tusker_push/lib/tusker_push_web/controllers/push_controller.ex

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

  require Logger

  def push(conn, %{"env" => env, "apns_device_token" => apns_device_token, "ctx" => context}) do
    OpenTelemetry.Tracer.set_attribute(:request_id, conn.assigns.request_id)

    with {:apns_env, apns_env} <- {:apns_env, get_apns_env(env)},
         {: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(apns_env, apns_device_token, body, salt, key, context)} do
      send_resp(conn, 200, "ok")
    else
      {:apns_env, nil} ->
        Logger.error("Bad environment: #{env}")
        send_resp(conn, 400, "bad env")

      {: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, :device_token_unregistered}} ->
        Logger.debug("APNS device token unregistered, removing registration")
        send_resp(conn, 400, "apns unregistered")

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

  defp get_apns_env("development"), do: :development
  defp get_apns_env("production"), do: :production
  defp get_apns_env(_), do: nil

  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