) {
			return true;
		}
		return false;
	}

	/**
	 * Was the current request made by a known bot?
	 *
	 * @param string|null $user_agent Optional. User agent string to check. If not provided, uses $_SERVER['HTTP_USER_AGENT'].
	 *
	 * @return boolean
	 */
	public static function is_bot( $user_agent = null ) {
		static $is_bot = null;

		if ( null === $user_agent ) {
			if ( empty( $_SERVER['HTTP_USER_AGENT'] ) ) {
				return false;
			}
			$user_agent = wp_unslash( $_SERVER['HTTP_USER_AGENT'] ); // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- This is validating.

			// Use cached result only when using the default $_SERVER['HTTP_USER_AGENT'].
			if ( $is_bot === null ) {
				$is_bot = self::is_bot_user_agent( $user_agent );
			}
			return $is_bot;
		}

		if ( empty( $user_agent ) ) {
			return false;
		}

		// Don't use cache when a custom user agent is provided.
		return self::is_bot_user_agent( $user_agent );
	}

	/**
	 * Is the given user-agent a known bot?
	 * If you want an is_bot check for the current request's UA, use is_bot() instead of passing a user-agent to this method.
	 *
	 * @param string $ua A user-agent string.
	 *
	 * @return boolean
	 */
	public static function is_bot_user_agent( $ua = null ) {

		if ( empty( $ua ) ) {
			return false;
		}

		// Some sourced via
		// https://github.com/ua-parser/uap-core/blob/432e95f6767cc8bab4c20c255784cd6f7e93bc15/regexes.yaml#L151
		$bot_agents = array(
			// Microsoft/Bing https://www.bing.com/webmasters/help/which-crawlers-does-bing-use-8c184ec0
			'bingbot', // Bing/Copilot
			'adidxbot', // Bing Ads
			'bingpreview', // Generates page snapshots for Bing
			'bingvideopreview', // Generates previews of videos for Bing
			'microsoft',

			// Google https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers
			'adsbot-google',
			'appengine-google',
			'feedfetcher-google',
			'mediapartners-google',
			'storebot-google', // https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers#google-storebot
			'google sketchup',
			'google-cloudbertexbot', // https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers#google-cloudvertexbot
			'google-extended', // Gemini https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers#google-extended
			'google-inspectiontool', // https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers
			'google-safety;', // https://www.google.com/bot.html
			'googlebot-mobile',
			'googlebot', // and googlebot-[image,video,news,] https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers#googlebot
			'googleother', // and googleother-[video,image] https://developers.google.com/search/docs/crawling-indexing/google-common-crawlers#googleother

			// OpenAI https://platform.openai.com/docs/bots
			'gptbot', // Crawler
			'chatgpt-user', // ChatGPT on behalf of user
			'oai-searchbot', // ChatGPT search features

			// Anthropic
			'claudebot', // chat citation fetch https://support.anthropic.com/en/articles/8896518
			'claude-web', // web-focused crawl https://darkvisitors.com/agents/claude-web
			'anthropic-ai', // bulk model training https://darkvisitors.com/agents/anthropic-ai

			// Perplexity
			'perplexitybot', // index builder https://docs.perplexity.ai/guides/bots
			'perplexity-user', // human-triggered visit https://docs.perplexity.ai/guides/bots

			// Meta https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/
			'facebookbot', // AI data scraper https://darkvisitors.com/agents/facebookbot
			'facebookexternalhit', // shares https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/#identify
			'facebookcatalog', // shares https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/#identify
			'meta-webindexer', // Meta AI search indexer https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/#meta-webindexer
			'meta-externalads', // web crawler improving ads https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/#meta-externalads
			'meta-externalagent', // training AI models https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/#identify-2
			'meta-externalfetcher', // user-initiated fetches, may skip robots.txt https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/#identify-3

