using System;
using System.IO;

namespace Org.BouncyCastle.Asn1;

public class Asn1StreamParser
{
	private readonly Stream _in;

	private readonly int _limit;

	private readonly byte[][] tmpBuffers;

	public Asn1StreamParser(Stream inStream)
		: this(inStream, Asn1InputStream.FindLimit(inStream))
	{
	}

	public Asn1StreamParser(Stream inStream, int limit)
	{
		if (!inStream.CanRead)
		{
			throw new ArgumentException("Expected stream to be readable", "inStream");
		}
		_in = inStream;
		_limit = limit;
		tmpBuffers = new byte[16][];
	}

	public Asn1StreamParser(byte[] encoding)
		: this(new MemoryStream(encoding, writable: false), encoding.Length)
	{
	}

	internal IAsn1Convertible ReadIndef(int tagValue)
	{
		return tagValue switch
		{
			8 => new DerExternalParser(this), 
			4 => new BerOctetStringParser(this), 
			16 => new BerSequenceParser(this), 
			17 => new BerSetParser(this), 
			_ => throw new Asn1Exception("unknown BER object encountered: 0x" + tagValue.ToString("X")), 
		};
	}

	internal IAsn1Convertible ReadImplicit(bool constructed, int tag)
	{
		if (_in is IndefiniteLengthInputStream)
		{
			if (!constructed)
			{
				throw new IOException("indefinite length primitive encoding encountered");
			}
			return ReadIndef(tag);
		}
		if (constructed)
		{
			switch (tag)
			{
			case 17:
				return new DerSetParser(this);
			case 16:
				return new DerSequenceParser(this);
			case 4:
				return new BerOctetStringParser(this);
			}
		}
		else
		{
			switch (tag)
			{
			case 17:
				throw new Asn1Exception("sequences must use constructed encoding (see X.690 8.9.1/8.10.1)");
			case 16:
				throw new Asn1Exception("sets must use constructed encoding (see X.690 8.11.1/8.12.1)");
			case 4:
				return new DerOctetStringParser((DefiniteLengthInputStream)_in);
			}
		}
		throw new Asn1Exception("implicit tagging not implemented");
	}

	internal Asn1Object ReadTaggedObject(bool constructed, int tag)
	{
		if (!constructed)
		{
			DefiniteLengthInputStream definiteLengthInputStream = (DefiniteLengthInputStream)_in;
			return new DerTaggedObject(explicitly: false, tag, new DerOctetString(definiteLengthInputStream.ToArray()));
		}
		Asn1EncodableVector asn1EncodableVector = ReadVector();
		if (_in is IndefiniteLengthInputStream)
		{
			if (asn1EncodableVector.Count != 1)
			{
				return new BerTaggedObject(explicitly: false, tag, BerSequence.FromVector(asn1EncodableVector));
			}
			return new BerTaggedObject(explicitly: true, tag, asn1EncodableVector[0]);
		}
		if (asn1EncodableVector.Count != 1)
		{
			return new DerTaggedObject(explicitly: false, tag, DerSequence.FromVector(asn1EncodableVector));
		}
		return new DerTaggedObject(explicitly: true, tag, asn1EncodableVector[0]);
	}

	public virtual IAsn1Convertible ReadObject()
	{
		int num = _in.ReadByte();
		if (num == -1)
		{
			return null;
		}
		Set00Check(enabled: false);
		int num2 = Asn1InputStream.ReadTagNumber(_in, num);
		bool flag = (num & 0x20) != 0;
		int num3 = Asn1InputStream.ReadLength(_in, _limit);
		if (num3 < 0)
		{
			if (!flag)
			{
				throw new IOException("indefinite length primitive encoding encountered");
			}
			IndefiniteLengthInputStream inStream = new IndefiniteLengthInputStream(_in, _limit);
			Asn1StreamParser asn1StreamParser = new Asn1StreamParser(inStream, _limit);
			if ((num & 0x40) != 0)
			{
				return new BerApplicationSpecificParser(num2, asn1StreamParser);
			}
			if ((num & 0x80) != 0)
			{
				return new BerTaggedObjectParser(constructed: true, num2, asn1StreamParser);
			}
			return asn1StreamParser.ReadIndef(num2);
		}
		DefiniteLengthInputStream definiteLengthInputStream = new DefiniteLengthInputStream(_in, num3);
		if ((num & 0x40) != 0)
		{
			return new DerApplicationSpecific(flag, num2, definiteLengthInputStream.ToArray());
		}
		if ((num & 0x80) != 0)
		{
			return new BerTaggedObjectParser(flag, num2, new Asn1StreamParser(definiteLengthInputStream));
		}
		if (flag)
		{
			return num2 switch
			{
				4 => new BerOctetStringParser(new Asn1StreamParser(definiteLengthInputStream)), 
				16 => new DerSequenceParser(new Asn1StreamParser(definiteLengthInputStream)), 
				17 => new DerSetParser(new Asn1StreamParser(definiteLengthInputStream)), 
				8 => new DerExternalParser(new Asn1StreamParser(definiteLengthInputStream)), 
				_ => throw new IOException("unknown tag " + num2 + " encountered"), 
			};
		}
		int num4 = num2;
		if (num4 == 4)
		{
			return new DerOctetStringParser(definiteLengthInputStream);
		}
		try
		{
			return Asn1InputStream.CreatePrimitiveDerObject(num2, definiteLengthInputStream, tmpBuffers);
		}
		catch (ArgumentException exception)
		{
			throw new Asn1Exception("corrupted stream detected", exception);
		}
	}

	private void Set00Check(bool enabled)
	{
		if (_in is IndefiniteLengthInputStream)
		{
			((IndefiniteLengthInputStream)_in).SetEofOn00(enabled);
		}
	}

	internal Asn1EncodableVector ReadVector()
	{
		Asn1EncodableVector asn1EncodableVector = new Asn1EncodableVector();
		IAsn1Convertible asn1Convertible;
		while ((asn1Convertible = ReadObject()) != null)
		{
			asn1EncodableVector.Add(asn1Convertible.ToAsn1Object());
		}
		return asn1EncodableVector;
	}
}