//******************************************************************************************************
//  BERCoderUtils.cs - Gbtc
//
//  Copyright © 2013, Grid Protection Alliance.  All Rights Reserved.
//
//  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See
//  the NOTICE file distributed with this work for additional information regarding copyright ownership.
//  The GPA licenses this file to you under the MIT License (MIT), the "License"; you may
//  not use this file except in compliance with the License. You may obtain a copy of the License at:
//
//      http://www.opensource.org/licenses/MIT
//
//  Unless agreed to in writing, the subject software distributed under the License is distributed on an
//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the
//  License for the specific language governing permissions and limitations.
//
//  Code Modification History:
//  ----------------------------------------------------------------------------------------------------
//  09/24/2013 - J. Ritchie Carroll
//       Derived original version of source code from BinaryNotes (http://bnotes.sourceforge.net).
//
//******************************************************************************************************

#region [ Contributor License Agreements ]

/*
    Copyright 2006-2011 Abdulla Abdurakhmanov (abdulla@latestbit.com)
    Original sources are available at www.latestbit.com

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

            http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

#endregion

using System;
using System.IO;
using GSF.ASN1.Attributes;
using GSF.ASN1.Metadata;

namespace GSF.ASN1.Coders.BER
{
    internal static class BERCoderUtils
    {
        public static DecodedObject<int> getTagValueForElement(ElementInfo info, int tagClass, int elemenType, int universalTag)
        {
            DecodedObject<int> result = new DecodedObject<int>();
            // result.Value =  tagClass | elemenType | universalTag;
            if (universalTag < UniversalTags.LastUniversal)
            {
                result.Value = tagClass | elemenType | universalTag;
            }
            else
                result = getTagValue(tagClass, elemenType, universalTag, universalTag, tagClass);

            result.Size = 1;
            if (info.hasPreparedInfo())
            {
                ASN1ElementMetadata meta = info.PreparedASN1ElementInfo;
                if (meta != null && meta.HasTag)
                {
                    result = getTagValue(tagClass, elemenType, universalTag,
                                         meta.Tag,
                                         meta.TagClass
                        );
                }
            }
            else
            {
                ASN1Element elementInfo = null;
                if (info.ASN1ElementInfo != null)
                {
                    elementInfo = info.ASN1ElementInfo;
                }
                else if (info.isAttributePresent<ASN1Element>())
                {
                    elementInfo = info.getAttribute<ASN1Element>();
                }

                if (elementInfo != null)
                {
                    if (elementInfo.HasTag)
                    {
                        result = getTagValue(tagClass, elemenType, universalTag, elementInfo.Tag, elementInfo.TagClass);
                    }
                }
            }
            return result;
        }

        public static DecodedObject<int> getTagValue(int tagClass, int elemenType, int universalTag, int userTag, int userTagClass)
        {
            DecodedObject<int> resultObj = new DecodedObject<int>();
            int result = tagClass | elemenType | universalTag;
            tagClass = userTagClass;
            if (userTag < 31)
            {
                result = tagClass | elemenType | userTag;
                resultObj.Size = 1;
            }
            else
            {
                result = tagClass | elemenType | 0x1F;
                if (userTag < 0x80)
                {
                    result <<= 8;
                    result |= userTag & 0x7F;
                    resultObj.Size = 2;
                }
                else if (userTag < 0x3FFF)
                {
                    result <<= 16;
                    result |= (((userTag & 0x3FFF) >> 7) | 0x80) << 8;
                    result |= ((userTag & 0x3FFF) & 0x7f);
                    resultObj.Size = 3;
                }
                else if (userTag < 0x3FFFF)
                {
                    result <<= 24;
                    result |= (((userTag & 0x3FFFF) >> 15) | 0x80) << 16;
                    result |= (((userTag & 0x3FFFF) >> 7) | 0x80) << 8;
                    result |= ((userTag & 0x3FFFF) & 0x3f);
                    resultObj.Size = 4;
                }
            }
            resultObj.Value = result;
            return resultObj;
        }

        public static int encodeLength(int length, Stream stream)
        {
            int resultSize = 0;

            if (length < 0)
            {
                throw new ArgumentException();
            }
            else if (length < 128)
            {
                stream.WriteByte((byte)length);
                resultSize++;
            }
            else if (length < 256)
            {
                stream.WriteByte((byte)length);
                stream.WriteByte((byte)0x81);
                resultSize += 2;
            }
            else if (length < 65536)
            {
                stream.WriteByte((byte)(length));
                stream.WriteByte((byte)(length >> 8));
                stream.WriteByte((byte)0x82);
                resultSize += 3;
            }
            else if (length < 16777126)
            {
                stream.WriteByte((byte)(length));
                stream.WriteByte((byte)(length >> 8));
                stream.WriteByte((byte)(length >> 16));
                stream.WriteByte((byte)0x83);
                resultSize += 4;
            }
            else
            {
                stream.WriteByte((byte)(length));
                stream.WriteByte((byte)(length >> 8));
                stream.WriteByte((byte)(length >> 16));
                stream.WriteByte((byte)(length >> 24));
                stream.WriteByte((byte)0x84);
                resultSize += 5;
            }
            return resultSize;
        }

        public static DecodedObject<int> decodeLength(Stream stream)
        {
            int result = 0;
            int bt = stream.ReadByte();
            if (bt == -1)
                throw new ArgumentException("Unexpected EOF when decoding!");

            int len = 1;
            if (bt < 128)
            {
                result = bt;
            }
            else
            {
                // Decode length bug fixed. Thanks to John 
                for (int i = bt - 128; i > 0; i--)
                {
                    int fBt = stream.ReadByte();
                    if (fBt == -1)
                        throw new ArgumentException("Unexpected EOF when decoding!");

                    result = result << 8;
                    result = result | fBt;
                    len++;
                }
            }
            return new DecodedObject<int>(result, len);
        }
    }
}