			// Semrush https://www.semrush.com/bot/
			'semrushbot',
			'siteauditbot',

			// Other bots (alphabetized list)
			'123metaspider-bot',
			'1470.net crawler',
			'50.nu',
			'8bo crawler bot',
			'aboundex',
			'ahrefsbot',
			'ai2bot', // AI2 crawler for LLMm training https://allenai.org/crawler
			'alexa',
			'altavista',
			'amazonbot', // https://developer.amazon.com/amazonbot
			'applebot', // https://support.apple.com/en-ca/HT204683
			'arcgis hub indexer',
			'archive.org_bot', // http://archive.org/details/archive.org_bot
			'archiver',
			'ask jeeves',
			'attentio',
			'baiduspider',
			'blexbot',
			'blitzbot',
			'blogbridge',
			'bloglovin',
			'bne.es_bot', // https://www.bne.es/es/colecciones/archivo-web-espanola/aviso-webmasters
			'boardreader blog indexer',
			'boardreader favicon fetcher',
			'boitho.com-dc',
			'botseer',
			'bubing',
			'bytespider', // ByteDance (owner of TikTok) to train LLMs for Doubao https://darkvisitors.com/agents/bytespider
			'catchpoint',
			'ccbot', // CommonCrawl non-profit https://commoncrawl.org/ccbot
			'charlotte',
			'checklinks',
			'chtml generic',
			'cityreview robot',
			'cloudflare-alwaysonline',
			'clumboot',
			'coccocbot', // Coc Coc https://darkvisitors.com/agents/coccocbot-web
			'cohere-ai', // Cohere AI https://darkvisitors.com/agents/cohere-ai
			'comodo http',
			'comodo-webinspector-crawler',
			'converacrawler',
			'cookieinformationscanner', // Internal ref p1699315886066389-slack-C0438NHCLSY
			'crawl-e',
			'crawlconvera',
			'crawldaddy',
			'crawler',
			'crawlfire',
			'csimplespider',
			'dataforseobot', // https://www.dataforseo.com/dataforseo-bot
			'daumoa',
			'diffbot', // https://docs.diffbot.com/docs/how-to-use-custom-user-agents-with-extract-apis & https://darkvisitors.com/agents/diffbot
			'domaintunocrawler',
			'dotbot', // https://darkvisitors.com/agents/dotbot
			'duckassistbot', // DuckDuckGo AI Assistant https://darkvisitors.com/agents/duckassistbot
			'elisabot',
			'ezlynxbot', // https://www.ezoic.com/bot
			'fastmobilecrawl',
			'feed seeker bot',
			'feedbin',
			'feedburner',
			'finderbots',
			'findlinks',
			'firefly',
			'flamingo_searchengine',
			'followsite bot',
			'froogle',
			'furlbot',
			'genieo',
			'germcrawler',
			'gigabot',
			'gomezagent',
			'gonzo1',
			'grapeshotcrawler',
			'grokkit-crawler',
			'grub-client',
			'gsa-crawler',
			'heritrix',
			'hiddenmarket',
			'holmes',
			'hoowwwer',
			'htdig',
			'httrack',
			'ia_archiver',
			'icarus6j',
			'icc-crawler',
			'ichiro',
			'iconsurf',
			'iescholar',
			'iltrovatore',
			'index crawler',
			'infoseek',
			'infuzapp',
			'innovazion crawler',
			'internetarchive',
			'irlbot',
			'jbot',
			'job roboter',
			'jumpbot',
			'kaloogabot',
			'kiwistatus spider',
			'kraken',
			'kurzor',
			'larbin',
			'leia',
			'lesnikbot',
			'lijit crawler',
			'linguee bot',
			'linkaider',
			'linkcheck',
			'linkdexbot',
			'linkedinbot',
			'linkfluence', // http://linkfluence.com/
			'linkwalker', // https://www.linkwalker.com/
			'lite bot',
			'livelapbot',
			'llaut',
			'lycos',
			'mail.ru_bot',
			'masidani_bot',
			'masscan',
			'mediapartners',
			'mediobot',
			'mj12bot',
			'mogimogi',
			'mojeekbot', // https://www.mojeek.com/bot.html
			'motionbot',
			'mozdex',
			'mshots',
			'msnbot',
			'msrbot',
			'mtps feed aggregation system',
			'netresearch',
			'netvibes',
			'newsgator',
			'ning',
			'nutch',
			'nymesis',
			'objectssearch',
			'ogscrper',
			'omgili', // Webz.io web crawler for a data seller https://darkvisitors.com/agents/omgili
			'oozbot',
			'openbot',
			'openhosebot',
			'orbiter',
			'pagepeeker',
			'pagesinventory',
			'paxleframework',
			'peeplo screenshot bot',
			'phpcrawl',
			'pingdom.com_bot',
			'plantynet_webrobot',
			'pompos',
			'pss-webkit-request',
			'pythumbnail',
			'queryseekersp ider',
			'queryseekerspider',
			'qwantify',
			'read%20later',
			'reaper',
			'redcarpet',
			'retreiver',
			'riddler',
			'rival iq',
			'scollspider',
			'scooter',
			'scrapy',
			'scrubby',
			'searchsight',
			'seekbot',
			'semanticdiscovery',
			'seostats',
			'simplepie',
			'simplerss',
			'simpy',
			'sitecat webbot',
			'sitecon',
			'slack-imgproxy',
			'slackbot-linkexpanding',
			'slurp',
			'snapbot',
			'snapchat', // https://developers.snap.com/robots
			'snappy',
			'speedy spider',
			'spider',
			'squrl java',
			'stringer',
			'taptubot',
			'technoratisnoop',
			'teoma',
			'theusefulbot',
			'thumbshots.ru',
			'thumbshotsbot',
			'timpibot', // LLM trainer https://darkvisitors.com/agents/timpibot
			'tiny tiny rss',
			'trendictionbot',  // http://www.trendiction.de/bot;
			'trends crawler',
			'tweetmemebot',
			'twiceler',
			'twitterbot', // https://developer.x.com/en/docs/x-for-websites/cards/guides/getting-started#crawling
			'url2png',
			'usyd-nlp-spider',
			'vagabondo',
			'voilabot',
			'vortex',
			'votay bot',
			'voyager',
			'wasalive.bot',
			'web-sniffer',
			'webthumb',
			'wesee',
			'whatsapp',
			'whatweb',
			'wire',
			'wordpress',
			'wotbox',
			'wp-e2e-tests', // WordPress e2e tests
			'www.almaden.ibm.com',
			'xenu',
			'yacybot', // http://yacy.net/bot.html
			'yahoo! slurp',
			'yahooseeker',
			'yahooysmcm',
			'yammybot',
			'yandexbot',
			'yottaamonitor',
			'youbot', // You.com AI assistant https://darkvisitors.com/agents/youbot
			'yowedo',
			'zao-crawler',
			'zao',
			'zebot_www.ze.bz',
			'zoombot', // SEOZOom https://darkvisitors.com/agents/zoombot
			'zooshot',
			'zyborg',
		);

		foreach ( $bot_agents as $bot_agent ) {
			if ( false !== stripos( $ua, $bot_agent ) ) {
				return true;
			}
		}

		return false;
	}
}