<?php

namespace Drupal\migrate_example\Plugin\migrate\source;

use Drupal\migrate\Plugin\migrate\source\SqlBase;

/**
 * This is an example of a simple SQL-based source plugin. Source plugins are
 * classes which deliver source data to the processing pipeline. For SQL
 * sources, the SqlBase class provides most of the functionality needed - for
 * a specific migration, you are required to implement the three simple public
 * methods you see below.
 *
 * This annotation tells Drupal that the name of the MigrateSource plugin
 * implemented by this class is "beer_term". This is the name that the migration
 * configuration references with the source "plugin" key.
 *
 * @MigrateSource(
 *   id = "beer_term"
 * )
 */
class BeerTerm extends SqlBase {

  /**
   * {@inheritdoc}
   */
  public function query() {
    /**
     * The most important part of a SQL source plugin is the SQL query to
     * retrieve the data to be imported. Note that the query is not executed
     * here - the migration process will control execution of the query. Also
     * note that it is constructed from a $this->select() call - this ensures
     * that the query is executed against the database configured for this
     * source plugin.
     */
    return $this->select('migrate_example_beer_topic', 'met')
      ->fields('met', ['style', 'details', 'style_parent', 'region', 'hoppiness'])
      // We sort this way to ensure parent terms are imported first.
      ->orderBy('style_parent', 'ASC');
  }

  /**
   * {@inheritdoc}
   */
  public function fields() {
    /**
     * This method simply documents the available source fields provided by
     * the source plugin, for use by front-end tools. It returns an array keyed
     * by field/column name, with the value being a translated string explaining
     * to humans what the field represents. You should always
     */
    $fields = [
      'style' => $this->t('Account ID'),
      'details' => $this->t('Blocked/Allowed'),
      'style_parent' => $this->t('Registered date'),
      // These values are not currently migrated - it's OK to skip fields you
      // don't need.
      'region' => $this->t('Region the style is associated with'),
      'hoppiness' => $this->t('Hoppiness of the style'),
    ];

    return $fields;
  }

  /**
   * {@inheritdoc}
   */
  public function getIds() {
    /**
     * This method indicates what field(s) from the source row uniquely identify
     * that source row, and what their types are. This is critical information
     * for managing the migration. The keys of the returned array are the field
     * names from the query which comprise the unique identifier. The values are
     * arrays indicating the type of the field, used for creating compatible
     * columns in the map tables that track processed items.
     */
    return [
      'style' => [
        'type' => 'string',
        // 'alias' is the alias for the table containing 'style' in the query
        // defined above. Optional in this case, but necessary if the same
        // column may occur in multiple tables in a join.
        'alias' => 'met',
      ],
    ];
  }

}