defmodule BerrypodWeb.AnalyticsHook do
  @moduledoc """
  LiveView on_mount hook for analytics — Layer 2 of the progressive pipeline.

  Reads analytics data from the session (set by the Plugs.Analytics plug) and
  tracks subsequent SPA navigations via handle_params. Skips the initial mount
  since the plug already recorded that pageview.

  Also handles the `analytics:screen` event from the JS hook (Layer 3) to
  capture screen width for device classification.
  """

  import Phoenix.Component, only: [assign: 3]
  import Phoenix.LiveView, only: [attach_hook: 4, connected?: 1]

  alias Berrypod.Analytics

  def on_mount(:track, _params, session, socket) do
    socket =
      socket
      |> assign(:analytics_visitor_hash, session["analytics_visitor_hash"])
      |> assign(:analytics_browser, session["analytics_browser"])
      |> assign(:analytics_os, session["analytics_os"])
      |> assign(:analytics_referrer, session["analytics_referrer"])
      |> assign(:analytics_referrer_source, session["analytics_referrer_source"])
      |> assign(:analytics_utm_source, session["analytics_utm_source"])
      |> assign(:analytics_utm_medium, session["analytics_utm_medium"])
      |> assign(:analytics_utm_campaign, session["analytics_utm_campaign"])
      |> assign(:analytics_screen_size, session["analytics_screen_size"])
      |> assign(:analytics_country_code, session["country_code"])
      |> assign(:analytics_initial_mount, true)

    socket =
      if connected?(socket) and socket.assigns.analytics_visitor_hash do
        socket
        |> attach_hook(:analytics_params, :handle_params, &handle_analytics_params/3)
        |> attach_hook(:analytics_events, :handle_event, &handle_analytics_event/3)
      else
        socket
      end

    {:cont, socket}
  end

  defp handle_analytics_params(_params, uri, socket) do
    # Skip the initial mount — the plug already recorded this pageview
    if socket.assigns.analytics_initial_mount do
      {:cont, assign(socket, :analytics_initial_mount, false)}
    else
      # Skip if admin user is browsing
      if admin?(socket) do
        {:cont, socket}
      else
        pathname = URI.parse(uri).path

        Analytics.track_pageview(%{
          pathname: pathname,
          visitor_hash: socket.assigns.analytics_visitor_hash,
          referrer: socket.assigns.analytics_referrer,
          referrer_source: socket.assigns.analytics_referrer_source,
          utm_source: socket.assigns.analytics_utm_source,
          utm_medium: socket.assigns.analytics_utm_medium,
          utm_campaign: socket.assigns.analytics_utm_campaign,
          country_code: socket.assigns.analytics_country_code,
          screen_size: socket.assigns.analytics_screen_size,
          browser: socket.assigns.analytics_browser,
          os: socket.assigns.analytics_os
        })

        # Clear referrer/UTMs after first SPA navigation — they only apply to the entry
        {:cont,
         socket
         |> assign(:analytics_referrer, nil)
         |> assign(:analytics_referrer_source, nil)
         |> assign(:analytics_utm_source, nil)
         |> assign(:analytics_utm_medium, nil)
         |> assign(:analytics_utm_campaign, nil)}
      end
    end
  end

  @doc """
  Extracts common analytics attributes from socket assigns.
  Call sites can merge their own fields (pathname, revenue, etc.) on top.
  """
  def attrs(socket) do
    %{
      visitor_hash: socket.assigns[:analytics_visitor_hash],
      browser: socket.assigns[:analytics_browser],
      os: socket.assigns[:analytics_os],
      screen_size: socket.assigns[:analytics_screen_size],
      country_code: socket.assigns[:analytics_country_code]
    }
  end

  defp handle_analytics_event("analytics:screen", %{"width" => width}, socket)
       when is_integer(width) do
    screen_size = classify_screen(width)
    {:cont, assign(socket, :analytics_screen_size, screen_size)}
  end

  defp handle_analytics_event(_event, _params, socket), do: {:cont, socket}

  defp classify_screen(width) when width < 768, do: "mobile"
  defp classify_screen(width) when width < 1024, do: "tablet"
  defp classify_screen(_width), do: "desktop"

  defp admin?(socket) do
    case socket.assigns[:current_scope] do
      %{user: %{}} -> true
      _ -> false
    end
  end
end