using Microsoft.Extensions.Configuration;
using Prism.Events;
using System.IO;
using System.Net.WebSockets;
using System.Text;
using System.Timers;
using YY.Admin.Core.Events;
using YY.Admin.Core.Services;
using YY.Admin.Core.Session;
using YY.Admin.Helper;
using YY.Admin.Infrastructure.Storage;

namespace YY.Admin.Infrastructure.Hubs;

public class StompWebSocketService : ISignalRService
{
    // STOMP heart-beat: send \n every 10 s, declare we want to receive every 10 s
    private const int HeartbeatMs = 10_000;
    // Watchdog: if nothing received in 3 × HeartbeatMs, treat connection as zombie
    private const int WatchdogMs = 30_000;

    private readonly IConfiguration _configuration;
    private readonly IEventAggregator _eventAggregator;
    private readonly TokenStore _tokenStore;
    private readonly INetworkMonitor _networkMonitor;

    private ClientWebSocket? _socket;
    private string _deviceId = "default-device";
    private string _token = string.Empty;

    private CancellationTokenSource? _connectionCts;
    private System.Timers.Timer? _heartbeatTimer;
    private System.Timers.Timer? _watchdogTimer;
    private volatile int _lastReceivedTick = Environment.TickCount;

    public StompWebSocketService(
        IConfiguration configuration,
        IEventAggregator eventAggregator,
        TokenStore tokenStore,
        INetworkMonitor networkMonitor)
    {
        _configuration = configuration;
        _eventAggregator = eventAggregator;
        _tokenStore = tokenStore;
        _networkMonitor = networkMonitor;

        // When the network comes back online, reconnect the STOMP channel if it is down.
        eventAggregator.GetEvent<NetworkStatusChangedEvent>()
            .Subscribe(OnNetworkStatusChanged, ThreadOption.BackgroundThread);
    }

    private void OnNetworkStatusChanged(NetworkStatusChangedPayload payload)
    {
        if (!payload.IsOnline || IsDisconnectedByUser())
        {
            return;
        }
        if (_socket == null || _socket.State != WebSocketState.Open)
        {
            _ = Task.Run(() => ConnectUnifiedDeviceChannelAsync(CancellationToken.None));
        }
    }

    /// <inheritdoc />
    public async Task ConnectAsync(string token, CancellationToken cancellationToken = default)
    {
        _token = token ?? string.Empty;
        await ConnectUnifiedDeviceChannelAsync(cancellationToken).ConfigureAwait(false);
    }

    /// <inheritdoc />
    public async Task ConnectUnifiedDeviceChannelAsync(CancellationToken cancellationToken = default)
    {
        if (IsDisconnectedByUser())
        {
            await DisconnectAsync(cancellationToken).ConfigureAwait(false);
            return;
        }

        var anonymous = _configuration.GetValue("JeecgIntegration:AnonymousMode", true);
        if (anonymous)
        {
            _token = string.Empty;
        }
        else if (string.IsNullOrWhiteSpace(_token))
        {
            _token = await _tokenStore.GetTokenAsync(cancellationToken).ConfigureAwait(false) ?? string.Empty;
        }

        _deviceId = ResolveDeviceId(_token);
        var wsUrl = ResolveWsUrl();
        var retryDelays = new[] { 0, 2, 5, 10, 30 };

        foreach (var delay in retryDelays)
        {
            if (delay > 0)
            {
                await Task.Delay(TimeSpan.FromSeconds(delay), cancellationToken).ConfigureAwait(false);
            }

            try
            {
                // Tear down previous session before opening a new one.
                var oldCts = Interlocked.Exchange(ref _connectionCts, null);
                oldCts?.Cancel();
                oldCts?.Dispose();
                StopTimers();
                _socket?.Dispose();

