using LMS.Common.RSAKey;
using System.Security.Cryptography;
using System.Text;
namespace LMS.Common.RSAKey
{
    public static class RsaKeyPairGenerator
    {

        /// <summary>
        /// 初始化一个RSA密钥对
        /// </summary>
        /// <returns></returns>
        public static RSAKeyGenerateModel InitRsaKey()
        {
            using RSACryptoServiceProvider rsa = new(2048);
            string publicKeyPem = ExportPublicKeyToPem(rsa);
            string privateKeyPem = ExportPrivateKeyToPem(rsa);

            // 随机生成一个AES密钥
            byte[] aesKey = GenerateRandomAesKey(32);
            byte[] aesIv = GenerateRandomAesKey(16);

            // 通过随机的密钥开始AES加密私钥
            string encryptPrivateKey = AESGenerate.Encrypt(privateKeyPem, aesKey, aesIv);

            return new RSAKeyGenerateModel
            {
                PublicKey = publicKeyPem,
                EncryptedPrivateKey = encryptPrivateKey,
                EncryptedKey = Convert.ToBase64String(ComplexKeyObfuscator.Obfuscate(aesKey)),
                EncryptionIV = Convert.ToBase64String(ComplexKeyObfuscator.Obfuscate(aesIv))
            };
        }

        private static byte[] GenerateRandomAesKey(int bits)
        {
            using var randomNumberGenerator = RandomNumberGenerator.Create();
            var randomBytes = new byte[bits]; // 256 bits
            randomNumberGenerator.GetBytes(randomBytes);
            return randomBytes;
        }

        public static void GenerateRsaKeyPair()
        {
            using RSACryptoServiceProvider rsa = new(2048);

            string publicKeyPem = ExportPublicKeyToPem(rsa);
            string privateKeyPem = ExportPrivateKeyToPem(rsa);

            Console.WriteLine("公钥 (PEM)：\n" + publicKeyPem);
            Console.WriteLine("私钥 (PEM)：\n" + privateKeyPem);

            Console.WriteLine();
            string original = "Hello, RSA!";
            var encrypted = Encrypt(publicKeyPem, original);
            Console.WriteLine("Encrypted: " + encrypted);

            Console.WriteLine();
            var decrypted = Decrypt(privateKeyPem, encrypted);
            Console.WriteLine("Decrypted: " + decrypted);

            var signData = SignData(privateKeyPem, original);
            Console.WriteLine("SignData: " + signData);

            var isVerify = VerifySignData(publicKeyPem, original, signData);
            Console.WriteLine("VerifySign: " + isVerify);
        }

        private static string ExportPublicKeyToPem(RSA rsa)
        {
            var publicKey = rsa.ExportSubjectPublicKeyInfo();
            var base64 = Convert.ToBase64String(publicKey);
            return $"-----BEGIN PUBLIC KEY-----\n{InsertNewLines(base64)}\n-----END PUBLIC KEY-----";
        }

        private static string ExportPrivateKeyToPem(RSA rsa)
        {
            var privateKey = rsa.ExportPkcs8PrivateKey();
            var base64 = Convert.ToBase64String(privateKey);
            return $"-----BEGIN PRIVATE KEY-----\n{InsertNewLines(base64)}\n-----END PRIVATE KEY-----";
        }

        private static string InsertNewLines(string input)
        {
            return string.Join("\n", Enumerable.Range(0, input.Length / 64 + 1)
                .Select(i => input.Substring(i * 64, Math.Min(64, input.Length - i * 64))));
        }

        public static string Encrypt(string publicKeyPem, string data)
        {
            using (var rsa = RSA.Create())
            {
                rsa.ImportFromPem(publicKeyPem);
                byte[] encryptedData = rsa.Encrypt(Encoding.UTF8.GetBytes(data), RSAEncryptionPadding.OaepSHA256);
                return Convert.ToBase64String(encryptedData);
            }
        }

        public static string Decrypt(string privateKeyPem, string data)
        {
            using (var rsa = RSA.Create())
            {
                rsa.ImportFromPem(privateKeyPem);
                byte[] decryptedData = rsa.Decrypt(Convert.FromBase64String(data), RSAEncryptionPadding.OaepSHA256);
                return Encoding.UTF8.GetString(decryptedData);
            }
        }

        public static string SignData(string privateKeyPem, string data)
        {
            using (var rsa = RSA.Create())
            {
                rsa.ImportFromPem(privateKeyPem);
                var inputBytes = Encoding.UTF8.GetBytes(data);
                var resultBytes = rsa.SignData(inputBytes, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
                return Convert.ToBase64String(resultBytes);
            }
        }

        public static bool VerifySignData(string publicKeyPem, string data, string sign)
        {
            using (var rsa = RSA.Create())
            {
                rsa.ImportFromPem(publicKeyPem);
                var dataBytes = Encoding.UTF8.GetBytes(data);
                var signBytes = Convert.FromBase64String(sign);
                return rsa.VerifyData(dataBytes, signBytes, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
            }
        }
    }
}