/*
    * DavMail POP/IMAP/SMTP/CalDav/LDAP Exchange Gateway
    * Copyright (C) 2009  Mickael Guessant
    *
    * This program is free software; you can redistribute it and/or
    * modify it under the terms of the GNU General Public License
    * as published by the Free Software Foundation; either version 2
    * of the License, or (at your option) any later version.
    *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
   */
  package davmail.exchange;
  
  import davmail.BundleMessage;
  import davmail.Settings;
  import davmail.exception.DavMailAuthenticationException;
  import davmail.exception.DavMailException;
  import davmail.exception.WebdavNotAvailableException;
  import davmail.exchange.auth.ExchangeAuthenticator;
  import davmail.exchange.auth.ExchangeFormAuthenticator;
  import davmail.exchange.dav.DavExchangeSession;
  import davmail.exchange.ews.EwsExchangeSession;
  import davmail.exchange.graph.GraphExchangeSession;
  import davmail.http.HttpClientAdapter;
  import davmail.http.request.GetRequest;
  import org.apache.http.HttpStatus;
  import org.apache.http.client.methods.CloseableHttpResponse;
  
  import java.awt.*;
  import java.io.IOException;
  import java.net.NetworkInterface;
  import java.net.SocketException;
  import java.net.UnknownHostException;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Objects;
  
  /**
   * Create ExchangeSession instances.
   */
  public final class ExchangeSessionFactory {
      private static final Object LOCK = new Object();
      private static final Map<PoolKey, ExchangeSession> POOL_MAP = new HashMap<>();
      private static volatile boolean configChecked;
      private static volatile boolean errorSent;
  
      static class PoolKey {
          final String url;
          final String userName;
          final String password;
  
          PoolKey(String url, String userName, String password) {
              this.url = url;
              this.userName = convertUserName(userName);
              this.password = password;
          }
  
          @Override
          public boolean equals(Object object) {
              return object == this ||
                      object instanceof PoolKey &&
                              ((PoolKey) object).url.equals(this.url) &&
                              ((PoolKey) object).userName.equals(this.userName) &&
                              ((PoolKey) object).password.equals(this.password);
          }
  
          @Override
          public int hashCode() {
              return Objects.hash(url, userName, password);
          }
      }
  
      private ExchangeSessionFactory() {
      }
  
      /**
       * Create authenticated Exchange session
       *
       * @param userName user login
       * @param password user password
       * @return authenticated session
       * @throws IOException on error
       */
      public static ExchangeSession getInstance(String userName, String password) throws IOException {
          String baseUrl = Settings.getProperty("davmail.url", Settings.getO365Url());
          if (Settings.getBooleanProperty("davmail.server")) {
              return getInstance(baseUrl, userName, password);
          } else {
              // serialize session creation in workstation mode to avoid multiple OTP requests
              synchronized (LOCK) {
                  return getInstance(baseUrl, userName, password);
             }
         }
     }
 
     private static String convertUserName(String userName) {
         String result = userName;
         // prepend default windows domain prefix
         String defaultDomain = Settings.getProperty("davmail.defaultDomain");
         if (defaultDomain != null && userName.indexOf('\\') < 0 && userName.indexOf('@') < 0) {
             result = defaultDomain + '\\' + userName;
         }
         return result;
     }
 
     /**
      * Create authenticated Exchange session
      *
      * @param baseUrl  OWA base URL
      * @param userName user login
      * @param password user password
      * @return authenticated session
      * @throws IOException on error
      */
     public static ExchangeSession getInstance(String baseUrl, String userName, String password) throws IOException {
         ExchangeSession session = null;
         try {
             String mode = Settings.getProperty("davmail.mode");
             if (Settings.O365.equals(mode)) {
                 // force url with O365
                 baseUrl = Settings.getO365Url();
             }
 
