using Grpc.Core;
using Grpc.Net.Client;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json.Linq;
using SHH.CameraSdk;
using SHH.Contracts.Grpc; // 引用 Proto 生成的命名空间

namespace SHH.CameraService
{
    /// <summary>
    /// gRPC 指令接收后台服务
    /// 职责：
    /// 1. 维护与 AiVideo 的 gRPC 长连接。
    /// 2. 完成节点逻辑注册。
    /// 3. 监听 Server Streaming 指令流并移交给 Dispatcher。
    /// </summary>
    public class GatewayService : BackgroundService
    {
        private readonly ILogger<GatewayService> _logger;
        private readonly ServiceConfig _config;
        private readonly CommandDispatcher _dispatcher;

        public GatewayService(
            ILogger<GatewayService> logger,
            ServiceConfig config,
            CommandDispatcher dispatcher)
        {
            _logger = logger;
            _config = config;
            _dispatcher = dispatcher;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            // 预留系统启动缓冲时间，确保数据库和 SDK 已就绪
            _logger.LogInformation("[gRPC Bus] 指令接收服务启动，等待环境预热...");
            await Task.Delay(3000, stoppingToken);

            while (!stoppingToken.IsCancellationRequested)
            {
                try
                {
                    // 1. 地址适配：将 tcp 转换为 http，并将 127.0.0.1 修正为 localhost 解决 Unimplemented 异常
                    var ep = _config.CommandEndpoints.First();
                    string targetUrl = ep.Uri.Replace("tcp://", "http://").Replace("127.0.0.1", "localhost");

                    using var channel = GrpcChannel.ForAddress(targetUrl);
                    var client = new GatewayProvider.GatewayProviderClient(channel);

                    // --- 第一步：发起节点逻辑注册 (Unary) ---
                    _logger.LogInformation("[gRPC Bus] 正在发起逻辑注册: {Url}", targetUrl);
                    var regResp = await client.RegisterInstanceAsync(new RegisterRequest
                    {
                        InstanceId = _config.AppId,
                        Version = "2.0.0-grpc",
                        ServerIp = "127.0.0.1",
                        StartTimeTicks = DateTime.Now.Ticks
                    }, cancellationToken: stoppingToken);

                    if (regResp.Success)
                    {
                        _logger.LogInformation("[gRPC Bus] 注册成功。正在建立双向指令通道...");

                        // --- 第二步：开启 Server Streaming 指令流 ---
                        using var call = client.OpenCommandChannel(new CommandStreamRequest
                        {
                            InstanceId = _config.AppId
                        }, cancellationToken: stoppingToken);

                        // --- 第三步：循环读取服务端推送的指令 ---
                        // 只要服务端流未断开，此处会一直阻塞等待新消息
                        while (await call.ResponseStream.MoveNext(stoppingToken))
                        {
                            var protoMsg = call.ResponseStream.Current;

                            // 核心变更：不再直接处理业务，而是通过分发器进行路由
                            // 使用 _ = 异步处理，避免某个 Handler 执行过慢导致指令流阻塞
                            _ = _dispatcher.DispatchAsync(protoMsg);
                        }
                    }
                }
                catch (OperationCanceledException)
                {
                    // 响应系统正常退出信号
                    break;
                }
                catch (RpcException ex)
                {
                    _logger.LogError("[gRPC Bus] RPC 异常 (Status: {Code}): {Msg}", ex.StatusCode, ex.Message);
                    // 链路异常，进入重连等待阶段
                    await Task.Delay(5000, stoppingToken);
                }
                catch (Exception ex)
                {
                    _logger.LogError("[gRPC Bus] 非预期链路异常: {Msg}，5秒后尝试重连", ex.Message);
                    await Task.Delay(5000, stoppingToken);
                }
            }
        }
    }
}