defmodule ToweropsWeb.UserAuth do
  @moduledoc """
  Authentication plugs and helpers for user session management.

  Provides Plug functions for:
  - Fetching current user from session
  - Requiring authenticated users
  - Redirecting guests and authenticated users
  - Managing remember-me tokens
  - User session lifecycle (login, logout)
  """
  use ToweropsWeb, :verified_routes
  use Gettext, backend: ToweropsWeb.Gettext

  import Phoenix.Controller
  import Plug.Conn
  import ToweropsWeb.GettextHelpers

  alias Phoenix.LiveView
  alias Towerops.Accounts
  alias Towerops.Accounts.Scope
  alias Towerops.Admin.AuditLogger
  alias ToweropsWeb.Helpers.StatusHelpers

  # Make the remember me cookie valid for 14 days. This should match
  # the session validity setting in UserToken.
  @max_cookie_age_in_days 14
  @remember_me_cookie "_towerops_web_user_remember_me"
  @remember_me_options [
    sign: true,
    max_age: @max_cookie_age_in_days * 24 * 60 * 60,
    same_site: "Lax"
  ]

  # How old the session token should be before a new one is issued. When a request is made
  # with a session token older than this value, then a new session token will be created
  # and the session and remember-me cookies (if set) will be updated with the new token.
  # Lowering this value will result in more tokens being created by active users. Increasing
  # it will result in less time before a session token expires for a user to get issued a new
  # token. This can be set to a value greater than `@max_cookie_age_in_days` to disable
  # the reissuing of tokens completely.
  @session_reissue_age_in_days 7

  @doc """
  Logs the user in.

  Redirects to the session's `:user_return_to` path
  or falls back to the `signed_in_path/1`.
  """
  def log_in_user(conn, user, params \\ %{}) do
    user_return_to = get_session(conn, :user_return_to)
    # Validate return path - ignore if it's an invalid destination
    valid_return_to = if valid_return_path?(user_return_to), do: user_return_to

    conn =
      conn
      |> create_or_extend_session(user, params)
      |> maybe_set_default_organization(user)
      |> delete_session(:user_return_to)

    redirect(conn, to: valid_return_to || signed_in_path(user))
  end

  @doc """
  Validates whether a return-to path is a safe application-local destination.
  Rejects external URLs, auth pages, double-slashes, and backslash variants.
  """
  def valid_return_path?(nil), do: false

  def valid_return_path?(path) when is_binary(path) do
    invalid_prefixes = [
      "/users/log-in",
      "/users/register",
      "/users/reset-password",
      "/users/confirm",
      "/dev/",
      "/assets/",
      "/health"
    ]

    path != "/" and
      String.starts_with?(path, "/") and
      not String.contains?(path, "//") and
      not String.contains?(path, "\\") and
      not Enum.any?(invalid_prefixes, &String.starts_with?(path, &1))
  end

  def valid_return_path?(_), do: false

  @doc """
  Logs the user out.

  It clears all session data for safety. See renew_session.
  """
  def log_out_user(conn) do
    user_token = get_session(conn, :user_token)
    user_token && Accounts.delete_user_session_token(user_token)

    _ =
      if live_socket_id = get_session(conn, :live_socket_id) do
        ToweropsWeb.Endpoint.broadcast(live_socket_id, "disconnect", %{})
      end

    conn
    |> renew_session(nil)
    |> delete_resp_cookie(@remember_me_cookie)
    |> redirect(to: ~p"/users/log-in")
  end

  @doc """
  Authenticates the user by looking into the session and remember me token.

