defmodule TuskerPushWeb.PushController do
  alias TuskerPush.Forwarder
  use TuskerPushWeb, :controller

  require Logger

  def push(conn, %{"id" => id}) do
    with {:registration, registration} when not is_nil(registration) <-
           {:registration, TuskerPush.get_registration(id)},
         :ok <- TuskerPush.check_registration_expired(registration),
         {:encoding, ["aesgcm"]} <- {:encoding, get_req_header(conn, "content-encoding")},
         {:body, {:ok, body, conn}} <- {:body, read_body(conn)},
         {:salt, salt} when not is_nil(salt) <- get_salt(conn),
         {:key, key} when not is_nil(key) <- get_key(conn),
         {:forward, :ok} <- {:forward, Forwarder.forward(registration, body, salt, key)} do
      send_resp(conn, 200, "ok")
    else
      {:registration, nil} ->
        send_resp(conn, 400, "unregistered")

      {:expired, registration} ->
        TuskerPush.unregister(registration)
        send_resp(conn, 400, "unregistered")

      {:encoding, encoding} ->
        Logger.warning("Unexpected encoding: #{inspect(encoding)}")
        send_resp(conn, 400, "bad encoding")

      {:body, {:more, _, conn}} ->
        Logger.error("Didn't finish reading")
        send_resp(conn, 500, "failed to read body")

      {:body, {:error, reason}} ->
        Logger.error("Reading body: #{inspect(reason)}")
        send_resp(conn, 500, "failed to read body")

      {:salt, nil} ->
        Logger.warning("Missing salt")
        send_resp(conn, 400, "missing salt")

      {:key, nil} ->
        Logger.warning("Missing key")
        send_resp(conn, 400, "missing key")

      {:forward, {:error, reason}} ->
        Logger.error("Sending notification: #{inspect(reason)}")
        send_resp(conn, 500, "failed to send")
    end
  end

  defp get_salt(conn) do
    conn
    |> get_req_header("encryption")
    |> case do
      ["salt=" <> salt] ->
        {:salt, salt}

      _ ->
        {:salt, nil}
    end
  end

  defp get_key(conn) do
    conn
    |> get_req_header("crypto-key")
    |> case do
      [value] ->
        dh =
          value
          |> String.split(";")
          |> Enum.find_value(fn
            "dh=" <> val -> val
            _ -> false
          end)

        {:key, dh}

      _ ->
        {:key, nil}
    end
  end
end