using System;
using System.IO;
using System.Collections;
using System.Text;

using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.CryptoPro;
using Org.BouncyCastle.Asn1.Oiw;
using Org.BouncyCastle.Asn1.Pkcs;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Asn1.X9;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;
using Org.BouncyCastle.Utilities;

namespace Org.BouncyCastle.X509
{
    /// <summary>
    /// A factory to produce Public Key Info Objects.
    /// </summary>
    public sealed class SubjectPublicKeyInfoFactory
    {
        private SubjectPublicKeyInfoFactory()
        {
        }

		/// <summary>
        /// Create a Subject Public Key Info object for a given public key.
        /// </summary>
        /// <param name="key">One of ElGammalPublicKeyParameters, DSAPublicKeyParameter, DHPublicKeyParameters, RsaKeyParameters or ECPublicKeyParameters</param>
        /// <returns>A subject public key info object.</returns>
        /// <exception cref="Exception">Throw exception if object provided is not one of the above.</exception>
        public static SubjectPublicKeyInfo CreateSubjectPublicKeyInfo(
			AsymmetricKeyParameter key)
        {
			if (key == null)
				throw new ArgumentNullException("key");
            if (key.IsPrivate)
                throw new ArgumentException("Private key passed - public key expected.", "key");

			if (key is ElGamalPublicKeyParameters)
            {
				ElGamalPublicKeyParameters _key = (ElGamalPublicKeyParameters)key;
				ElGamalParameters kp = _key.Parameters;

				SubjectPublicKeyInfo info = new SubjectPublicKeyInfo(
					new AlgorithmIdentifier(
						OiwObjectIdentifiers.ElGamalAlgorithm,
						new ElGamalParameter(kp.P, kp.G).ToAsn1Object()),
						new DerInteger(_key.Y));

				return info;
            }

			if (key is DsaPublicKeyParameters)
            {
                DsaPublicKeyParameters _key = (DsaPublicKeyParameters) key;
				DsaParameters kp = _key.Parameters;
				Asn1Encodable ae = kp == null
					?	null
					:	new DsaParameter(kp.P, kp.Q, kp.G).ToAsn1Object();

				return new SubjectPublicKeyInfo(
                    new AlgorithmIdentifier(X9ObjectIdentifiers.IdDsa, ae),
					new DerInteger(_key.Y));
            }

			if (key is DHPublicKeyParameters)
            {
                DHPublicKeyParameters _key = (DHPublicKeyParameters) key;
				DHParameters kp = _key.Parameters;

				SubjectPublicKeyInfo info = new SubjectPublicKeyInfo(
                    new AlgorithmIdentifier(
						_key.AlgorithmOid,
						new DHParameter(kp.P, kp.G, kp.L).ToAsn1Object()),
						new DerInteger(_key.Y));

				return info;
            } // End of DH

            if (key is RsaKeyParameters)
            {
                RsaKeyParameters _key = (RsaKeyParameters) key;

				SubjectPublicKeyInfo info = new SubjectPublicKeyInfo(
					new AlgorithmIdentifier(PkcsObjectIdentifiers.RsaEncryption, DerNull.Instance),
					new RsaPublicKeyStructure(_key.Modulus, _key.Exponent).ToAsn1Object());

				return info;
            } // End of RSA.

			if (key is ECPublicKeyParameters)
            {
                ECPublicKeyParameters _key = (ECPublicKeyParameters) key;

				if (_key.AlgorithmName == "ECGOST3410")
				{
					if (_key.PublicKeyParamSet == null)
						throw Platform.CreateNotImplementedException("Not a CryptoPro parameter set");

					ECPoint q = _key.Q;
					BigInteger bX = q.X.ToBigInteger();
					BigInteger bY = q.Y.ToBigInteger();

					byte[] encKey = new byte[64];
					ExtractBytes(encKey, 0, bX);
					ExtractBytes(encKey, 32, bY);

					Gost3410PublicKeyAlgParameters gostParams = new Gost3410PublicKeyAlgParameters(
						_key.PublicKeyParamSet, CryptoProObjectIdentifiers.GostR3411x94CryptoProParamSet);

					AlgorithmIdentifier algID = new AlgorithmIdentifier(
						CryptoProObjectIdentifiers.GostR3410x2001,
						gostParams.ToAsn1Object());

					return new SubjectPublicKeyInfo(algID, new DerOctetString(encKey));
				}
				else
				{
					X962Parameters x962;
					if (_key.PublicKeyParamSet == null)
					{
						ECDomainParameters kp = _key.Parameters;
						X9ECParameters ecP = new X9ECParameters(kp.Curve, kp.G, kp.N, kp.H, kp.GetSeed());

						x962 = new X962Parameters(ecP);
					}
					else
					{
						x962 = new X962Parameters(_key.PublicKeyParamSet);
					}

					Asn1OctetString p = (Asn1OctetString)(new X9ECPoint(_key.Q).ToAsn1Object());

					AlgorithmIdentifier algID = new AlgorithmIdentifier(
						X9ObjectIdentifiers.IdECPublicKey, x962.ToAsn1Object());

					return new SubjectPublicKeyInfo(algID, p.GetOctets());
				}
			} // End of EC

			if (key is Gost3410PublicKeyParameters)
			{
				Gost3410PublicKeyParameters _key = (Gost3410PublicKeyParameters) key;

				if (_key.PublicKeyParamSet == null)
					throw Platform.CreateNotImplementedException("Not a CryptoPro parameter set");

				byte[] keyEnc = _key.Y.ToByteArrayUnsigned();
				byte[] keyBytes = new byte[keyEnc.Length];

				for (int i = 0; i != keyBytes.Length; i++)
				{
					keyBytes[i] = keyEnc[keyEnc.Length - 1 - i]; // must be little endian
				}

				Gost3410PublicKeyAlgParameters algParams = new Gost3410PublicKeyAlgParameters(
					_key.PublicKeyParamSet, CryptoProObjectIdentifiers.GostR3411x94CryptoProParamSet);

				AlgorithmIdentifier algID = new AlgorithmIdentifier(
					CryptoProObjectIdentifiers.GostR3410x94,
					algParams.ToAsn1Object());

				return new SubjectPublicKeyInfo(algID, new DerOctetString(keyBytes));
			}

			throw new ArgumentException("Class provided no convertible: " + key.GetType().FullName);
		}

		private static void ExtractBytes(
			byte[]		encKey,
			int			offset,
			BigInteger	bI)
		{
			byte[] val = bI.ToByteArray();
			int n = (bI.BitLength + 7) / 8;

			for (int i = 0; i < n; ++i)
			{
				encKey[offset + i] = val[val.Length - 1 - i];
			}
		}
	}
}
