defmodule HareMq.DynamicSupervisor do
  use DynamicSupervisor
  alias HareMq.AutoScalerConfiguration
  @timeout 70_000

  def start_link([config: _, consume: _] = opts) do
    DynamicSupervisor.start_link(__MODULE__, opts, name: __MODULE__)
  end

  @impl true
  @doc """
  Initializes the dynamic supervisor with the specified options.

  It starts a Task to asynchronously run the start_consumers function and initializes
  the dynamic supervisor with a one_for_one restart strategy.

  ## Examples

      iex> HareMq.DynamicSupervisor.start_link([config: %{consumer_count: 3}, consume: MyApp.Consumer])
      {:ok, #PID<0.123.0>}
  """
  def init([config: _, consume: _] = opts) do
    {:ok, _} =
      Task.start_link(fn ->
        start_consumers(opts)
        start_auto_scaler(opts)
      end)

    DynamicSupervisor.init(strategy: :one_for_one)
  end

  defp start_consumers([config: config, consume: _] = opts) do
    Enum.each(1..config[:consumer_count], fn number ->
      start_child(
        worker: config[:consumer_worker],
        name: "#{config[:module_name]}.W#{number}",
        opts: opts
      )
    end)
  end

  @doc """
  Starts a child worker process with the specified worker and options.

  ## Examples

      iex> HareMq.DynamicSupervisor.start_child(worker: MyApp.Consumer, name: :consumer1, opts: [config: %{}, consume: MyApp.Consumer])
      {:ok, #PID<0.124.0>}
  """
  def start_child(worker: worker, name: name, opts: opts) do
    DynamicSupervisor.start_child(__MODULE__, {worker, {name, opts}})
  end

  @doc """
  Adds a new consumer process to the dynamic supervisor.

  ## Examples

      iex> HareMq.DynamicSupervisor.add_consumer(worker: MyApp.Consumer, name: "MyApp.Consumer.W4", opts: [config: %{}, consume: MyApp.Consumer])
      {:ok, #PID<0.125.0>}
  """
  def add_consumer(worker: worker, name: name, opts: opts) do
    start_child(worker: worker, name: name, opts: opts)
  end

  @doc """
  This function looks up the consumer by name in the `:consumers` registry,
  sends a cancellation message to the consumer to allow it to stop processing,
  and then terminates the child process.

  ## Examples

      iex> HareMq.DynamicSupervisor.remove_consumer("MyApp.Consumer.W4")
      :ok
  """
  def remove_consumer(name) do
    case Registry.lookup(:consumers, name) do
      [{pid, nil}] ->
        # Send a cancellation message to allow the consumer to finish processing gracefully
        GenServer.call(pid, :cancel_consume, @timeout)
        DynamicSupervisor.terminate_child(__MODULE__, pid)

      _ ->
        :ok
    end
  end

  @doc """
  Returns a list of all consumers managed by this dynamic supervisor.
  """
  def list_consumers do
    DynamicSupervisor.which_children(__MODULE__)
  end

  @doc """
  Starts the AutoScaler as a child under this DynamicSupervisor.
  """
  def start_auto_scaler([config: config, consume: consume] = opts) do
    if config[:auto_scaling] do
      configuration =
        AutoScalerConfiguration.get_auto_scaler_configuration(
          queue_name: config[:queue_name],
          consumer_worker: config[:consumer_worker],
          module_name: config[:module_name],
          consumer_count: config[:consumer_count],
          consume: consume,
          auto_scaling: config[:auto_scaling],
          consumer_opts: opts
        )

      DynamicSupervisor.start_child(__MODULE__, {HareMq.AutoScaler, configuration})
    else
      :ok
    end
  end
end