using System;
using System.Collections.Generic;
using System.IO;

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security.Certificates;
using Org.BouncyCastle.Utilities;
using Org.BouncyCastle.X509.Extension;

namespace Org.BouncyCastle.X509
{
    /// <summary>
    /// A class to Generate Version 3 X509Certificates.
    /// </summary>
    public class X509V3CertificateGenerator
    {
		private readonly X509ExtensionsGenerator extGenerator = new X509ExtensionsGenerator();

		private V3TbsCertificateGenerator tbsGen;

		public X509V3CertificateGenerator()
        {
            tbsGen = new V3TbsCertificateGenerator();
        }

		/// <summary>Create a generator for a version 3 certificate, initialised with another certificate.</summary>
		/// <param name="template">Template certificate to base the new one on.</param>
		public X509V3CertificateGenerator(X509Certificate template)
			: this(template.CertificateStructure)
		{
		}

		public X509V3CertificateGenerator(X509CertificateStructure template)
		{
			tbsGen = new V3TbsCertificateGenerator();
			tbsGen.SetSerialNumber(template.SerialNumber);
			tbsGen.SetIssuer(template.Issuer);
			tbsGen.SetStartDate(template.StartDate);
			tbsGen.SetEndDate(template.EndDate);
			tbsGen.SetSubject(template.Subject);
			tbsGen.SetSubjectPublicKeyInfo(template.SubjectPublicKeyInfo);

			var extensions = template.TbsCertificate.Extensions;

            foreach (var oid in extensions.ExtensionOids)
            {
                if (X509Extensions.SubjectAltPublicKeyInfo.Equals(oid) ||
                    X509Extensions.AltSignatureAlgorithm.Equals(oid) ||
                    X509Extensions.AltSignatureValue.Equals(oid))
                {
                    continue;
                }

                X509Extension ext = extensions.GetExtension(oid);
                extGenerator.AddExtension(oid, ext.critical, ext.Value.GetOctets());
            }
		}

		/// <summary>
		/// Reset the Generator.
		/// </summary>
		public void Reset()
		{
			tbsGen = new V3TbsCertificateGenerator();
			extGenerator.Reset();
		}

		/// <summary>
        /// Set the certificate's serial number.
        /// </summary>
        /// <remarks>Make serial numbers long, if you have no serial number policy make sure the number is at least 16 bytes of secure random data.
        /// You will be surprised how ugly a serial number collision can Get.</remarks>
        /// <param name="serialNumber">The serial number.</param>
        public void SetSerialNumber(
			BigInteger serialNumber)
        {
			if (serialNumber.SignValue <= 0)
			{
				throw new ArgumentException("serial number must be a positive integer", "serialNumber");
			}

			tbsGen.SetSerialNumber(new DerInteger(serialNumber));
        }

		/// <summary>
        /// Set the distinguished name of the issuer.
        /// The issuer is the entity which is signing the certificate.
        /// </summary>
        /// <param name="issuer">The issuer's DN.</param>
        public void SetIssuerDN(
            X509Name issuer)
        {
            tbsGen.SetIssuer(issuer);
        }

		/// <summary>
        /// Set the date that this certificate is to be valid from.
        /// </summary>
        /// <param name="date"/>
        public void SetNotBefore(
            DateTime date)
        {
            tbsGen.SetStartDate(new Time(date));
        }

        /// <summary>
        /// Set the date after which this certificate will no longer be valid.
        /// </summary>
        /// <param name="date"/>
        public void SetNotAfter(
			DateTime date)
        {
            tbsGen.SetEndDate(new Time(date));
        }

		/// <summary>
		/// Set the DN of the entity that this certificate is about.
		/// </summary>
		/// <param name="subject"/>
        public void SetSubjectDN(
			X509Name subject)
        {
            tbsGen.SetSubject(subject);
        }

		/// <summary>
        /// Set the public key that this certificate identifies.
        /// </summary>
        /// <param name="publicKey"/>
        public void SetPublicKey(
			AsymmetricKeyParameter publicKey)
        {
            tbsGen.SetSubjectPublicKeyInfo(SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(publicKey));
        }

		/// <summary>
		/// Set the subject unique ID - note: it is very rare that it is correct to do this.
		/// </summary>
		/// <param name="uniqueID"/>
		public void SetSubjectUniqueID(
			bool[] uniqueID)
		{
			tbsGen.SetSubjectUniqueID(BooleanToBitString(uniqueID));
		}

		/// <summary>
		/// Set the issuer unique ID - note: it is very rare that it is correct to do this.
		/// </summary>
		/// <param name="uniqueID"/>
		public void SetIssuerUniqueID(
			bool[] uniqueID)
		{
			tbsGen.SetIssuerUniqueID(BooleanToBitString(uniqueID));
		}

		/// <summary>
		/// Add a given extension field for the standard extensions tag (tag 3).
		/// </summary>
		/// <param name="oid">string containing a dotted decimal Object Identifier.</param>
		/// <param name="critical">Is it critical.</param>
		/// <param name="extensionValue">The value.</param>
		public void AddExtension(
			string			oid,
			bool			critical,
			Asn1Encodable	extensionValue)
		{
			extGenerator.AddExtension(new DerObjectIdentifier(oid), critical, extensionValue);
		}

		/// <summary>
        /// Add an extension to this certificate.
        /// </summary>
        /// <param name="oid">Its Object Identifier.</param>
        /// <param name="critical">Is it critical.</param>
        /// <param name="extensionValue">The value.</param>
        public void AddExtension(
			DerObjectIdentifier	oid,
			bool				critical,
			Asn1Encodable		extensionValue)
        {
			extGenerator.AddExtension(oid, critical, extensionValue);
        }

