using System;

using Org.BouncyCastle.Math;
using Org.BouncyCastle.Utilities;

namespace Org.BouncyCastle.Asn1.X509
{
    public class BasicConstraints
        : Asn1Encodable
    {
		public static BasicConstraints GetInstance(Asn1TaggedObject obj, bool explicitly)
        {
            return GetInstance(Asn1Sequence.GetInstance(obj, explicitly));
        }

		public static BasicConstraints GetInstance(object obj)
        {
            if (obj is BasicConstraints)
                return (BasicConstraints)obj;
            if (obj is X509Extension)
                return GetInstance(X509Extension.ConvertValueToObject((X509Extension)obj));
            if (obj == null)
                return null;
            return new BasicConstraints(Asn1Sequence.GetInstance(obj));
		}

        public static BasicConstraints FromExtensions(X509Extensions extensions)
        {
            return GetInstance(X509Extensions.GetExtensionParsedValue(extensions, X509Extensions.BasicConstraints));
        }

        private readonly DerBoolean cA;
        private readonly DerInteger pathLenConstraint;

        private BasicConstraints(
            Asn1Sequence seq)
        {
			if (seq.Count > 0)
			{
				if (seq[0] is DerBoolean)
				{
					this.cA = DerBoolean.GetInstance(seq[0]);
				}
				else
				{
					this.pathLenConstraint = DerInteger.GetInstance(seq[0]);
				}

				if (seq.Count > 1)
				{
					if (this.cA == null)
						throw new ArgumentException("wrong sequence in constructor", "seq");

					this.pathLenConstraint = DerInteger.GetInstance(seq[1]);
				}
			}
        }

		public BasicConstraints(
            bool cA)
        {
			if (cA)
			{
				this.cA = DerBoolean.True;
			}
        }

		/**
         * create a cA=true object for the given path length constraint.
         *
         * @param pathLenConstraint
         */
        public BasicConstraints(
            int pathLenConstraint)
        {
            this.cA = DerBoolean.True;
            this.pathLenConstraint = new DerInteger(pathLenConstraint);
        }

		public bool IsCA()
        {
            return cA != null && cA.IsTrue;
        }

		public BigInteger PathLenConstraint
        {
            get { return pathLenConstraint == null ? null : pathLenConstraint.Value; }
        }

		/**
         * Produce an object suitable for an Asn1OutputStream.
         * <pre>
         * BasicConstraints := Sequence {
         *    cA                  Boolean DEFAULT FALSE,
         *    pathLenConstraint   Integer (0..MAX) OPTIONAL
         * }
         * </pre>
         */
        public override Asn1Object ToAsn1Object()
        {
            Asn1EncodableVector v = new Asn1EncodableVector(2);
            v.AddOptional(cA,
                pathLenConstraint); // yes some people actually do this when cA is false...
            return new DerSequence(v);
        }

		public override string ToString()
        {
            if (pathLenConstraint == null)
            {
				return "BasicConstraints: isCa(" + this.IsCA() + ")";
            }

			return "BasicConstraints: isCa(" + this.IsCA() + "), pathLenConstraint = " + pathLenConstraint.Value;
        }
    }
}