  Will reissue the session token if it is older than the configured age.
  Handles impersonation by checking session state.
  """
  def fetch_current_scope_for_user(conn, _opts) do
    # Check if currently impersonating
    if get_session(conn, :impersonating) do
      superuser_id = get_session(conn, :superuser_id)
      target_user_id = get_session(conn, :target_user_id)

      fetch_impersonation_scope(conn, superuser_id, target_user_id)
    else
      # Normal authentication flow
      with {token, conn} <- ensure_user_token(conn),
           {user, token_inserted_at} <- Accounts.get_user_by_session_token(token) do
        conn
        |> assign(:current_scope, Scope.for_user(user))
        |> maybe_reissue_user_session_token(user, token_inserted_at)
      else
        nil -> assign(conn, :current_scope, Scope.for_user(nil))
      end
    end
  end

  defp fetch_impersonation_scope(conn, superuser_id, target_user_id)
       when is_binary(superuser_id) and is_binary(target_user_id) do
    with superuser when not is_nil(superuser) <- Accounts.get_user(superuser_id),
         target_user when not is_nil(target_user) <- Accounts.get_user(target_user_id) do
      assign(conn, :current_scope, Scope.for_impersonation(superuser, target_user))
    else
      _ ->
        # Impersonation invalid, clear it
        clear_impersonation_session(conn)
    end
  end

  defp fetch_impersonation_scope(conn, _superuser_id, _target_user_id) do
    # Missing IDs, clear invalid impersonation state
    clear_impersonation_session(conn)
  end

  defp clear_impersonation_session(conn) do
    conn
    |> delete_session(:superuser_id)
    |> delete_session(:target_user_id)
    |> delete_session(:impersonating)
    |> assign(:current_scope, Scope.for_user(nil))
  end

  defp ensure_user_token(conn) do
    if token = get_session(conn, :user_token) do
      {token, conn}
    else
      conn = fetch_cookies(conn, signed: [@remember_me_cookie])

      if token = conn.cookies[@remember_me_cookie] do
        {token, conn |> put_token_in_session(token) |> put_session(:user_remember_me, true)}
      end
    end
  end

  # Reissue the session token if it is older than the configured reissue age.
  defp maybe_reissue_user_session_token(conn, user, token_inserted_at) do
    token_age = DateTime.diff(DateTime.utc_now(:second), token_inserted_at, :day)

    if token_age >= @session_reissue_age_in_days do
      create_or_extend_session(conn, user, %{})
    else
      conn
    end
  end

  # This function is the one responsible for creating session tokens
  # and storing them safely in the session and cookies. It may be called
  # either when logging in, during sudo mode, or to renew a session which
  # will soon expire.
  #
  # When the session is created, rather than extended, the renew_session
  # function will clear the session to avoid fixation attacks. See the
  # renew_session function to customize this behaviour.
  defp create_or_extend_session(conn, user, params) do
    {token, user_token} = Accounts.generate_user_session_token_with_record(user)
    remember_me = get_session(conn, :user_remember_me)

    # Create browser session in background with metadata
    _ =
      Task.Supervisor.start_child(Towerops.TaskSupervisor, fn ->
        create_browser_session_from_conn(conn, user, user_token)
      end)

    # Record successful login attempt in background
    _ =
      Task.Supervisor.start_child(Towerops.TaskSupervisor, fn ->
        record_successful_login(conn, user, params)
      end)

    conn
    |> renew_session(user)
    |> put_token_in_session(token)
    |> maybe_write_remember_me_cookie(token, params, remember_me)
  end

  # Do not renew session if the user is already logged in
  # to prevent CSRF errors or data being lost in tabs that are still open
  defp renew_session(conn, user)
       when is_map_key(conn.assigns, :current_scope) and not is_nil(conn.assigns.current_scope) and
              not is_nil(conn.assigns.current_scope.user) and conn.assigns.current_scope.user.id == user.id do
    conn
  end

  # This function renews the session ID and erases the whole
  # session to avoid fixation attacks. If there is any data
  # in the session you may want to preserve after log in/log out,
  # you must explicitly fetch the session data before clearing
  # and then immediately set it after clearing, for example:
  #
  #     defp renew_session(conn, _user) do
  #       delete_csrf_token()
  #       preferred_locale = get_session(conn, :preferred_locale)
  #
  #       conn
  #       |> configure_session(renew: true)
  #       |> clear_session()
  #       |> put_session(:preferred_locale, preferred_locale)
  #     end
  #
  defp renew_session(conn, _user) do
    delete_csrf_token()