                _socket = new ClientWebSocket();
                _socket.Options.AddSubProtocol("v12.stomp");
                await _socket.ConnectAsync(new Uri(wsUrl), cancellationToken).ConfigureAwait(false);

                var connectFrame = anonymous || string.IsNullOrWhiteSpace(_token)
                    ? BuildConnectFrame(null, _deviceId)
                    : BuildConnectFrame(_token, _deviceId);
                await SendFrameAsync(connectFrame, cancellationToken).ConfigureAwait(false);

                // 用户镜像变更：订阅 /topic/sync/jeecg-users
                await SendFrameAsync(
                    BuildSubscribeFrame("sub-jeecg-users", "/topic/sync/jeecg-users"),
                    cancellationToken).ConfigureAwait(false);

                // 车辆数据变更：订阅 /topic/sync/mes-vehicles
                await SendFrameAsync(
                    BuildSubscribeFrame("sub-mes-vehicles", "/topic/sync/mes-vehicles"),
                    cancellationToken).ConfigureAwait(false);

                // 客户数据变更：订阅 /topic/sync/mes-customers
                await SendFrameAsync(
                    BuildSubscribeFrame("sub-mes-customers", "/topic/sync/mes-customers"),
                    cancellationToken).ConfigureAwait(false);
                // 供应商数据变更：订阅 /topic/sync/mes-suppliers
                await SendFrameAsync(
                    BuildSubscribeFrame("sub-mes-suppliers", "/topic/sync/mes-suppliers"),
                    cancellationToken).ConfigureAwait(false);
                // 磅单数据变更：订阅 /topic/sync/mes-weight-records
                await SendFrameAsync(
                    BuildSubscribeFrame("sub-mes-weight-records", "/topic/sync/mes-weight-records"),
                    cancellationToken).ConfigureAwait(false);

                // 订阅服务端 PONG 回复（应用层假在线检测）
                await SendFrameAsync(
                    BuildSubscribeFrame("sub-device-pong", $"/topic/device/{_deviceId}/pong"),
                    cancellationToken).ConfigureAwait(false);

                if (!anonymous && !string.IsNullOrWhiteSpace(_token))
                {
                    await SendFrameAsync(
                        BuildSubscribeFrame("sub-device-command", $"/user/{_deviceId}/queue/command"),
                        cancellationToken).ConfigureAwait(false);
                }

                // Reset watchdog baseline to now.
                _lastReceivedTick = Environment.TickCount;

                var cts = new CancellationTokenSource();
                _connectionCts = cts;

                StartHeartbeatTimer(cts.Token);
                StartWatchdogTimer(cts.Token);

                _networkMonitor.SetStompTransportOnline(true);

                _ = Task.Run(() => ReceiveLoopAsync(cts.Token), cts.Token);
                return;
            }
            catch
            {
                _networkMonitor.SetStompTransportOnline(false);
            }
        }
    }

    /// <inheritdoc />
    public async Task SendDeviceStatusAsync(object status, CancellationToken cancellationToken = default)
    {
        if (IsDisconnectedByUser() || _socket == null || _socket.State != WebSocketState.Open)
        {
            return;
        }
        var json = System.Text.Json.JsonSerializer.Serialize(status);
        var frame = "SEND\n" +
                    "destination:/app/device/status\n" +
                    "content-type:application/json\n" +
                    $"content-length:{Encoding.UTF8.GetByteCount(json)}\n\n" +
                    $"{json}\0";
        await SendFrameAsync(frame, cancellationToken).ConfigureAwait(false);
    }

    public async Task DisconnectAsync(CancellationToken cancellationToken = default)
    {
        var cts = Interlocked.Exchange(ref _connectionCts, null);
        cts?.Cancel();
        cts?.Dispose();
        StopTimers();

        var socket = _socket;
        _socket = null;
        if (socket == null)
        {
            _networkMonitor.SetStompTransportOnline(false);
            return;
        }

        try
        {
            if (socket.State == WebSocketState.Open || socket.State == WebSocketState.CloseReceived)
            {
                await socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "manual disconnect", cancellationToken).ConfigureAwait(false);
            }
        }
        catch
        {
            socket.Abort();
        }
        finally
        {
            socket.Dispose();
            _networkMonitor.SetStompTransportOnline(false);
        }
    }

