using GostCryptography.Properties;
using System;
using System.IO;

namespace GostCryptography.Asn1.Ber
{
    public class Asn1BerDecodeBuffer : Asn1DecodeBuffer
    {
        private readonly IntHolder _lenHolder;
        private readonly Asn1Tag _tagHolder;

        private Asn1Tag _lastParsedTag;
        private MemoryStream _openTypeCaptureBuffer;
        private MemoryStream _parserCaptureBuffer;

        public Asn1BerDecodeBuffer(byte[] msgdata)
            : base(msgdata)
        {
            _tagHolder = new Asn1Tag();
            _lenHolder = new IntHolder();
        }

        public Asn1BerDecodeBuffer(Stream inputStream)
            : base(inputStream)
        {
            _tagHolder = new Asn1Tag();
            _lenHolder = new IntHolder();
        }

        public virtual Asn1Tag LastTag
        {
            get { return _lastParsedTag; }
        }

        public static int CalcIndefLen(byte[] data, int offset, int len)
        {
            Asn1BerDecodeBuffer buffer;

            if ((offset == 0) && (len == data.Length))
            {
                buffer = new Asn1BerDecodeBuffer(data);
            }
            else
            {
                var destinationArray = new byte[len];
                Array.Copy(data, offset, destinationArray, 0, len);
                buffer = new Asn1BerDecodeBuffer(destinationArray);
            }

            var tag = new Asn1Tag();
            var num = buffer.DecodeTagAndLength(tag);

            if (num == Asn1Status.IndefiniteLength)
            {
                var num2 = 1;
                num = 0;

                while (num2 > 0)
                {
                    var byteCount = buffer.ByteCount;
                    var num4 = buffer.DecodeTagAndLength(tag);
                    num += buffer.ByteCount - byteCount;

                    if (num4 > 0)
                    {
                        buffer.Skip(num4);
                        num += num4;
                    }
                    else
                    {
                        if (num4 == Asn1Status.IndefiniteLength)
                        {
                            num2++;
                            continue;
                        }
                        if (tag.IsEoc() && (num4 == 0))
                        {
                            num2--;
                        }
                    }
                }
            }

            return num;
        }

        public virtual int DecodeLength()
        {
            var num3 = 0;
            var num2 = Read();

            if (num2 < 0)
            {
                throw ExceptionUtility.CryptographicException(Resources.Asn1EndOfBufferException, ByteCount);
            }

            if (num2 <= 0x80)
            {
                if (num2 == 0x80)
                {
                    return Asn1Status.IndefiniteLength;
                }

                return num2;
            }

            var num = num2 & 0x7f;

            if (num > 4)
            {
                throw ExceptionUtility.CryptographicException(Resources.Asn1InvalidLengthException);
            }

            while (num > 0)
            {
                num2 = Read();

                if (num2 < 0)
                {
                    throw ExceptionUtility.CryptographicException(Resources.Asn1EndOfBufferException, ByteCount);
                }

                num3 = (num3 * 0x100) + num2;
                num--;
            }

            return num3;
        }

        public virtual byte[] DecodeOpenType()
        {
            return DecodeOpenType(true);
        }

        public virtual byte[] DecodeOpenType(bool saveData)
        {
            if (saveData)
            {
                if (_openTypeCaptureBuffer == null)
                {
                    _openTypeCaptureBuffer = new MemoryStream(0x100);
                }
                else
                {
                    _openTypeCaptureBuffer.Seek(0L, SeekOrigin.Begin);
                    _openTypeCaptureBuffer.SetLength(0L);
                }

                AddCaptureBuffer(_openTypeCaptureBuffer);
            }

            DecodeOpenTypeElement(_tagHolder, _lenHolder, saveData);

            if (saveData)
            {
                var buffer = _openTypeCaptureBuffer.ToArray();
                RemoveCaptureBuffer(_openTypeCaptureBuffer);
                return buffer;
            }

            return null;
        }

        private void DecodeOpenTypeElement(Asn1Tag tag, IntHolder len, bool saveData)
        {
            var nbytes = DecodeTagAndLength(tag);
            var byteCount = base.ByteCount;

            if (nbytes > 0)
            {
                if (saveData)
                {
                    Capture(nbytes);
                }
                else
                {
                    Skip(nbytes);
                }
            }
            else if (nbytes == Asn1Status.IndefiniteLength)
            {
                MovePastEoc(saveData);
            }

            len.Value = base.ByteCount - byteCount;
        }

        public virtual void DecodeTag(Asn1Tag tag)
        {
            var num = Read();

            if (num < 0)
            {
                throw ExceptionUtility.CryptographicException(Resources.Asn1EndOfBufferException, ByteCount);
            }

            tag.Class = (short)(num & 0xc0);
            tag.Form = (short)(num & 0x20);
            tag.IdCode = num & 0x1f;

            if (tag.IdCode == 0x1f)
            {
                var num2 = 0L;
                var num3 = 0;

                do
                {
                    num = Read();

                    if (num < 0)
                    {
                        throw ExceptionUtility.CryptographicException(Resources.Asn1EndOfBufferException, ByteCount);
                    }

                    num2 = (num2 * 0x80L) + (num & 0x7f);

                    if ((num2 > 0x7fffffffL) || (num3++ > 8))
                    {
                        throw ExceptionUtility.CryptographicException(Resources.Asn1InvalidTagValue);
                    }

