using System;
using System.Buffers.Text;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using YuanXuan.IM.Common.Exceptions;
using YuanXuan.IM.Common.Helpers;
using YuanXuan.IM.Infrastructure.Redis;

namespace YuanXuan.IM.Api.Helper
{
    /// <summary>
    /// 手机跳H5用户签名帮助类
    /// </summary>
    public static class MobileToH5UserSign
    {
        /// <summary>
        /// 获取用户跳转H5的签名，并缓存sign 1小时
        /// </summary>
        /// <param name="UserId"></param>
        /// <param name="DataId"></param>
        /// <returns></returns>
        public static string GetUserSign(string UserId, long? DataId)
        {
            //生成sign，规则为：Id + "&" + userId
            var sign = $"{UserId}";
            if (DataId != null)
            {
                sign = $"{DataId}&" + sign;
            }
            //aes加密sign
            sign = AesEncryptHelper.EncryptToShortString(sign);
            //sign进行base64
            // 将字符串转换为字节数组
            byte[] byteArray = Encoding.UTF8.GetBytes(sign);
            // 将字节数组转换为Base64字符串
            string base64String = Convert.ToBase64String(byteArray);
            //存储到redis中，有效期1小时
            RedisHelper.Instance.Set(base64String, $"{DataId}&{UserId}", TimeSpan.FromHours(1));
            return base64String;
        }
        /// <summary>
        /// 解密用户跳转H5的签名，获取Id（有可能为null）和userId
        /// </summary>
        /// <param name="sign"></param>
        /// <param name="parCount">正确参数个数</param>
        /// <returns></returns>
        /// <exception cref="Exception"></exception>
        public static (long? DataId, long UserId) DecryptUserSign(string sign, int parCount)
        {
            //判断redis中是否存在sign
            var redisSign = RedisHelper.Instance.Get(sign);
            if (string.IsNullOrEmpty(redisSign))
            {
                throw new BusinessException("链接已过期，请重新获取");
            }
            //sign的base64解码
            byte[] decodedBytes = Convert.FromBase64String(sign);
            // 转换为UTF8字符串
            string decodedString = Encoding.UTF8.GetString(decodedBytes);
            //解密sign
            sign = AesEncryptHelper.DecryptFromShortString(decodedString);
            var arr = sign.Split('&');
            if (parCount!=arr.Length)
            {
                throw new BusinessException("参数错误");
            }
            if (arr.Length == 1)
            {
                var userId = Convert.ToInt64(arr[0]);

                return (null, userId);
            }
            else if (true)
            {
                var id = Convert.ToInt64(arr[0]);
                var userId = Convert.ToInt64(arr[1]);
                return (id, userId);
            }
            else
            {
                throw new BusinessException("参数错误");
            }
        }
    }
}