public static function background_installer( $plugin_to_install_id, $plugin_to_install ) {
		// Explicitly clear the event.
		$args = func_get_args();

		if ( ! empty( $plugin_to_install['repo-slug'] ) ) {
			require_once ABSPATH . 'wp-admin/includes/file.php';
			require_once ABSPATH . 'wp-admin/includes/plugin-install.php';
			require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
			require_once ABSPATH . 'wp-admin/includes/plugin.php';

			WP_Filesystem();

			$skin              = new Automatic_Upgrader_Skin();
			$upgrader          = new WP_Upgrader( $skin );
			$installed_plugins = array_reduce( array_keys( get_plugins() ), array( __CLASS__, 'associate_plugin_file' ) );
			if ( empty( $installed_plugins ) ) {
				$installed_plugins = array();
			}
			$plugin_slug = $plugin_to_install['repo-slug'];
			$plugin_file = isset( $plugin_to_install['file'] ) ? $plugin_to_install['file'] : $plugin_slug . '.php';
			$installed   = false;
			$activate    = false;

			// See if the plugin is installed already.
			if ( isset( $installed_plugins[ $plugin_file ] ) ) {
				$installed = true;
				$activate  = ! is_plugin_active( $installed_plugins[ $plugin_file ] );
			}

			// Install this thing!
			if ( ! $installed ) {
				// Suppress feedback.
				ob_start();

				try {
					$plugin_information = plugins_api(
						'plugin_information',
						array(
							'slug'   => $plugin_slug,
							'fields' => array(
								'short_description' => false,
								'sections'          => false,
								'requires'          => false,
								'rating'            => false,
								'ratings'           => false,
								'downloaded'        => false,
								'last_updated'      => false,
								'added'             => false,
								'tags'              => false,
								'homepage'          => false,
								'donate_link'       => false,
								'author_profile'    => false,
								'author'            => false,
							),
						)
					);

					if ( is_wp_error( $plugin_information ) ) {
						throw new Exception( $plugin_information->get_error_message() );
					}

					$package  = $plugin_information->download_link;
					$download = $upgrader->download_package( $package );

					if ( is_wp_error( $download ) ) {
						throw new Exception( $download->get_error_message() );
					}

					$working_dir = $upgrader->unpack_package( $download, true );

					if ( is_wp_error( $working_dir ) ) {
						throw new Exception( $working_dir->get_error_message() );
					}

					$result = $upgrader->install_package(
						array(
							'source'                      => $working_dir,
							'destination'                 => WP_PLUGIN_DIR,
							'clear_destination'           => false,
							'abort_if_destination_exists' => false,
							'clear_working'               => true,
							'hook_extra'                  => array(
								'type'   => 'plugin',
								'action' => 'install',
							),
						)
					);

					if ( is_wp_error( $result ) ) {
						throw new Exception( $result->get_error_message() );
					}

					$activate = true;

				} catch ( Exception $e ) {
					WC_Admin_Notices::add_custom_notice(
						$plugin_to_install_id . '_install_error',
						sprintf(
							// translators: 1: plugin name, 2: error message, 3: URL to install plugin manually.
							__( '%1$s could not be installed (%2$s). <a href="%3$s">Please install it manually by clicking here.</a>', 'woocommerce' ),
							$plugin_to_install['name'],
							$e->getMessage(),
							esc_url( admin_url( 'index.php?wc-install-plugin-redirect=' . $plugin_slug ) )
						)
					);
				}

				// Discard feedback.
				ob_end_clean();
			}

			wp_clean_plugins_cache();

			// Activate this thing.
			if ( $activate ) {
				try {
					add_action( 'add_option_mailchimp_woocommerce_plugin_do_activation_redirect', array( __CLASS__, 'remove_mailchimps_redirect' ), 10, 2 );
					$result = activate_plugin( $installed ? $installed_plugins[ $plugin_file ] : $plugin_slug . '/' . $plugin_file );

					if ( is_wp_error( $result ) ) {
						throw new Exception( $result->get_error_message() );
					}
				} catch ( Exception $e ) {
					WC_Admin_Notices::add_custom_notice(
						$plugin_to_install_id . '_install_error',
						sprintf(
							// translators: 1: plugin name, 2: URL to WP plugin page.
							__( '%1$s was installed but could not be activated. <a href="%2$s">Please activate it manually by clicking here.</a>', 'woocommerce' ),
							$plugin_to_install['name'],
							admin_url( 'plugins.php' )
						)
					);
				}
			}
		}
	}