    # Preserve return path across session renewal for sudo mode re-auth
    user_return_to = get_session(conn, :user_return_to)

    conn =
      conn
      |> configure_session(renew: true)
      |> clear_session()

    if user_return_to do
      put_session(conn, :user_return_to, user_return_to)
    else
      conn
    end
  end

  defp maybe_write_remember_me_cookie(conn, token, %{"remember_me" => "true"}, _),
    do: write_remember_me_cookie(conn, token)

  defp maybe_write_remember_me_cookie(conn, token, _params, true), do: write_remember_me_cookie(conn, token)

  defp maybe_write_remember_me_cookie(conn, _token, _params, _), do: conn

  defp maybe_set_default_organization(conn, user) do
    # Set the first organization in the session to support routes that require organization context
    case Towerops.Organizations.list_user_organizations(user.id) do
      [first_org | _] ->
        put_session(conn, :current_organization_id, first_org.id)

      [] ->
        conn
    end
  end

  defp write_remember_me_cookie(conn, token) do
    conn
    |> put_session(:user_remember_me, true)
    |> put_resp_cookie(@remember_me_cookie, token, @remember_me_options)
  end

  defp put_token_in_session(conn, token) do
    put_session(conn, :user_token, token)
  end

  @doc """
  Plug for routes that require sudo mode.

  Checks if the user's sudo mode is active (within 10 minutes).
  If TOTP is enabled, redirects to TOTP-only verification page.
  If TOTP is not enabled, redirects to enrollment.
  """
  def require_sudo_mode(conn, _opts) do
    user = conn.assigns.current_scope.user

    case {Accounts.sudo_mode?(user, -10), Accounts.totp_enabled?(user)} do
      {true, _} ->
        conn

      {false, true} ->
        conn
        |> put_flash(:error, t_auth("Please verify your identity to continue."))
        |> maybe_store_return_to()
        |> redirect(to: ~p"/users/sudo-verify")
        |> halt()

      {false, false} ->
        conn
        |> put_flash(:error, t_auth("Two-factor authentication is required for this action."))
        |> redirect(to: ~p"/account/totp-enrollment")
        |> halt()
    end
  end

  @doc """
  Plug for routes that require the user to not be authenticated.
  """
  def redirect_if_user_is_authenticated(conn, _opts) do
    if conn.assigns.current_scope && conn.assigns.current_scope.user do
      user = conn.assigns.current_scope.user

      conn
      |> redirect(to: signed_in_path(user))
      |> halt()
    else
      conn
    end
  end

  defp signed_in_path(user) when is_struct(user) do
    # Check if user has TOTP enabled (mandatory for all users)
    if Accounts.totp_enabled?(user) do
      # Get user's organizations (ordered by most recently joined first)
      case Towerops.Organizations.list_user_organizations(user.id) do
        [_first_org | _] ->
          # Dashboard page
          ~p"/dashboard"

        [] ->
          # No organizations yet, go to org list
          ~p"/orgs"
      end
    else
      ~p"/account/totp-enrollment"
    end
  end

  defp signed_in_path(_), do: ~p"/orgs"

  @doc """
  Plug for routes that require the user to be authenticated.
  """
  def set_user_locale(conn, _opts) do
    _ =
      if conn.assigns[:current_scope] && conn.assigns.current_scope.user do
        locale = conn.assigns.current_scope.user.language || "en"
        Gettext.put_locale(ToweropsWeb.Gettext, locale)
      end

    conn
  end

  def require_authenticated_user(conn, _opts) do
    if conn.assigns.current_scope && conn.assigns.current_scope.user do
      conn
    else
      conn
      |> put_flash(:error, t_auth("You must log in to access this page."))
      |> maybe_store_return_to()
      |> redirect(to: ~p"/users/log-in")
      |> halt()
    end
  end

  @doc """
  Plug for routes that require the user to be a superuser.
  """
  def require_superuser(conn, _opts) do
    user = conn.assigns.current_scope && conn.assigns.current_scope.user

    if user && user.is_superuser do
      conn
    else
      conn
      |> put_flash(:error, t_auth("You must be a superuser to access this page."))
      |> redirect(to: ~p"/orgs")
      |> halt()
    end
  end

  defp maybe_store_return_to(%{method: "GET"} = conn) do
    put_session(conn, :user_return_to, current_path(conn))
  end

  defp maybe_store_return_to(conn), do: conn

  @doc """
  Plug to store the current path for LiveView routes.

