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//
// 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.
//
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// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
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//
// 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.
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License, version 2.0, for more details.
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using MySql.Data.MySqlClient;
using System.Collections.Generic;
using Sog.Properties;

namespace MySql.Data.Failover
{
    /// <summary>
    /// Manages the hosts available for client side failover using the Sequential Failover method.
    /// The Sequential Failover method attempts to connect to the hosts specified in the list one after another until the initial host is reached.
    /// </summary>
    internal class SequentialFailoverGroup : FailoverGroup
    {
        /// <summary>
        /// The initial host taken from the list.
        /// </summary>
        private FailoverServer _initialHost;

        /// <summary>
        /// The index of the current host.
        /// </summary>
        private int _hostIndex;

        /// <summary>
        /// The host for the current connection attempt.
        /// </summary>
        private FailoverServer _currentHost;

        public SequentialFailoverGroup(List<FailoverServer> hosts) : base(hosts)
        {
            this._hostIndex = 0;
        }

        /// <summary>
        /// Sets the initial active host.
        /// </summary>
        protected internal override void SetInitialActiveServer()
        {
            if (this.Hosts == null || this.Hosts.Count == 0)
            {
                throw new MySqlException(Resources.Replication_NoAvailableServer);
            }

            this._initialHost = this.Hosts[0];
            this.Hosts[0].IsActive = true;
            this._activeHost = this.Hosts[0];
            this._currentHost = this._activeHost;
        }

        /// <summary>
        /// Determines the next host.
        /// </summary>
        /// <returns>A <see cref="FailoverServer"/> object that represents the next available host.</returns>
        protected internal override FailoverServer GetNextHost()
        {
            if (this.Hosts == null || this.Hosts?.Count == 0)
            {
                throw new MySqlException(Resources.Replication_NoAvailableServer);
            }

            var currentServer = this.Hosts.Find(h => h.Host == this._currentHost.Host && h.Port == this._currentHost.Port);
            currentServer.IsActive = false;
            this._hostIndex = this.Hosts.IndexOf(currentServer);
            if (this.Hosts.Count > 1)
            {
                this._activeHost = this._hostIndex == this.Hosts.Count - 1 ? this.Hosts[0] : this.Hosts[this._hostIndex + 1];
                this._activeHost.IsActive = true;
                this._currentHost = this._activeHost;
                this._hostIndex++;
            }
            else
            {
                this._activeHost = this._initialHost;
            }

            return this._activeHost;
        }
    }
}