using System;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;

using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.OpenSsl;

public static class FileHashRsaHelper
{
    // 公钥（硬编码）
    private const string PublicKeyPem = """
        -----BEGIN PUBLIC KEY-----
        MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAyN+Z04RmVOvzI2Z8Li1t
        xB9yv80Y4Pd+M0wiuW9BHccmVlm7LVlWDRZgaAykQxIt0UskZbaIQ5eR4mqywVoM
        BygfWqurVtgC6dO3SSbhZiOuSA3g1xJLgje6TOQIPWDGw1Ap0sbWrCuk+bxPFjSi
        XANksY3Qfl1e6YETYEEpptTXorM8enM4368/KkvEhFswBqE5/Qf2x7XUpPAfnh3Y
        cl45bUu87yDeyAnX4HEuA+aZPHEgXFPmhndtqMiUsLEajQNd8zZQHKmjMbubAq9s
        l10w7smZUck+bozHO0RP31ytI6n/7I0T9PXOb/rwjeXBxXD1K0kvU3DPuq2+a5sa
        iwIDAQAB
        -----END PUBLIC KEY-----
        """;

    // 私钥（硬编码）
    private const string PrivateKeyPem = """
        -----BEGIN RSA PRIVATE KEY-----
        MIIEpAIBAAKCAQEAyN+Z04RmVOvzI2Z8Li1txB9yv80Y4Pd+M0wiuW9BHccmVlm7
        LVlWDRZgaAykQxIt0UskZbaIQ5eR4mqywVoMBygfWqurVtgC6dO3SSbhZiOuSA3g
        1xJLgje6TOQIPWDGw1Ap0sbWrCuk+bxPFjSiXANksY3Qfl1e6YETYEEpptTXorM8
        enM4368/KkvEhFswBqE5/Qf2x7XUpPAfnh3Ycl45bUu87yDeyAnX4HEuA+aZPHEg
        XFPmhndtqMiUsLEajQNd8zZQHKmjMbubAq9sl10w7smZUck+bozHO0RP31ytI6n/
        7I0T9PXOb/rwjeXBxXD1K0kvU3DPuq2+a5saiwIDAQABAoIBAACdcETZkedzXBM5
        6WofTAof4bWOgovvHJCipBgOiubPKPdG5jNq/bHX2/kSnbl2eWWMQUEuGIiYJccG
        /6zF6GDQ3FqHZcNbp8M4gbymNZV0TfTB0KOTyDAaojQ381LgyIK1DcWBHdw2wCRZ
        vo6v1BXez4evaUy5ckXQfAA9POiAH6Im7QQlPamaUJfBCfRqFNvTcL6YQngHg8RW
        4xFvN8Lxhgnqftw0dY1YzNkDBz+toQ+211LTAJWYC4vZ2sHoGvR74YxZUWPS4wms
        QdIq50kRwL45Z9IZcxqp1x27W0pEwBsOO2DhnM6r7mB7Mg9BMEjUFf3oM+vrx67W
        w6McEXkCgYEA8q+Bb6ldNqWNa5uLmAziEqXCnN/X9o1Cr81YIeWZpx4Ovx2aR3wH
        4OtWl9VmYrU7w758nhPH27q8ADxjSbIB3ShPPdfLcKBoW/5eg+K8Bexr5Fb6Lyqo
        SMhFLptxOdNzYLej99XppzRk4CV3s7IZsfQd6okSdfvlqka5ExFjXDkCgYEA0+TZ
        IBsc0nCZFTlcDxxMCkmj+c4+c01BGgSeoVSKIgyp5d5DSZoNjxXsrP3Nw3uq2+fh
        v4DD/V76BpzQ6v7P+Xg9YbW1QO6QdsG4Cf1bnAFYaTwQwdm2To5SXixYpVnON4Xv
        4fOWVL0qrn3PK6aUTJCcEOdhx1YtBl+P4gVq9OMCgYEAhtLcDOXBhE96/rI+Xi2i
        FwwBz1dISo/14WcqNEKzFzXKqYBPqrEMS3dS9y02IVZgKoIUB1oj6T2XnmXuHw4G
        nQ/83fWZ7ysebyUk6w42uO+8jPGJMlT3gt/IF3mB8Mc5TR0YueIcWajw9dm645jp
        T4S4bgjSubtEv1FlFmPNmHkCgYAtmq5ka5FrdVJtL/gxRFzVRf4lsI7eT/039VCS
        1lgYdfNHBuwidiZ+6jATF1jmvsIKLED472S/LmbPb4bDXO4z+f3z/qCxBedPt+e9
        Nqs1y1BU7dmJbyr+g0EVBaRaihaI+qmjTsLHICOEhI1HDsYSKHl+Zd40gcaU/ZJB
        Cft4EwKBgQDeK/3k6OJTPuzskuqMsQy6yHd7hesxvdsfUH78tZrkRB2B9fciOa2v
        ulfBss9KKVCQeKaC+91ptLpMOlSJhc9tZUsWvE19vVlNmN0ezQyfSFn+E09Ouqin
        0cMfedRgHigwi+T818aFnC8qPzTMqCMQyxRTYxEC43OB9VcPyzo1yA==
        -----END RSA PRIVATE KEY-----
        """;
    private static AsymmetricKeyParameter GetPublicKey()
    {
        using var reader = new StringReader(PublicKeyPem);
        var pemReader = new PemReader(reader);
        return (AsymmetricKeyParameter)pemReader.ReadObject();
    }

