defmodule Mix.Tasks.Nomad.DatabaseInstance.List do
  use Mix.Task

  @moduledoc """
  Task for automatically listing all remote SQL databases on a pre-determined
  cloud provider. The instance listing is done through the cloud provider's
  API.

  Usage:
    
    mix nomad.database_instance.list 
  """

  @shortdoc"Lists all SQL database instances on the chosen cloud provider's SQL service."

  @provider Application.get_env(:nomad, :cloud_provider)

  @doc """
  Runs the task for the chosen cloud provider.
  """
  @spec run(list) :: binary
  def run(_args) do 
    case @provider do 
      :aws -> 
        Application.ensure_all_started(:ex_aws)
        Application.ensure_all_started(:httpoison)
      :gcl -> 
        Application.ensure_all_started(:httpoison)
        Application.ensure_all_started(:goth)
        Application.ensure_all_started(:gcloudex)
    end

    list_instances_api_call
  end

  defp list_instances_api_call do
    provider =
      case @provider do
        :aws -> "Amazon Web Services"
        :gcl -> "Google Cloud Platform"
      end

    res = Nomad.SQL.list_instances

    if is_list(res) && res != [] do 
      res = res
      |> convert_instance_tuples_to_lists
      |> stringify

      TableRex.quick_render!(
        res, 
        ["Name", "Region", "Address", "Status", "Storage"],
        "SQL Database Instances on #{provider}")
      |> Mix.Shell.IO.info
    else
      if res == [] do 
        Mix.Shell.IO.info("There are no instances to be listed.")
      else
        Mix.Shell.IO.info("There was a problem listing the instances:\n#{res}")
      end
    end
  end

  defp convert_instance_tuples_to_lists(instances) do
    instances 
    |> Enum.map(fn instance -> Tuple.to_list(instance) end)    
  end

  defp stringify(rows) do
    Enum.map rows, fn row ->
      Enum.map(row, &to_string/1)
    end
  end    
end