             PoolKey poolKey = new PoolKey(baseUrl, userName, password);
 
             synchronized (LOCK) {
                 session = POOL_MAP.get(poolKey);
             }
             if (session != null) {
                 ExchangeSession.LOGGER.debug("Got session " + session + " from cache");
             }
 
             if (session != null && session.isExpired()) {
                 synchronized (LOCK) {
                     session.close();
                     ExchangeSession.LOGGER.debug("Session " + session + " for user " + session.userName + " expired");
                     session = null;
                     // expired session, remove from cache
                     POOL_MAP.remove(poolKey);
                 }
             }
 
             if (session == null) {
                 // convert old setting
                 if (mode == null) {
                     if ("false".equals(Settings.getProperty("davmail.enableEws"))) {
                         mode = Settings.WEBDAV;
                     } else {
                         mode = Settings.EWS;
                     }
                 }
                 // check for overridden authenticator
                 String authenticatorClass = Settings.getProperty("davmail.authenticator");
                 if (authenticatorClass == null && mode.startsWith("O365")) {
                     // set authenticator class based on authentication mode
                     String authentication = Settings.getProperty("davmail.authentication");
                     authenticatorClass = getAuthenticatorClass(authentication);
                     if (authenticatorClass == null) {
                         // fallback to legacy modes
                         authenticatorClass = getAuthenticatorClass(mode);
                     }
                 }
 
                 if (authenticatorClass != null) {
                     ExchangeAuthenticator authenticator = (ExchangeAuthenticator) Class.forName(authenticatorClass)
                             .getDeclaredConstructor().newInstance();
                     authenticator.setUsername(poolKey.userName);
                     authenticator.setPassword(poolKey.password);
                     authenticator.authenticate();
 
                     if (Settings.isGraphEnabled()) {
                         session = new GraphExchangeSession(authenticator.getHttpClientAdapter(), authenticator.getToken(), poolKey.userName);
                     } else {
                         session = new EwsExchangeSession(authenticator.getExchangeUri(), authenticator.getToken(), poolKey.userName);
                     }
 
                 } else if (
                     // new mode
                         Settings.EXCHANGE_EWS.equals(mode)
                                 // legacy
                                 || Settings.EWS.equals(mode) || Settings.O365.equals(mode)
                                 // direct EWS even if mode is different
                                 || poolKey.url.toLowerCase().endsWith("/ews/exchange.asmx")
                                 || poolKey.url.toLowerCase().endsWith("/ews/services.wsdl")) {
                     if (poolKey.url.toLowerCase().endsWith("/ews/exchange.asmx")
                             || poolKey.url.toLowerCase().endsWith("/ews/services.wsdl")) {
                         ExchangeSession.LOGGER.debug("Direct EWS authentication");
                         session = new EwsExchangeSession(poolKey.url, poolKey.userName, poolKey.password);
                     } else {
                         ExchangeSession.LOGGER.debug("OWA authentication in EWS mode");
                         ExchangeFormAuthenticator exchangeFormAuthenticator = new ExchangeFormAuthenticator();
                         exchangeFormAuthenticator.setUrl(poolKey.url);
                         exchangeFormAuthenticator.setUsername(poolKey.userName);
                         exchangeFormAuthenticator.setPassword(poolKey.password);
                         exchangeFormAuthenticator.authenticate();
                         session = new EwsExchangeSession(exchangeFormAuthenticator.getHttpClientAdapter(),
                                 exchangeFormAuthenticator.getExchangeUri(), exchangeFormAuthenticator.getUsername());
                     }
                 } else {
                     // Legacy Exchange 2003 WebDav mode
                     ExchangeFormAuthenticator exchangeFormAuthenticator = new ExchangeFormAuthenticator();
                     exchangeFormAuthenticator.setUrl(poolKey.url);
                     exchangeFormAuthenticator.setUsername(poolKey.userName);
                     exchangeFormAuthenticator.setPassword(poolKey.password);
                     exchangeFormAuthenticator.authenticate();
                     try {
                         session = new DavExchangeSession(exchangeFormAuthenticator.getHttpClientAdapter(),
                                 exchangeFormAuthenticator.getExchangeUri(),
                                 exchangeFormAuthenticator.getUsername());
                     } catch (WebdavNotAvailableException e) {
                         if (Settings.AUTO.equals(mode)) {
                             ExchangeSession.LOGGER.debug(e.getMessage() + ", retry with EWS");
                             session = new EwsExchangeSession(poolKey.url, poolKey.userName, poolKey.password);
                         } else {
                             throw e;
                         }
                     }
                 }
                 try {
                     checkWhiteList(session.getEmail());
                 } catch (DavMailAuthenticationException e) {
                     session.close();
                     session = null;
                     throw e;
                 }
                 ExchangeSession.LOGGER.debug("Created new session " + session + " for user " + poolKey.userName);
             }
             // successful login, put session in cache
             synchronized (LOCK) {
                 POOL_MAP.put(poolKey, session);
             }
             // session opened; future failure will mean network down
             configChecked = true;
             // Reset so next time a problem occurs message is sent once
             errorSent = false;
         } catch (DavMailException | IllegalStateException | NullPointerException exc) {
             throw exc;
         } catch (Exception exc) {
             handleNetworkDown(exc);
         }
         return session;
     }
 