		/// <summary>
		/// Add an extension using a string with a dotted decimal OID.
		/// </summary>
		/// <param name="oid">string containing a dotted decimal Object Identifier.</param>
		/// <param name="critical">Is it critical.</param>
		/// <param name="extensionValue">byte[] containing the value of this extension.</param>
		public void AddExtension(
			string	oid,
			bool	critical,
			byte[]	extensionValue)
		{
			extGenerator.AddExtension(new DerObjectIdentifier(oid), critical, new DerOctetString(extensionValue));
		}

		/// <summary>
        /// Add an extension to this certificate.
        /// </summary>
        /// <param name="oid">Its Object Identifier.</param>
        /// <param name="critical">Is it critical.</param>
        /// <param name="extensionValue">byte[] containing the value of this extension.</param>
        public void AddExtension(
			DerObjectIdentifier	oid,
			bool				critical,
			byte[]				extensionValue)
        {
			extGenerator.AddExtension(oid, critical, new DerOctetString(extensionValue));
        }

		/// <summary>
		/// Add a given extension field for the standard extensions tag (tag 3),
		/// copying the extension value from another certificate.
		/// </summary>
		public void CopyAndAddExtension(
			string			oid,
			bool			critical,
			X509Certificate	cert)
		{
			CopyAndAddExtension(new DerObjectIdentifier(oid), critical, cert);
		}

		/**
		 * add a given extension field for the standard extensions tag (tag 3)
		 * copying the extension value from another certificate.
		 * @throws CertificateParsingException if the extension cannot be extracted.
		 */
		public void CopyAndAddExtension(
			DerObjectIdentifier	oid,
			bool				critical,
			X509Certificate		cert)
		{
			Asn1OctetString extValue = cert.GetExtensionValue(oid);
			if (extValue == null)
				throw new CertificateParsingException("extension " + oid + " not present");

			try
			{
				Asn1Encodable value = X509ExtensionUtilities.FromExtensionValue(extValue);

				this.AddExtension(oid, critical, value);
			}
			catch (Exception e)
			{
				throw new CertificateParsingException(e.Message, e);
			}
		}

		/// <summary>
		/// Generate a new <see cref="X509Certificate"/> using the provided <see cref="ISignatureFactory"/>.
		/// </summary>
		/// <param name="signatureFactory">A <see cref="ISignatureFactory">signature factory</see> with the necessary
		/// algorithm details.</param>
		/// <returns>An <see cref="X509Certificate"/>.</returns>
		public X509Certificate Generate(ISignatureFactory signatureFactory)
		{
			var sigAlgID = (AlgorithmIdentifier)signatureFactory.AlgorithmDetails;

			tbsGen.SetSignature(sigAlgID);

            if (!extGenerator.IsEmpty)
            {
                tbsGen.SetExtensions(extGenerator.Generate());
            }

            var tbsCertificate = tbsGen.GenerateTbsCertificate();

			var signature = X509Utilities.GenerateSignature(signatureFactory, tbsCertificate);

			return new X509Certificate(new X509CertificateStructure(tbsCertificate, sigAlgID, signature));
        }

        /// <summary>
        /// Generate a new <see cref="X509Certificate"/> using the provided <see cref="ISignatureFactory"/> and
        /// containing altSignatureAlgorithm and altSignatureValue extensions based on the passed
        /// <paramref name="altSignatureFactory"/>.
        /// </summary>
        /// <param name="signatureFactory">A <see cref="ISignatureFactory">signature factory</see> with the necessary
        /// algorithm details.</param>
		/// <param name="isCritical">Whether the 'alt' extensions should be marked critical.</param>
        /// <param name="altSignatureFactory">A <see cref="ISignatureFactory">signature factory</see> used to create the
		/// altSignatureAlgorithm and altSignatureValue extensions.</param>
        /// <returns>An <see cref="X509Certificate"/>.</returns>
        public X509Certificate Generate(ISignatureFactory signatureFactory, bool isCritical,
			ISignatureFactory altSignatureFactory)
		{
            tbsGen.SetSignature(null);

            var altSigAlgID = (AlgorithmIdentifier)altSignatureFactory.AlgorithmDetails;
			extGenerator.AddExtension(X509Extensions.AltSignatureAlgorithm, isCritical, altSigAlgID);

            tbsGen.SetExtensions(extGenerator.Generate());

			var altSignature = X509Utilities.GenerateSignature(altSignatureFactory, tbsGen.GeneratePreTbsCertificate());
			extGenerator.AddExtension(X509Extensions.AltSignatureValue, isCritical, altSignature);

			return Generate(signatureFactory);
		}

		/// <summary>
		/// Allows enumeration of the signature names supported by the generator.
		/// </summary>
		public IEnumerable<string> SignatureAlgNames => X509Utilities.GetAlgNames();

        private static DerBitString BooleanToBitString(bool[] id)
        {
            int byteLength = (id.Length + 7) / 8;

#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
            Span<byte> bytes = byteLength <= 512
                ? stackalloc byte[byteLength]
                : new byte[byteLength];
#else
			byte[] bytes = new byte[byteLength];
#endif

            for (int i = 0; i != id.Length; i++)
            {
                if (id[i])
                {
                    bytes[i >> 3] |= (byte)(0x80 >> (i & 7));
                }
            }

            return new DerBitString(bytes, (8 - id.Length) & 7);
        }
    }
}