using YLErp.BLL;
using YLErp.DBModels;
using YLErp.DBModels.Consts;
using YLErp.DBModels.Enums;

namespace YLErp.Modules.TradeModule.DocGenerateModule
{
    /// <summary>
    /// 国贸交易确认书编号生成器
    /// 规则：
    /// - 对客交易（OpponentRole为"甲方"）：GLMS-{对手方代码}-{成交日期(yyyyMMdd)}-FICC-{当日第N笔对客交易(数字递增)}-{标的代码}，从01开始
    ///   例：GLMS-IS-20260424-01-250210IB
    /// - 非对客交易（OpponentRole为"乙方"）：GLMS-{对手方代码}-{成交日期(yyyyMMdd)}-FICC-{当日第N笔非对客交易使用字母递增}-{标的代码}，从A开始
    ///   例：GLMS-IS-20260424-A-250210IB
    /// </summary>
    public class GuolianContractNoGenerator
    {
        private static readonly object _syncLock = new object();

        /// <summary>
        /// 生成国贸交易确认书编号
        /// </summary>
        /// <param name="dbContext">数据库上下文</param>
        /// <param name="trade">交易记录</param>
        /// <param name="clientCode">客户代码</param>
        /// <returns>确认书编号</returns>
        public static string Generate(
            YLContext dbContext,
            trade trade,
            string clientCode)
        {
            // 根据trade的OpponentRole判断是否为对客交易（甲方=对客）。glms客户规定甲方=对客
            var isClientTrade = trade.OpponentRole == "甲方";
            var underlyingCode = (trade.UnderlyingCode ?? "").Replace(".", ""); // 去掉标的代码中的点号
            var tradeDate = trade.TradeDate ?? DateTime.MinValue;
            var tradeDateStr = tradeDate.ToString("yyyyMMdd");
            var prefix = $"GLMS-{clientCode}-{tradeDateStr}-FICC-";

            lock (_syncLock)
            {
                // 幂等：如果已生成过确认书编号，直接返回
                var existingForTrade = dbContext.trade_contract_r
                    .Where(r => r.TradeId == trade.id && r.Type == ContractTypeEnum.Trade && r.IsValid)
                    .Select(r => r.ContractCode)
                    .FirstOrDefault();

                if (!string.IsNullOrWhiteSpace(existingForTrade))
                {
                    return existingForTrade;
                }

                // 通过当天同客户同类交易的 id 排序确定序号（幂等），每个客户独立递增
                var tradeDateStart = tradeDate.Date;
                var sameDayTradesCount = dbContext.trade
                    .Count(t => t.TradeDate >= tradeDateStart
                        && t.TradeDate < tradeDateStart.AddDays(1)
                        && t.ClientId == trade.ClientId
                        && t.OpponentRole == trade.OpponentRole
                        && t.id < trade.id);
                var sequenceNo = sameDayTradesCount + 1;

                if (isClientTrade)
                {
                    return $"{prefix}{sequenceNo:D2}-{underlyingCode}";
                }
                else
                {
                    return $"{prefix}{NumberToLetter(sequenceNo)}-{underlyingCode}";
                }
            }
        }

        /// <summary>
        /// 将数字转换为字母序列（1=A, 2=B, 26=Z, 27=AA, 28=AB...）
        /// </summary>
        private static string NumberToLetter(int number)
        {
            if (number <= 0)
            {
                return "A";
            }

            string result = "";
            while (number > 0)
            {
                number--; // 调整为从0开始
                result = (char)('A' + (number % 26)) + result;
                number /= 26;
            }
            return result;
        }
    }
}