Leaky Bucket GenServer in Elixir

bucket.ex

defmodule LeakyBucket.Bucket do
  @moduledoc """
  Simulates a leaky bucket implementation
  """
  use GenServer

  @initial_amount 0
  @increment_rate 1
  @leak_rate 2
  @leak_interval 500
  @size 40

  # Public

  @doc """
  Increments the amount of water in the bucket
  """
  def increment do
    GenServer.call(__MODULE__, :increment)
  end

  # Private

  @doc """
  Starts Bucket with initial amount
  """
  def start_link() do
    GenServer.start_link(__MODULE__, %{count: @initial_amount}, [name: __MODULE__])
  end

  @doc """
  Initiates the leak counter
  """
  def init(state) do
    send self(), :leak
    {:ok, state}
  end

  @doc """
  Returns an error because bucket will be too full
  """
  def handle_call(:increment, _from, %{count: count}) when (count + @increment_rate) > @size do
    {:reply, :too_many_requests, %{count: count}}
  end

  @doc """
  Increments the amount of water in the bucket
  """
  def handle_call(:increment, _from, %{count: count}) do
    {:reply, count + @increment_rate, %{count: count + @increment_rate}}
  end

  @doc """
  Set count to 0 if count is less than leak rate
  """
  def handle_info(:leak, %{count: count}) when count < @leak_rate do
    Process.send_after(self(), :leak, @leak_interval)
    {:noreply, %{count: 0}}
  end

  @doc """
  Leak amount from bucket
  """
  def handle_info(:leak, %{count: count}) do
    Process.send_after(self(), :leak, @leak_interval)
    {:noreply, %{count: count - @leak_rate}}
  end

end