  This runs in the pipeline before LiveView mount, allowing us to store
  the return path in the session before on_mount callbacks run. Always
  overwrites any existing return path to ensure sudo mode redirects work correctly.
  """
  def store_return_to_for_liveview(conn, _opts) do
    # Skip authentication-related, public, dev, and asset paths
    skip_paths = [
      "/users/log-in",
      "/users/register",
      "/users/reset-password",
      "/users/confirm",
      "/users/sudo",
      "/docs/api",
      "/privacy",
      "/terms",
      "/help",
      "/dev/",
      "/assets/",
      "/health"
    ]

    should_store =
      conn.method == "GET" &&
        !Enum.any?(skip_paths, &String.starts_with?(conn.request_path, &1)) &&
        conn.request_path != "/"

    if should_store do
      put_session(conn, :user_return_to, current_path(conn))
    else
      conn
    end
  end

  @doc """
  Plug to load the current organization from the URL slug.

  Expects the organization slug to be in path_params as "org_slug".
  Verifies that the current user is a member of the organization.
  """
  def load_current_organization(conn, _opts) do
    org_slug = conn.path_params["org_slug"]
    scope = conn.assigns.current_scope

    if org_slug && scope && scope.user do
      organization = Towerops.Organizations.get_organization_by_slug!(org_slug)
      membership = Towerops.Organizations.get_membership(organization.id, scope.user.id)

      if membership do
        alias Towerops.Organizations.Policy

        conn
        |> assign(:current_scope, Scope.put_organization(scope, organization))
        |> assign(:current_membership, membership)
        |> assign(:can_view_financials, Policy.can_view_financials?(membership))
        |> put_session(:current_organization_id, organization.id)
      else
        # Log failed authorization attempt
        _ =
          AuditLogger.log_failed_access_attempt(
            conn,
            scope.user.id,
            "organization:#{organization.id}",
            "not_member"
          )

        conn
        |> put_flash(:error, t_auth("You don't have access to this organization."))
        |> redirect(to: ~p"/orgs")
        |> halt()
      end
    else
      conn
      |> put_flash(:error, t_auth("Organization not found."))
      |> redirect(to: ~p"/orgs")
      |> halt()
    end
  rescue
    Ecto.NoResultsError ->
      conn
      |> put_flash(:error, t_auth("Organization not found."))
      |> redirect(to: ~p"/orgs")
      |> halt()
  end

  @doc """
  Mounts authentication state for LiveView routes.

  ## Hooks

    * `:redirect_if_user_is_authenticated` - Redirects authenticated users
    * `:require_authenticated_user` - Requires user authentication
    * `:load_current_organization` - Loads organization from URL slug
    * `:require_organization_owner` - Requires user to be an owner of the current organization

  """
  def on_mount(:redirect_if_user_is_authenticated, _params, session, socket) do
    socket = mount_current_scope(socket, session)

    if socket.assigns.current_scope && socket.assigns.current_scope.user do
      user = socket.assigns.current_scope.user
      {:halt, LiveView.redirect(socket, to: signed_in_path(user))}
    else
      {:cont, socket}
    end
  end

  def on_mount(:require_authenticated_user, _params, session, socket) do
    socket = mount_current_scope(socket, session)

    if socket.assigns.current_scope && socket.assigns.current_scope.user do
      locale = socket.assigns.current_scope.user.language || "en"
      _ = Gettext.put_locale(ToweropsWeb.Gettext, locale)
      {:cont, socket}
    else
      socket =
        socket
        |> LiveView.put_flash(:error, t_auth("You must log in to access this page."))
        |> LiveView.redirect(to: ~p"/users/log-in")

