using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;

namespace AIK.Common.SysCommon.UserCommon
{
    public static class UserTokenHelper
    {
        public static (bool Success, long? UserId, long? Exp) ParseJwtPayload(string jwt)
        {
            try
            {
                var parts = jwt.Split('.');
                if (parts.Length != 3) return (false, null, null);

                var payloadJson = Base64UrlDecode(parts[1]);
                using var doc = JsonDocument.Parse(payloadJson);
                var root = doc.RootElement;

                long? userId = root.TryGetProperty("userId", out var uid) ? uid.GetInt64() : null;
                long? exp = root.TryGetProperty("exp", out var e) ? e.GetInt64() : null;

                return (true, userId, exp);
            }
            catch
            {
                return (false, null, null);
            }
        }

        private static string Base64UrlDecode(string input)
        {
            // 补齐 padding
            string padded = input.Replace('-', '+').Replace('_', '/');
            switch (padded.Length % 4)
            {
                case 2: padded += "=="; break;
                case 3: padded += "="; break;
            }
            byte[] data = Convert.FromBase64String(padded);
            return System.Text.Encoding.UTF8.GetString(data);
        }
    }
}