using Microsoft.Extensions.Logging;
using Org.BouncyCastle.Asn1.Pkcs;
using Org.BouncyCastle.Asn1.Sec;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Operators;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Pkcs;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.X509;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.OpenSsl;
using static System.Runtime.InteropServices.JavaScript.JSType;

namespace CAUtilLib
{
    public static class BouncyCastleWrapper
    {
        public static ILogger? Logger = null;
        static SecureRandom secureRandom = new SecureRandom();

        public static AsymmetricCipherKeyPair GenerateRsaKeyPair(int length = 4096)
        {
            var keygenParam = new KeyGenerationParameters(secureRandom, length);

            var keyGenerator = new RsaKeyPairGenerator();
            keyGenerator.Init(keygenParam);
            return keyGenerator.GenerateKeyPair();
        }

        public static AsymmetricCipherKeyPair GenerateEcKeyPair(string curveName)
        {
            var ecParam = SecNamedCurves.GetByName(curveName);
            var ecDomain = new ECDomainParameters(ecParam.Curve, ecParam.G, ecParam.N);
            var keygenParam = new ECKeyGenerationParameters(ecDomain, secureRandom);

            var keyGenerator = new ECKeyPairGenerator();
            keyGenerator.Init(keygenParam);
            return keyGenerator.GenerateKeyPair();
        }

        public static X509Certificate GenerateCertificate(
            X509Name issuer, X509Name subject,
            AsymmetricCipherKeyPair issuerKey,
            AsymmetricKeyParameter subjectPublic,
            BigInteger? issuerSerialNumber = null,
            List<AddExtensionData> extensionDatas = null,
            int days = 36500)
        {
            var selfserilaNumber = BigInteger.ProbablePrime(120, secureRandom);
            if (issuerSerialNumber is null)
            {
                issuerSerialNumber = selfserilaNumber;
            }

            ISignatureFactory signatureFactory;
            signatureFactory = new Asn1SignatureFactory(
                PkcsObjectIdentifiers.Sha256WithRsaEncryption.ToString(),
                issuerKey.Private);
            //signatureFactory = new Asn1SignatureFactory(
            //    PkcsObjectIdentifiers.Sha512WithRsaEncryption.ToString(),
            //    issuerKey.Private);

            var certGenerator = new X509V3CertificateGenerator();
            certGenerator.SetIssuerDN(issuer);
            certGenerator.SetSubjectDN(subject);
            certGenerator.SetSerialNumber(selfserilaNumber);
            certGenerator.SetNotAfter(DateTime.UtcNow.AddDays(days));
            certGenerator.SetNotBefore(DateTime.UtcNow);
            certGenerator.SetPublicKey(subjectPublic);

            certGenerator.AddExtension(X509Extensions.AuthorityKeyIdentifier.Id, false,
                new AuthorityKeyIdentifier(
                    SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(issuerKey.Public)
                    )
                );

            certGenerator.AddExtension(X509Extensions.SubjectKeyIdentifier.Id, false,
                new SubjectKeyIdentifier(
                    SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(subjectPublic)
                    )
                );

            if (extensionDatas != null)
            {
                foreach (var data in extensionDatas)
                {
                    certGenerator.AddExtension(data.OID, data.Critical, data.ExtensionValue);
                }
            }

            //if (isCertificateAuthority)
            //{
            //    certGenerator.AddExtension(X509Extensions.BasicConstraints.Id, true,
            //        new BasicConstraints(0));
            //    certGenerator.AddExtension(X509Extensions.KeyUsage.Id, true,
            //        new KeyUsage(KeyUsage.KeyCertSign));
            //}

            return certGenerator.Generate(signatureFactory);
        }

        public static bool ValidateCertificateChain(List<X509Certificate> certificates)
        {
            for (int index = 0; index < certificates.Count - 1; index++)
            {
                var validateCertificate = certificates[index];
                var sourceCertificate = certificates[index + 1]; 
                if (!ValidateCert(validateCertificate, sourceCertificate.GetPublicKey()))
                {
                    return false;
                }
            }
            return true;
        }

        public static bool ValidateCert(X509Certificate cert, List<X509Certificate> certChain)
        {
            if (!ValidateCertificateChain(certChain))
            {
                return false;
            }

            for (int index = 0; index < certChain.Count; index++)
            {
                var validateCertificate = cert;
                var sourceCertificate = certChain[index];
                if (ValidateCert(validateCertificate, sourceCertificate.GetPublicKey()))
                {
                    return true;
                }
            }
            return false;
        }

