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

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Utilities;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Security.Certificates;
using Org.BouncyCastle.Utilities;
using Org.BouncyCastle.Utilities.Collections;
using Org.BouncyCastle.Utilities.Date;
using Org.BouncyCastle.Utilities.Encoders;
using Org.BouncyCastle.X509.Extension;
using Org.BouncyCastle.Crypto.Operators;

namespace Org.BouncyCastle.X509
{
	/**
	 * The following extensions are listed in RFC 2459 as relevant to CRLs
	 *
	 * Authority Key Identifier
	 * Issuer Alternative Name
	 * CRL Number
	 * Delta CRL Indicator (critical)
	 * Issuing Distribution Point (critical)
	 */
	public class X509Crl
		: X509ExtensionBase
		// TODO Add interface Crl?
	{
		private readonly CertificateList c;
		private readonly string sigAlgName;
		private readonly byte[] sigAlgParams;
		private readonly bool isIndirect;

		public X509Crl(
			CertificateList c)
		{
			this.c = c;

			try
			{
				this.sigAlgName = X509SignatureUtilities.GetSignatureName(c.SignatureAlgorithm);

				if (c.SignatureAlgorithm.Parameters != null)
				{
					this.sigAlgParams = ((Asn1Encodable)c.SignatureAlgorithm.Parameters).GetDerEncoded();
				}
				else
				{
					this.sigAlgParams = null;
				}

				this.isIndirect = IsIndirectCrl;
			}
			catch (Exception e)
			{
				throw new CrlException("CRL contents invalid: " + e);
			}
		}

		protected override X509Extensions GetX509Extensions()
		{
			return Version == 2
				?	c.TbsCertList.Extensions
				:	null;
		}

		public virtual byte[] GetEncoded()
		{
			try
			{
				return c.GetDerEncoded();
			}
			catch (Exception e)
			{
				throw new CrlException(e.ToString());
			}
		}

		public virtual void Verify(
			AsymmetricKeyParameter publicKey)
		{
            Verify(new Asn1SignatureVerifierProvider(publicKey));
		}

        /// <summary>
        /// Verify the CRL's signature using a verifier created using the passed in verifier provider.
        /// </summary>
        /// <param name="verifierProvider">An appropriate provider for verifying the CRL's signature.</param>
        /// <returns>True if the signature is valid.</returns>
        /// <exception cref="Exception">If verifier provider is not appropriate or the CRL algorithm is invalid.</exception>
        public virtual void Verify(
            ISignatureVerifierProvider verifierProvider)
        {
            CheckSignature(verifierProvider.CreateSignatureVerifier(c.SignatureAlgorithm));
        }

        protected virtual void CheckSignature(
            ISignatureVerifier verifier)
        {
            if (!c.SignatureAlgorithm.Equals(c.TbsCertList.Signature))
            {
                throw new CrlException("Signature algorithm on CertificateList does not match TbsCertList.");
            }

            Asn1Encodable parameters = c.SignatureAlgorithm.Parameters;

            IStreamCalculator streamCalculator = verifier.CreateCalculator();

            byte[] b = this.GetTbsCertList();

            streamCalculator.Stream.Write(b, 0, b.Length);

            streamCalculator.Stream.Close();

            if (!((IVerifier)streamCalculator.GetResult()).IsVerified(this.GetSignature()))
            {
                throw new InvalidKeyException("CRL does not verify with supplied public key.");
            }
        }

        public virtual int Version
		{
			get { return c.Version; }
		}

		public virtual X509Name IssuerDN
		{
			get { return c.Issuer; }
		}

		public virtual DateTime ThisUpdate
		{
			get { return c.ThisUpdate.ToDateTime(); }
		}

		public virtual DateTimeObject NextUpdate
		{
			get
			{
				return c.NextUpdate == null
					?	null
					:	new DateTimeObject(c.NextUpdate.ToDateTime());
			}
		}

		private ISet LoadCrlEntries()
		{
			ISet entrySet = new HashSet();
			IEnumerable certs = c.GetRevokedCertificateEnumeration();

			X509Name previousCertificateIssuer = IssuerDN;
			foreach (CrlEntry entry in certs)
			{
				X509CrlEntry crlEntry = new X509CrlEntry(entry, isIndirect, previousCertificateIssuer);
				entrySet.Add(crlEntry);
				previousCertificateIssuer = crlEntry.GetCertificateIssuer();
			}

			return entrySet;
		}

		public virtual X509CrlEntry GetRevokedCertificate(
			BigInteger serialNumber)
		{
			IEnumerable certs = c.GetRevokedCertificateEnumeration();

			X509Name previousCertificateIssuer = IssuerDN;
			foreach (CrlEntry entry in certs)
			{
				X509CrlEntry crlEntry = new X509CrlEntry(entry, isIndirect, previousCertificateIssuer);

				if (serialNumber.Equals(entry.UserCertificate.Value))
				{
					return crlEntry;
				}

				previousCertificateIssuer = crlEntry.GetCertificateIssuer();
			}

			return null;
		}

		public virtual ISet GetRevokedCertificates()
		{
			ISet entrySet = LoadCrlEntries();

			if (entrySet.Count > 0)
			{
				return entrySet; // TODO? Collections.unmodifiableSet(entrySet);
			}

			return null;
		}

		public virtual byte[] GetTbsCertList()
		{
			try
			{
				return c.TbsCertList.GetDerEncoded();
			}
			catch (Exception e)
			{
				throw new CrlException(e.ToString());
			}
		}

		public virtual byte[] GetSignature()
		{
			return c.Signature.GetBytes();
		}

		public virtual string SigAlgName
		{
			get { return sigAlgName; }
		}

		public virtual string SigAlgOid
		{
			get { return c.SignatureAlgorithm.ObjectID.Id; }
		}

		public virtual byte[] GetSigAlgParams()
		{
			return Arrays.Clone(sigAlgParams);
		}

		public override bool Equals(
			object obj)
		{
			if (obj == this)
				return true;

