<?php

use Drupal\Core\Installer\InstallerKernel;

/**
 * Implements hook_requirements().
 */
function gin_toolbar_requirements($phase) {
  $requirements = [];

  if ($phase === 'install') {
    // We need to check if Gin theme is installed.
    $installed = \Drupal::service('theme_handler')->themeExists('gin');

    // If the Gin theme isn't installed then check whether currently Drupal is
    // being installed and whether the Gin theme will be installed.
    if (!$installed && InstallerKernel::installationAttempted()) {
      global $install_state;
      if (isset($install_state['profile_info']['themes']) && !in_array('gin', $install_state['profile_info']['themes'], TRUE)) {
        $requirements['gin'] = [
          'title' => t('Gin'),
          'description' => t('The Gin Toolbar module works with <a href="https://www.drupal.org/project/gin" target="_blank">Gin</a> theme only'),
          'severity' => REQUIREMENT_ERROR,
        ];
      }
    }
  }

  return $requirements;
}