defmodule Elstat.Error.Service do
  defexception message: "default message"
end

defmodule Elstat.ServiceWorker do
  require Logger

  def start_link(service) do
    Logger.info "spawning worker for #{inspect service.id}"

    worker_pid = spawn(fn ->
      worker_func(service)
    end)
    
    {:ok, worker_pid}
  end

  def worker_func(service) do
    adapter = service.adapter
 
    result = adapter.check(service.adapter_opts)
    Logger.info "result from #{inspect adapter} #{inspect service.id}: #{inspect result}"

    man_pid = :global.whereis_name Elstat.Manager
    send man_pid, {:service_info, {service.id, result}}
    
    Process.sleep(service.poll * 1000)
    worker_func(service)
  end
end

defmodule Elstat.Manager do
  @moduledoc """
  Elstat's service manager.
  """
  use GenServer
  require Logger

  def start_link(opts) do
    GenServer.start_link(__MODULE__, :ok, [name: {:global, Elstat.Manager}] ++ opts)
  end

  def build_services() do
    services = Application.fetch_env!(:elstat, :services)

    workers = services
    |> Enum.map(fn service ->
      service_id = service.id

      # each service worker will enter an infinite loop
      # polling the service (via an adapter) and giving
      # information back to the manager, so it can
      # process and show those via its API.
      %{
        id: service_id,
        start: {Elstat.ServiceWorker, :start_link, [service]}
      }
    end)

    # spawn the managere alongside service workers
    [ Elstat.Manager | workers]
  end

  # server callbacks
  def init(:ok) do
    services = Application.fetch_env!(:elstat, :services)

    # TODO : send data to db
    
    {:ok, %{
        services: services,
     }}
  end
  
  def handle_info({:service_info, data}, state) do
    Logger.debug "got service data! #{inspect data}"
    {:noreply, state}
  end
  
end