Search Host Manager v1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NLog;

namespace Common
{
    /// <summary>
    /// Provides server hosts for the search service
    /// </summary>
    public class SearchHostManager
    {
        static readonly Logger _logger = LogManager.GetCurrentClassLogger();

        readonly object syncRoot = new object();
        readonly string[] _allhosts;
        readonly List<string> _availableHosts;
        readonly int _secondsToReset;
        readonly int _searchTimeOut;
        DateTime _lastHostReset = DateTime.Now;

        public SearchHostManager(string[] hosts, int timeout = 5000, int resetInSeconds = 60)
        {
            _allhosts = hosts.ToArray();
            _availableHosts = new List<string>(_allhosts);
            _searchTimeOut = timeout;
            _secondsToReset = resetInSeconds;
        }

        /// <summary>
        /// Gets all hosts regardless if they are valid or not
        /// </summary>
        public string[] AllHosts
        {
            get { return _allhosts.ToArray(); }
        }

        /// <summary>
        /// Gets the number of seconds to reset failed hosts back to the original hosts. The default value is 60 seconds (1 minute).
        /// </summary>
        public int SecondsToReset
        {
            get { return _secondsToReset; }
        }
        /// <summary>
        /// Gets the number of milliseconds to wait before the request times out. The default value is 5000 milliseconds (5 seconds).
        /// </summary>
        public int SearchTimeOut
        {
            get { return _searchTimeOut; }
        }

        /// <summary>
        /// Gets the number of maximum attempts that can be made with the hosts
        /// </summary>
        public int MaxSearchAttempts
        {
            get { return _allhosts.Length; }
        }

        /// <summary>
        /// Returns an array of available hosts that are valid
        /// </summary>
        public string[] GetAvailableHosts()
        {
            lock (syncRoot)
            {
                if (DateTime.Now.Subtract(_lastHostReset) > TimeSpan.FromSeconds(_secondsToReset))
                {
                    _lastHostReset = DateTime.Now;
                    _availableHosts.Clear();
                    _availableHosts.AddRange(_allhosts);
                    _logger.Debug("Search hosts reset");
                }

                var hosts = _availableHosts.ToArray();
                if (hosts.Length == 0)
                {
                    _availableHosts.AddRange(_allhosts);
                    hosts = _availableHosts.ToArray();
                }
                return hosts;
            }
        }

        /// <summary>
        /// Removes a failed host from the available hosts
        /// </summary>
        public void RemoveHost(string host)
        {
            lock (syncRoot)
                _availableHosts.Remove(host);
        }

        /// <summary>
        /// Returns a random host from the available hosts
        /// </summary>
        public string GetNextHost(string currentHost = null)
        {
            var hosts = GetAvailableHosts().ToList();
            if(!string.IsNullOrWhiteSpace(currentHost))
                hosts.Remove(currentHost);
            return GetNextHost(hosts.ToArray());
        }

        /// <summary>
        /// Returns a random host from the available hosts
        /// </summary>
        public string GetNextHost(string[] hosts)
        {
            if (hosts.Length == 0)
                return null;
            Random rnd = new Random(Math.Abs(Guid.NewGuid().ToString().GetHashCode()));
            string h = hosts[rnd.Next(0, hosts.Length)];
            return h;
        }

        /// <summary>
        /// Replaces the host and port (if non-standard) in the provided url
        /// </summary>
        public string ReplaceHostInUrl(string url, string host)
        {
            string h = host;
            int port = url.StartsWith("https") ? 443 : 80;

            if (host.IndexOf(":") > 0)
            {
                var parts = host.Split(":".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
                if (parts.Length == 2)
                {
                    h = parts[0];
                    int.TryParse(parts[1], out port);
                }
            }

            UriBuilder ubuilder = new UriBuilder(url);
            ubuilder.Host = h;
            if (port > 0)
                ubuilder.Port = port;
            return ubuilder.Uri.ToString();
        }
    }
}