     private static String getAuthenticatorClass(String authentication) throws DavMailException {
         String authenticatorClass = null;
         if (authentication != null) {
             switch (authentication) {
                 case Settings.O365_INTERACTIVE:
                     authenticatorClass = "davmail.exchange.auth.O365InteractiveAuthenticator";
                     if (GraphicsEnvironment.isHeadless()) {
                         throw new DavMailException("EXCEPTION_DAVMAIL_CONFIGURATION", "O365Interactive not supported in headless mode");
                     }
                     break;
                 case Settings.O365_MANUAL:
                     authenticatorClass = "davmail.exchange.auth.O365ManualAuthenticator";
                     break;
                 case Settings.O365_DEVICECODE:
                     authenticatorClass = "davmail.exchange.auth.O365DeviceCodeAuthenticator";
                     break;
                 case Settings.O365_TRANSPARENT:
                 case Settings.O365_MODERN:
                     authenticatorClass = "davmail.exchange.auth.O365Authenticator";
                     break;
             }
         }
         return authenticatorClass;
     }
 
     /**
      * Check if whitelist is empty or email is allowed.
      * userWhiteList is a comma-separated list of values.
      * \@company.com means all domain users are allowed
      *
      * @param email user email
      */
     private static void checkWhiteList(String email) throws DavMailAuthenticationException {
         String whiteListString = Settings.getProperty("davmail.userWhiteList");
         if (whiteListString != null && !whiteListString.isEmpty()) {
             for (String whiteListValue : whiteListString.split(",")) {
                 if (whiteListValue.startsWith("@") && email.endsWith(whiteListValue)) {
                     return;
                 } else if (email.equalsIgnoreCase(whiteListValue)) {
                     return;
                 }
             }
             ExchangeSession.LOGGER.warn(email + " not allowed by whitelist");
             throw new DavMailAuthenticationException("EXCEPTION_AUTHENTICATION_FAILED");
         }
     }
 
     /**
      * Get a non-expired session.
      * If the current session is not expired, return current session, else try to create a new session
      *
      * @param currentSession current session
      * @param userName       user login
      * @param password       user password
      * @return authenticated session
      * @throws IOException on error
      */
     public static ExchangeSession getInstance(ExchangeSession currentSession, String userName, String password)
             throws IOException {
         ExchangeSession session = currentSession;
         try {
             if (session.isExpired()) {
                 ExchangeSession.LOGGER.debug("Session " + session + " expired, trying to open a new one");
                 session = null;
                 String baseUrl = Settings.getProperty("davmail.url", Settings.getO365Url());
                 PoolKey poolKey = new PoolKey(baseUrl, userName, password);
                 // expired session, remove from cache
                 synchronized (LOCK) {
                     POOL_MAP.remove(poolKey);
                 }
                 session = getInstance(userName, password);
             }
         } catch (DavMailAuthenticationException exc) {
             ExchangeSession.LOGGER.debug("Unable to reopen session", exc);
             throw exc;
         } catch (Exception exc) {
             ExchangeSession.LOGGER.debug("Unable to reopen session", exc);
             handleNetworkDown(exc);
         }
         return session;
     }
 