    // ── Heartbeat ──────────────────────────────────────────────────────────

    private void StartHeartbeatTimer(CancellationToken cancellationToken)
    {
        _heartbeatTimer = new System.Timers.Timer(HeartbeatMs) { AutoReset = true };
        _heartbeatTimer.Elapsed += async (_, _) =>
        {
            if (cancellationToken.IsCancellationRequested)
            {
                return;
            }
            // STOMP protocol keepalive (\n frame)
            await SendStompHeartbeatAsync(cancellationToken).ConfigureAwait(false);
            // Application-layer PING: server replies to /topic/device/{id}/pong
            await SendAppPingAsync(cancellationToken).ConfigureAwait(false);
        };
        _heartbeatTimer.Start();
    }

    private async Task SendStompHeartbeatAsync(CancellationToken cancellationToken)
    {
        if (_socket == null || _socket.State != WebSocketState.Open)
        {
            return;
        }
        try
        {
            // STOMP spec: a single LF (0x0A) constitutes a heartbeat frame.
            await _socket.SendAsync(
                new ArraySegment<byte>(new byte[] { 0x0A }),
                WebSocketMessageType.Text,
                true,
                cancellationToken).ConfigureAwait(false);
        }
        catch
        {
            // Send failure will be caught by the watchdog.
        }
    }

    private async Task SendAppPingAsync(CancellationToken cancellationToken)
    {
        if (_socket == null || _socket.State != WebSocketState.Open)
        {
            return;
        }
        try
        {
            var body = $"{{\"cmd\":\"PING_DEVICE\",\"deviceId\":\"{_deviceId}\",\"ts\":{DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()}}}";
            var frame = "SEND\n" +
                        "destination:/app/device/ping\n" +
                        "content-type:application/json\n" +
                        $"content-length:{Encoding.UTF8.GetByteCount(body)}\n\n" +
                        $"{body}\0";
            await SendFrameAsync(frame, cancellationToken).ConfigureAwait(false);
        }
        catch
        {
            // Watchdog handles reconnect.
        }
    }

    // ── Watchdog ───────────────────────────────────────────────────────────

    private void StartWatchdogTimer(CancellationToken cancellationToken)
    {
        _watchdogTimer = new System.Timers.Timer(WatchdogMs) { AutoReset = true };
        _watchdogTimer.Elapsed += (_, _) =>
        {
            if (cancellationToken.IsCancellationRequested)
            {
                return;
            }
            // TickCount wraps; unchecked subtraction handles it correctly.
            var silenceMs = unchecked(Environment.TickCount - _lastReceivedTick);
            if (silenceMs >= WatchdogMs)
            {
                // No frame (heartbeat or MESSAGE) received for WatchdogMs — zombie connection.
                _ = Task.Run(() => ConnectUnifiedDeviceChannelAsync(CancellationToken.None));
            }
        };
        _watchdogTimer.Start();
    }

    private void StopTimers()
    {
        _heartbeatTimer?.Stop();
        _heartbeatTimer?.Dispose();
        _heartbeatTimer = null;

        _watchdogTimer?.Stop();
        _watchdogTimer?.Dispose();
        _watchdogTimer = null;
    }

    // ── Receive loop ───────────────────────────────────────────────────────

    private async Task ReceiveLoopAsync(CancellationToken cancellationToken)
    {
        if (_socket == null)
        {
            return;
        }
        var buffer = new byte[8192];
        while (_socket.State == WebSocketState.Open && !cancellationToken.IsCancellationRequested)
        {
            using var ms = new MemoryStream();
            WebSocketReceiveResult result;
            do
            {
                result = await _socket.ReceiveAsync(new ArraySegment<byte>(buffer), cancellationToken).ConfigureAwait(false);
                if (result.MessageType == WebSocketMessageType.Close)
                {
                    _networkMonitor.SetStompTransportOnline(false);
                    await ConnectUnifiedDeviceChannelAsync(cancellationToken).ConfigureAwait(false);
                    return;
                }
                ms.Write(buffer, 0, result.Count);
            } while (!result.EndOfMessage);

