shop_url
              |> Shopifex.Shops.get_shop_by_url()
              |> Shopifex.Shops.update_shop(params)
              |> Shopifex.Shops.configure_webhooks()

            redirect(conn,
              external:
                "https://#{shop_url}/admin/apps/#{Application.fetch_env!(:shopifex, :api_key)}"
            )

          error ->
            raise(Shopifex.UpdateError, message: "Update failed for shop #{shop_url}")
        end
      end

      defoverridable after_install: 2, insert_shop: 1
    end
  end
end