// Copyright (c) 2014, 2020, Oracle and/or its affiliates.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
// but not limited to OpenSSL) that is licensed under separate terms,
// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// 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, version 2.0, 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 St, Fifth Floor, Boston, MA 02110-1301  USA



using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using Sog.Properties;

namespace MySql.Data.MySqlClient.Replication
{
    /// <summary>
    /// Base class used to implement load balancing features.
    /// </summary>
    public abstract class ReplicationServerGroup
    {
        /// <summary>
        /// List of servers available for replication.
        /// </summary>
        protected List<ReplicationServer> servers = new List<ReplicationServer>();

        /// <param name="name">The group name.</param>
        /// <param name="retryTime">The number of seconds to perform a retry.</param>
        public ReplicationServerGroup(string name, int retryTime)
        {
            this.Servers = this.servers;
            this.Name = name;
            this.RetryTime = retryTime;
        }

        /// <summary>
        /// Gets the group name.
        /// </summary>
        public string Name { get; protected set; }

        /// <summary>
        /// Gets the retry time between connections to failed servers.
        /// </summary>
        public int RetryTime { get; protected set; }

        /// <summary>
        /// Gets the server list in the group.
        /// </summary>
        protected IList<ReplicationServer> Servers { get; private set; }

        /// <summary>
        /// Adds a server into the group.
        /// </summary>
        /// <param name="name">The server name.</param>
        /// <param name="isSource">A flag indicating if the server to add is source or replica.</param>
        /// <param name="connectionString">The connection string used by this server.</param>
        /// <returns>A <see cref="ReplicationServer"/> object representing the recently added object.</returns>
        internal protected ReplicationServer AddServer(string name, bool isSource, string connectionString)
        {
            ReplicationServer server = new ReplicationServer(name, isSource, connectionString);
            this.servers.Add(server);
            return server;
        }

        /// <summary>
        /// Removes a server from the group.
        /// </summary>
        /// <param name="name">The server name.</param>
        internal protected void RemoveServer(string name)
        {
            ReplicationServer serverToRemove = this.GetServer(name);
            if (serverToRemove == null)
            {
                throw new MySqlException(String.Format(Resources.ReplicationServerNotFound, name));
            }

            this.servers.Remove(serverToRemove);
        }

        /// <summary>
        /// Gets a server by name.
        /// </summary>
        /// <param name="name">The server name.</param>
        /// <returns>The replication server.</returns>
        internal protected ReplicationServer GetServer(string name)
        {
            foreach (var server in this.servers)
            {
                if (String.Compare(name, server.Name, StringComparison.OrdinalIgnoreCase) == 0)
                {
                    return server;
                }
            }

            return null;
        }

        /// <summary>
        /// Must be implemented. Defines the next server for a custom load balancing implementation.
        /// </summary>
        /// <param name="isSource">Defines if the server to return is a source or any.</param>
        /// <returns>The next server based on the load balancing implementation.
        /// Null if no available server is found.
        /// </returns>
        internal protected abstract ReplicationServer GetServer(bool isSource);

        /// <summary>
        /// Defines the next server for a custom load balancing implementation.
        /// </summary>
        /// <param name="isSource">Defines if the server to return is a source or any.</param>
        /// <param name="settings">Currently not being used.</param>
        /// <returns>The next server based on the load balancing implementation.
        /// Null if no available server is found.
        /// </returns>
        internal protected virtual ReplicationServer GetServer(bool isSource, MySqlConnectionStringBuilder settings)
        {
            return this.GetServer(isSource);
        }

        /// <summary>
        /// Handles a failed connection to a server.
        /// </summary>
        /// <param name="server">The failed server.</param>
        /// <remarks>This method can be overrided to implement a custom failover handling.</remarks>
        internal protected virtual void HandleFailover(ReplicationServer server)
        {
            BackgroundWorker worker = new BackgroundWorker();
            worker.DoWork += delegate (object sender, DoWorkEventArgs e)
            {
                bool isRunning = false;
                ReplicationServer server1 = e.Argument as ReplicationServer;
                System.Timers.Timer timer = new System.Timers.Timer(this.RetryTime * 1000.0);

                System.Timers.ElapsedEventHandler elapsedEvent = delegate (object sender1, System.Timers.ElapsedEventArgs e1)
          {
                  if (isRunning)
                  {
                      return;
                  }

                  try
                  {
                      isRunning = true;
                      using (MySqlConnection connectionFailed = new MySqlConnection(server.ConnectionString))
                      {
                          connectionFailed.Open();
                          server1.IsAvailable = true;
                          timer.Stop();
                      }
                  }
                  catch
                  {
                      MySqlTrace.LogWarning(
                          0,
                  string.Format(Resources.Replication_ConnectionAttemptFailed, server1.Name));
                  }
                  finally
                  {
                      isRunning = false;
                  }
              };
                timer.Elapsed += elapsedEvent;
                timer.Start();
                elapsedEvent(sender, null);
            };

            worker.RunWorkerAsync(server);
        }

        /// <summary>
        /// Handles a failed connection to a server.
        /// </summary>
        /// <param name="server">The failed server.</param>
        /// <param name="exception">The exception that caused the failover.</param>
        internal protected virtual void HandleFailover(ReplicationServer server, Exception exception)
        {
            this.HandleFailover(server);
        }
    }
}