        public static bool ValidateCert(X509Certificate cert, ICipherParameters pubKey)
        {
            try
            {
                cert.CheckValidity(DateTime.UtcNow);
                var tbsCert = cert.GetTbsCertificate();
                var sig = cert.GetSignature();

                var signer = SignerUtilities.GetSigner(cert.SigAlgName);
                signer.Init(false, pubKey);
                signer.BlockUpdate(tbsCert, 0, tbsCert.Length);
                var verifyResult = signer.VerifySignature(sig);
                if (!verifyResult)
                {
                    Logger?.LogDebug("validation failed");
                }
                return verifyResult;
            }
            catch (Exception e)
            {
                Logger?.LogDebug("validation failed: {0}", e.Message);
                return false;
            }
        }

        public static X509Certificate GenerateSelfSignedRootCertificate(
            X509Name subject,
            AsymmetricCipherKeyPair kp,
            int days = 36500
            )
        {
            List<AddExtensionData> datas = new List<AddExtensionData>() { 
                new AddExtensionData(){
                    OID = X509Extensions.BasicConstraints.Id,
                    Critical = true,
                    ExtensionValue = new BasicConstraints(true)
                },
                new AddExtensionData()
                {
                    OID= X509Extensions.KeyUsage.Id,
                    Critical = true,
                    ExtensionValue = new KeyUsage(KeyUsage.DigitalSignature | KeyUsage.KeyCertSign | KeyUsage.CrlSign)
                }
            };
            return GenerateCertificate(subject, subject, kp, kp.Public, extensionDatas: datas, days: days);
        }

        public static X509Certificate GenerateIntermediateCertificate(
            Pkcs10CertificationRequest csr,
            X509Certificate rca,
            AsymmetricCipherKeyPair issuerKey,
            int pathLengthConstraint
            )
        {
            var csrInfo = csr.GetCertificationRequestInfo();

            List<AddExtensionData> datas = new List<AddExtensionData>() {
                new AddExtensionData(){
                    OID = X509Extensions.BasicConstraints.Id,
                    Critical = true,
                    ExtensionValue = new BasicConstraints(pathLengthConstraint)
                },
                new AddExtensionData()
                {
                    OID= X509Extensions.KeyUsage.Id,
                    Critical = true,
                    ExtensionValue = new KeyUsage(KeyUsage.DigitalSignature | KeyUsage.KeyCertSign | KeyUsage.CrlSign)
                }
            };
            return GenerateCertificate(rca.SubjectDN, csrInfo.Subject, issuerKey, csr.GetPublicKey(), extensionDatas: datas);
        }

        public static X509Certificate GenerateEndCertificate(
            Pkcs10CertificationRequest csr,
            X509Certificate rca,
            AsymmetricCipherKeyPair issuerKey
            )
        {
            var csrInfo = csr.GetCertificationRequestInfo();

            List<AddExtensionData> datas = new List<AddExtensionData>() {
                new AddExtensionData()
                {
                    OID= X509Extensions.KeyUsage.Id,
                    Critical = true,
                    ExtensionValue = new KeyUsage(KeyUsage.DigitalSignature | KeyUsage.NonRepudiation | KeyUsage.KeyEncipherment)
                }
            };
            return GenerateCertificate(rca.SubjectDN, csrInfo.Subject, issuerKey, csr.GetPublicKey(), extensionDatas: datas);
        }

        public static X509Certificate SignCertificate(
            Pkcs10CertificationRequest csr,
            X509Certificate rca, 
            AsymmetricCipherKeyPair issuerKey)
        {
            var csrInfo = csr.GetCertificationRequestInfo();
            return GenerateCertificate(rca.SubjectDN, csrInfo.Subject, issuerKey, csr.GetPublicKey(), issuerSerialNumber: rca.SerialNumber);
        }

        public static Pkcs10CertificationRequest CreateCertificateReq(AsymmetricCipherKeyPair kp, string commonName, string organizationName)
        {
            var subject = CreateX509Name(commonName: commonName, organizationName: organizationName);

            var csr = new Pkcs10CertificationRequest(
                PkcsObjectIdentifiers.Sha256WithRsaEncryption.ToString(),
                subject,
                kp.Public,
                null,
                kp.Private
                );

            return csr;
        }

        public static X509Name CreateX509Name(
            string? commonName = null,
            string? organizationName = null,
            string? country = null,
            string? state = null)
        {
            var values = new Dictionary<DerObjectIdentifier, string> { };

            if (!string.IsNullOrEmpty(commonName))
            {
                values.Add(X509Name.CN, commonName);
            }
            if (!string.IsNullOrEmpty(organizationName))
            {
                values.Add(X509Name.O, organizationName);
            }
            if (!string.IsNullOrEmpty(country))
            {
                values.Add(X509Name.C, country);
            }
            if (!string.IsNullOrEmpty(state))
            {
                values.Add(X509Name.ST, state);
            }
            return new X509Name(values.Keys.Reverse().ToList(), values);
        }

