class StaticMenuLinkOverrides

class StaticMenuLinkOverrides implements StaticMenuLinkOverridesInterface {
    
    /**
     * The config name used to store the overrides.
     *
     * This configuration can not be overridden by configuration overrides because
     * menu links and these overrides are cached in a way that is not override
     * aware.
     *
     * @var string
     */
    protected $configName = 'core.menu.static_menu_link_overrides';
    
    /**
     * The menu link overrides config object.
     *
     * @var \Drupal\Core\Config\Config
     */
    protected $config;
    
    /**
     * The config factory object.
     *
     * @var \Drupal\Core\Config\ConfigFactoryInterface
     */
    protected $configFactory;
    
    /**
     * Constructs a StaticMenuLinkOverrides object.
     *
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   A configuration factory instance.
     */
    public function __construct(ConfigFactoryInterface $config_factory) {
        $this->configFactory = $config_factory;
    }
    
    /**
     * Gets the configuration object when needed.
     *
     * Since this service is injected into all static menu link objects, but
     * only used when updating one, avoid actually loading the config when it's
     * not needed.
     */
    protected function getConfig() {
        if (empty($this->config)) {
            // Get an override free and editable configuration object.
            $this->config = $this->configFactory
                ->getEditable($this->configName);
        }
        return $this->config;
    }
    
    /**
     * {@inheritdoc}
     */
    public function reload() {
        $this->config = NULL;
        $this->configFactory
            ->reset($this->configName);
    }
    
    /**
     * {@inheritdoc}
     */
    public function loadOverride($id) {
        assert(is_string($id), 'Menu link plugin ID should be a string.');
        $all_overrides = $this->getConfig()
            ->get('definitions');
        $id = static::encodeId($id);
        return $all_overrides[$id] ?? [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteMultipleOverrides(array $ids) {
        $all_overrides = $this->getConfig()
            ->get('definitions');
        $save = FALSE;
        foreach ($ids as $id) {
            $id = static::encodeId($id);
            if (isset($all_overrides[$id])) {
                unset($all_overrides[$id]);
                $save = TRUE;
            }
        }
        if ($save) {
            $this->getConfig()
                ->set('definitions', $all_overrides)
                ->save();
        }
        return $save;
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteOverride($id) {
        return $this->deleteMultipleOverrides([
            $id,
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function loadMultipleOverrides(array $ids) {
        $result = [];
        if ($ids) {
            $all_overrides = $this->getConfig()
                ->get('definitions') ?: [];
            foreach ($ids as $id) {
                $encoded_id = static::encodeId($id);
                if (isset($all_overrides[$encoded_id])) {
                    $result[$id] = $all_overrides[$encoded_id];
                }
            }
        }
        return $result;
    }
    
    /**
     * {@inheritdoc}
     */
    public function saveOverride($id, array $definition) {
        // Only allow to override a specific subset of the keys.
        $expected = [
            'menu_name' => '',
            'parent' => '',
            'weight' => 0,
            'expanded' => FALSE,
            'enabled' => FALSE,
        ];
        // Filter the overrides to only those that are expected.
        $definition = array_intersect_key($definition, $expected);
        // Ensure all values are set.
        $definition = $definition + $expected;
        if ($definition) {
            // Cast keys to avoid config schema during save.
            $definition['menu_name'] = (string) $definition['menu_name'];
            $definition['parent'] = (string) $definition['parent'];
            $definition['weight'] = (int) $definition['weight'];
            $definition['expanded'] = (bool) $definition['expanded'];
            $definition['enabled'] = (bool) $definition['enabled'];
            $id = static::encodeId($id);
            $all_overrides = $this->getConfig()
                ->get('definitions');
            // Combine with any existing data.
            $all_overrides[$id] = $definition + $this->loadOverride($id);
            $this->getConfig()
                ->set('definitions', $all_overrides)
                ->save(TRUE);
        }
        return array_keys($definition);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheTags() {
        return $this->getConfig()
            ->getCacheTags();
    }
    
    /**
     * Encodes the ID by replacing dots with double underscores.
     *
     * This is done because config schema uses dots for its internal type
     * hierarchy. Double underscores are converted to triple underscores to
     * avoid accidental conflicts.
     *
     * @param string $id
     *   The menu plugin ID.
     *
     * @return string
     *   The menu plugin ID with double underscore instead of dots.
     */
    protected static function encodeId($id) {
        return strtr($id, [
            '.' => '__',
            '__' => '___',
        ]);
    }

}