public function sales_sparkline( $id = '', $days = 7, $type = 'sales' ) {

		if ( $id ) {
			$meta_key = ( 'sales' === $type ) ? '_line_total' : '_qty';

			$data = $this->get_order_report_data(
				array(
					'data'         => array(
						'_product_id' => array(
							'type'            => 'order_item_meta',
							'order_item_type' => 'line_item',
							'function'        => '',
							'name'            => 'product_id',
						),
						$meta_key     => array(
							'type'            => 'order_item_meta',
							'order_item_type' => 'line_item',
							'function'        => 'SUM',
							'name'            => 'sparkline_value',
						),
						'post_date'   => array(
							'type'     => 'post_data',
							'function' => '',
							'name'     => 'post_date',
						),
					),
					'where'        => array(
						array(
							'key'      => 'post_date',
							'value'    => date( 'Y-m-d', strtotime( 'midnight -' . ( $days - 1 ) . ' days', current_time( 'timestamp' ) ) ),
							'operator' => '>',
						),
						array(
							'key'      => 'order_item_meta__product_id.meta_value',
							'value'    => $id,
							'operator' => '=',
						),
					),
					'group_by'     => 'YEAR(posts.post_date), MONTH(posts.post_date), DAY(posts.post_date)',
					'query_type'   => 'get_results',
					'filter_range' => false,
				)
			);
		} else {

			$data = $this->get_order_report_data(
				array(
					'data'         => array(
						'_order_total' => array(
							'type'     => 'meta',
							'function' => 'SUM',
							'name'     => 'sparkline_value',
						),
						'post_date'    => array(
							'type'     => 'post_data',
							'function' => '',
							'name'     => 'post_date',
						),
					),
					'where'        => array(
						array(
							'key'      => 'post_date',
							'value'    => date( 'Y-m-d', strtotime( 'midnight -' . ( $days - 1 ) . ' days', current_time( 'timestamp' ) ) ),
							'operator' => '>',
						),
					),
					'group_by'     => 'YEAR(posts.post_date), MONTH(posts.post_date), DAY(posts.post_date)',
					'query_type'   => 'get_results',
					'filter_range' => false,
				)
			);
		}

		$total = 0;
		foreach ( $data as $d ) {
			$total += $d->sparkline_value;
		}

		if ( 'sales' === $type ) {
			/* translators: 1: total income 2: days */
			$tooltip = sprintf( __( 'Sold %1$s worth in the last %2$d days', 'woocommerce' ), strip_tags( wc_price( $total ) ), $days );
		} else {
			/* translators: 1: total items sold 2: days */
			$tooltip = sprintf( _n( 'Sold %1$d item in the last %2$d days', 'Sold %1$d items in the last %2$d days', $total, 'woocommerce' ), $total, $days );
		}

		$sparkline_data = array_values( $this->prepare_chart_data( $data, 'post_date', 'sparkline_value', $days - 1, strtotime( 'midnight -' . ( $days - 1 ) . ' days', current_time( 'timestamp' ) ), 'day' ) );

		return '<span class="wc_sparkline ' . ( ( 'sales' === $type ) ? 'lines' : 'bars' ) . ' tips" data-color="#777" data-tip="' . esc_attr( $tooltip ) . '" data-barwidth="' . 60 * 60 * 16 * 1000 . '" data-sparkline="' . wc_esc_json( wp_json_encode( $sparkline_data ) ) . '"></span>';
	}