        public static X509Certificate ToBouncyCastle(this System.Security.Cryptography.X509Certificates.X509Certificate2 msCert)
        {
            return Org.BouncyCastle.Security.DotNetUtilities.FromX509Certificate(msCert);
        }

        public static System.Security.Cryptography.X509Certificates.X509Certificate2 ToMs(this X509Certificate bcCert)
        {
            return System.Security.Cryptography.X509Certificates.X509Certificate2.CreateFromPem(ToStringAsPem(bcCert).Result);
        }

        public static string? GetFirstValue(this X509Name x509Name, DerObjectIdentifier identifier)
        {
            return x509Name.GetValueList(identifier).FirstOrDefault();
        }

        public static async Task<bool> TrySaveAsPemAsync(string name, object[] items)
        {
            try
            {
                using TextWriter textWriter = new StreamWriter(name);
                using PemWriter pemWriter = new PemWriter(textWriter);
                foreach (object obj in items)
                {
                    pemWriter.WriteObject(obj);
                }
                await pemWriter.Writer.FlushAsync();
                return true;
            }
            catch (Exception ex)
            {
                Logger?.LogDebug("SaveAsPemAsync failed {0}", ex.Message);
                return false;
            }
        }

        public static Task<string> ToStringAsPem(object item)
        {
            return ToStringAsPem(new object[] { item });
        }

        public static async Task<string> ToStringAsPem(object[] items)
        {
            using StringWriter stringWriter = new StringWriter();
            using PemWriter pemWriter = new PemWriter(stringWriter);
            foreach (object obj in items)
            {
                pemWriter.WriteObject(obj);
            }
            await pemWriter.Writer.FlushAsync();
            return stringWriter.ToString();
        }

        public static Task<X509Certificate?> LoadPemCertFromFile(string name)
        {
            return TryLoadPemFromFile<X509Certificate>(name);
        }

        public static X509Certificate? LoadPemCertFromString(string source)
        {
            return TryLoadPemFromString<X509Certificate>(source);
        }

        public static Task<AsymmetricCipherKeyPair?> LoadPemKeyFromFile(string name)
        {
            return TryLoadPemFromFile<AsymmetricCipherKeyPair>(name);
        }

        public static AsymmetricCipherKeyPair? LoadPemKeyFromString(string source)
        {
            return TryLoadPemFromString<AsymmetricCipherKeyPair>(source);
        }

        internal static Task<Pkcs10CertificationRequest?> LoadPemCsrFromFile(string source)
        {
            return TryLoadPemFromFile<Pkcs10CertificationRequest>(source);
        }

        public static Pkcs10CertificationRequest? LoadPemCsrFromString(string source)
        {
            return TryLoadPemFromString<Pkcs10CertificationRequest>(source);
        }

        public static List<X509Certificate> LoadPemCrtChaingFromString(string source)
        {
            var readList = TryLoadPemListFromString(source);
            return readList.Where(x => x is X509Certificate).Select(x => (X509Certificate)x).ToList();
        }

        internal static async Task<T?> TryLoadPemFromFile<T>(string name)
        {
            try
            {
                using var fileReader = new StreamReader(name);
                var result = await fileReader.ReadToEndAsync();
                return TryLoadPemFromString<T>(result);
            }
            catch (Exception ex)
            {
                Logger?.LogDebug("TryLoadPemFromFile failed: {0}", ex.Message);
                return default(T);
            }
        }

        internal static T? TryLoadPemFromString<T>(string rawString)
        {
            try
            {
                using TextReader textReader = new StringReader(rawString);
                using PemReader pemReader = new PemReader(textReader);
                return (T)pemReader.ReadObject();
            }
            catch (Exception ex)
            {
                Logger?.LogDebug("TryLoadPemFromString failed: {0}", ex.Message);
                return default(T);
            }
        }
        internal static List<object> TryLoadPemListFromString(string rawString)
        {
            try
            {
                using TextReader textReader = new StringReader(rawString);
                using PemReader pemReader = new PemReader(textReader);

                List<object> toReturn = new List<object>();
                object result = null;
                do
                {
                    result = pemReader.ReadObject();
                    if (result is null)
                    {
                        break;
                    }
                    toReturn.Add(result);
                }
                while (true);

                return toReturn;
            }
            catch (Exception ex)
            {
                Logger?.LogDebug("TryLoadPemFromString failed: {0}", ex.Message);
                return default;
            }
        }
    }
}