defmodule Diffuser.Generator.PromptRequestQueue do
  use GenServer
  alias Diffuser.Generator.PromptRequestWorker

  ### GenServer API

  @doc """
  GenServer.init/1 callback
  """
  def init(state) do
    {:ok, state}
  end

  @doc """
  GenServer.handle_call/3 callback
  """
  def handle_call(:dequeue, _from, [value | state]) do
    {:reply, value, state}
  end

  def handle_call(:dequeue, _from, []), do: {:reply, nil, []}

  def handle_call(:queue, _from, state), do: {:reply, state, state}

  @doc """
  GenServer.handle_cast/2 callback
  """
  def handle_cast({:enqueue, value}, state) do
    {:noreply, state, {:continue, {:enqueue, value}}}
  end

  def handle_continue({:enqueue, value}, state) when length(state) > 0 do
    {:continue, {:enqueue, value}, state}
  end

  def handle_continue({:enqueue, value}, state) do
    PromptRequestWorker.start(value)
    {:noreply, state}
  end

  ### Client API / Helper functions

  def start_link(state \\ []) do
    GenServer.start_link(__MODULE__, state, name: __MODULE__)
  end

  def queue, do: GenServer.call(__MODULE__, :queue)
  def enqueue(value), do: GenServer.cast(__MODULE__, {:enqueue, value})
  def dequeue, do: GenServer.call(__MODULE__, :dequeue)
end