// ============================================================================
// 会员服务器 · 客户端加密通讯参考实现 (C# / .NET Framework 3.5+，零第三方依赖)
// ============================================================================
// 用法概览(配合 fnnas.huiyuan v1.4.0 全站 HTTPS + 信封加密):
//   var cli = new HuiyuanSecureClient("https://192.168.9.21:12701");
//   string resp = cli.EncryptedCall("/api/login", "{\"手机号\":\"138...\",\"密码\":\"xx\"}");
//   cli.UploadProject("138...", "密码", "20260917001", "项目名", zipBytes);
//   byte[] zip = cli.DownloadProject("138...", "密码", "20260917001");
//
// 加密协议(与服务器 /api/enc 对应):
//   1. GET  /api/pubkey            → {"ok":true,"pubkey":"-----BEGIN PUBLIC KEY..."}
//   2. 每次调用:
//      aesKey = 随机 32 字节; iv = 随机 16 字节; nonce = 随机 16 字节 hex
//      data = BASE64( AES-256-CBC( iv, 业务JSON ) )          [PKCS7 填充]
//      k    = BASE64( RSA-OAEP-SHA1( 公钥, aesKey ) )
//      mac  = HEX( HMAC-SHA256( aesKey, ts + "." + nonce + "." + iv + "." + data ) )
//      POST /api/enc  {"k":k,"iv":iv,"ts":毫秒时间戳,"nonce":nonce,"mac":mac,"data":data}
//   3. 响应: {"ok":true,"iv":hex,"mac":HEX( HMAC( aesKey, iv+"."+data ) ),"data":BASE64(AES(结果JSON))}
//      → AES 解密得到业务结果(与直连 HTTP 时代的接口字段完全一致)
// 注意:
//   · 业务字段与旧协议完全一致，只是外面套了加密信封
//   · 首次使用请先在浏览器打开 https://NAS:12701/settings.html 下载证书并安装到
//     "受信任的根证书颁发机构"(或保留下面的证书校验跳过回调)
// ============================================================================
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;

namespace HuiyuanClient
{
    public class HuiyuanSecureClient
    {
        private string _baseUrl;          // 如 https://192.168.9.21:12701
        private string _pubKeyPem;        // 服务器 RSA 公钥(PEM)
        private RSACryptoServiceProvider _rsa;

        static HuiyuanSecureClient()
        {
            // 信任自签证书(已安装服务器证书到受信任根的可删除此回调)
            ServicePointManager.ServerCertificateValidationCallback =
                (object s, X509Certificate cert, X509Chain chain, SslPolicyErrors err) => true;
            // 启用 TLS 1.2(值 3072;老系统默认只开 TLS1.0)
            try { ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072; } catch { }
            ServicePointManager.Expect100Continue = false;
        }

        public HuiyuanSecureClient(string baseUrl)
        {
            _baseUrl = baseUrl.TrimEnd('/');
        }

        // ---------- 公开方法 ----------

        /// <summary>初始化:拉取服务器 RSA 公钥(每次程序启动调用一次)</summary>
        public void Init()
        {
            string json = HttpRaw("GET", _baseUrl + "/api/pubkey", null, null);
            _pubKeyPem = ExtractString(json, "pubkey");
            if (string.IsNullOrEmpty(_pubKeyPem)) throw new Exception("获取服务器公钥失败: " + json);
            _rsa = PemToRsa(_pubKeyPem);
        }

        /// <summary>加密调用业务接口(登录/注册/查会员/改密/项目云列表/删除)。
        /// body 为 JSON 字符串，返回解密后的结果 JSON 字符串。</summary>
        public string EncryptedCall(string apiPath, string bodyJson)
        {
            if (_rsa == null) throw new Exception("请先调用 Init()");

            // 1. 组内层业务报文
            string inner = "{\"path\":\"" + apiPath + "\",\"body\":" + (bodyJson == null ? "null" : bodyJson) + "}";

            // 2. 随机 AES-256 密钥 + IV + nonce
            byte[] aesKey = new byte[32]; Random.NextBytes(aesKey);
            byte[] iv = new byte[16]; Random.NextBytes(iv);
            byte[] nonce = new byte[16]; Random.NextBytes(nonce);
            string nonceHex = ToHex(nonce);

            // 3. AES 加密业务数据
            string data = ToBase64(AesEncrypt(Encoding.UTF8.GetBytes(inner), aesKey, iv));

            // 4. RSA-OAEP 封装 AES 密钥
            string k = ToBase64(_rsa.Encrypt(aesKey, true));   // true = OAEP-SHA1

            // 5. HMAC 签名: ts + "." + nonce + "." + iv + "." + data
            string ts = DateTimeOffset.Now.ToUnixTimeMilliseconds().ToString();
            string ivHex = ToHex(iv);
            string mac = HmacHex(aesKey, ts + "." + nonceHex + "." + ivHex + "." + data);

            string envelope = "{\"k\":\"" + k + "\",\"iv\":\"" + ivHex + "\",\"ts\":" + ts
                            + ",\"nonce\":\"" + nonceHex + "\",\"mac\":\"" + mac + "\",\"data\":\"" + data + "\"}";

