oglimmer/lunchy

package de.oglimmer.lunchy.services;

import java.util.regex.Pattern;

public enum BotDetectionService {
    INSTANCE;

    static class Constancts {
        // as per https://support.google.com/webmasters/answer/1061943?hl=en
        private static final String GOOGLEBOT_1 = RegExService.INSTANCE
                .escape("Googlebot/2.1 (+http://www.google.com/bot.html)");
        private static final String GOOGLEBOT_2 = RegExService.INSTANCE
                .escape("Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)");

        public static final String DEFAULT_BOT_REGEX = ".*(bot|crawler|spider|yahoo! slurp).*";
        public static final String DEFAULT_NO_BOT_REGEX = ".*(" + BotDetectionService.Constancts.GOOGLEBOT_1 + "|"
                + BotDetectionService.Constancts.GOOGLEBOT_2 + ").*";
    }

    private Pattern patBot;
    private Pattern patNoBot;

    private BotDetectionService() {
        initRegEx();
        LunchyProperties.INSTANCE.registerOnReload(this::initRegEx);
    }

    private void initRegEx() {
        patBot = Pattern.compile(LunchyProperties.INSTANCE.getReloadable().getIsBot());
        patNoBot = Pattern.compile(LunchyProperties.INSTANCE.getReloadable().getIsNoBot());
    }

    public boolean isBot(String userAgent) {
        if (userAgent == null || userAgent.isEmpty()) {
            return false;
        }
        String lowerCaseUserAgent = userAgent.toLowerCase().trim();

        // Some bots (e.g. google) can understand Angular, we don't treat it as a bot and show the regular page
        if (patNoBot.matcher(lowerCaseUserAgent).matches()) {
            return false;
        }

        return patBot.matcher(lowerCaseUserAgent).matches();
    }

}