defmodule Argos.Parallel.Monitor do
  @moduledoc """
  Monitor de estado agregado de workers paralelos.

  Se suscribe al `Leader`, transforma eventos en un mapa de `WorkerState` y
  emite actualizaciones consolidadas a sus suscriptores. Ofrece estadísticas.
  """

  use GenServer
  alias Argos.Parallel.{Leader, MonitorState, WorkerState}

  @default_call_timeout 30_000

  def start_link(opts \\ []) do
    name = Keyword.get(opts, :name, __MODULE__)
    GenServer.start_link(__MODULE__, opts, name: name)
  end

  @doc """
  Obtiene el estado completo del monitor.

  ## Opciones

    * `:timeout` - Timeout para la llamada GenServer (por defecto: 30 segundos)
  """
  @spec get_state(GenServer.server(), keyword()) :: MonitorState.t()
  def get_state(server \\ __MODULE__, opts \\ []) do
    timeout = Keyword.get(opts, :timeout, @default_call_timeout)
    GenServer.call(server, :get_state, timeout)
  end

  @doc """
  Obtiene el estado de un worker específico.

  ## Opciones

    * `:timeout` - Timeout para la llamada GenServer (por defecto: 30 segundos)

  ## Retorna

    `WorkerState.t()` si el worker existe, `nil` si no existe.
  """
  @spec get_worker_state(term(), GenServer.server(), keyword()) :: WorkerState.t() | nil
  def get_worker_state(worker_id, server \\ __MODULE__, opts \\ []) do
    timeout = Keyword.get(opts, :timeout, @default_call_timeout)
    GenServer.call(server, {:get_worker_state, worker_id}, timeout)
  end

  @doc """
  Suscribe el proceso actual para recibir actualizaciones consolidadas del monitor.

  ## Opciones

    * `:timeout` - Timeout para la llamada GenServer (por defecto: 30 segundos)
  """
  @spec subscribe(GenServer.server(), keyword()) :: :ok
  def subscribe(server \\ __MODULE__, opts \\ []) do
    timeout = Keyword.get(opts, :timeout, @default_call_timeout)
    GenServer.call(server, {:subscribe, self()}, timeout)
  end

  @doc """
  Desuscribe el proceso actual del monitor.

  ## Opciones

    * `:timeout` - Timeout para la llamada GenServer (por defecto: 30 segundos)
  """
  @spec unsubscribe(GenServer.server(), keyword()) :: :ok
  def unsubscribe(server \\ __MODULE__, opts \\ []) do
    timeout = Keyword.get(opts, :timeout, @default_call_timeout)
    GenServer.call(server, {:unsubscribe, self()}, timeout)
  end

  @doc """
  Obtiene estadísticas agregadas de todos los workers.

  ## Opciones

    * `:timeout` - Timeout para la llamada GenServer (por defecto: 30 segundos)
  """
  @spec get_stats(GenServer.server(), keyword()) :: map()
  def get_stats(server \\ __MODULE__, opts \\ []) do
    timeout = Keyword.get(opts, :timeout, @default_call_timeout)
    GenServer.call(server, :get_stats, timeout)
  end

  @impl true
  def init(opts) do
    leader = Keyword.get(opts, :leader, Argos.Parallel.Leader)
    state = %MonitorState{leader: leader}

    Leader.subscribe(leader)
    {:ok, state}
  end

  @impl true
  def handle_call(:get_state, _from, state) do
    {:reply, state, state}
  end

  @impl true
  def handle_call({:get_worker_state, worker_id}, _from, state) do
    worker_state = Map.get(state.workers, worker_id)
    {:reply, worker_state, state}
  end

  @impl true
  def handle_call({:subscribe, pid}, _from, %MonitorState{subscribers: subs} = state) do
    Process.monitor(pid)
    {:reply, :ok, %{state | subscribers: MapSet.put(subs, pid)}}
  end

  @impl true
  def handle_call({:unsubscribe, pid}, _from, %MonitorState{subscribers: subs} = state) do
    {:reply, :ok, %{state | subscribers: MapSet.delete(subs, pid)}}
  end

  @impl true
  def handle_call(:get_stats, _from, state) do
    stats = calculate_stats(state.workers)
    {:reply, stats, state}
  end

  @impl true
  def handle_info({:parallel_event, _leader, event}, state) do
    state = update_state_from_event(state, event)
    notify_subscribers(state)
    {:noreply, state}
  end

  @impl true
  def handle_info({:DOWN, _ref, :process, pid, _reason}, %MonitorState{subscribers: subs} = state) do
    {:noreply, %{state | subscribers: MapSet.delete(subs, pid)}}
  end

  @impl true
  def handle_info(_msg, state) do
    {:noreply, state}
  end

  defp update_state_from_event(state, %{worker_id: worker_id, type: type, data: data}) do
    current_workers = state.workers

    updated_workers =
      case type do
        :started ->
          Map.put(current_workers, worker_id, WorkerState.new(worker_id))

        :progress ->
          Map.update(
            current_workers,
            worker_id,
            WorkerState.new(worker_id)
            |> WorkerState.running(data.percent, data.total, data.task_index),
            fn worker ->
              WorkerState.running(worker, data.percent, data.total, data.task_index)
            end
          )

        :result ->
          Map.update(
            current_workers,
            worker_id,
            WorkerState.new(worker_id),
            fn worker ->
              WorkerState.add_result(worker, data.task_index, data.result)
            end
          )

        :finished ->
          Map.update(
            current_workers,
            worker_id,
            WorkerState.new(worker_id) |> WorkerState.finished(),
            fn worker ->
              WorkerState.finished(worker)
            end
          )

        :error ->
          Map.update(
            current_workers,
            worker_id,
            WorkerState.new(worker_id) |> WorkerState.error(data.reason, data.task_index),
            fn worker ->
              WorkerState.error(worker, data.reason, data.task_index)
            end
          )

        _ ->
          current_workers
      end

    %{state | workers: updated_workers, last_update: DateTime.utc_now()}
  end

  defp notify_subscribers(%MonitorState{subscribers: subs} = state) do
    Enum.each(subs, fn pid ->
      send(pid, {:parallel_monitor_update, state})
    end)
  end

  defp calculate_stats(workers) do
    total_workers = map_size(workers)

    status_counts =
      Enum.reduce(workers, %{}, fn {_, worker}, acc ->
        status = worker.status
        Map.update(acc, status, 1, &(&1 + 1))
      end)

    total_tasks =
      Enum.reduce(workers, 0, fn {_, worker}, acc ->
        acc + (worker.total || 0)
      end)

    completed_tasks =
      Enum.reduce(workers, 0, fn {_, worker}, acc ->
        if worker.current_task do
          acc + worker.current_task
        else
          acc
        end
      end)

    %{
      total_workers: total_workers,
      status_counts: status_counts,
      total_tasks: total_tasks,
      completed_tasks: completed_tasks,
      progress_percentage: if(total_tasks > 0, do: (completed_tasks / total_tasks * 100) |> Float.round(1), else: 0)
    }
  end
end