using CloudBuilder.Core.DatabaseAccessor.Entity;
using CloudBuilder.Master.Data;
using CloudBuilder.Security.Policy;
using System;
using System.IO;
using System.Text.RegularExpressions;

namespace CloudBuilder.Master.Service.FamilyTreeUtility
{
    /// <summary>
    /// 族谱全系/小系 .fm 交换文件的规则：目录、文件名、系统因子。
    /// 不新增配置节——目录与身份证/头像上传同根（FileServiceSettings:UploadFileDirectory），固定挂在 FamilyTree 子目录下
    /// </summary>
    public static class FamilyTreeExchangePolicy
    {
        /// <summary>交换目录名（身份证用 FamilyPersonAvatar/IdCard，这里同款机制）</summary>
        public const string EXCHANGE_FOLDER_NAME = "FamilyTree";

        public const string FILE_EXTENSION = ".fm";

        /// <summary>D2 系统因子：前端 PBKDF2(用户密码⊕因子) 派生 AES 密钥，防「只漏密码」离线破解</summary>
        public const string EXCHANGE_FACTOR = "YouJiaLa.FamilyTree.Exchange.v1";

        // D1 文件名：全系 A{treeId}_{ts}.fm；小系 P{treeId}-{personId}_{ts}.fm（ts=yyyyMMddHHmmss）
        private static readonly Regex ALL_FILE = new Regex(@"^AT\w+_\d{14}\.fm$", RegexOptions.IgnoreCase | RegexOptions.Compiled);
        private static readonly Regex SUB_FILE = new Regex(@"^PT\w+-P\w+_\d{14}\.fm$", RegexOptions.IgnoreCase | RegexOptions.Compiled);

        // R6 备份文件名：BK{treeId}_{ts}.json（替换前自动落盘的整谱回滚点，存 Backup 子目录，不进交换文件白名单）
        private static readonly Regex BACKUP_FILE = new Regex(@"^BKT\w+_\d{14}\.json$", RegexOptions.IgnoreCase | RegexOptions.Compiled);

        /// <summary>备份目录名（挂在交换目录下）</summary>
        public const string BACKUP_FOLDER_NAME = "Backup";

        /// <summary>R5 备份保留窗口：列表与还原都只认一年内</summary>
        public static readonly int BACKUP_KEEP_YEARS = 1;

        /// <summary>
        /// 备份密文魔数前缀：备份含成员权限行（账号名等隐私），统一用服务端 AES 密钥加密落盘；
        /// 前缀区分新老格式（无此前缀视为旧明文库，向后兼容），不新增配置节（复用 EncryptHelper 内置密钥）
        /// </summary>
        public const string BACKUP_ENCRYPT_PREFIX = "ENC:";

        /// <summary>备份明文 JSON → 密文文本（写盘前调用）</summary>
        public static string EncryptBackup(string plainJson)
        {
            return BACKUP_ENCRYPT_PREFIX + EncryptHelper.AesEncrypt(plainJson);
        }

        /// <summary>备份文件文本 → 明文 JSON（带 ENC: 前缀解密；旧明文备份直接透传）</summary>
        public static string DecryptBackup(string fileContent)
        {
            if (string.IsNullOrEmpty(fileContent)) return fileContent;
            return fileContent.StartsWith(BACKUP_ENCRYPT_PREFIX)
                ? EncryptHelper.AesDecrpt(fileContent.Substring(BACKUP_ENCRYPT_PREFIX.Length))
                : fileContent;
        }

        public static string GetExchangeDirectory(IApplicationService service)
        {
            return Path.Combine(ServiceSettingsPolicy.GetUploadFileDirectory(service), EXCHANGE_FOLDER_NAME);
        }

        /// <summary>生成 D1 规范文件名</summary>
        public static string BuildFileName(string scope, string treeId, string anchorPersonId)
        {
            string ts = DateTime.Now.ToString("yyyyMMddHHmmss");
            return scope == FamilyTreeExchangeScope.SUB
                ? $"P{treeId}-{anchorPersonId}_{ts}{FILE_EXTENSION}"
                : $"A{treeId}_{ts}{FILE_EXTENSION}";
        }

        /// <summary>校验文件名：只准 D1 两种格式，且拒绝任何目录成分（防 ../ 路径穿越）</summary>
        public static bool IsValidFileName(string fileName)
        {
            if (string.IsNullOrEmpty(fileName)) return false;
            if (fileName != Path.GetFileName(fileName)) return false;
            return ALL_FILE.IsMatch(fileName) || SUB_FILE.IsMatch(fileName);
        }

        /// <summary>从合法文件名反解析 (treeId, anchorPersonId, scope)；非法返回 null</summary>
        public static Tuple<string, string, string> ParseFileName(string fileName)
        {
            if (!IsValidFileName(fileName)) return null;
            // 去掉前缀字母与时间戳，取中间的 id 段
            string body = fileName.Substring(1, fileName.Length - 1 - FILE_EXTENSION.Length).Split('_')[0];
            if (fileName[0].ToString().Equals("A", StringComparison.OrdinalIgnoreCase))
                return Tuple.Create(body, "", FamilyTreeExchangeScope.ALL);
            string[] parts = body.Split('-');
            return Tuple.Create(parts[0], parts[1], FamilyTreeExchangeScope.SUB);
        }

        public static string GetBackupDirectory(IApplicationService service)
        {
            return Path.Combine(GetExchangeDirectory(service), BACKUP_FOLDER_NAME);
        }

        /// <summary>生成备份文件名（谱号+秒级时间戳，同谱同秒重名由覆盖兼容：秒内连点两次导入的极小概率场景）</summary>
        public static string BuildBackupFileName(string treeId)
        {
            return $"BK{treeId}_{DateTime.Now:yyyyMMddHHmmss}.json";
        }

        /// <summary>校验备份文件名：只准 BK 格式，拒绝任何目录成分（还原入口防路径穿越/拿 *.fm 灌数据）</summary>
        public static bool IsValidBackupFileName(string fileName)
        {
            if (string.IsNullOrEmpty(fileName)) return false;
            if (fileName != Path.GetFileName(fileName)) return false;
            return BACKUP_FILE.IsMatch(fileName);
        }

        /// <summary>从合法备份文件名反解析 (treeId, 备份时刻)；非法返回 null。时刻以文件名为准（不依赖文件系统时间戳）</summary>
        public static Tuple<string, DateTime> ParseBackupFileName(string fileName)
        {
            if (!IsValidBackupFileName(fileName)) return null;
            string body = fileName.Substring(2, fileName.Length - 2 - ".json".Length);
            string[] parts = body.Split('_');
            if (!DateTime.TryParseExact(parts[1], "yyyyMMddHHmmss", System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out DateTime ts))
                return null;
            return Tuple.Create(parts[0], ts);
        }
    }
}