defmodule LocationSimulator do
  @moduledoc """
  This is main api of library.

  To start simple call
    iex> LocationSimulator.start()

  Or start with your config
    iex> config = LocationSimulator.default_config()
    iex> config = Map.put(config, :worker, 1)
    iex> LocationSimulator.start(config)

  """
  require Logger

  alias LocationSimulator.DynamicSupervisor, as: Sup

  @doc """
  Start with config.

  The config is a map type.

  Config has info like:

    ```
    %{
      worker: 3,  # number of worker will run
      event: 100, # number of GPS events will be trigger for a worker
      interval: 1000, # this & random_range used for sleep between GPS events, if value is :infinity worker will run forever (you still stop by return {:stop, reason})
      random_range: 0, # 0 mean no random, other positive will be used for generate extra random sleep time
      callback: MyCallbackModule # your module will handle data
    }
    ```


  If you need pass your data to callback module you can add that in the config.

  The config can be change after every event.
  """
  def start(config) when is_map(config) do
    config
    |> generate_worker()
    |> Sup.start_simulator()
  end

  @doc """
  Start with default config.

  In this case, library just uses Logger to log data in every event.
  """
  def start() do
    default_config()
    |> generate_worker()
    |> Sup.start_simulator()
  end

  @doc """
  Get default config of library.
  """
  def default_config() do
    Logger.debug("generating worker from config")
    config = Application.get_env(:location_simulator, :default_config)
    worker =
      case config[:worker] do
        # default is one worker.
        nil ->
          1
        n when is_integer(n) and n > 0 ->
          n
      end

    event =
      case config[:event] do
        nil ->
          raise "missed counter for location simulator"
        n when is_integer(n)->
            n
      end

    interval =
      case config[:interval] do
        nil ->
          100
        n when is_integer(n)->
            n
      end

    random_range =
      case config[:random_range] do
        nil ->
          10
        n when is_integer(n)->
            n
      end

    mod =
      case config[:callback] do
        nil ->
          raise "missed callback module"
        m ->
            m
      end

    %{
      worker: worker,
      event: event,
      interval: interval,
      random_range: random_range,
      direction: :random,
      callback: mod
    }
  end

  ## private functions ##

  defp generate_worker(config) do
    %{worker: worker} = config
    generate_worker(worker, config, [])
  end

  defp generate_worker(0, _config, workers) do
    workers
  end

  defp generate_worker(counter, config, workers) do
    generate_worker(counter-1, config, [{LocationSimulator.Worker, config} | workers])
  end
end