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;
using SHH.Contracts.Grpc; // 引用 Proto 生成的命名空间
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace SHH.CameraService
{
    /// <summary>
    /// gRPC 指令接收后台服务
    /// 负责：1. 逻辑注册 2. 维持指令长连接 3. 指令分发
    /// </summary>
    public class GrpcCommandReceiverWorker : BackgroundService
    {
        private readonly ILogger<GrpcCommandReceiverWorker> _logger;
        private readonly ServiceConfig _config;
        private readonly IEnumerable<ICommandHandler> _handlers; // 自动注入所有指令处理器

        public GrpcCommandReceiverWorker(
            ILogger<GrpcCommandReceiverWorker> logger,
            ServiceConfig config,
            IEnumerable<ICommandHandler> handlers)
        {
            _logger = logger;
            _config = config;
            _handlers = handlers;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            // 给 SDK 和数据库留出几秒钟的加载时间
            _logger.LogInformation("[gRPC Bus] 后台 Worker 准备就绪，3秒后发起连接...");
            await Task.Delay(3000, stoppingToken);

            while (!stoppingToken.IsCancellationRequested)
            {
                try
                {
                    // 1. 地址预处理 (将 127.0.0.1 强制转换为 localhost 解决 Unimplemented 问题)
                    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] 逻辑注册成功。正在开启长连接指令通道...");

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

                        // --- 第三步：阻塞式监听服务端推送 ---
                        // 只要服务端通过 responseStream.WriteAsync 发消息，这里就会命中
                        while (await call.ResponseStream.MoveNext(stoppingToken))
                        {
                            var protoMsg = call.ResponseStream.Current;
                            _logger.LogInformation("[gRPC Bus] 收到远程指令: {CmdCode}", protoMsg.CmdCode);

                            // 异步分发，不阻塞接收循环
                            _ = DispatchCommandAsync(protoMsg);
                        }
                    }
                }
                catch (OperationCanceledException) { break; }
                catch (Exception ex)
                {
                    _logger.LogError("[gRPC Bus] 链路异常，5秒后重试: {Msg}", ex.Message);
                    await Task.Delay(5000, stoppingToken);
                }
            }
        }

        /// <summary>
        /// 指令分发逻辑
        /// </summary>
        private async Task DispatchCommandAsync(CommandPayloadProto msg)
        {
            try
            {
                // 1. 寻找匹配的处理器 (SyncCameraHandler / RemoveCameraHandler)
                var handler = _handlers.FirstOrDefault(h => h.ActionName == msg.CmdCode);

                if (handler != null)
                {
                    // 2. 将 Proto 的参数转为 JToken，保持与原有处理器兼容
                    var jsonParams = JToken.Parse(msg.JsonParams);
                    await handler.ExecuteAsync(jsonParams);
                    _logger.LogInformation("[gRPC Bus] 指令 {CmdCode} 执行完成", msg.CmdCode);
                }
                else
                {
                    _logger.LogWarning("[gRPC Bus] 未找到处理 {CmdCode} 的处理器", msg.CmdCode);
                }
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "[gRPC Bus] 指令执行失败: {CmdCode}", msg.CmdCode);
            }
        }
    }
}