// Copyright 2003-2015 Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland
// www.source-code.biz, www.inventec.ch/chdh
//
// This module is multi-licensed and may be used under the terms
// of any of the following licenses:
//
//  EPL, Eclipse Public License, V1.0 or later, http://www.eclipse.org/legal
//  LGPL, GNU Lesser General Public License, V2.1 or later, http://www.gnu.org/licenses/lgpl.html
//  GPL, GNU General Public License, V2 or later, http://www.gnu.org/licenses/gpl.html
//  AGPL, GNU Affero General Public License V3 or later, http://www.gnu.org/licenses/agpl.html
//  AL, Apache License, V2.0 or later, http://www.apache.org/licenses
//  BSD, BSD License, http://www.opensource.org/licenses/bsd-license.php
//  MIT, MIT License, http://www.opensource.org/licenses/MIT
//
// Please contact the author if you need another license.
// This module is provided "as is", without warranties of any kind.
//
// Project home page: www.source-code.biz/base64coder
//
// Ported from Java to C# by Martins Andersons.

using ArgumentException = System.ArgumentException;
using Encoding          = System.Text.Encoding;
using Math              = System.Math;
using StringBuilder     = System.Text.StringBuilder;

namespace source_code_biz
{

    /**
    * A Base64 encoder/decoder.
    *
    * <p>
    * This class is used to encode and decode data in Base64 format as described in RFC 1521.
    */
    public class Base64Coder
    {

        // The line separator string of the operating system.
        private static readonly string systemLineSeparator = System.Environment.NewLine;

        static Base64Coder()
        {
            // map1
            int i = 0;
            for (char c = 'A'; c <= 'Z'; c++) map1[i++] = c;
            for (char c = 'a'; c <= 'z'; c++) map1[i++] = c;
            for (char c = '0'; c <= '9'; c++) map1[i++] = c;
            map1[i++] = '+'; map1[i++] = '/';

            // map2
            for (i = 0; i < map2.Length; i++) map2[i] = unchecked((byte)-1);
            for (i = 0; i < 64; i++) map2[map1[i]] = (byte)i;
        }

        // Mapping table from 6-bit nibbles to Base64 characters.
        private static readonly char[] map1 = new char[64];

        // Mapping table from Base64 characters to 6-bit nibbles.
        private static readonly byte[] map2 = new byte[128];

        /**
        * Encodes a string into Base64 format.
        * No blanks or line breaks are inserted.
        * @param s  A String to be encoded.
        * @return   A String containing the Base64 encoded data.
        */
        public static string EncodeString(string s)
        {
            return new string(Encode(Encoding.UTF8.GetBytes(s)));
        }

        /**
        * Encodes a byte array into Base 64 format and breaks the output into lines of 76 characters.
        * @param in  An array containing the data bytes to be encoded.
        * @return    A String containing the Base64 encoded data, broken into lines.
        */
        public static string EncodeLines(byte[] input)
        {
            return EncodeLines(input, 0, input.Length, 76, systemLineSeparator);
        }

        /**
        * Encodes a byte array into Base 64 format and breaks the output into lines.
        * @param in            An array containing the data bytes to be encoded.
        * @param iOff          Offset of the first byte in <code>in</code> to be processed.
        * @param iLen          Number of bytes to be processed in <code>in</code>, starting at <code>iOff</code>.
        * @param lineLen       Line length for the output data. Should be a multiple of 4.
        * @param lineSeparator The line separator to be used to separate the output lines.
        * @return              A String containing the Base64 encoded data, broken into lines.
        */
        public static string EncodeLines(byte[] input, int iOff, int iLen, int lineLen, string lineSeparator)
        {
            int blockLen = (lineLen * 3) / 4;
            if (blockLen <= 0) throw new ArgumentException();
            int lines = (iLen + blockLen - 1) / blockLen;
            int bufLen = ((iLen + 2) / 3) * 4 + lines * lineSeparator.Length;
            StringBuilder buf = new StringBuilder(bufLen);
            int ip = 0;
            while (ip < iLen)
            {
                int l = Math.Min(iLen - ip, blockLen);
                buf.Append(Encode(input, iOff + ip, l));
                buf.Append(lineSeparator);
                ip += l;
            }
            return buf.ToString();
        }

        /**
        * Encodes a byte array into Base64 format.
        * No blanks or line breaks are inserted in the output.
        * @param in  An array containing the data bytes to be encoded.
        * @return    A character array containing the Base64 encoded data.
        */
        public static char[] Encode(byte[] input)
        {
            return Encode(input, 0, input.Length);
        }

        /**
        * Encodes a byte array into Base64 format.
        * No blanks or line breaks are inserted in the output.
        * @param in    An array containing the data bytes to be encoded.
        * @param iLen  Number of bytes to process in <code>in</code>.
        * @return      A character array containing the Base64 encoded data.
        */
        public static char[] Encode(byte[] input, int iLen)
        {
            return Encode(input, 0, iLen);
        }

