public function apply_coupon( $coupon, $validate = true ) {
		if ( ! is_a( $coupon, 'WC_Coupon' ) ) {
			return new WP_Error( 'invalid_coupon', __( 'Invalid coupon', 'woocommerce' ) );
		}

		$is_coupon_valid = $validate ? $this->is_coupon_valid( $coupon ) : true;

		if ( is_wp_error( $is_coupon_valid ) ) {
			return $is_coupon_valid;
		}

		if ( ! isset( $this->discounts[ $coupon->get_code() ] ) ) {
			$this->discounts[ $coupon->get_code() ] = array_fill_keys( array_keys( $this->items ), 0 );
		}

		$items_to_apply = $this->get_items_to_apply_coupon( $coupon );

		// Core discounts are handled here as of 3.2.
		switch ( $coupon->get_discount_type() ) {
			case 'percent':
				$this->apply_coupon_percent( $coupon, $items_to_apply );
				break;
			case 'fixed_product':
				$this->apply_coupon_fixed_product( $coupon, $items_to_apply );
				break;
			case 'fixed_cart':
				$this->apply_coupon_fixed_cart( $coupon, $items_to_apply );
				break;
			default:
				$this->apply_coupon_custom( $coupon, $items_to_apply );
				break;
		}

		return true;
	}