using Microsoft.Extensions.Configuration;
using Prism.Events;
using System.Net.Http;
using YY.Admin.Core.Events;
using YY.Admin.Core.Services;
using YY.Admin.Helper;

namespace YY.Admin.Infrastructure.Network;

public class NetworkMonitor : INetworkMonitor
{
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IConfiguration _configuration;
    private readonly IEventAggregator _eventAggregator;
    private readonly SemaphoreSlim _startLock = new(1, 1);
    private readonly object _aggregateLock = new();
    private Task? _loopTask;
    private CancellationTokenSource? _cts;
    private volatile bool _httpProbeOnline;
    private volatile bool _stompTransportOnline;
    private volatile bool _isOnline;

    public NetworkMonitor(
        IHttpClientFactory httpClientFactory,
        IConfiguration configuration,
        IEventAggregator eventAggregator)
    {
        _httpClientFactory = httpClientFactory;
        _configuration = configuration;
        _eventAggregator = eventAggregator;
    }

    public bool IsOnline => _isOnline;

    public event Action<bool>? StatusChanged;

    /// <inheritdoc />
    public void SetStompTransportOnline(bool online)
    {
        _stompTransportOnline = online;
        RecomputeAggregatedOnline();
    }

    public async Task StartAsync(CancellationToken cancellationToken = default)
    {
        await _startLock.WaitAsync(cancellationToken).ConfigureAwait(false);
        try
        {
            if (_cts != null)
            {
                return;
            }

            _cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
            _loopTask = Task.Run(() => MonitorLoopAsync(_cts.Token), _cts.Token);
        }
        finally
        {
            _startLock.Release();
        }
    }

    private async Task MonitorLoopAsync(CancellationToken cancellationToken)
    {
        // 启动后立即探活一次，避免首屏 10 秒内 IsOnline 恒为 false
        await RunHttpProbeAndRecomputeAsync(cancellationToken).ConfigureAwait(false);

        using var timer = new PeriodicTimer(TimeSpan.FromSeconds(10));
        while (await timer.WaitForNextTickAsync(cancellationToken).ConfigureAwait(false))
        {
            await RunHttpProbeAndRecomputeAsync(cancellationToken).ConfigureAwait(false);
        }
    }

    private async Task RunHttpProbeAndRecomputeAsync(CancellationToken cancellationToken)
    {
        var httpOk = await ProbeAsync(cancellationToken).ConfigureAwait(false);
        _httpProbeOnline = httpOk;
        RecomputeAggregatedOnline();
    }

    private void RecomputeAggregatedOnline()
    {
        var combined = ComputeCombinedOnline();
        bool newValue;
        lock (_aggregateLock)
        {
            if (combined == _isOnline)
            {
                return;
            }

            _isOnline = combined;
            newValue = combined;
        }

        StatusChanged?.Invoke(newValue);
        _eventAggregator.GetEvent<NetworkStatusChangedEvent>().Publish(new NetworkStatusChangedPayload
        {
            IsOnline = newValue,
            ChangedAt = DateTime.UtcNow
        });
    }

    private bool ComputeCombinedOnline()
    {
        if (IsDisconnectedByUser())
        {
            return false;
        }

        return _httpProbeOnline || _stompTransportOnline;
    }

    private async Task<bool> ProbeAsync(CancellationToken cancellationToken)
    {
        if (IsDisconnectedByUser())
        {
            return false;
        }

        var baseUrl = _configuration.GetValue<string>("JeecgIntegration:BaseUrl")?.TrimEnd('/');
        if (string.IsNullOrWhiteSpace(baseUrl))
        {
            return false;
        }

        // 探活策略：优先调用免登录接口，失败后再降级到健康检查接口
        var probeUrls = new[]
        {
            $"{baseUrl}/sys/user/scada/queryUser?current=1&pageSize=1",
            $"{baseUrl}/sys/dict/scada/queryDictItem?pageNo=1&pageSize=1",
            $"{baseUrl}/actuator/health"
        };

        using var timeoutCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        timeoutCts.CancelAfter(TimeSpan.FromSeconds(3));
        var client = _httpClientFactory.CreateClient("JeecgApi");
        foreach (var url in probeUrls)
        {
            try
            {
                using var req = new HttpRequestMessage(HttpMethod.Get, url);
                using var resp = await client.SendAsync(req, timeoutCts.Token).ConfigureAwait(false);
                if (resp.IsSuccessStatusCode)
                {
                    return true;
                }
            }
            catch
            {
                // 当前探活地址失败后继续尝试下一个降级地址
            }
        }

        return false;
    }

    private static bool IsDisconnectedByUser()
    {
        try
        {
            return ServerSettingsStore.Load().DisconnectConnection;
        }
        catch
        {
            return false;
        }
    }
}