defmodule Hobot do
  @moduledoc """
  A bot framework working on Erlang VM(Beam)

  ## Examples

  For example, we can create an echo bot following like:

  ```
  bot_name = "EchoBot"
  adapter = %{module: Hobot.Plugin.Adapter.Shell}
  handlers = [%{module: Hobot.Plugin.Handler.Echo, args: [["on_message"]]}]
  {:ok, bot_pid} = Hobot.create(bot_name, adapter, handlers)

  # Check behavior created bot
  context = Hobot.context(bot_pid)
  adapter_pid = Hobot.pid(context.adapter)
  send(adapter_pid, "hello") # => "hello"
  ```
  """

  def create(name, adapter, handlers, options \\ []) do
    application_process = %Hobot.ApplicationProcess{
      logger: Keyword.get(options, :logger, Logger),
      name_registry: Keyword.get(options, :name_registry, Hobot.Application.name_registry()),
      pub_sub: Keyword.get(options, :pub_sub, Hobot.Application.pub_sub()),
      task_supervisor: Keyword.get(options, :task_supervisor, Hobot.Application.task_supervisor())
    }

    handlers_with_index = Enum.with_index(handlers)

    Hobot.Supervisor.start_child(%{
      name: name,
      adapter: adapter,
      handlers: handlers_with_index,
      application_process: application_process
    })
  end

  def context(value, name_registry \\ Hobot.Application.name_registry())

  def context(name, name_registry) when is_binary(name) do
    Agent.get({:via, Registry, {name_registry, Hobot.Bot.context(name)}}, & &1)
  catch
    :exit, _ ->
      nil
  end

  def context(pid, name_registry) when is_pid(pid) do
    children = Supervisor.which_children(pid)

    case Enum.find(children, fn {process_name, _, _, _} ->
           Regex.match?(~r"Context", process_name)
         end) do
      {context_process_name, _, _, _} ->
        Agent.get({:via, Registry, {name_registry, context_process_name}}, & &1)

      _ ->
        nil
    end
  end

  def pid(name, name_registry \\ Hobot.Application.name_registry()) do
    case Registry.lookup(name_registry, name) do
      [{pid, _}] -> pid
      [] -> nil
    end
  end

  def child_spec(opts \\ []) do
    %{
      id: __MODULE__,
      start: {__MODULE__, :create, opts},
      restart: :permanent,
      shutdown: 5000,
      type: :worker
    }
  end
end