using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using WorkCameraExport.Models;
using WorkCameraExport.Services.Interfaces;

namespace WorkCameraExport.Services
{
    /// <summary>
    /// 配置服务实现 - 负责配置文件和登录凭证的管理
    /// </summary>
    public class ConfigService : IConfigService
    {
        private readonly string _appDataPath;
        private readonly string _configFilePath;
        private readonly string _credentialsFilePath;
        private readonly string _tempPath;
        private readonly string _logPath;

        // 用于加密凭证的密钥（AES-256 需要 32 字节密钥，16 字节 IV）
        private static readonly byte[] EncryptionKey = Encoding.UTF8.GetBytes("WorkCameraExport2025SecretKey!!!");  // 32 bytes
        private static readonly byte[] EncryptionIV = Encoding.UTF8.GetBytes("WCE2025InitVect!");  // 16 bytes

        private static readonly JsonSerializerOptions JsonOptions = new()
        {
            WriteIndented = true,
            PropertyNameCaseInsensitive = true
        };

        public ConfigService()
        {
            _appDataPath = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
                "WorkCameraExport");
            _configFilePath = Path.Combine(_appDataPath, "config.json");
            _credentialsFilePath = Path.Combine(_appDataPath, "credentials.dat");
            _tempPath = Path.Combine(_appDataPath, "temp");
            _logPath = Path.Combine(_appDataPath, "logs");

            EnsureDirectoriesExist();
        }

        /// <summary>
        /// 用于测试的构造函数，允许指定自定义路径
        /// </summary>
        public ConfigService(string appDataPath)
        {
            _appDataPath = appDataPath;
            _configFilePath = Path.Combine(_appDataPath, "config.json");
            _credentialsFilePath = Path.Combine(_appDataPath, "credentials.dat");
            _tempPath = Path.Combine(_appDataPath, "temp");
            _logPath = Path.Combine(_appDataPath, "logs");

            EnsureDirectoriesExist();
        }

        #region IConfigService 实现

        public string AppDataPath => _appDataPath;
        public string TempPath => _tempPath;
        public string LogPath => _logPath;

        public bool HasSavedCredentials => File.Exists(_credentialsFilePath);

        public AppConfig LoadConfig()
        {
            try
            {
                if (File.Exists(_configFilePath))
                {
                    var json = File.ReadAllText(_configFilePath);
                    var config = JsonSerializer.Deserialize<AppConfig>(json, JsonOptions);
                    if (config != null)
                    {
                        config.Validate();
                        return config;
                    }
                }
            }
            catch
            {
                // 加载失败时返回默认配置
            }

            return AppConfig.CreateDefault();
        }

        public void SaveConfig(AppConfig config)
        {
            config.Validate();
            var json = JsonSerializer.Serialize(config, JsonOptions);
            File.WriteAllText(_configFilePath, json);
        }

        public void SaveCredentials(string serverUrl, string token, string username)
        {
            var credentials = new CredentialsData
            {
                ServerUrl = serverUrl,
                Token = token,
                Username = username,
                SavedAt = DateTime.Now
            };

            var json = JsonSerializer.Serialize(credentials, JsonOptions);
            var encrypted = Encrypt(json);
            File.WriteAllBytes(_credentialsFilePath, encrypted);
        }

        public (string ServerUrl, string Token, string Username)? LoadCredentials()
        {
            try
            {
                if (!File.Exists(_credentialsFilePath))
                    return null;

                var encrypted = File.ReadAllBytes(_credentialsFilePath);
                var json = Decrypt(encrypted);
                var credentials = JsonSerializer.Deserialize<CredentialsData>(json, JsonOptions);

                if (credentials != null && 
                    !string.IsNullOrEmpty(credentials.ServerUrl) && 
                    !string.IsNullOrEmpty(credentials.Token))
                {
                    return (credentials.ServerUrl, credentials.Token, credentials.Username);
                }
            }
            catch
            {
                // 解密失败时清除凭证
                ClearCredentials();
            }

            return null;
        }

        public void ClearCredentials()
        {
            try
            {
                if (File.Exists(_credentialsFilePath))
                {
                    File.Delete(_credentialsFilePath);
                }
            }
            catch
            {
                // 忽略删除错误
            }
        }

        public void CleanTempFiles()
        {
            try
            {
                if (Directory.Exists(_tempPath))
                {
                    var directory = new DirectoryInfo(_tempPath);
                    foreach (var file in directory.GetFiles())
                    {
                        try { file.Delete(); } catch { }
                    }
                    foreach (var dir in directory.GetDirectories())
                    {
                        try { dir.Delete(true); } catch { }
                    }
                }
            }
            catch
            {
                // 忽略清理错误
            }
        }

        #endregion

        #region 私有方法

        private void EnsureDirectoriesExist()
        {
            if (!Directory.Exists(_appDataPath))
                Directory.CreateDirectory(_appDataPath);
            if (!Directory.Exists(_tempPath))
                Directory.CreateDirectory(_tempPath);
            if (!Directory.Exists(_logPath))
                Directory.CreateDirectory(_logPath);
        }

        private static byte[] Encrypt(string plainText)
        {
            using var aes = Aes.Create();
            aes.Key = EncryptionKey;
            aes.IV = EncryptionIV;

            using var encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
            using var ms = new MemoryStream();
            using (var cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
            using (var sw = new StreamWriter(cs))
            {
                sw.Write(plainText);
            }
            return ms.ToArray();
        }

        private static string Decrypt(byte[] cipherText)
        {
            using var aes = Aes.Create();
            aes.Key = EncryptionKey;
            aes.IV = EncryptionIV;

            using var decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
            using var ms = new MemoryStream(cipherText);
            using var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read);
            using var sr = new StreamReader(cs);
            return sr.ReadToEnd();
        }

        #endregion

        #region 内部类

        private class CredentialsData
        {
            public string ServerUrl { get; set; } = "";
            public string Token { get; set; } = "";
            public string Username { get; set; } = "";
            public DateTime SavedAt { get; set; }
        }

        #endregion
    }
}