using System;
using System.IO;

namespace Org.BouncyCastle.Asn1
{
    /**
     * Parser for definite-length tagged objects.
     */
    internal class DLTaggedObjectParser
        : BerTaggedObjectParser
    {
        private readonly bool m_constructed;

        internal DLTaggedObjectParser(int tagClass, int tagNo, bool constructed, Asn1StreamParser parser)
            : base(tagClass, tagNo, parser)
        {
            m_constructed = constructed;
        }

        public override bool IsConstructed
        {
            get { return m_constructed; }
        }

        public override IAsn1Convertible ParseBaseUniversal(bool declaredExplicit, int baseTagNo)
        {
            if (declaredExplicit)
            {
                if (!m_constructed)
                    throw new IOException("Explicit tags must be constructed (see X.690 8.14.2)");

                return m_parser.ParseObject(baseTagNo);
            }

            return m_constructed
                ?  m_parser.ParseImplicitConstructedDL(baseTagNo)
                :  m_parser.ParseImplicitPrimitive(baseTagNo);
        }

        public override IAsn1Convertible ParseExplicitBaseObject()
        {
            if (!m_constructed)
                throw new IOException("Explicit tags must be constructed (see X.690 8.14.2)");

            return m_parser.ReadObject();
        }

        public override Asn1TaggedObjectParser ParseExplicitBaseTagged()
        {
            if (!m_constructed)
                throw new IOException("Explicit tags must be constructed (see X.690 8.14.2)");

            return m_parser.ParseTaggedObject();
        }

        public override Asn1TaggedObjectParser ParseImplicitBaseTagged(int baseTagClass, int baseTagNo)
        {
            // TODO[asn1] Special handling can be removed once ASN1ApplicationSpecificParser types removed.
            if (Asn1Tags.Application == baseTagClass)
            {
                // This cast is ensuring the current user-expected return type.
                return (DLApplicationSpecific)m_parser.LoadTaggedDL(baseTagClass, baseTagNo, m_constructed);
            }

            return new DLTaggedObjectParser(baseTagClass, baseTagNo, m_constructed, m_parser);
        }

        public override Asn1Object ToAsn1Object()
		{
			try
			{
                return m_parser.LoadTaggedDL(TagClass, TagNo, m_constructed);
            }
			catch (IOException e)
			{
				throw new Asn1ParsingException(e.Message);
			}
		}
    }
}