using System.Diagnostics;
using System.Net;
using System.Net.NetworkInformation;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Proxd_man.Config;
using Proxd_man.Config.Outbound;
using Proxd_man.Subscribe;

namespace Proxd_man.Monitor;

public class OutboundMonitor
{

    private static readonly Uri HttpLatencyTestUrl = new("https://cp.cloudflare.com/generate_204");
    private static readonly Uri HttpBandwidthTestUrl = new("https://speed.cloudflare.com/__down?bytes=51200000");

    private readonly ILogger<OutboundMonitor> _logger;
    private readonly IOptionsMonitor<ProxdConfig> _configProvider;
    private readonly SubscribeManager _subscribeManager;
    private readonly XrayCoreManager _xrayCoreManager;

    private ProxdConfig _config => _configProvider.CurrentValue;
    
    public OutboundMonitor(ILogger<OutboundMonitor> logger, IOptionsMonitor<ProxdConfig> configProvider, SubscribeManager subscribeManager, XrayCoreManager xrayCoreManager)
    {
        _logger = logger;
        _configProvider = configProvider;
        _subscribeManager = subscribeManager;
        _xrayCoreManager = xrayCoreManager;
        subscribeManager.SubscribeUpdated += async subscribeOutbounds =>
        {
            await ReselectOutbound(subscribeOutbounds);
        };
    }

    private async Task ReselectOutbound(IDictionary<SubscribeSource, List<BaseOutboundSetting>> subscribeOutbounds)
    {
        
        _logger.LogInformation("开始重新选择代理...");
        foreach (var (source, outboundSettings) in subscribeOutbounds)
        {
            _logger.LogDebug("开始测试订阅 {SubscribeName} 的代理...", source.Name);
            foreach (var outboundSetting in outboundSettings)
            {
                if (outboundSetting.Address == null)
                {
                    _logger.LogDebug("跳过代理 {OutboundSettingName} ({OutboundSettingTag}), 因为 Address 为空", 
                        outboundSetting.Name, outboundSetting.GetTag());
                    continue;
                }
                
                using var ping = new Ping();
                var pingReply = ping.Send(outboundSetting.Address, 5000);
                
                if (pingReply.Status != IPStatus.Success)
                {
                    _logger.LogWarning("无法 Ping 到代理 {OutboundSettingName} ({OutboundSettingTag}), 地址: {OutboundSettingAddress}, 错误: {PingReplyStatus}",
                        outboundSetting.Name, outboundSetting.GetTag(), outboundSetting.Address, pingReply.Status);
                    continue;
                }
                
                // 如果 Ping 成功, 则开始测试代理的延迟和带宽
                _logger.LogDebug("开始测试代理 {OutboundSettingName} ({OutboundSettingTag}), 地址: {OutboundSettingAddress}", 
                    outboundSetting.Name, outboundSetting.GetTag(), outboundSetting.Address);
                
                // 随机选择一个端口进行测试
                var port = (ushort) new Random().Next(50000, 60000);
                var outboundTestProcess = _xrayCoreManager.CreateOutboundTestProcess(port, outboundSetting);
                outboundTestProcess.Start();

                // 等 Xray-Core 就绪.
                await Task.Delay(500);
                
                // 先测试代理的延迟.
                var (latencies, bandwidths) = await MeasureOutbound(port);
                if (latencies.All(l => l == -1))
                {
                    _logger.LogWarning("代理 {OutboundSettingName} ({OutboundSettingTag}) 的延迟测试失败, 地址: {OutboundSettingAddress}", 
                        outboundSetting.Name, outboundSetting.GetTag(), outboundSetting.Address);
                    continue;
                }
                
                // 计算平均延迟.
                var avgLatency = latencies.Where(l => l != -1).Average();
                _logger.LogDebug("代理 {OutboundSettingName} ({OutboundSettingTag}) 的平均延迟为 {AvgLatency}ms, 地址: {OutboundSettingAddress}", 
                    outboundSetting.Name, outboundSetting.GetTag(), avgLatency, outboundSetting.Address);
            }
        }
    }
    
    public void StartMonitor()
    {
        Task.Run(async () =>
        {
            
        });
    }
    
    private static async Task<(long[] latencies, long[] bandwidths)> MeasureOutbound(ushort port, bool withBandwidth = false, CancellationToken cancellationToken = default)
    {
        var latencies = await MeasureHttpLatency(port, cancellationToken);
        var bandwidths = withBandwidth ? await MeasureHttpBandwidth(port, cancellationToken) : [];
        return (latencies, bandwidths);
    }

    private static async Task<long[]> MeasureHttpLatency(ushort port, CancellationToken cancellationToken = default)
    {
        var httpClient = new HttpClient(new HttpClientHandler
        {
            Proxy = new WebProxy
            {
                Address = new Uri($"http://127.0.0.1:{port}")
            },
            UseProxy = true,
        })
        {
            Timeout = TimeSpan.FromSeconds(10)
        };
        
        // 发起 8 次请求，取平均值
        var latencies = new long[8];
        for (var i = 0; i < 9; i++)
        {
            // 第一次请求不计入统计, 因为此时代理可能还未完全启动
            if (i == 0)
            {
                await httpClient.GetAsync(HttpLatencyTestUrl, cancellationToken);
                continue;
            }
            
            var sw = Stopwatch.StartNew();
            try
            {
                using var response = await httpClient.GetAsync(HttpLatencyTestUrl, cancellationToken);
                sw.Stop();
                response.EnsureSuccessStatusCode();
                latencies[i - 1] = sw.ElapsedMilliseconds;
            }
            catch (Exception)
            {
                sw.Stop();
                latencies[i - 1] = -1;
            }

            await Task.Delay(400, cancellationToken);
        }
        
        return latencies;
    }
    
    private static async Task<long[]> MeasureHttpBandwidth(ushort port, CancellationToken cancellationToken = default)
    {
        var httpClient = new HttpClient(new HttpClientHandler
        {
            Proxy = new WebProxy
            {
                Address = new Uri($"http://127.0.0.1:{port}")
            },
            UseProxy = true,
        })
        {
            Timeout = TimeSpan.FromSeconds(10)
        };
        
        // 进行 3 次下载，取平均值
        var bandwidths = new long[3];
        for (var i = 0; i < 3; i++)
        {
            var sw = Stopwatch.StartNew();
            try
            {
                using var response = await httpClient.GetAsync(HttpBandwidthTestUrl, cancellationToken);
                sw.Stop();
                response.EnsureSuccessStatusCode();
                bandwidths[i] = 51200000 / (sw.ElapsedMilliseconds / 1000);
            }
            catch (Exception)
            {
                sw.Stop();
                bandwidths[i] = -1;
            }

            await Task.Delay(1000, cancellationToken);
        }
        
        return bandwidths;
    }
}