using LiveForum.Code.Redis.Contract;
using LiveForum.IService.Messages;
using LiveForum.Model.Events;
using Microsoft.Extensions.Logging;
using StackExchange.Redis;
using System;
using System.Text.Json;
using System.Threading.Tasks;

namespace LiveForum.Service.Messages
{
    /// <summary>
    /// 基于Redis的消息事件总线实现
    /// </summary>
    public class RedisMessageEventBus : IMessageEventBus
    {
        private readonly IRedisService _redisService;
        private readonly ILogger<RedisMessageEventBus> _logger;
        private readonly IDatabase _database;

        // 队列名称常量
        private const string LIKE_QUEUE = "message:events:like";
        private const string COMMENT_QUEUE = "message:events:comment";
        private const string CUSTOM_QUEUE = "message:events:custom";

        public RedisMessageEventBus(
            IRedisService redisService,
            ILogger<RedisMessageEventBus> logger,
            IDatabase database)
        {
            _redisService = redisService;
            _logger = logger;
            _database = database;
        }

        /// <summary>
        /// 发布消息事件到Redis队列
        /// </summary>
        public async Task PublishAsync<T>(T eventData) where T : MessageEventBase
        {
            try
            {
                // 根据事件类型选择队列
                var queueName = GetQueueName(eventData);
                
                // 序列化事件数据
                var json = JsonSerializer.Serialize(eventData, new JsonSerializerOptions
                {
                    PropertyNamingPolicy = JsonNamingPolicy.CamelCase
                });

                // 推入Redis List队列（右侧推入，左侧弹出，保证FIFO）
                await _database.ListRightPushAsync(queueName, json);

                _logger.LogInformation(
                    "[EventBus] 事件已发布: {EventType}, EventId: {EventId}, Queue: {Queue}",
                    eventData.EventType, eventData.EventId, queueName);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, 
                    "[EventBus] 发布事件失败: {EventType}, EventId: {EventId}", 
                    eventData.EventType, eventData.EventId);
                
                // 发布失败不应该阻塞主业务流程，只记录日志
                // 但也可以选择抛出异常让调用方处理
                throw;
            }
        }

        /// <summary>
        /// 获取队列长度
        /// </summary>
        public async Task<long> GetQueueLengthAsync(string queueName)
        {
            try
            {
                return await _database.ListLengthAsync(queueName);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "[EventBus] 获取队列长度失败: {Queue}", queueName);
                return -1;
            }
        }

        /// <summary>
        /// 根据事件类型获取队列名称
        /// </summary>
        private string GetQueueName(MessageEventBase eventData)
        {
            return eventData switch
            {
                LikeEvent => LIKE_QUEUE,
                CommentReplyEvent => COMMENT_QUEUE,
                CustomMessageEvent => CUSTOM_QUEUE,
                _ => throw new ArgumentException($"未知的事件类型: {eventData.GetType().Name}")
            };
        }
    }
}