            // Any received frame (heartbeat \n or MESSAGE) resets the watchdog.
            _lastReceivedTick = Environment.TickCount;

            var text = Encoding.UTF8.GetString(ms.ToArray());
            if (!text.StartsWith("MESSAGE", StringComparison.OrdinalIgnoreCase))
            {
                continue;
            }
            var idx = text.IndexOf("\n\n", StringComparison.Ordinal);
            if (idx < 0)
            {
                continue;
            }
            var body = text[(idx + 2)..].TrimEnd('\0');
            _eventAggregator.GetEvent<RemoteCommandReceivedEvent>().Publish(new RemoteCommandPayload
            {
                DeviceId = _deviceId,
                CommandJson = body
            });
        }
    }

    private async Task SendFrameAsync(string frame, CancellationToken cancellationToken)
    {
        if (_socket == null || _socket.State != WebSocketState.Open)
        {
            return;
        }
        var data = Encoding.UTF8.GetBytes(frame);
        await _socket.SendAsync(
            new ArraySegment<byte>(data),
            WebSocketMessageType.Text,
            true,
            cancellationToken).ConfigureAwait(false);
    }

    // ── Helpers ────────────────────────────────────────────────────────────

    private string ResolveWsUrl()
    {
        var baseUrl = _configuration.GetValue<string>("JeecgIntegration:BaseUrl")?.TrimEnd('/');
        if (string.IsNullOrWhiteSpace(baseUrl))
        {
            return "ws://127.0.0.1:8080/jeecg-boot/ws/device";
        }
        if (baseUrl.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
        {
            return "wss://" + baseUrl["https://".Length..] + "/ws/device";
        }
        return "ws://" + baseUrl["http://".Length..] + "/ws/device";
    }

    private static string ResolveDeviceId(string token)
    {
        try
        {
            var parts = token.Split('.');
            if (parts.Length < 2)
            {
                return "default-device";
            }
            var payload = parts[1].Replace('-', '+').Replace('_', '/');
            payload = payload.PadRight(payload.Length + (4 - payload.Length % 4) % 4, '=');
            var json = Encoding.UTF8.GetString(Convert.FromBase64String(payload));
            using var doc = System.Text.Json.JsonDocument.Parse(json);
            if (doc.RootElement.TryGetProperty("deviceId", out var deviceId))
            {
                return deviceId.GetString() ?? "default-device";
            }
            if (doc.RootElement.TryGetProperty("username", out var username))
            {
                return username.GetString() ?? "default-device";
            }
            return "default-device";
        }
        catch
        {
            return "default-device";
        }
    }

    private static string BuildConnectFrame(string? token, string deviceId)
    {
        var user = AppSession.CurrentUser;
        var sb = new System.Text.StringBuilder();
        sb.Append("CONNECT\n");
        sb.Append("accept-version:1.2\n");
        sb.Append($"heart-beat:{HeartbeatMs},{HeartbeatMs}\n");
        if (!string.IsNullOrWhiteSpace(token))
            sb.Append($"Authorization:Bearer {token}\n");
        sb.Append("platform:desktop\n");
        sb.Append($"hostName:{Environment.MachineName}\n");
        sb.Append($"deviceId:{deviceId}\n");
        sb.Append($"userName:{user?.Account ?? "unknown"}\n");
        sb.Append($"realName:{user?.RealName ?? ""}\n");
        sb.Append("\n\0");
        return sb.ToString();
    }

    private static string BuildSubscribeFrame(string subscriptionId, string destination)
    {
        return "SUBSCRIBE\n" +
               $"id:{subscriptionId}\n" +
               $"destination:{destination}\n" +
               "ack:auto\n\n\0";
    }

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