public static function authenticate_wccom( $user_id ) {
		if ( ! empty( $user_id ) || ! self::is_request_to_wccom_site_rest_api() ) {
			return $user_id;
		}

		$auth_header = trim( self::get_authorization_header() );

		if ( stripos( $auth_header, 'Bearer ' ) === 0 ) {
			$access_token = trim( substr( $auth_header, 7 ) );
		} elseif ( ! empty( $_GET['token'] ) && is_string( $_GET['token'] ) ) {  // phpcs:ignore WordPress.Security.NonceVerification.Recommended
			$access_token = trim( $_GET['token'] );  // phpcs:ignore WordPress.Security.NonceVerification.Recommended, WordPress.Security.ValidatedSanitizedInput.MissingUnslash, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
		} else {
			add_filter(
				self::AUTH_ERROR_FILTER_NAME,
				function() {
					return new WP_Error(
						WC_REST_WCCOM_Site_Installer_Errors::NO_ACCESS_TOKEN_CODE,
						WC_REST_WCCOM_Site_Installer_Errors::NO_ACCESS_TOKEN_MESSAGE,
						array( 'status' => WC_REST_WCCOM_Site_Installer_Errors::NO_ACCESS_TOKEN_HTTP_CODE )
					);
				}
			);
			return false;
		}

		if ( ! empty( $_SERVER['HTTP_X_WOO_SIGNATURE'] ) ) {
			$signature = trim( $_SERVER['HTTP_X_WOO_SIGNATURE'] ); // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.MissingUnslash,WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
		} elseif ( ! empty( $_GET['signature'] ) && is_string( $_GET['signature'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
			$signature = trim( $_GET['signature'] ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended, WordPress.Security.ValidatedSanitizedInput.MissingUnslash, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
		} else {
			add_filter(
				self::AUTH_ERROR_FILTER_NAME,
				function() {
					return new WP_Error(
						WC_REST_WCCOM_Site_Installer_Errors::NO_SIGNATURE_CODE,
						WC_REST_WCCOM_Site_Installer_Errors::NO_SIGNATURE_MESSAGE,
						array( 'status' => WC_REST_WCCOM_Site_Installer_Errors::NO_SIGNATURE_HTTP_CODE )
					);
				}
			);
			return false;
		}

		require_once WC_ABSPATH . 'includes/admin/helper/class-wc-helper-options.php';
		$site_auth = WC_Helper_Options::get( 'auth' );

		if ( empty( $site_auth['access_token'] ) ) {
			add_filter(
				self::AUTH_ERROR_FILTER_NAME,
				function() {
					return new WP_Error(
						WC_REST_WCCOM_Site_Installer_Errors::SITE_NOT_CONNECTED_CODE,
						WC_REST_WCCOM_Site_Installer_Errors::SITE_NOT_CONNECTED_MESSAGE,
						array( 'status' => WC_REST_WCCOM_Site_Installer_Errors::SITE_NOT_CONNECTED_HTTP_CODE )
					);
				}
			);
			return false;
		}

		if ( ! hash_equals( $access_token, $site_auth['access_token'] ) ) {
			add_filter(
				self::AUTH_ERROR_FILTER_NAME,
				function() {
					return new WP_Error(
						WC_REST_WCCOM_Site_Installer_Errors::INVALID_TOKEN_CODE,
						WC_REST_WCCOM_Site_Installer_Errors::INVALID_TOKEN_MESSAGE,
						array( 'status' => WC_REST_WCCOM_Site_Installer_Errors::INVALID_TOKEN_HTTP_CODE )
					);
				}
			);
			return false;
		}

		$body = WP_REST_Server::get_raw_data();

		if ( ! self::verify_wccom_request( $body, $signature, $site_auth['access_token_secret'] ) ) {
			add_filter(
				self::AUTH_ERROR_FILTER_NAME,
				function() {
					return new WP_Error(
						WC_REST_WCCOM_Site_Installer_Errors::REQUEST_VERIFICATION_FAILED_CODE,
						WC_REST_WCCOM_Site_Installer_Errors::REQUEST_VERIFICATION_FAILED_MESSAGE,
						array( 'status' => WC_REST_WCCOM_Site_Installer_Errors::REQUEST_VERIFICATION_FAILED_HTTP_CODE )
					);
				}
			);
			return false;
		}

		$user = get_user_by( 'id', $site_auth['user_id'] );
		if ( ! $user ) {
			add_filter(
				self::AUTH_ERROR_FILTER_NAME,
				function() {
					return new WP_Error(
						WC_REST_WCCOM_Site_Installer_Errors::USER_NOT_FOUND_CODE,
						WC_REST_WCCOM_Site_Installer_Errors::USER_NOT_FOUND_MESSAGE,
						array( 'status' => WC_REST_WCCOM_Site_Installer_Errors::USER_NOT_FOUND_HTTP_CODE )
					);
				}
			);
			return false;
		}

		return $user;
	}