interface MigrateSourceInterface

interface MigrateSourceInterface extends \Countable, \Iterator, PluginInspectionInterface {
    
    /**
     * Indicates that the source is not countable.
     */
    const NOT_COUNTABLE = -1;
    
    /**
     * Returns available fields on the source.
     *
     * @return array
     *   Available fields in the source, keys are the field machine names as used
     *   in field mappings, values are descriptions.
     */
    public function fields();
    
    /**
     * Adds additional data to the row.
     *
     * @param \Drupal\migrate\Row $row
     *   The row object.
     *
     * @return bool
     *   FALSE if this row needs to be skipped.
     */
    public function prepareRow(Row $row);
    
    /**
     * Allows class to decide how it will react when it is treated like a string.
     */
    public function __toString();
    
    /**
     * Defines the source fields uniquely identifying a source row.
     *
     * None of these fields should contain a NULL value. If necessary, use
     * prepareRow() or hook_migrate_prepare_row() to rewrite NULL values to
     * appropriate empty values (such as '' or 0).
     *
     * @return array[]
     *   An associative array of field definitions keyed by field ID. Values are
     *   associative arrays with a structure that contains the field type ('type'
     *   key). The other keys are the field storage settings as they are returned
     *   by FieldStorageDefinitionInterface::getSettings().
     *
     *   Examples:
     *
     *   A composite source primary key that is defined by an integer and a string
     *   might look like this:
     *   @code
     *     return [
     *       'id' => [
     *         'type' => 'integer',
     *         'unsigned' => FALSE,
     *         'size' => 'big',
     *       ],
     *       'version' => [
     *         'type' => 'string',
     *         'max_length' => 64,
     *         'is_ascii' => TRUE,
     *       ],
     *     ];
     *   @endcode
     *
     *   If 'type' points to a field plugin with multiple columns and needs to
     *   refer to a column different than 'value', the key of that column will be
     *   appended as a suffix to the plugin name, separated by dot ('.'). Example:
     *   @code
     *     return [
     *       'format' => [
     *         'type' => 'text.format',
     *       ],
     *     ];
     *   @endcode
     *
     *   Additional custom keys/values that are not part of field storage
     *   definition can be added as shown below. The most common setting
     *   passed along to the ID definition is table 'alias', used by the SqlBase
     *   source plugin in order to distinguish between ambiguous column names -
     *   for example, when a SQL source query joins two tables with the same
     *   column names.
     *   @code
     *     return [
     *       'nid' => [
     *         'type' => 'integer',
     *         'alias' => 'n',
     *       ],
     *     ];
     *   @endcode
     *
     * @see \Drupal\Core\Field\FieldStorageDefinitionInterface::getSettings()
     * @see \Drupal\Core\Field\Plugin\Field\FieldType\IntegerItem
     * @see \Drupal\Core\Field\Plugin\Field\FieldType\StringItem
     * @see \Drupal\text\Plugin\Field\FieldType\TextItem
     * @see \Drupal\migrate\Plugin\migrate\source\SqlBase
     */
    public function getIds();
    
    /**
     * Gets the source module providing the source data.
     *
     * @return string|null
     *   The source module or NULL if not found.
     */
    public function getSourceModule();

}