using Furion.DependencyInjection;
using Furion.FriendlyException;
using Microsoft.Extensions.Logging;
using SqlSugar;
using YD_Event.Core.Entities;

namespace YD_Event.Core.Domain;

/// <summary>
/// 订单号生成器服务
/// 提供分布式唯一订单号生成，确保高并发下的唯一性
/// </summary>
public class OrderNoGeneratorService : ITransient
{
    private static readonly object _lock = new();
    private static long _lastTimestamp = -1;
    private static int _sequence = 0;
    private const int MaxSequence = 9999;
    private readonly ISqlSugarRepository<EventRegistration> _registrationRepository;
    private readonly ILogger<OrderNoGeneratorService> _logger;

    public OrderNoGeneratorService(
        ISqlSugarRepository<EventRegistration> registrationRepository,
        ILogger<OrderNoGeneratorService> logger)
    {
        _registrationRepository = registrationRepository;
        _logger = logger;
    }

    /// <summary>
    /// 生成唯一订单号
    /// 格式：yyyyMMddHHmmss + 4位序列号
    /// 保证高并发下的唯一性
    /// </summary>
    /// <returns>唯一订单号</returns>
    public async Task<string> GenerateOrderNoAsync()
    {
        string orderNo;
        int retryCount = 0;
        const int maxRetry = 5;

        do
        {
            orderNo = GenerateOrderNoInternal();
            retryCount++;

            // 检查数据库中是否已存在
            var exists = await _registrationRepository.IsAnyAsync(r => r.OrderNo == orderNo);
            if (!exists)
            {
                _logger.LogDebug("生成订单号成功: {OrderNo}", orderNo);
                return orderNo;
            }

            _logger.LogWarning("订单号冲突，重试中 ({RetryCount}/{MaxRetry}): {OrderNo}", 
                retryCount, maxRetry, orderNo);
            
            // 短暂延迟后重试
            await Task.Delay(10);

        } while (retryCount < maxRetry);

        _logger.LogError("订单号生成失败，已达到最大重试次数: {MaxRetry}", maxRetry);
        throw Oops.Bah("订单号生成失败，请稍后重试");
    }

    /// <summary>
    /// 生成退款订单号
    /// 格式：REF + yyyyMMddHHmmss + 4位序列号
    /// </summary>
    /// <returns>退款订单号</returns>
    public async Task<string> GenerateRefundOrderNoAsync()
    {
        var baseOrderNo = await GenerateOrderNoAsync();
        return "REF" + baseOrderNo;
    }

    /// <summary>
    /// 内部生成订单号（带线程安全的序列号）
    /// </summary>
    private string GenerateOrderNoInternal()
    {
        lock (_lock)
        {
            var timestamp = DateTime.Now;
            var currentTimestamp = GetTimestamp(timestamp);

            // 如果是同一毫秒，增加序列号
            if (currentTimestamp == _lastTimestamp)
            {
                _sequence++;
                if (_sequence > MaxSequence)
                {
                    // 序列号溢出，等待下一毫秒
                    Thread.Sleep(1);
                    timestamp = DateTime.Now;
                    currentTimestamp = GetTimestamp(timestamp);
                    _sequence = 0;
                }
            }
            else
            {
                // 不同毫秒，重置序列号
                _sequence = 0;
            }

            _lastTimestamp = currentTimestamp;

            // 格式：yyyyMMddHHmmss + 4位序列号（补零）
            return timestamp.ToString("yyyyMMddHHmmss") + _sequence.ToString("D4");
        }
    }

    /// <summary>
    /// 获取时间戳（用于比较）
    /// </summary>
    private static long GetTimestamp(DateTime dateTime)
    {
        return new DateTimeOffset(dateTime).ToUnixTimeMilliseconds();
    }
}