      {:halt, socket}
    end
  end

  def on_mount(:load_current_organization, %{"org_slug" => org_slug}, _session, socket) do
    scope = socket.assigns.current_scope

    if org_slug && scope && scope.user do
      organization = Towerops.Organizations.get_organization_by_slug!(org_slug)
      membership = Towerops.Organizations.get_membership(organization.id, scope.user.id)

      if membership do
        {:cont,
         socket
         |> Phoenix.Component.assign(:current_scope, Scope.put_organization(scope, organization))
         |> Phoenix.Component.assign(:current_membership, membership)}
      else
        socket =
          socket
          |> LiveView.put_flash(:error, t_auth("You don't have access to this organization."))
          |> LiveView.redirect(to: ~p"/orgs")

        {:halt, socket}
      end
    else
      socket =
        socket
        |> LiveView.put_flash(:error, t_auth("Organization not found."))
        |> LiveView.redirect(to: ~p"/orgs")

      {:halt, socket}
    end
  rescue
    Ecto.NoResultsError ->
      socket =
        socket
        |> LiveView.put_flash(:error, t_auth("Organization not found."))
        |> LiveView.redirect(to: ~p"/orgs")

      {:halt, socket}
  end

  def on_mount(:load_current_organization, _params, _session, socket) do
    {:cont, socket}
  end

  def on_mount(:subscribe_to_status_updates, _params, _session, socket) do
    organization = socket.assigns[:current_scope] && socket.assigns.current_scope.organization

    alert_count =
      if organization, do: Towerops.Alerts.count_active_alerts(organization.id), else: 0

    Process.put(:unresolved_alert_count, alert_count)

    socket =
      socket
      |> maybe_subscribe_to_status_updates(organization)
      |> attach_status_title_hook(organization)
      |> attach_alert_count_hook(organization)

    {:cont, socket}
  end

  def on_mount(:load_default_organization, _params, session, socket) do
    user = socket.assigns.current_scope && socket.assigns.current_scope.user

    if user do
      load_organization_for_user(socket, session, user)
    else
      {:cont, socket}
    end
  end

  def on_mount(:require_superuser, _params, session, socket) do
    socket = mount_current_scope(socket, session)
    user = socket.assigns.current_scope && socket.assigns.current_scope.user

    if user && user.is_superuser do
      {:cont, socket}
    else
      socket =
        socket
        |> LiveView.put_flash(:error, t_auth("You must be a superuser to access this page."))
        |> LiveView.redirect(to: ~p"/orgs")

      {:halt, socket}
    end
  end

  def on_mount(:require_sudo_mode, _params, session, socket) do
    # Force refetch user from session to ensure we have latest data (including last_sudo_at)
    # We need to refetch because the user may have just verified sudo mode
    scope = build_scope_from_session(session)
    socket = Phoenix.Component.assign(socket, :current_scope, scope)
    user = scope && scope.user

    case {user && Accounts.sudo_mode?(user, -10), user && Accounts.totp_enabled?(user)} do
      {true, _} ->
        {:cont, socket}

      {false, true} ->
        socket =
          socket
          |> LiveView.put_flash(:error, t_auth("Please verify your identity to continue."))
          |> LiveView.redirect(to: ~p"/users/sudo-verify")

        {:halt, socket}

      {false, false} ->
        socket =
          socket
          |> LiveView.put_flash(:error, t_auth("Two-factor authentication is required for this action."))
          |> LiveView.redirect(to: ~p"/account/totp-enrollment")

        {:halt, socket}

      _ ->
        {:halt, LiveView.redirect(socket, to: ~p"/users/log-in")}
    end
  end

  def on_mount(:require_totp_enrollment, _params, _session, socket) do
    scope = socket.assigns.current_scope
    user = scope && scope.user

    # Skip TOTP requirement when impersonating - superuser has already authenticated
    if scope && scope.impersonating? do
      {:cont, socket}
    else
      if user && !Accounts.totp_enabled?(user) do
        socket =
          socket
          |> LiveView.put_flash(:error, t_auth("You must set up two-factor authentication to continue."))
          |> LiveView.redirect(to: ~p"/account/totp-enrollment")