            // 6. 发送并解密响应
            string respJson = HttpRaw("POST", _baseUrl + "/api/enc", envelope,
                new Dictionary<string, string> { { "Content-Type", "application/json" } });

            if (respJson.IndexOf("\"ok\":true") != 0 && respJson.IndexOf("{\"ok\":true") != 0)
                return respJson;   // 信封层错误(时间戳过期/重放/签名失败等),原文返回给上层判断

            string respIv = ExtractString(respJson, "iv");
            string respMac = ExtractString(respJson, "mac");
            string respData = ExtractString(respJson, "data");
            string wantMac = HmacHex(aesKey, respIv + "." + respData);
            if (wantMac != respMac) throw new Exception("响应签名校验失败(数据可能被篡改)");
            return Encoding.UTF8.GetString(AesDecrypt(FromBase64(respData), aesKey, FromHex(respIv)));
        }

        /// <summary>上传项目 zip(走 TLS 直连,body = JSON头 + \n\n + zip 二进制)</summary>
        public string UploadProject(string phone, string password, string code, string name, byte[] zipBytes)
        {
            string head = "{\"手机号\":\"" + phone + "\",\"编号\":\"" + code + "\",\"名称\":\"" + name
                        + "\",\"密码\":\"" + password + "\",\"时间\":\""
                        + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "\"}";
            byte[] headB = Encoding.UTF8.GetBytes(head + "\n\n");
            byte[] all = new byte[headB.Length + zipBytes.Length];
            Array.Copy(headB, 0, all, 0, headB.Length);
            Array.Copy(zipBytes, 0, all, headB.Length, zipBytes.Length);
            return HttpRaw("POST", _baseUrl + "/api/proj/upload", all,
                new Dictionary<string, string> { { "Content-Type", "application/octet-stream" } });
        }

        /// <summary>下载项目 zip(走 TLS 直连)</summary>
        public byte[] DownloadProject(string phone, string password, string code)
        {
            string url = _baseUrl + "/api/proj/download?手机号=" + Uri.EscapeDataString(phone)
                       + "&编号=" + Uri.EscapeDataString(code)
                       + "&密码=" + Uri.EscapeDataString(password);
            using (WebClient wc = new WebClient()) { return wc.DownloadData(url); }
        }

        // ---------- 内部工具 ----------

        private static readonly Random Random = new Random();

        private string HttpRaw(string method, string url, byte[] body, Dictionary<string, string> headers)
        {
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.Method = method;
            req.Timeout = 30000;
            if (headers != null) foreach (KeyValuePair<string, string> kv in headers) req.Headers[kv.Key] = kv.Value;
            if (body != null)
            {
                req.ContentLength = body.Length;
                using (Stream s = req.GetRequestStream()) s.Write(body, 0, body.Length);
            }
            using (HttpWebResponse resp = (HttpWebResponse)req.GetResponse())
            using (StreamReader r = new StreamReader(resp.GetResponseStream(), Encoding.UTF8))
                return r.ReadToEnd();
        }

        private static byte[] AesEncrypt(byte[] plain, byte[] key, byte[] iv)
        {
            using (Aes aes = Aes.Create())
            {
                aes.KeySize = 256; aes.Mode = CipherMode.CBC; aes.Padding = PaddingMode.PKCS7;
                aes.Key = key; aes.IV = iv;
                using (ICryptoTransform enc = aes.CreateEncryptor()) return enc.TransformFinalBlock(plain, 0, plain.Length);
            }
        }

        private static byte[] AesDecrypt(byte[] cipher, byte[] key, byte[] iv)
        {
            using (Aes aes = Aes.Create())
            {
                aes.KeySize = 256; aes.Mode = CipherMode.CBC; aes.Padding = PaddingMode.PKCS7;
                aes.Key = key; aes.IV = iv;
                using (ICryptoTransform dec = aes.CreateDecryptor()) return dec.TransformFinalBlock(cipher, 0, cipher.Length);
            }
        }

        private static RSACryptoServiceProvider PemToRsa(string pem)
        {
            string b64 = pem.Replace("-----BEGIN PUBLIC KEY-----", "")
                            .Replace("-----END PUBLIC KEY-----", "")
                            .Replace("\r", "").Replace("\n", "").Trim();
            byte[] der = Convert.FromBase64String(b64);
            try { return RsaFromSpki(der); }
            catch { throw new Exception("公钥解析失败,请确认服务器版本 >= v1.4.0"); }
        }

