package org.appsec.securityrat.security;

import org.appsec.securityrat.domain.PersistentToken;
import org.appsec.securityrat.repository.PersistentTokenRepository;
import org.appsec.securityrat.repository.UserRepository;


import io.github.jhipster.config.JHipsterProperties;
import io.github.jhipster.security.PersistentTokenCache;
import io.github.jhipster.security.RandomUtil;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.dao.DataAccessException;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.security.web.authentication.rememberme.*;
import org.springframework.stereotype.Service;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.Serializable;
import java.time.LocalDate;
import java.util.*;
import org.appsec.securityrat.domain.User;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.support.TransactionTemplate;

/**
 * Custom implementation of Spring Security's RememberMeServices.
 * <p>
 * Persistent tokens are used by Spring Security to automatically log in users.
 * <p>
 * This is a specific implementation of Spring Security's remember-me authentication, but it is much
 * more powerful than the standard implementations:
 * <ul>
 * <li>It allows a user to see the list of his currently opened sessions, and invalidate them</li>
 * <li>It stores more information, such as the IP address and the user agent, for audit purposes<li>
 * <li>When a user logs out, only his current session is invalidated, and not all of his sessions</li>
 * </ul>
 * <p>
 * Please note that it allows the use of the same token for 5 seconds, and this value stored in a specific
 * cache during that period. This is to allow concurrent requests from the same user: otherwise, two
 * requests being sent at the same time could invalidate each other's token.
 * <p>
 * This is inspired by:
 * <ul>
 * <li><a href="http://jaspan.com/improved_persistent_login_cookie_best_practice">Improved Persistent Login Cookie
 * Best Practice</a></li>
 * <li><a href="https://github.com/blog/1661-modeling-your-app-s-user-session">GitHub's "Modeling your App's User Session"</a></li>
 * </ul>
 * <p>
 * The main algorithm comes from Spring Security's {@code PersistentTokenBasedRememberMeServices}, but this class
 * couldn't be cleanly extended.
 */
@Service
public class PersistentTokenRememberMeServices extends
    AbstractRememberMeServices {

    private final Logger log = LoggerFactory.getLogger(PersistentTokenRememberMeServices.class);

    // Token is valid for one month
    private static final int TOKEN_VALIDITY_DAYS = 31;

    private static final int TOKEN_VALIDITY_SECONDS = 60 * 60 * 24 * TOKEN_VALIDITY_DAYS;

    private static final long UPGRADED_TOKEN_VALIDITY_MILLIS = 5000l;

    private final PersistentTokenCache<UpgradedRememberMeToken> upgradedTokenCache;

    private final PersistentTokenRepository persistentTokenRepository;

    private final UserRepository userRepository;
    
    private final TransactionTemplate transactionTemplate;

    public PersistentTokenRememberMeServices(JHipsterProperties jHipsterProperties,
            org.springframework.security.core.userdetails.UserDetailsService userDetailsService,
            PersistentTokenRepository persistentTokenRepository, UserRepository userRepository,
            PlatformTransactionManager transactionManager) {

        super(jHipsterProperties.getSecurity().getRememberMe().getKey(), userDetailsService);
        this.persistentTokenRepository = persistentTokenRepository;
        this.userRepository = userRepository;
        this.upgradedTokenCache = new PersistentTokenCache<>(UPGRADED_TOKEN_VALIDITY_MILLIS);
        this.transactionTemplate = new TransactionTemplate(transactionManager);
    }

    @Override
    protected UserDetails processAutoLoginCookie(String[] cookieTokens, HttpServletRequest request,
        HttpServletResponse response) {

        synchronized (this) { // prevent 2 authentication requests from the same user in parallel
            String login = null;
            UpgradedRememberMeToken upgradedToken = upgradedTokenCache.get(cookieTokens[0]);
            if (upgradedToken != null) {
                login = upgradedToken.getUserLoginIfValid(cookieTokens);
                log.debug("Detected previously upgraded login token for user '{}'", login);
            }

            if (login == null) {
                PersistentToken token = getPersistentToken(cookieTokens);
                login = token.getUser().getLogin();

                // Token also matches, so login is valid. Update the token value, keeping the *same* series number.
                log.debug("Refreshing persistent login token for user '{}', series '{}'", login, token.getSeries());
                token.setTokenDate(LocalDate.now());
                token.setTokenValue(RandomUtil.generateRandomAlphanumericString());
                token.setIpAddress(request.getRemoteAddr());
                token.setUserAgent(request.getHeader("User-Agent"));
                try {
                    persistentTokenRepository.saveAndFlush(token);
                } catch (DataAccessException e) {
                    log.error("Failed to update token: ", e);
                    throw new RememberMeAuthenticationException("Autologin failed due to data access problem", e);
                }
                addCookie(token, request, response);
                upgradedTokenCache.put(cookieTokens[0], new UpgradedRememberMeToken(cookieTokens, login));
            }
            return getUserDetailsService().loadUserByUsername(login);
        }
    }