        {:halt, socket}
      else
        {:cont, socket}
      end
    end
  end

  def on_mount(:require_organization_owner, _params, _session, socket) do
    membership = Map.get(socket.assigns, :current_membership)

    if membership && membership.role == :owner do
      {:cont, socket}
    else
      socket =
        socket
        |> LiveView.put_flash(:error, t_auth("You must be an organization owner to access this page."))
        |> LiveView.redirect(to: ~p"/orgs")

      {:halt, socket}
    end
  end

  def on_mount(:load_cookie_consent, _params, session, socket) do
    requires_consent = Map.get(session, "requires_cookie_consent", false)

    socket =
      socket
      |> Phoenix.Component.assign(:requires_cookie_consent, requires_consent)
      |> LiveView.attach_hook(:persist_cookie_consent, :handle_params, fn _params, _url, socket ->
        # Ensure the assign persists across navigation
        socket = Phoenix.Component.assign(socket, :requires_cookie_consent, requires_consent)
        {:cont, socket}
      end)

    {:cont, socket}
  end

  def on_mount(:handle_policy_consent, _params, _session, socket) do
    # Attach LiveView event handler for accepting updated policies
    socket =
      LiveView.attach_hook(socket, :policy_consent_handler, :handle_event, fn
        "accept_updated_policies", _params, socket ->
          # Grant consent for all policies that need re-consent
          policies_needing_consent = Map.get(socket.assigns, :policies_needing_consent, [])
          user_id = socket.assigns.current_scope.user.id

          Enum.each(policies_needing_consent, fn policy_type ->
            Accounts.grant_consent(user_id, policy_type)
          end)

          # Clear the policies_needing_consent list and show success message
          socket =
            socket
            |> Phoenix.Component.assign(:policies_needing_consent, [])
            |> LiveView.put_flash(:info, t_auth("Thank you for accepting the updated policies."))

          {:halt, socket}

        _event, _params, socket ->
          {:cont, socket}
      end)

    {:cont, socket}
  end

  defp load_organization_for_user(socket, session, user) do
    org_id = session["current_organization_id"]
    organization = find_user_organization(org_id, user.id)

    case organization do
      nil ->
        halt_with_error(socket, "Please select an organization.")

      org ->
        assign_organization_and_membership(socket, org, user.id)
    end
  end

  defp find_user_organization(org_id, user_id) when is_binary(org_id) do
    # Try session org first
    org =
      try do
        Towerops.Organizations.get_organization!(org_id)
      rescue
        Ecto.NoResultsError -> nil
      end

    # Verify user has access to this org
    if org do
      membership = Towerops.Organizations.get_membership(org.id, user_id)
      if membership, do: org
    end
  end

  defp find_user_organization(_org_id, user_id) do
    user = Accounts.get_user(user_id)
    default_org_id = user && user.default_organization_id

    # Try user's default organization first
    with true <- not is_nil(default_org_id),
         default_org = try_get_organization(default_org_id),
         true <- not is_nil(default_org),
         membership = Towerops.Organizations.get_membership(default_org.id, user_id),
         true <- not is_nil(membership) do
      default_org
    else
      _ -> fallback_to_first_org(user_id)
    end
  end

  defp try_get_organization(org_id) do
    Towerops.Organizations.get_organization!(org_id)
  rescue
    Ecto.NoResultsError -> nil
  end

  defp fallback_to_first_org(user_id) do
    case Towerops.Organizations.list_user_organizations(user_id) do
      [first_org | _] -> first_org
      [] -> nil
    end
  end

  defp assign_organization_and_membership(socket, organization, user_id) do
    membership = Towerops.Organizations.get_membership(organization.id, user_id)

    case membership do
      nil ->
        halt_with_error(socket, "You don't have access to any organizations.")

