defmodule <%= @module_name %>.ClassMerger.Cache do
  @moduledoc """
  ETS-backed cache for memoising resolved Tailwind class strings.

  Stores `{input_key, resolved_string}` pairs so that identical
  lists of class tokens are merged only once per application lifetime.
  """

  use GenServer

  @table __MODULE__

  # --- Public API -----------------------------------------------------------

  @doc "Starts the cache and registers it under its module name."
  def start_link(_opts) do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  @doc "Returns the cached string for `key`, or `nil` if absent."
  @spec get(term()) :: String.t() | nil
  def get(key), do: lookup(key)

  @doc "Stores `value` under `key` and returns `value`."
  @spec put(term(), String.t()) :: String.t()
  def put(key, value) do
    :ets.insert(@table, {key, value})
    value
  end

  # --- GenServer callbacks ---------------------------------------------------

  @impl GenServer
  def init(_) do
    :ets.new(@table, [:named_table, :public, read_concurrency: true])
    {:ok, []}
  end

  # --- Private helpers -------------------------------------------------------

  defp lookup(key) do
    case :ets.lookup(@table, key) do
      [{^key, value}] -> value
      [] -> nil
    end
  end
end