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using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
 
namespace VueWebCoreApi.SignalR
{
    /// <summary>
    /// 用户连接ID与用户编码映射存储(线程安全版)
    /// 解决多线程并发读写导致的字典数据错乱问题
    /// </summary>
    public static class UserIdsStore
    {
        // 替换为线程安全的并发字典
        private static readonly Dictionary<string, string> _ids = new Dictionary<string, string>();
        // 加锁保证字典操作的原子性(比ConcurrentDictionary更灵活控制批量操作)
        private static readonly object _lockObj = new object();
 
        /// <summary>
        /// 对外暴露的连接映射(只读,避免外部直接修改)
        /// </summary>
        public static IReadOnlyDictionary<string, string> Ids
        {
            get
            {
                lock (_lockObj)
                {
                    // 返回新字典,避免外部拿到引用后修改
                    return new Dictionary<string, string>(_ids);
                }
            }
        }
 
        /// <summary>
        /// 添加/更新用户连接(原子操作)
        /// </summary>
        /// <param name="connectionId">SignalR连接ID</param>
        /// <param name="userCode">用户编码</param>
        public static void AddOrUpdateUser(string connectionId, string userCode)
        {
            if (string.IsNullOrEmpty(connectionId) || string.IsNullOrEmpty(userCode))
                throw new ArgumentNullException("连接ID和用户编码不能为空");
 
            lock (_lockObj)
            {
                // 先移除该用户的旧连接(一个用户只保留最新的连接)
                var oldConnIds = _ids.Where(kv => kv.Value == userCode).Select(kv => kv.Key).ToList();
                foreach (var oldConnId in oldConnIds)
                {
                    _ids.Remove(oldConnId);
                }
                // 添加新连接(覆盖同名connectionId,避免重复)
                if (_ids.ContainsKey(connectionId))
                {
                    _ids[connectionId] = userCode;
                }
                else
                {
                    _ids.Add(connectionId, userCode);
                }
            }
        }
 
        /// <summary>
        /// 移除指定连接ID的映射
        /// </summary>
        /// <param name="connectionId">SignalR连接ID</param>
        public static void RemoveUser(string connectionId)
        {
            if (string.IsNullOrEmpty(connectionId))
                return;
 
            lock (_lockObj)
            {
                if (_ids.ContainsKey(connectionId))
                {
                    _ids.Remove(connectionId);
                }
            }
        }
 
        /// <summary>
        /// 根据用户编码获取所有在线连接ID(一个用户可能多端登录时返回多个)
        /// </summary>
        /// <param name="userCodes">用户编码列表</param>
        /// <returns>连接ID列表</returns>
        public static List<string> GetConnectionIdsByUserCodes(List<string> userCodes)
        {
            if (userCodes == null || userCodes.Count == 0)
                return new List<string>();
 
            lock (_lockObj)
            {
                return _ids.Where(kv => userCodes.Contains(kv.Value))
                           .Select(kv => kv.Key)
                           .Distinct() // 去重,避免重复推送
                           .ToList();
            }
        }
    }
}