        /**
        * Encodes a byte array into Base64 format.
        * No blanks or line breaks are inserted in the output.
        * @param in    An array containing the data bytes to be encoded.
        * @param iOff  Offset of the first byte in <code>in</code> to be processed.
        * @param iLen  Number of bytes to process in <code>in</code>, starting at <code>iOff</code>.
        * @return      A character array containing the Base64 encoded data.
        */
        public static char[] Encode(byte[] input, int iOff, int iLen)
        {
            int oDataLen = (iLen * 4 + 2) / 3;       // output length without padding
            int oLen = ((iLen + 2) / 3) * 4;         // output length including padding
            char[] output = new char[oLen];
            int ip = iOff;
            int iEnd = iOff + iLen;
            int op = 0;
            while (ip < iEnd)
            {
                int i0 = input[ip++];
                int i1 = ip < iEnd ? input[ip++] : 0;
                int i2 = ip < iEnd ? input[ip++] : 0;
                int o0 = i0 >> 2;
                int o1 = ((i0 & 3) << 4) | (i1 >> 4);
                int o2 = ((i1 & 0xf) << 2) | (i2 >> 6);
                int o3 = i2 & 0x3F;
                output[op++] = map1[o0];
                output[op++] = map1[o1];
                output[op] = op < oDataLen ? map1[o2] : '='; op++;
                output[op] = op < oDataLen ? map1[o3] : '='; op++;
            }
            return output;
        }

        /**
        * Decodes a string from Base64 format.
        * No blanks or line breaks are allowed within the Base64 encoded input data.
        * @param s  A Base64 String to be decoded.
        * @return   A String containing the decoded data.
        * @throws   ArgumentException If the input is not valid Base64 encoded data.
        */
        public static string DecodeString(string s)
        {
            return Encoding.UTF8.GetString(Decode(s));
        }

        /**
        * Decodes a byte array from Base64 format and ignores line separators, tabs and blanks.
        * CR, LF, Tab and Space characters are ignored in the input data.
        * @param s  A Base64 String to be decoded.
        * @return   An array containing the decoded data bytes.
        * @throws   ArgumentException If the input is not valid Base64 encoded data.
        */
        public static byte[] DecodeLines(string s)
        {
            char[] buf = new char[s.Length];
            int p = 0;
            for (int ip = 0; ip < s.Length; ip++)
            {
                char c = s[ip];
                if (c != ' ' && c != '\r' && c != '\n' && c != '\t')
                    buf[p++] = c;
            }
            return Decode(buf, 0, p);
        }

        /**
        * Decodes a byte array from Base64 format.
        * No blanks or line breaks are allowed within the Base64 encoded input data.
        * @param s  A Base64 string to be decoded.
        * @return   An array containing the decoded data bytes.
        * @throws   ArgumentException If the input is not valid Base64 encoded data.
        */
        public static byte[] Decode(string s)
        {
            return Decode(s.ToCharArray());
        }

        /**
        * Decodes a byte array from Base64 format.
        * No blanks or line breaks are allowed within the Base64 encoded input data.
        * @param in  A character array containing the Base64 encoded data.
        * @return    An array containing the decoded data bytes.
        * @throws    ArgumentException If the input is not valid Base64 encoded data.
        */
        public static byte[] Decode(char[] input)
        {
            return Decode(input, 0, input.Length);
        }

        /**
        * Decodes a byte array from Base64 format.
        * No blanks or line breaks are allowed within the Base64 encoded input data.
        * @param in    A character array containing the Base64 encoded data.
        * @param iOff  Offset of the first character in <code>in</code> to be processed.
        * @param iLen  Number of characters to process in <code>in</code>, starting at <code>iOff</code>.
        * @return      An array containing the decoded data bytes.
        * @throws      ArgumentException If the input is not valid Base64 encoded data.
        */
        public static byte[] Decode(char[] input, int iOff, int iLen)
        {
            if (iLen % 4 != 0) throw new ArgumentException("Length of Base64 encoded input string is not a multiple of 4.");
            while (iLen > 0 && input[iOff + iLen - 1] == '=') iLen--;
            int oLen = (iLen * 3) / 4;
            byte[] output = new byte[oLen];
            int ip = iOff;
            int iEnd = iOff + iLen;
            int op = 0;
            while (ip < iEnd)
            {
                int i0 = input[ip++];
                int i1 = input[ip++];
                int i2 = ip < iEnd ? input[ip++] : 'A';
                int i3 = ip < iEnd ? input[ip++] : 'A';
                if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
                    throw new ArgumentException("Illegal character in Base64 encoded data.");
                int b0 = map2[i0];
                int b1 = map2[i1];
                int b2 = map2[i2];
                int b3 = map2[i3];
                if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
                    throw new ArgumentException("Illegal character in Base64 encoded data.");
                int o0 = (b0 << 2) | (b1 >> 4);
                int o1 = ((b1 & 0xf) << 4) | (b2 >> 2);
                int o2 = ((b2 & 3) << 6) | b3;
                output[op++] = (byte)o0;
                if (op < oLen) output[op++] = (byte)o1;
                if (op < oLen) output[op++] = (byte)o2;
            }
            return output;
        }

    }

}