using Microsoft.Extensions.Options;

using System;

using System.Collections.Concurrent;

using System.Collections.Generic;

using System.Linq;

namespace NetCoreStack.Proxy

{

public class RoundRobinManager

{

private static readonly object _lockObj = new object();

public readonly ConcurrentDictionary<string, Queue<string>> ProxyRegionDict =

new ConcurrentDictionary<string, Queue<string>>();

protected ProxyOptions Options { get; }

public RoundRobinManager(IOptions<ProxyOptions> options)

{

if (options == null)

{

throw new ArgumentNullException(nameof(options));

}

if (options.Value == null || options.Value.RegionKeys == null)

{

throw new ArgumentNullException(nameof(options.Value.RegionKeys));

}

Options = options.Value;

Dictionary<string, string> regionKeys = new Dictionary<string, string>();

foreach (KeyValuePair<string, string> entry in Options.RegionKeys)

{

if (string.IsNullOrEmpty(entry.Value))

continue;

var urls = entry.Value.Split(',').Select(p => p.Trim()).ToList();

ProxyRegionDict.TryAdd(entry.Key, new Queue<string>(urls));

}

}

public UriBuilder RoundRobinUri(string regionKey)

{

UriBuilder uri = null;

Queue<string> queue;

if (!ProxyRegionDict.TryGetValue(regionKey, out queue))

{

throw new ArgumentOutOfRangeException($"Region could not be found! {nameof(RoundRobinManager)}: \"{regionKey}\"");

}

lock (_lockObj)

{

var url = queue.Dequeue();

uri = new UriBuilder(url);

queue.Enqueue(url);

return uri;

}

}

}

}