     /**
      * Send a request to Exchange server to check current settings.
      *
      * @throws IOException if unable to access Exchange server
      */
     public static void checkConfig() throws IOException {
         String url;
         if (Settings.isGraphEnabled()) {
             // In Graph mode, check the Graph endpoint instead of the legacy EWS endpoint
             url = Settings.getGraphUrl();
         } else {
             url = Settings.getProperty("davmail.url", Settings.getO365Url());
         }
         if (url == null || (!url.startsWith("http://") && !url.startsWith("https://"))) {
             throw new DavMailException("LOG_INVALID_URL", url);
         }
         try (
                 HttpClientAdapter httpClientAdapter = new HttpClientAdapter(url);
                 CloseableHttpResponse response = httpClientAdapter.execute(new GetRequest(url))
         ) {
             // get webMail root url (will not follow redirects)
             int status = response.getStatusLine().getStatusCode();
             ExchangeSession.LOGGER.debug("Test configuration status: " + status);
             if (status != HttpStatus.SC_OK && status != HttpStatus.SC_UNAUTHORIZED
                     && !HttpClientAdapter.isRedirect(status)) {
                 throw new DavMailException("EXCEPTION_CONNECTION_FAILED", url, status);
             }
             // session opened; future failure will mean network down
             configChecked = true;
             // Reset so next time a problem occurs message is sent once
             errorSent = false;
         } catch (Exception exc) {
             handleNetworkDown(exc);
         }
 
     }
 
     private static void handleNetworkDown(Exception exc) throws DavMailException {
         if (!checkNetwork() || configChecked) {
             ExchangeSession.LOGGER.warn(BundleMessage.formatLog("EXCEPTION_NETWORK_DOWN"));
             // log full stack trace for unknown errors
             if (!((exc instanceof UnknownHostException) || (exc instanceof NetworkDownException))) {
                 ExchangeSession.LOGGER.debug(exc, exc);
             }
             throw new NetworkDownException("EXCEPTION_NETWORK_DOWN");
         } else {
             BundleMessage message = new BundleMessage("EXCEPTION_CONNECT", exc.getClass().getName(), exc.getMessage());
             if (errorSent) {
                 ExchangeSession.LOGGER.warn(message);
                 throw new NetworkDownException("EXCEPTION_DAVMAIL_CONFIGURATION", message);
             } else {
                 // Mark that an error has been sent so you only get one
                 // error in a row (not a repeating string of errors).
                 errorSent = true;
                 ExchangeSession.LOGGER.error(message);
                 throw new DavMailException("EXCEPTION_DAVMAIL_CONFIGURATION", message);
             }
         }
     }
 
     /**
      * Get user password from session pool for SASL authentication
      *
      * @param userName Exchange username
      * @return user password
      */
     public static String getUserPassword(String userName) {
         String fullUserName = convertUserName(userName);
         synchronized (LOCK) {
             for (PoolKey poolKey : POOL_MAP.keySet()) {
                 if (poolKey.userName.equals(fullUserName)) {
                     return poolKey.password;
                 }
             }
         }
         return null;
     }
 
     /**
      * Check if at least one network interface is up and active (i.e., has an address)
      *
      * @return true if network available
      */
     static boolean checkNetwork() {
         boolean up = false;
         Enumeration<NetworkInterface> enumeration;
         try {
             enumeration = NetworkInterface.getNetworkInterfaces();
             while (!up && enumeration.hasMoreElements()) {
                 NetworkInterface networkInterface = enumeration.nextElement();
                 up = networkInterface.isUp() && !networkInterface.isLoopback()
                         && networkInterface.getInetAddresses().hasMoreElements();
                 if (up) {
                     ExchangeSession.LOGGER.debug(networkInterface.getDisplayName() + " is up");
                 }
             }
         } catch (NoSuchMethodError error) {
             ExchangeSession.LOGGER.debug("Unable to test network interfaces (not available under Java 1.5)");
             up = true;
         } catch (SocketException exc) {
             ExchangeSession.LOGGER.error("DavMail configuration exception: \n Error listing network interfaces " + exc.getMessage(), exc);
         }
         return up;
     }
 
     /**
      * Reset config check status and clear session pool.
      */
     public static void shutdown() {
         configChecked = false;
         errorSent = false;
         synchronized (LOCK) {
             for (ExchangeSession session : POOL_MAP.values()) {
                 session.close();
             }
             POOL_MAP.clear();
         }
     }
 }