			X509Crl other = obj as X509Crl;

			if (other == null)
				return false;

			return c.Equals(other.c);

			// NB: May prefer this implementation of Equals if more than one certificate implementation in play
			//return Arrays.AreEqual(this.GetEncoded(), other.GetEncoded());
		}

		public override int GetHashCode()
		{
			return c.GetHashCode();
		}

		/**
		 * Returns a string representation of this CRL.
		 *
		 * @return a string representation of this CRL.
		 */
		public override string ToString()
		{
			StringBuilder buf = new StringBuilder();
			string nl = Platform.NewLine;

			buf.Append("              Version: ").Append(this.Version).Append(nl);
			buf.Append("             IssuerDN: ").Append(this.IssuerDN).Append(nl);
			buf.Append("          This update: ").Append(this.ThisUpdate).Append(nl);
			buf.Append("          Next update: ").Append(this.NextUpdate).Append(nl);
			buf.Append("  Signature Algorithm: ").Append(this.SigAlgName).Append(nl);

			byte[] sig = this.GetSignature();

			buf.Append("            Signature: ");
			buf.Append(Hex.ToHexString(sig, 0, 20)).Append(nl);

			for (int i = 20; i < sig.Length; i += 20)
			{
				int count = System.Math.Min(20, sig.Length - i);
				buf.Append("                       ");
				buf.Append(Hex.ToHexString(sig, i, count)).Append(nl);
			}

			X509Extensions extensions = c.TbsCertList.Extensions;

			if (extensions != null)
			{
				IEnumerator e = extensions.ExtensionOids.GetEnumerator();

				if (e.MoveNext())
				{
					buf.Append("           Extensions: ").Append(nl);
				}

				do
				{
					DerObjectIdentifier oid = (DerObjectIdentifier) e.Current;
					X509Extension ext = extensions.GetExtension(oid);

					if (ext.Value != null)
					{
						Asn1Object asn1Value = X509ExtensionUtilities.FromExtensionValue(ext.Value);

						buf.Append("                       critical(").Append(ext.IsCritical).Append(") ");
						try
						{
							if (oid.Equals(X509Extensions.CrlNumber))
							{
								buf.Append(new CrlNumber(DerInteger.GetInstance(asn1Value).PositiveValue)).Append(nl);
							}
							else if (oid.Equals(X509Extensions.DeltaCrlIndicator))
							{
								buf.Append(
									"Base CRL: "
									+ new CrlNumber(DerInteger.GetInstance(
									asn1Value).PositiveValue))
									.Append(nl);
							}
							else if (oid.Equals(X509Extensions.IssuingDistributionPoint))
							{
								buf.Append(IssuingDistributionPoint.GetInstance((Asn1Sequence) asn1Value)).Append(nl);
							}
							else if (oid.Equals(X509Extensions.CrlDistributionPoints))
							{
								buf.Append(CrlDistPoint.GetInstance((Asn1Sequence) asn1Value)).Append(nl);
							}
							else if (oid.Equals(X509Extensions.FreshestCrl))
							{
								buf.Append(CrlDistPoint.GetInstance((Asn1Sequence) asn1Value)).Append(nl);
							}
							else
							{
								buf.Append(oid.Id);
								buf.Append(" value = ").Append(
									Asn1Dump.DumpAsString(asn1Value))
									.Append(nl);
							}
						}
						catch (Exception)
						{
							buf.Append(oid.Id);
							buf.Append(" value = ").Append("*****").Append(nl);
						}
					}
					else
					{
						buf.Append(nl);
					}
				}
				while (e.MoveNext());
			}

			ISet certSet = GetRevokedCertificates();
			if (certSet != null)
			{
				foreach (X509CrlEntry entry in certSet)
				{
					buf.Append(entry);
					buf.Append(nl);
				}
			}

			return buf.ToString();
		}

		/**
		 * Checks whether the given certificate is on this CRL.
		 *
		 * @param cert the certificate to check for.
		 * @return true if the given certificate is on this CRL,
		 * false otherwise.
		 */
//		public bool IsRevoked(
//			Certificate cert)
//		{
//			if (!cert.getType().Equals("X.509"))
//			{
//				throw new RuntimeException("X.509 CRL used with non X.509 Cert");
//			}
		public virtual bool IsRevoked(
			X509Certificate cert)
		{
			CrlEntry[] certs = c.GetRevokedCertificates();

			if (certs != null)
			{
//				BigInteger serial = ((X509Certificate)cert).SerialNumber;
				BigInteger serial = cert.SerialNumber;

				for (int i = 0; i < certs.Length; i++)
				{
					if (certs[i].UserCertificate.Value.Equals(serial))
					{
						return true;
					}
				}
			}

			return false;
		}

		protected virtual bool IsIndirectCrl
		{
			get
			{
				Asn1OctetString idp = GetExtensionValue(X509Extensions.IssuingDistributionPoint);
				bool isIndirect = false;

				try
				{
					if (idp != null)
					{
						isIndirect = IssuingDistributionPoint.GetInstance(
							X509ExtensionUtilities.FromExtensionValue(idp)).IsIndirectCrl;
					}
				}
				catch (Exception e)
				{
					// TODO
//					throw new ExtCrlException("Exception reading IssuingDistributionPoint", e);
					throw new CrlException("Exception reading IssuingDistributionPoint" + e);
				}

				return isIndirect;
			}
		}
	}
}