defmodule Pollin.Backend.Memory.CallbackWorker do
  @moduledoc """
  Worker for callbacks
  """

  use GenServer
  use Pollin.CallbackInterface
  alias Pollin.Backend.Memory.EndpointWorker

  @doc false
  def start_link(id) when is_atom(id),
    do: GenServer.start_link(__MODULE__, [], name: id)

  @doc false
  def init(_opts),
    do: {:ok, []}

  ## Private API

  @doc false
  def handle_cast({:push, id, cb, secret}, state) do
    endpoint = EndpointWorker.find("#{id}")
    if endpoint && endpoint.secret == secret do
      if endpoint.ttl > 0 do
        Process.send_after(self, {:delete, cb.id}, endpoint.ttl)
      end
      {:noreply, List.insert_at(state, -1, {cb.id, cb})}
    else
      {:noreply, state}
    end
  end

  @doc false
  def handle_cast({:reset}, _state),
    do: {:noreply, []}

  @doc false
  def handle_cast({:delete, key}, state) do
    new_state = List.keydelete(state, key, 0)
    {:noreply, new_state}
  end

  @doc false
  def handle_cast({:update_status, key, status}, state) do
    case List.keyfind(state, key, 0) do
      {key, cb} ->
        cb = Map.put(cb, :status, status)
        {:noreply, List.keyreplace(state, key, 0, {key, cb})}
      nil -> {:noreply, state}
    end
  end

  @doc false
  def handle_call({:pop}, _from, [{_key, cb} | state]),
    do: {:reply, cb, state}

  @doc false
  def handle_call({:pop, key}, _from, state) when is_binary(key) do
    case List.keytake(state, key, 0) do
      {{_key, cb}, new_state} -> {:reply, cb, new_state}
      nil -> {:reply, nil, state}
    end
  end

  @doc false
  def handle_call({:pop, %{status: status, offset: offset, limit: limit}}, _from, state) do
    items =
      state
      |> Enum.group_by(fn {_key, cb} -> cb.status end)
      |> Map.get(status, [])
      |> Enum.slice(offset, limit)

    {:reply, items |> Enum.map(fn {_key, cb} -> cb end), state -- items}
  end

  @doc false
  def handle_call({:pop, %{offset: offset, limit: limit}}, _from, state) do
    items =
      state
      |> Enum.slice(offset, limit)

    {:reply, items |> Enum.map(fn {_key, cb} -> cb end), state -- items}
  end

 @doc false
  def handle_call({:fetch}, _from, [{_key, cb} | _state] = state),
    do: {:reply, cb, state}

  @doc false
  def handle_call({:fetch, key}, _from, state) when is_binary(key) do
    case List.keyfind(state, key, 0) do
      {_key, cb} -> {:reply, cb, state}
      nil -> {:reply, nil, state}
    end
  end

  @doc false
  def handle_call({:fetch, %{status: status, offset: offset, limit: limit}}, _from, state) do
    items =
      state
      |> Enum.group_by(fn {_key, cb} -> cb.status end)
      |> Map.get(status, [])
      |> Enum.slice(offset, limit)
      |> Enum.map(fn {_key, cb} -> cb end)

    {:reply, items, state}
  end

  @doc false
  def handle_call({:fetch, %{offset: offset, limit: limit}}, _from, state) do
    items =
      state
      |> Enum.slice(offset, limit)
      |> Enum.map(fn {_key, cb} -> cb end)

    {:reply, items, state}
  end

  @doc false
  def handle_call({:fetch_reverse, %{status: status, offset: offset, limit: limit}}, _from, state) do
    items =
      state
      |> Enum.reverse
      |> Enum.group_by(fn {_key, cb} -> cb.status end)
      |> Map.get(status, [])
      |> Enum.slice(offset, limit)
      |> Enum.map(fn {_key, cb} -> cb end)

    {:reply, items, state}
  end

  @doc false
  def handle_call({:fetch_reverse, %{offset: offset, limit: limit}}, _from, state) do
    items =
      state
      |> Enum.reverse
      |> Enum.slice(offset, limit)
      |> Enum.map(fn {_key, cb} -> cb end)

    {:reply, items, state}
  end

  @doc false
  def handle_call({:count}, _from, state),
    do: {:reply, Enum.count(state), state}

  @doc false
  def handle_call({:count, %{status: status}}, _from, state) do
    count =
      state
      |> Enum.group_by(fn {_key, cb} -> cb.status end)
      |> Map.get(status, [])
      |> Enum.count
    {:reply, count, state}
  end

  @doc false
  def handle_call({:dump}, _from, state) do
    items =
      state
      |> Enum.map(fn {_key, cb} -> cb end)

    {:reply, items, state}
  end
end