        /// <summary>解析 SubjectPublicKeyInfo(PKCS#1 内嵌)为 RSA(通用写法,2048 位)</summary>
        private static RSACryptoServiceProvider RsaFromSpki(byte[] der)
        {
            // SubjectPublicKeyInfo ::= { algorithm AlgorithmIdentifier, subjectPublicKey BIT STRING }
            // 定位 BIT STRING,内层为 PKCS#1 RSAPublicKey
            int i = 0;
            if (der[i++] != 0x30) throw new Exception();
            int len = der[i++]; if (len > 0x80) { int n = len & 0x7f; len = 0; for (int j = 0; j < n; j++) len = len * 256 + der[i++]; }
            // AlgorithmIdentifier 跳过
            if (der[i++] != 0x30) throw new Exception();
            int alen = der[i++]; if (alen > 0x80) { int n = alen & 0x7f; alen = 0; for (int j = 0; j < n; j++) alen = alen * 256 + der[i++]; }
            i += alen;
            if (der[i++] != 0x03) throw new Exception();          // BIT STRING
            int blen = der[i++]; if (blen > 0x80) { int n = blen & 0x7f; blen = 0; for (int j = 0; j < n; j++) blen = blen * 256 + der[i++]; }
            i++;                                                   // 未使用位 0x00
            // PKCS#1 RSAPublicKey ::= { modulus INTEGER, publicExponent INTEGER }
            if (der[i++] != 0x30) throw new Exception();
            int plen = der[i++]; if (plen > 0x80) { int n = plen & 0x7f; plen = 0; for (int j = 0; j < n; j++) plen = plen * 256 + der[i++]; }
            if (der[i++] != 0x02) throw new Exception();          // modulus
            int mlen = der[i++]; if (mlen > 0x80) { int n = mlen & 0x7f; mlen = 0; for (int j = 0; j < n; j++) mlen = mlen * 256 + der[i++]; }
            byte[] modulus = new byte[mlen]; Array.Copy(der, i, modulus, 0, mlen); i += mlen;
            if (modulus[0] == 0) { byte[] t = new byte[mlen - 1]; Array.Copy(modulus, 1, t, 0, mlen - 1); modulus = t; mlen--; }
            if (der[i++] != 0x02) throw new Exception();          // exponent
            int elen = der[i++]; if (elen > 0x80) { int n = elen & 0x7f; elen = 0; for (int j = 0; j < n; j++) elen = elen * 256 + der[i++]; }
            byte[] exponent = new byte[elen]; Array.Copy(der, i, exponent, 0, elen);

            RSAParameters p = new RSAParameters { Modulus = modulus, Exponent = exponent };
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(2048);
            rsa.ImportParameters(p);
            return rsa;
        }

        private static string HmacHex(byte[] key, string message)
        {
            using (HMACSHA256 h = new HMACSHA256(key))
                return ToHex(h.ComputeHash(Encoding.UTF8.GetBytes(message)));
        }

        private static string ToHex(byte[] b)
        {
            StringBuilder sb = new StringBuilder(b.Length * 2);
            foreach (byte x in b) sb.Append(x.ToString("x2"));
            return sb.ToString();
        }

        private static byte[] FromHex(string s)
        {
            byte[] b = new byte[s.Length / 2];
            for (int i = 0; i < b.Length; i++) b[i] = Convert.ToByte(s.Substring(i * 2, 2), 16);
            return b;
        }

        private static string ToBase64(byte[] b) { return Convert.ToBase64String(b); }
        private static byte[] FromBase64(string s) { return Convert.FromBase64String(s); }

        /// <summary>从扁平 JSON 取顶层字符串值(本协议响应结构固定,够用;复杂解析建议用 JSON 库)</summary>
        private static string ExtractString(string json, string key)
        {
            string k = "\"" + key + "\":\"";
            int i = json.IndexOf(k, StringComparison.Ordinal);
            if (i < 0) return null;
            i += k.Length;
            StringBuilder sb = new StringBuilder();
            while (i < json.Length && json[i] != '"')
            {
                if (json[i] == '\\' && i + 1 < json.Length) { i++; sb.Append(json[i] == 'n' ? '\n' : json[i]); }
                else sb.Append(json[i]);
                i++;
            }
            return sb.ToString();
        }
    }

    // ======================= 调用示例 =======================
    // class Demo {
    //     static void Main() {
    //         var cli = new HuiyuanSecureClient("https://192.168.9.21:12701");
    //         cli.Init();
    //         // 登录(信封加密)
    //         Console.WriteLine(cli.EncryptedCall("/api/login",
    //             "{\"手机号\":\"示例手机号\",\"密码\":\"示例密码\"}"));
    //         // 项目云列表(信封加密)
    //         Console.WriteLine(cli.EncryptedCall("/api/proj/list",
    //             "{\"手机号\":\"示例手机号\",\"密码\":\"示例密码\"}"));
    //         // 上传项目 zip(TLS 直连)
    //         // Console.WriteLine(cli.UploadProject("示例手机号", "示例密码", "20260917001", "项目名", File.ReadAllBytes("d:/x.zip")));
    //         // 下载项目 zip(TLS 直连)
    //         // byte[] zip = cli.DownloadProject("示例手机号", "示例密码", "20260917001");
    //     }
    // }
}