package org.metricshub.ipmi.core.connection;
   
   /*-
    * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
    * IPMI Java Client
    * ჻჻჻჻჻჻
    * Copyright 2023 Verax Systems, MetricsHub
    * ჻჻჻჻჻჻
    * This program is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Lesser General Public License as
   * published by the Free Software Foundation, either version 3 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 Lesser Public License for more details.
   *
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-3.0.html>.
   * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
   */
  
  import org.metricshub.ipmi.core.api.async.ConnectionHandle;
  import org.metricshub.ipmi.core.api.sol.CipherSuiteSelectionHandler;
  import org.metricshub.ipmi.core.api.sync.IpmiConnector;
  import org.metricshub.ipmi.core.coding.commands.PrivilegeLevel;
  import org.metricshub.ipmi.core.coding.security.CipherSuite;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.net.InetAddress;
  import java.util.List;
  import java.util.concurrent.ConcurrentHashMap;
  
  /**
   * Manages multiple {@link Session}s.
   */
  public class SessionManager {
  
      private static final Logger logger = LoggerFactory.getLogger(SessionManager.class);
  
      private static Integer sessionId = 100;
  
      /**
       * The session ID generated by the {@link SessionManager}.
       * Auto-incremented.
       */
      public static synchronized int generateSessionId() {
          sessionId %= (Integer.MAX_VALUE / 4);
          return sessionId++;
      }
  
      public static Session establishSession(IpmiConnector connector, String remoteHost, int remotePort, String user, String password,
                                             CipherSuiteSelectionHandler cipherSuiteSelectionHandler) throws SessionException {
          ConnectionHandle handle = null;
  
          try {
              handle = connector.createConnection(InetAddress.getByName(remoteHost), remotePort);
  
              List<CipherSuite> availableCipherSuites = connector.getAvailableCipherSuites(handle);
              CipherSuite cipherSuite = cipherSuiteSelectionHandler.choose(availableCipherSuites);
  
              if (cipherSuite == null) {
                  cipherSuite = CipherSuite.getEmpty();
              }
  
              connector.getChannelAuthenticationCapabilities(handle, cipherSuite, PrivilegeLevel.Administrator);
  
              return connector.openSession(handle, user, password, null);
          } catch (Exception e) {
              closeConnection(connector, handle);
  
              throw new SessionException("Cannot create new session due to exception", e);
          }
      }
  
      private static void closeConnection(IpmiConnector connector, ConnectionHandle handle) {
          try {
              if (connector != null && handle != null) {
                  connector.closeSession(handle);
                  connector.tearDown();
              }
          } catch (Exception e) {
              logger.error("Cannot close connection after exception thrown during session establishment.", e);
          }
      }
  
      private final ConcurrentHashMap<Integer, Session> sessionsPerConnectionHandle;
  
      public SessionManager() {
          this.sessionsPerConnectionHandle = new ConcurrentHashMap<Integer, Session>();
      }
  
      /**
       * Either returns the {@link Session} registered for given connection, or creates new IPMI {@link Session}
       * and registers it for the given connection handle, if no session was found for the connection.
      *
      * @param connectionHandle
      *          handle of the connection, for which this session should be registered.
      * @return newly created session object or session already registered for the connection
      */
     public Session registerSession(int sessionId, ConnectionHandle connectionHandle) {
         if (connectionHandle.getUser() == null || connectionHandle.getRemoteAddress() == null) {
             throw new IllegalArgumentException("Given connection handle is incomplete (lacks user or remote address)");
         }
 
         Session newSession = new Session(sessionId, connectionHandle);
         Session currentSession = sessionsPerConnectionHandle.putIfAbsent(connectionHandle.getHandle(), newSession);
 
         return currentSession != null ? currentSession : newSession;
     }
 
     /**
      * Unregisters session for given connection handle.
      *
      * @param connectionHandle
      *          handle of the connection, for which the session should be unregistered.
      */
     public void unregisterSession(ConnectionHandle connectionHandle) {
         sessionsPerConnectionHandle.remove(connectionHandle.getHandle());
     }
 
     /**
      * Returns session already bound to given connection handle fulfilling given criteria.
      *
      * @param remoteAddress
      *          IP addres of the managed system
      * @param remotePort
      *          UDP port of the managed system
      * @param user
      *          IPMI user for whom the connection is established
      * @return session object fulfilling given criteria, or null if no session was registered for such connection.
      */
     public Session getSessionForCriteria(InetAddress remoteAddress, int remotePort, String user) {
         for (Session session : sessionsPerConnectionHandle.values()) {
             ConnectionHandle sessionConnectionHandle = session.getConnectionHandle();
 
             if (sessionConnectionHandle.getUser().equals(user)
                     && sessionConnectionHandle.getRemoteAddress().equals(remoteAddress)
                     && sessionConnectionHandle.getRemotePort() == remotePort) {
                 return session;
             }
         }
 
         return null;
     }
 }