<?php
namespace Controllers;

class UsersController
{
  private const ADMIN_USER_ID = 1;
  private const IMPERSONATOR_SESSION_KEY = 'impersonator_user';

  public static function mainView()
  {
    global $user;

    if ( !$user )
      return \controls\Users::login_form();

    $impersonator_user = self::getImpersonatorUser();
    if ( !self::canManageUsers( $user, $impersonator_user ) )
      self::forbiddenRedirect();

    $users_repository = new \Domain\Users\UserRepository();

    return \Tpl::view( 'users/main-view', self::buildMainViewModel(
      $user,
      $impersonator_user,
      $users_repository -> all()
    ) );
  }

  public static function loginAs()
  {
    global $user;

    if ( !$user )
      return \controls\Users::login_form();

    $impersonator_user = self::getImpersonatorUser();
    if ( !self::canManageUsers( $user, $impersonator_user ) )
      self::forbiddenRedirect();

    $target_user_id = (int)\S::get( 'user_id' );
    $users_repository = new \Domain\Users\UserRepository();
    $target_user = $users_repository -> byId( $target_user_id );

    if ( !$target_user )
    {
      \S::alert( 'Nie znaleziono wskazanego uzytkownika.' );
      header( 'Location: /users/main_view/' );
      exit;
    }

    $new_session_state = self::impersonationStateAfterLoginAs( $user, $target_user, $impersonator_user );

    \S::set_session( 'user', $new_session_state['user'] );
    \S::set_session( self::IMPERSONATOR_SESSION_KEY, $new_session_state['impersonator_user'] );

    \S::alert( 'Zalogowano jako: ' . $target_user['name'] . ' ' . $target_user['surname'] . '.' );
    header( 'Location: /' );
    exit;
  }

  public static function switchBackToAdmin()
  {
    $impersonator_user = self::getImpersonatorUser();

    if ( !$impersonator_user or !isset( $impersonator_user['id'] ) or (int)$impersonator_user['id'] !== self::ADMIN_USER_ID )
    {
      \S::alert( 'Brak aktywnej sesji podszywania.' );
      header( 'Location: /' );
      exit;
    }

    \S::set_session( 'user', $impersonator_user );
    \S::del_session( self::IMPERSONATOR_SESSION_KEY );

    \S::alert( 'Powrot do konta administratora.' );
    header( 'Location: /users/main_view/' );
    exit;
  }

  public static function canManageUsers( $current_user, $impersonator_user = null )
  {
    if ( !is_array( $current_user ) )
      return false;

    if ( isset( $current_user['id'] ) and (int)$current_user['id'] === self::ADMIN_USER_ID )
      return true;

    if ( is_array( $impersonator_user ) and isset( $impersonator_user['id'] ) and (int)$impersonator_user['id'] === self::ADMIN_USER_ID )
      return true;

    return false;
  }

  public static function buildMainViewModel( $current_user, $impersonator_user, array $users )
  {
    return [
      'current_user' => $current_user,
      'impersonator_user' => $impersonator_user,
      'users' => $users,
      'can_switch_back' => is_array( $impersonator_user ) and isset( $impersonator_user['id'] ) and (int)$impersonator_user['id'] === self::ADMIN_USER_ID
    ];
  }

  public static function impersonationStateAfterLoginAs( $current_user, $target_user, $existing_impersonator_user = null )
  {
    $impersonator_user = $existing_impersonator_user;

    if ( !is_array( $impersonator_user ) )
      $impersonator_user = ( is_array( $current_user ) and isset( $current_user['id'] ) and (int)$current_user['id'] === self::ADMIN_USER_ID ) ? $current_user : null;

    return [
      'user' => $target_user,
      'impersonator_user' => $impersonator_user
    ];
  }

  private static function getImpersonatorUser()
  {
    $session_value = \S::get_session( self::IMPERSONATOR_SESSION_KEY );

    if ( is_array( $session_value ) )
      return $session_value;

    return null;
  }

  private static function forbiddenRedirect()
  {
    \S::alert( 'Brak uprawnien do zarzadzania uzytkownikami.' );
    header( 'Location: /' );
    exit;
  }
}