using System;
using System.IO;

using Org.BouncyCastle.Utilities;

namespace Org.BouncyCastle.Asn1.Cms
{
    /**
	* <pre>
	* SignedData ::= SEQUENCE {
	*     version CMSVersion,
	*     digestAlgorithms DigestAlgorithmIdentifiers,
	*     encapContentInfo EncapsulatedContentInfo,
	*     certificates [0] IMPLICIT CertificateSet OPTIONAL,
	*     crls [1] IMPLICIT CertificateRevocationLists OPTIONAL,
	*     signerInfos SignerInfos
	*   }
	* </pre>
	*/
    public class SignedDataParser
    {
        private Asn1SequenceParser _seq;
        private DerInteger _version;
        private object _nextObject;
        private bool _certsCalled;
        private bool _crlsCalled;

        public static SignedDataParser GetInstance(
            object o)
        {
            if (o is Asn1Sequence)
                return new SignedDataParser(((Asn1Sequence)o).Parser);

            if (o is Asn1SequenceParser)
                return new SignedDataParser((Asn1SequenceParser)o);

            throw new IOException("unknown object encountered: " + Platform.GetTypeName(o));
        }

        public SignedDataParser(
            Asn1SequenceParser seq)
        {
            this._seq = seq;
            this._version = (DerInteger)seq.ReadObject();
        }

        public DerInteger Version
        {
            get { return _version; }
        }

        public Asn1SetParser GetDigestAlgorithms()
        {
            return (Asn1SetParser)_seq.ReadObject();
        }

        public ContentInfoParser GetEncapContentInfo()
        {
            return new ContentInfoParser((Asn1SequenceParser)_seq.ReadObject());
        }

        public Asn1SetParser GetCertificates()
        {
            _certsCalled = true;
            _nextObject = _seq.ReadObject();

            if (_nextObject is Asn1TaggedObjectParser o)
            {
                if (o.HasContextTag(0))
                {
                    Asn1SetParser certs = (Asn1SetParser)o.ParseBaseUniversal(false, Asn1Tags.SetOf);
                    _nextObject = null;
                    return certs;
                }
            }

            return null;
        }

        public Asn1SetParser GetCrls()
        {
            if (!_certsCalled)
                throw new IOException("GetCerts() has not been called.");

            _crlsCalled = true;

            if (_nextObject == null)
            {
                _nextObject = _seq.ReadObject();
            }

            if (_nextObject is Asn1TaggedObjectParser o)
            {
                if (o.HasContextTag(1))
                {
                    Asn1SetParser crls = (Asn1SetParser)o.ParseBaseUniversal(false, Asn1Tags.SetOf);
                    _nextObject = null;
                    return crls;
                }
            }

            return null;
        }

        public Asn1SetParser GetSignerInfos()
        {
            if (!_certsCalled || !_crlsCalled)
                throw new IOException("GetCerts() and/or GetCrls() has not been called.");

            if (_nextObject == null)
            {
                _nextObject = _seq.ReadObject();
            }

            return (Asn1SetParser)_nextObject;
        }
    }
}