Filter Woocommerce Orders by Coupons Used

defined( 'ABSPATH' ) or exit;

// fire it up!
add_action( 'plugins_loaded', 'wc_filter_orders_by_coupon' );

 class WC_Filter_Orders_By_Coupon {
	const VERSION = '1.1.0';

	/** @var WC_Filter_Orders_By_Coupon single instance of this plugin */
	protected static $instance;
	public function __construct() {

		// load translations
		add_action( 'init', array( $this, 'load_translation' ) );
		if ( is_admin() && ! defined( 'DOING_AJAX' ) ) {

			// adds the coupon filtering dropdown to the orders page
			add_action( 'restrict_manage_posts', array( $this, 'filter_orders_by_coupon_used' ) );

			// makes coupons filterable
			add_filter( 'posts_join',  array( $this, 'add_order_items_join' ) );
			add_filter( 'posts_where', array( $this, 'add_filterable_where' ) );
		}
	}

	public function filter_orders_by_coupon_used() {
		global $typenow;

		if ( 'shop_order' === $typenow ) {

			$args = array(
				'posts_per_page' => - 1,
				'orderby'        => 'title',
				'order'          => 'asc',
				'post_type'      => 'shop_coupon',
				'post_status'    => 'publish',
			);

			$coupons = get_posts( $args );

			if ( ! empty( $coupons ) ) : ?>

				<select name="_coupons_used" id="dropdown_coupons_used">
					<option value="">
						<?php esc_html_e( 'Filter by coupon used', 'wc-filter-orders' ); ?>
					</option>
					<?php foreach ( $coupons as $coupon ) : ?>
						<option value="<?php echo esc_attr( $coupon->post_title ); ?>" <?php echo esc_attr( isset( $_GET['_coupons_used'] ) ? selected( $coupon->post_title, $_GET['_coupons_used'], false ) : '' ); ?>>
							<?php echo esc_html( $coupon->post_title ); ?>
						</option>
					<?php endforeach; ?>
				</select>
			<?php endif;
		}
	}

	public function add_order_items_join( $join ) {
		global $typenow, $wpdb;

		if ( 'shop_order' === $typenow && isset( $_GET['_coupons_used'] ) && ! empty( $_GET['_coupons_used'] ) ) {

			$join .= "LEFT JOIN {$wpdb->prefix}woocommerce_order_items woi ON {$wpdb->posts}.ID = woi.order_id";
		}

		return $join;
	}

	public function add_filterable_where( $where ) {
		global $typenow, $wpdb;

		if ( 'shop_order' === $typenow && isset( $_GET['_coupons_used'] ) && ! empty( $_GET['_coupons_used'] ) ) {

			// Main WHERE query part
			$where .= $wpdb->prepare( " AND woi.order_item_type='coupon' AND woi.order_item_name='%s'", wc_clean( $_GET['_coupons_used'] ) );
		}

		return $where;
	}

	public function load_translation() {
		// localization
		load_plugin_textdomain( 'wc-filter-orders', false, dirname( plugin_basename( __FILE__ ) ) . '/i18n/languages' );
	}

	public static function instance() {
		if ( is_null( self::$instance ) ) {
		 	self::$instance = new self();
		}
		return self::$instance;
	}

	public function __clone() {
		/* translators: Placeholders: %s - plugin name */
		_doing_it_wrong( __FUNCTION__, sprintf( esc_html__( 'You cannot clone instances of %s.', 'wc-filter-orders' ), 'Filter WC Orders by Coupon' ), '1.1.0' );
	}

	public function __wakeup() {
		/* translators: Placeholders: %s - plugin name */
		_doing_it_wrong( __FUNCTION__, sprintf( esc_html__( 'You cannot unserialize instances of %s.', 'wc-filter-orders' ), 'Filter WC Orders by Coupon' ), '1.1.0' );
	}
}

function wc_filter_orders_by_coupon() {
	return WC_Filter_Orders_By_Coupon::instance();
}