                }
                while ((num & 0x80) != 0);

                tag.IdCode = (int)num2;
            }

            _lastParsedTag = tag;
        }

        public virtual int DecodeTagAndLength(Asn1Tag tag)
        {
            DecodeTag(tag);
            return DecodeLength();
        }

        public virtual bool MatchTag(Asn1Tag tag)
        {
            return MatchTag(tag.Class, tag.Form, tag.IdCode, null, null);
        }

        public virtual bool MatchTag(Asn1Tag tag, Asn1Tag parsedTag, IntHolder parsedLen)
        {
            return MatchTag(tag.Class, tag.Form, tag.IdCode, parsedTag, parsedLen);
        }

        public virtual bool MatchTag(short tagClass, short tagForm, int tagIdCode, Asn1Tag parsedTag, IntHolder parsedLen)
        {
            Mark();

            var tag = parsedTag ?? _tagHolder;
            var holder = parsedLen ?? _lenHolder;

            holder.Value = DecodeTagAndLength(tag);

            if (!tag.Equals(tagClass, tagForm, tagIdCode))
            {
                Reset();
                return false;
            }

            return true;
        }

        protected void MovePastEoc(bool saveData)
        {
            var tag = new Asn1Tag();
            var num = 1;

            while (num > 0)
            {
                var nbytes = DecodeTagAndLength(tag);

                if (nbytes > 0)
                {
                    if (saveData)
                    {
                        Capture(nbytes);
                    }
                    else
                    {
                        Skip(nbytes);
                    }
                }
                else if (nbytes == Asn1Status.IndefiniteLength)
                {
                    num++;
                }
                else if (tag.IsEoc() && (nbytes == 0))
                {
                    num--;
                }
            }
        }

        public virtual void Parse(IAsn1TaggedEventHandler handler)
        {
            if (_parserCaptureBuffer == null)
            {
                RemoveCaptureBuffer(_parserCaptureBuffer);
            }

            if (_parserCaptureBuffer == null)
            {
                _parserCaptureBuffer = new MemoryStream(0x100);
                AddCaptureBuffer(_parserCaptureBuffer);
            }
            else
            {
                _parserCaptureBuffer.Seek(0L, SeekOrigin.Begin);
                _parserCaptureBuffer.SetLength(0L);
            }

            ParseElement(handler, _tagHolder, _lenHolder);
        }

        private void ParseCons(IAsn1TaggedEventHandler handler, int len)
        {
            var tag2 = new Asn1Tag();
            var holder = new IntHolder();
            var byteCount = base.ByteCount;

            while (true)
            {
                ParseElement(handler, tag2, holder);

                if (len == Asn1Status.IndefiniteLength)
                {
                    if (tag2.IsEoc() && (holder.Value == 0))
                    {
                        return;
                    }

                    continue;
                }

                if ((base.ByteCount - byteCount) >= len)
                {
                    return;
                }
            }
        }

        private void ParseElement(IAsn1TaggedEventHandler handler, Asn1Tag tag, IntHolder len)
        {
            _parserCaptureBuffer.Seek(0L, SeekOrigin.Begin);
            _parserCaptureBuffer.SetLength(0L);

            len.Value = DecodeTagAndLength(tag);

            if (!tag.IsEoc() || (len.Value != 0))
            {
                handler.StartElement(tag, len.Value, _parserCaptureBuffer.ToArray());

                _parserCaptureBuffer.Seek(0L, SeekOrigin.Begin);
                _parserCaptureBuffer.SetLength(0L);

                if ((len.Value > 0) || (len.Value == Asn1Status.IndefiniteLength))
                {
                    if (tag.Constructed)
                    {
                        ParseCons(handler, len.Value);
                    }
                    else
                    {
                        ParsePrim(handler, len.Value);
                    }
                }

                handler.EndElement(tag);
            }
        }

        private void ParsePrim(IAsn1TaggedEventHandler handler, int len)
        {
            var buffer = new byte[len];
            Read(buffer);
            handler.Contents(buffer);
        }

        public virtual Asn1Tag PeekTag()
        {
            var parsedTag = new Asn1Tag();
            PeekTag(parsedTag);
            return parsedTag;
        }

        public virtual void PeekTag(Asn1Tag parsedTag)
        {
            Mark();
            DecodeTag(parsedTag);
            Reset();
        }

        public override int ReadByte()
        {
            return Read();
        }
    }
}