defmodule Plausible.Workers.SpikeNotifier do
  use Plausible.Repo
  alias Plausible.Stats.Query
  alias Plausible.Site.SpikeNotification
  use Oban.Worker, queue: :spike_notifications
  @at_most_every "12 hours"

  @impl Oban.Worker
  def perform(_job, clickhouse \\ Plausible.Stats.Clickhouse) do
    notifications =
      Repo.all(
        from sn in SpikeNotification,
          where: is_nil(sn.last_sent),
          or_where: sn.last_sent < fragment("now() - INTERVAL ?", @at_most_every),
          join: s in Plausible.Site,
          on: sn.site_id == s.id,
          where: not s.locked,
          preload: [site: s]
      )

    for notification <- notifications do
      query = Query.from(notification.site, %{"period" => "realtime"})
      current_visitors = clickhouse.current_visitors(notification.site, query)

      if current_visitors >= notification.threshold do
        sources = clickhouse.top_sources_for_spike(notification.site, query, 3, 1)
        notify(notification, current_visitors, sources)
      end
    end

    :ok
  end

  defp notify(notification, current_visitors, sources) do
    for recipient <- notification.recipients do
      send_notification(recipient, notification.site, current_visitors, sources)
    end

    notification
    |> SpikeNotification.was_sent()
    |> Repo.update()
  end

  defp send_notification(recipient, site, current_visitors, sources) do
    site = Repo.preload(site, :members)

    dashboard_link =
      if Enum.any?(site.members, &(&1.email == recipient)) do
        PlausibleWeb.Endpoint.url() <> "/" <> URI.encode_www_form(site.domain)
      end

    template =
      PlausibleWeb.Email.spike_notification(
        recipient,
        site,
        current_visitors,
        sources,
        dashboard_link
      )

    Plausible.Mailer.send(template)
  end
end