    @Override
    protected void onLoginSuccess(HttpServletRequest request, HttpServletResponse response, Authentication
        successfulAuthentication) {

        String login = successfulAuthentication.getName();

        log.debug("Creating new persistent login for user {}", login);
        PersistentToken token = userRepository.findOneByLogin(login).map(u -> {
            PersistentToken t = new PersistentToken();
            t.setSeries(RandomUtil.generateRandomAlphanumericString());
            t.setUser(u);
            t.setTokenValue(RandomUtil.generateRandomAlphanumericString());
            t.setTokenDate(LocalDate.now());
            t.setIpAddress(request.getRemoteAddr());
            t.setUserAgent(request.getHeader("User-Agent"));
            return t;
        }).orElseThrow(() -> new UsernameNotFoundException("User " + login + " was not found in the database"));
        try {
            persistentTokenRepository.saveAndFlush(token);
            addCookie(token, request, response);
        } catch (DataAccessException e) {
            log.error("Failed to save persistent token ", e);
        }
    }

    /**
     * When logout occurs, only invalidate the current token, and not all user sessions.
     * <p>
     * The standard Spring Security implementations are too basic: they invalidate all tokens for the
     * current user, so when he logs out from one browser, all his other sessions are destroyed.
     *
     * @param request the request.
     * @param response the response.
     * @param authentication the authentication.
     */
    @Override
    public void logout(HttpServletRequest request, HttpServletResponse response, Authentication authentication) {
        String rememberMeCookie = extractRememberMeCookie(request);
        if (rememberMeCookie != null && rememberMeCookie.length() != 0) {
            try {
                String[] cookieTokens = decodeCookie(rememberMeCookie);
                PersistentToken token = getPersistentToken(cookieTokens);
                
                this.transactionTemplate.executeWithoutResult((a) -> {
                    Optional<User> optionalUser =
                            this.userRepository.findOneById(
                                    token.getUser().getId());
                    
                    if (optionalUser.isEmpty()) {
                        return;
                    }
                    
                    User user = optionalUser.get();
                    user.getPersistentTokens().remove(token);
                    this.userRepository.save(user);
                });
            } catch (InvalidCookieException ice) {
                log.info("Invalid cookie, no persistent token could be deleted", ice);
            } catch (RememberMeAuthenticationException rmae) {
                log.debug("No persistent token found, so no token could be deleted", rmae);
            }
        }
        super.logout(request, response, authentication);
    }

    /**
     * Validate the token and return it.
     */
    private PersistentToken getPersistentToken(String[] cookieTokens) {
        if (cookieTokens.length != 2) {
            throw new InvalidCookieException("Cookie token did not contain " + 2 +
                " tokens, but contained '" + Arrays.asList(cookieTokens) + "'");
        }
        String presentedSeries = cookieTokens[0];
        String presentedToken = cookieTokens[1];
        Optional<PersistentToken> optionalToken = persistentTokenRepository.findById(presentedSeries);
        if (!optionalToken.isPresent()) {
            // No series match, so we can't authenticate using this cookie
            throw new RememberMeAuthenticationException("No persistent token found for series id: " + presentedSeries);
        }
        PersistentToken token = optionalToken.get();
        // We have a match for this user/series combination
        log.info("presentedToken={} / tokenValue={}", presentedToken, token.getTokenValue());
        if (!presentedToken.equals(token.getTokenValue())) {
            // Token doesn't match series value. Delete this session and throw an exception.
            persistentTokenRepository.deleteById(token.getSeries());
            throw new CookieTheftException("Invalid remember-me token (Series/token) mismatch. Implies previous " +
                "cookie theft attack.");
        }
        if (token.getTokenDate().plusDays(TOKEN_VALIDITY_DAYS).isBefore(LocalDate.now())) {
            persistentTokenRepository.deleteById(token.getSeries());
            throw new RememberMeAuthenticationException("Remember-me login has expired");
        }
        return token;
    }

    private void addCookie(PersistentToken token, HttpServletRequest request, HttpServletResponse response) {
        setCookie(
            new String[]{token.getSeries(), token.getTokenValue()},
            TOKEN_VALIDITY_SECONDS, request, response);
    }

    private static class UpgradedRememberMeToken implements Serializable {

        private static final long serialVersionUID = 1L;

        private final String[] upgradedToken;

        private final String userLogin;

        UpgradedRememberMeToken(String[] upgradedToken, String userLogin) {
            this.upgradedToken = upgradedToken;
            this.userLogin = userLogin;
        }

        String getUserLoginIfValid(String[] currentToken) {
            if (currentToken[0].equals(this.upgradedToken[0]) &&
                    currentToken[1].equals(this.upgradedToken[1])) {
                return this.userLogin;
            }
            return null;
        }
    }
}
