using GostCryptography.Properties;
using System;
using System.Text;

namespace GostCryptography.Asn1.Ber
{
    public static class Asn1Value
    {
        private static byte[] AllocBitArray(int numbits)
        {
            var num = numbits / 8;

            if ((numbits % 8) != 0)
            {
                num++;
            }

            return new byte[num];
        }

        public static byte[] ParseString(string data)
        {
            return ParseString(data, null);
        }

        public static byte[] ParseString(string data, IntHolder numbits)
        {
            char ch;
            int num;
            int num2;
            int num3;
            int num4;
            int num5;

            char ch2 = data[0];
            byte[] buffer;

            switch (ch2)
            {
                case '\'':
                case '"':
                    if (!data.EndsWith("B"))
                    {
                        if (data.EndsWith("H"))
                        {
                            var builder = new StringBuilder();
                            num3 = (data.Length - 3) * 4;
                            buffer = AllocBitArray(num3);
                            builder.Length = 2;
                            num = 1;
                            num2 = 0;
                            ch = '\0';

                            while ((num < data.Length) && (ch != ch2))
                            {
                                ch = data[num++];

                                if (ch != ch2)
                                {
                                    builder[0] = ch;
                                    ch = (num >= data.Length) ? '0' : data[num];
                                    builder[1] = (ch == ch2) ? '0' : ch;
                                    buffer[num2++] = (byte)Convert.ToInt32(builder.ToString(), 0x10);
                                }

                                num++;
                            }
                        }
                        else
                        {
                            if (data[data.Length - 1] != ch2)
                            {
                                throw ExceptionUtility.CryptographicException(Resources.Asn1ValueParseException, data, data.Length - 1);
                            }

                            num3 = (data.Length - 2) * 8;
                            buffer = AllocBitArray(num3);
                            num = 1;
                            ch = '\0';

                            while ((num < data.Length) && (ch != ch2))
                            {
                                ch = data[num];

                                if (ch != ch2)
                                {
                                    buffer[num - 1] = (byte)ch;
                                }

                                num++;
                            }
                        }

                        return SetNumBits(numbits, num3, buffer);
                    }

                    num3 = data.Length - 3;
                    buffer = AllocBitArray(num3);
                    num5 = 0x80;
                    num = 1;
                    num4 = 0;
                    num2 = 0;

                    while (num < data.Length)
                    {
                        ch = data[num];

                        if (ch == '1')
                        {
                            num4 |= num5;
                        }
                        else
                        {
                            if (ch == ch2)
                            {
                                break;
                            }
                            if (ch != '0')
                            {
                                ExceptionUtility.CryptographicException(Resources.Asn1ValueParseException, data, num);
                            }
                        }

                        num5 = num5 >> 1;

                        if (num5 == 0)
                        {
                            buffer[num2++] = (byte)num4;
                            num5 = 0x80;
                            num4 = 0;
                        }

                        num++;
                    }
                    break;
                default:
                    num3 = data.Length * 8;
                    buffer = AllocBitArray(num3);
                    num = 0;

                    while (num < data.Length)
                    {
                        ch = data[num];
                        buffer[num] = (byte)ch;
                        num++;
                    }

                    return SetNumBits(numbits, num3, buffer);
            }

            if (num5 != 0x80)
            {
                buffer[num2] = (byte)num4;
            }

            return SetNumBits(numbits, num3, buffer);
        }

        private static byte[] SetNumBits(IntHolder numbits, int num3, byte[] buffer)
        {
            if (numbits != null)
            {
                numbits.Value = num3;
            }

            return buffer;
        }
    }
}