      mem ->
        alias Towerops.Organizations.Policy

        scope = socket.assigns.current_scope

        {:cont,
         socket
         |> Phoenix.Component.assign(:current_scope, Scope.put_organization(scope, organization))
         |> Phoenix.Component.assign(:current_membership, mem)
         |> Phoenix.Component.assign(:can_view_financials, Policy.can_view_financials?(mem))}
    end
  end

  defp halt_with_error(socket, message) do
    socket =
      socket
      |> LiveView.put_flash(:error, message)
      |> LiveView.redirect(to: ~p"/orgs")

    {:halt, socket}
  end

  defp mount_current_scope(socket, session) do
    socket =
      Phoenix.Component.assign_new(socket, :current_scope, fn ->
        build_scope_from_session(session)
      end)

    # Get timezone from user profile, connect params, or default to UTC
    user = socket.assigns.current_scope && socket.assigns.current_scope.user
    connect_timezone = get_in(socket.private, [:connect_params, "timezone"])

    timezone =
      cond do
        user && user.timezone -> user.timezone
        connect_timezone -> connect_timezone
        true -> "UTC"
      end

    # If user is logged in but doesn't have a timezone set, update their profile
    _ =
      if user && !user.timezone && connect_timezone do
        Task.Supervisor.start_child(Towerops.TaskSupervisor, fn ->
          Accounts.update_user_profile(user, %{timezone: connect_timezone})
        end)
      end

    Phoenix.Component.assign(socket, :timezone, timezone)
  end

  defp build_scope_from_session(session) do
    if session["impersonating"] do
      build_impersonation_scope(session)
    else
      build_normal_scope(session)
    end
  end

  defp build_impersonation_scope(session) do
    superuser_id = session["superuser_id"]
    target_user_id = session["target_user_id"]

    if superuser_id && target_user_id do
      fetch_impersonation_users(superuser_id, target_user_id)
    else
      Scope.for_user(nil)
    end
  end

  defp fetch_impersonation_users(superuser_id, target_user_id) do
    with superuser when not is_nil(superuser) <- Accounts.get_user(superuser_id),
         target_user when not is_nil(target_user) <- Accounts.get_user(target_user_id) do
      Scope.for_impersonation(superuser, target_user)
    else
      _ -> Scope.for_user(nil)
    end
  end

  defp build_normal_scope(session) do
    case session["user_token"] do
      nil -> Scope.for_user(nil)
      user_token -> fetch_user_from_token(user_token)
    end
  end

  defp fetch_user_from_token(user_token) do
    case Accounts.get_user_by_session_token(user_token) do
      {user, _token_inserted_at} -> Scope.for_user(user)
      nil -> Scope.for_user(nil)
    end
  end

  @doc """
  Start impersonating a user as a superuser.

  Stores the original superuser ID in the session and updates the current scope
  to show the impersonated user. Creates an audit log entry.
  """
  def start_impersonation(conn, target_user_id) do
    superuser = conn.assigns.current_scope.user
    target_user = Accounts.get_user!(target_user_id)

    # Prevent impersonating self
    if target_user.id == superuser.id do
      conn
      |> put_flash(:error, t_admin("You cannot impersonate yourself."))
      |> redirect(to: ~p"/admin/users")
      |> halt()
    else
      # Create audit log
      ip = to_string(:inet_parse.ntoa(conn.remote_ip))

      Towerops.Admin.create_audit_log(%{
        action: "impersonate_start",
        superuser_id: superuser.id,
        target_user_id: target_user.id,
        metadata: %{target_email: target_user.email, target_is_superuser: target_user.is_superuser},
        ip_address: ip
      })

      # Store superuser ID and target user ID in session and update scope
      conn
      |> put_session(:superuser_id, superuser.id)
      |> put_session(:target_user_id, target_user.id)
      |> put_session(:impersonating, true)
      |> assign(:current_scope, Scope.for_impersonation(superuser, target_user))
      |> maybe_set_default_organization(target_user)
      |> put_flash(:info, t_admin("Now impersonating %{email}", email: target_user.email))
      |> redirect(to: ~p"/orgs")
    end
  end

  @doc """
  Stop impersonating and restore the superuser session.

