class Variable

class Variable extends DrupalSqlBase {
    
    /**
     * The variable names to fetch.
     *
     * @var array
     */
    protected $variables;
    
    /**
     * The variables that result in no row if any are missing from the source.
     *
     * @var array
     */
    protected $variablesNoRowIfMissing;
    
    /**
     * {@inheritdoc}
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, StateInterface $state, EntityTypeManagerInterface $entity_type_manager) {
        parent::__construct($configuration, $plugin_id, $plugin_definition, $migration, $state, $entity_type_manager);
        $this->variablesNoRowIfMissing = $this->configuration['variables_no_row_if_missing'] ?? [];
        $variables = $this->configuration['variables'] ?? [];
        $this->variables = array_unique(array_merge(array_values($variables), array_values($this->variablesNoRowIfMissing)));
    }
    
    /**
     * {@inheritdoc}
     */
    protected function initializeIterator() {
        if ($this->count()) {
            return new \ArrayIterator([
                $this->values(),
            ]);
        }
        return new \ArrayIterator();
    }
    
    /**
     * Return the values of the variables specified in the plugin configuration.
     *
     * @return array
     *   An associative array where the keys are the variables specified in the
     *   plugin configuration and the values are the values found in the source.
     *   Only those values are returned that are actually in the database.
     */
    protected function values() {
        // Create an ID field so we can record migration in the map table.
        // Arbitrarily, use the first variable name.
        $values['id'] = reset($this->variables);
        return $values + array_map('unserialize', $this->prepareQuery()
            ->execute()
            ->fetchAllKeyed());
    }
    
    /**
     * {@inheritdoc}
     */
    protected function doCount() {
        if (empty($this->variablesNoRowIfMissing)) {
            return 1;
        }
        $variable_names = array_keys($this->query()
            ->execute()
            ->fetchAllAssoc('name'));
        if (!empty(array_diff($this->variablesNoRowIfMissing, $variable_names))) {
            return 0;
        }
        return 1;
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        return array_combine($this->variables, $this->variables);
    }
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        return $this->getDatabase()
            ->select('variable', 'v')
            ->fields('v', [
            'name',
            'value',
        ])
            ->condition('name', $this->variables, 'IN');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['id']['type'] = 'string';
        return $ids;
    }

}