    private static AsymmetricKeyParameter GetPrivateKey()
    {
        using var reader = new StringReader(PrivateKeyPem);
        var pemReader = new PemReader(reader);
        var keyPair = (AsymmetricCipherKeyPair)pemReader.ReadObject();
        return keyPair.Private;
    }

    private static byte[] ComputeFileHash(string filePath)
    {
        using var sha256 = SHA256.Create();
        using var stream = File.OpenRead(filePath);
        return sha256.ComputeHash(stream);
    }

    private static byte[] EncryptData(byte[] data, AsymmetricKeyParameter publicKey)
    {
        var rsaEngine = new Org.BouncyCastle.Crypto.Engines.RsaEngine();
        rsaEngine.Init(true, publicKey);
        return rsaEngine.ProcessBlock(data, 0, data.Length);
    }

    private static byte[] DecryptData(byte[] encryptedData, AsymmetricKeyParameter privateKey)
    {
        var rsaEngine = new Org.BouncyCastle.Crypto.Engines.RsaEngine();
        rsaEngine.Init(false, privateKey);
        return rsaEngine.ProcessBlock(encryptedData, 0, encryptedData.Length);
    }

    public static void GenerateEncFile(string directoryPath)
    {
        var publicKey = GetPublicKey();
        var files = Directory.GetFiles(directoryPath, "*.rvt", SearchOption.AllDirectories);
        var encFilePath = Path.Combine(directoryPath, "hashes.enc");

        using var fs = new FileStream(encFilePath, FileMode.Create, FileAccess.Write);
        using var bw = new BinaryWriter(fs);

        foreach (var file in files)
        {
            var fileName = Path.GetFileName(file);
            var fileHash = ComputeFileHash(file);
            var nameBytes = Encoding.UTF8.GetBytes(fileName);
            var combined = nameBytes.Concat(fileHash).ToArray();
            var encrypted = EncryptData(combined, publicKey);

            bw.Write(nameBytes.Length);
            bw.Write(nameBytes);
            bw.Write(encrypted.Length);
            bw.Write(encrypted);
        }
    }

    public static void VerifyEncFile(string directoryPath)
    {
        var privateKey = GetPrivateKey();
        var encFilePath = Path.Combine(directoryPath, "hashes.enc");

        if (!File.Exists(encFilePath))
        {
            Console.WriteLine("enc 文件未找到。");
            return;
        }

        var allFiles = Directory.GetFiles(directoryPath, "*.rvt", SearchOption.AllDirectories)
                                .ToDictionary(f => Path.GetFileName(f), f => f, StringComparer.OrdinalIgnoreCase);

        using var fs = new FileStream(encFilePath, FileMode.Open, FileAccess.Read);
        using var br = new BinaryReader(fs);

        while (fs.Position < fs.Length)
        {
            var nameLen = br.ReadInt32();
            //if (nameLen <= 0 || nameLen > 256) // 假设文件名长度不超过256字节
            //{
            //    Console.WriteLine("无效的文件名长度。");
            //    continue;
            //}
            var nameBytes = br.ReadBytes(nameLen);
            var fileName = Encoding.UTF8.GetString(nameBytes);

            var encLen = br.ReadInt32();
            var encrypted = br.ReadBytes(encLen);

            if (!allFiles.TryGetValue(fileName, out var actualFilePath))
            {
                Console.WriteLine($"文件 {fileName} 未找到");
                continue;
            }

            var decrypted = DecryptData(encrypted, privateKey);
            var expectedName = Encoding.UTF8.GetString(decrypted, 0, nameBytes.Length);
            var expectedHash = decrypted.Skip(nameBytes.Length).ToArray();

            var currentHash = ComputeFileHash(actualFilePath);
            bool match = expectedName == fileName && currentHash.SequenceEqual(expectedHash);

            Console.WriteLine($"{fileName}: {(match ? "未被篡改" : "被篡改")}");
        }
    }
}