  Removes impersonation state from the session and restores the original superuser
  scope. Creates an audit log entry.
  """
  def stop_impersonation(conn) do
    superuser_id = get_session(conn, :superuser_id)
    target_user = conn.assigns.current_scope.user
    superuser = Accounts.get_user!(superuser_id)

    # Create audit log
    ip = to_string(:inet_parse.ntoa(conn.remote_ip))

    Towerops.Admin.create_audit_log(%{
      action: "impersonate_end",
      superuser_id: superuser_id,
      target_user_id: target_user.id,
      metadata: %{target_email: target_user.email},
      ip_address: ip
    })

    conn
    |> delete_session(:superuser_id)
    |> delete_session(:target_user_id)
    |> delete_session(:impersonating)
    |> assign(:current_scope, Scope.for_user(superuser))
    |> maybe_set_default_organization(superuser)
    |> put_flash(:info, t_admin("Stopped impersonating"))
    |> redirect(to: signed_in_path(superuser))
  end

  ## Login tracking helpers

  defp create_browser_session_from_conn(conn, user, user_token) do
    ip_address = extract_ip_address(conn)
    user_agent = extract_user_agent(conn)
    now = DateTime.utc_now()
    expires_at = DateTime.add(now, @max_cookie_age_in_days * 24 * 60 * 60, :second)

    Accounts.create_browser_session(%{
      user_id: user.id,
      user_token_id: user_token.id,
      ip_address: ip_address,
      user_agent: user_agent,
      last_activity_at: now,
      expires_at: expires_at
    })
  end

  defp record_successful_login(conn, user, params) do
    ip_address = extract_ip_address(conn)
    user_agent = extract_user_agent(conn)
    method = determine_login_method(conn, params)

    Accounts.record_login_attempt(%{
      user_id: user.id,
      email: user.email,
      success: true,
      method: method,
      ip_address: ip_address,
      user_agent: user_agent
    })
  end

  defp extract_ip_address(conn) do
    # Try X-Forwarded-For first (for proxies/load balancers)
    case get_req_header(conn, "x-forwarded-for") do
      [forwarded | _] ->
        # Take the first IP in the chain
        forwarded
        |> String.split(",")
        |> List.first()
        |> String.trim()

      [] ->
        # Fall back to remote_ip
        conn.remote_ip
        |> :inet_parse.ntoa()
        |> to_string()
    end
  end

  defp extract_user_agent(conn) do
    case get_req_header(conn, "user-agent") do
      [ua | _] -> ua
      [] -> nil
    end
  end

  defp determine_login_method(_conn, %{"remember_me" => _}), do: "password"
  defp determine_login_method(_conn, _params), do: "password"

  defp maybe_subscribe_to_status_updates(socket, organization) do
    _ =
      if organization && LiveView.connected?(socket) do
        Phoenix.PubSub.subscribe(Towerops.PubSub, "organization:#{organization.id}:alerts")
      end

    socket
  end

  defp attach_status_title_hook(socket, nil), do: socket

  defp attach_status_title_hook(socket, organization) do
    LiveView.attach_hook(socket, :status_title_updates, :handle_info, fn
      {:alert_changed, org_id}, socket when org_id == organization.id ->
        emoji = StatusHelpers.status_emoji(organization)
        {:cont, LiveView.push_event(socket, "update_status_emoji", %{emoji: emoji})}

      _message, socket ->
        {:cont, socket}
    end)
  end

  defp attach_alert_count_hook(socket, nil), do: socket

  defp attach_alert_count_hook(socket, organization) do
    LiveView.attach_hook(socket, :alert_count_updates, :handle_info, fn
      {:alert_changed, org_id}, socket when org_id == organization.id ->
        count = Towerops.Alerts.count_active_alerts(organization.id)
        Process.put(:unresolved_alert_count, count)
        {:cont, Phoenix.Component.assign(socket, :_alert_count_tick, count)}

      _message, socket ->
        {:cont, socket}
    end)
  end
end