defmodule Cache.Agent do
  @moduledoc """
  This module is the Agent adapter. Very lightweight use only
  """

  use Agent

  @behaviour Cache

  @impl Cache
  def opts_definition, do: []

  @impl Cache
  def start_link(opts \\ []) do
    with {:error, {:already_started, pid}} <- Agent.start_link(fn -> %{} end, opts) do
      {:ok, pid}
    end
  end

  @impl Cache
  def child_spec({cache_name, opts}) do
    %{
      id: "#{cache_name}_elixir_cache_agent",
      start: {Cache.Agent, :start_link, [Keyword.put(opts, :name, cache_name)]}
    }
  end

  @impl Cache
  def get(cache_name, key, _opts \\ []) do
    Agent.get(cache_name, fn state ->
      {:ok, Map.get(state, key)}
    end)
  end

  @impl Cache
  def put(cache_name, key, _ttl \\ nil, value, _opts \\ []) do
    Agent.update(cache_name, fn state ->
      Map.put(state, key, value)
    end)
  end

  @impl Cache
  def delete(cache_name, key, _opts \\ []) do
    Agent.update(cache_name, fn state ->
      Map.delete(state, key)
    end)
  end
end