using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using NetworkTool.Client.Models;

namespace NetworkTool.Client.Services;

public sealed class NetworkAdapterService
{
    public IReadOnlyList<AdapterInfo> GetEthernetAdapters()
    {
        return NetworkInterface
            .GetAllNetworkInterfaces()
            .Where(IsSupportedEthernetAdapter)
            .Select(BuildAdapterInfo)
            .OrderByDescending(adapter => adapter.RecommendationScore)
            .ThenBy(adapter => adapter.Name)
            .ToList();
    }

    public AdapterInfo? GetRecommendedAdapter(IReadOnlyList<AdapterInfo> adapters)
    {
        return adapters
            .OrderByDescending(adapter => adapter.RecommendationScore)
            .ThenBy(adapter => adapter.Name)
            .FirstOrDefault();
    }

    public async Task ProbeMaintenanceReachabilityAsync(IReadOnlyList<AdapterInfo> adapters, CancellationToken cancellationToken = default)
    {
        foreach (var adapter in adapters)
        {
            if (!adapter.HasLink || string.IsNullOrWhiteSpace(adapter.IPv4Address))
            {
                adapter.ProbeStatus = "不可达";
                adapter.ProbeReason = "该网卡当前没有可用的 IPv4 或链路未连接。";
                adapter.IsReachableToMaintenance = false;
                continue;
            }

            var reachable = await CanReachMaintenanceAsync(adapter.IPv4Address, cancellationToken);
            adapter.IsReachableToMaintenance = reachable;
            if (reachable)
            {
                adapter.ProbeStatus = "可达";
                adapter.ProbeReason = "该网卡可连接到管理口 169.254.100.2:48888。";
                adapter.RecommendationScore += 100;
                adapter.RecommendationLabel = "推荐";
                adapter.RecommendationReason = "该网卡已实际探测到可与 Linux 管理口建立连接，优先使用。";
            }
            else
            {
                adapter.ProbeStatus = "未通";
                adapter.ProbeReason = "该网卡当前无法连接到管理口 169.254.100.2:48888。";
            }
        }
    }

    private static bool IsSupportedEthernetAdapter(NetworkInterface adapter)
    {
        if (adapter.NetworkInterfaceType is not NetworkInterfaceType.Ethernet and not NetworkInterfaceType.GigabitEthernet)
        {
            return false;
        }

        return adapter.Description.Contains("VMware", System.StringComparison.OrdinalIgnoreCase)
            || !adapter.Description.Contains("Virtual", System.StringComparison.OrdinalIgnoreCase);
    }

    private static AdapterInfo BuildAdapterInfo(NetworkInterface adapter)
    {
        var ipv4Address = adapter
            .GetIPProperties()
            .UnicastAddresses
            .FirstOrDefault(address => address.Address.AddressFamily == AddressFamily.InterNetwork)
            ?.Address
            .ToString() ?? string.Empty;

        var score = GetRecommendationScore(adapter, ipv4Address);
        var (label, reason) = GetRecommendation(score, adapter, ipv4Address);

        return AdapterInfo.FromNetworkInterface(adapter, ipv4Address, score, label, reason);
    }

    private static int GetRecommendationScore(NetworkInterface adapter, string ipv4Address)
    {
        var score = 0;
        var description = adapter.Description;
        var isVirtual = IsVirtualAdapter(description);

        if (adapter.NetworkInterfaceType is NetworkInterfaceType.Ethernet or NetworkInterfaceType.GigabitEthernet)
        {
            score += 50;
        }

        if (adapter.OperationalStatus == OperationalStatus.Up)
        {
            score += 40;
        }

        if (ipv4Address.StartsWith("169.254.", System.StringComparison.Ordinal))
        {
            score += 30;
        }

        if (!isVirtual)
        {
            score += 20;
        }

        if (description.Contains("Intel", System.StringComparison.OrdinalIgnoreCase)
            || description.Contains("Realtek", System.StringComparison.OrdinalIgnoreCase)
            || description.Contains("Broadcom", System.StringComparison.OrdinalIgnoreCase))
        {
            score += 10;
        }

        if (isVirtual)
        {
            score -= 40;
        }

        return score;
    }

    private static (string Label, string Reason) GetRecommendation(int score, NetworkInterface adapter, string ipv4Address)
    {
        if (score >= 90)
        {
            if (ipv4Address.StartsWith("169.254.", System.StringComparison.Ordinal))
            {
                return ("推荐", "已连接且当前 IPv4 为 169.254 网段，最像初始化直连网卡。");
            }

            return ("推荐", "已检测到已连接的有线网卡，适合作为初始化连接口。");
        }

        if (score >= 40)
        {
            return ("可选", "该网卡可用，但不是最优候选，请确认是否为实际直连接口。");
        }

        return ("不建议", "该网卡更像虚拟或非直连接口，通常不建议用于设备初始化。");
    }

    private static bool IsVirtualAdapter(string description)
    {
        return description.Contains("VMware", System.StringComparison.OrdinalIgnoreCase)
            || description.Contains("Virtual", System.StringComparison.OrdinalIgnoreCase)
            || description.Contains("Hyper-V", System.StringComparison.OrdinalIgnoreCase)
            || description.Contains("TAP", System.StringComparison.OrdinalIgnoreCase)
            || description.Contains("VPN", System.StringComparison.OrdinalIgnoreCase)
            || description.Contains("Loopback", System.StringComparison.OrdinalIgnoreCase);
    }

    private static async Task<bool> CanReachMaintenanceAsync(string localIPv4, CancellationToken cancellationToken)
    {
        try
        {
            using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            socket.Bind(new IPEndPoint(IPAddress.Parse(localIPv4), 0));
            using var timeoutCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
            timeoutCts.CancelAfter(TimeSpan.FromMilliseconds(500));
            await socket.ConnectAsync(IPAddress.Parse("169.254.100.2"), 48888, timeoutCts.Token);
            return socket.Connected;
        }
        catch
        {
            return false;
        }
    }
}