defmodule Aprsme.Telemetry.DatabaseMetricsTest do
  # Attaches telemetry handlers at test-specific event names so each test is
  # isolated, but we still keep async: false to avoid handler-name collisions
  # in process-global state.
  use ExUnit.Case, async: false

  alias Aprsme.Telemetry.DatabaseMetrics

  defp attach_collector(event, tag \\ to_string(System.unique_integer([:positive]))) do
    test_pid = self()
    handler_id = "test-#{tag}-#{Enum.join(event, ",")}"

    :telemetry.attach(
      handler_id,
      event,
      fn ^event, measurements, metadata, _ ->
        send(test_pid, {:telemetry, event, measurements, metadata})
      end,
      nil
    )

    on_exit(fn -> :telemetry.detach(handler_id) end)
    handler_id
  end

  describe "collect_postgres_metrics/0 in :test env" do
    test "is a no-op returning :ok" do
      original = Application.get_env(:aprsme, :env)
      Application.put_env(:aprsme, :env, :test)

      try do
        assert DatabaseMetrics.collect_postgres_metrics() == :ok
      after
        Application.put_env(:aprsme, :env, original)
      end
    end
  end

  describe "collect_db_pool_metrics/0" do
    test "emits [:aprsme, :repo, :pool] telemetry with pool_size from config" do
      attach_collector([:aprsme, :repo, :pool])
      DatabaseMetrics.collect_db_pool_metrics()

      assert_receive {:telemetry, [:aprsme, :repo, :pool], measurements, _}, 1_000
      assert Map.has_key?(measurements, :size)
      assert Map.has_key?(measurements, :idle)
      assert Map.has_key?(measurements, :busy)
      assert Map.has_key?(measurements, :available)
      assert Map.has_key?(measurements, :queue_length)
      assert Map.has_key?(measurements, :total)
    end
  end

  describe "collect_pgbouncer_metrics/0" do
    test "is a no-op returning :ok" do
      assert DatabaseMetrics.collect_pgbouncer_metrics() == :ok
    end
  end
end