// Base64 encoder/decoder with UTF-8 support
//
// Copyright (c) 2011 Vitaly Puzrin
// Copyright (c) 2011 Aleksey V Zapparov
//
// Author: Aleksey V Zapparov AKA ixti (http://www.ixti.net/)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.


// Based on original artworks of base64 encoder/decoder by [Mozilla][1]
// [1]: http://lxr.mozilla.org/mozilla/source/extensions/xml-rpc/src/nsXmlRpcClient.js


'use strict';

/* eslint-env browser */
/* eslint-disable no-bitwise */

function noop() {}

var logger   = { warn: noop, error: noop },
    padding  = '=',
    chrTable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz' +
               '0123456789+/',
    binTable = [
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1,  0, -1, -1,
      -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
      15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
      -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
      41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
    ];

if (window.console) {
  logger = window.console;
  logger.warn = logger.warn || logger.error || logger.log || noop;
  logger.error = logger.error || logger.warn || logger.log || noop;
}

// internal helpers //////////////////////////////////////////////////////////

function utf8Encode(str) {
  var bytes = [], offset = 0, length, char;

  str = encodeURI(str);
  length = str.length;

  while (offset < length) {
    char = str.charAt(offset);
    offset += 1;

    if (char !== '%') {
      bytes.push(char.charCodeAt(0));
    } else {
      char = str.charAt(offset) + str.charAt(offset + 1);
      bytes.push(parseInt(char, 16));
      offset += 2;
    }
  }

  return bytes;
}

function utf8Decode(bytes) {
  var chars = [], offset = 0, length = bytes.length, c1, c2, c3;

  while (offset < length) {
    c1 = bytes[offset];
    c2 = bytes[offset + 1];
    c3 = bytes[offset + 2];

    if (c1 < 128) {
      chars.push(String.fromCharCode(c1));
      offset += 1;
    } else if (191 < c1 && c1 < 224) {
      chars.push(String.fromCharCode(((c1 & 31) << 6) | (c2 & 63)));
      offset += 2;
    } else {
      chars.push(String.fromCharCode(((c1 & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63)));
      offset += 3;
    }
  }

  return chars.join('');
}

// public api ////////////////////////////////////////////////////////////////

function encode(str) {
  var result = '',
      bytes = utf8Encode(str),
      length = bytes.length,
      i;

  // Convert every three bytes to 4 ascii characters.
  for (i = 0; i < (length - 2); i += 3) {
    result += chrTable[bytes[i] >> 2];
    result += chrTable[((bytes[i] & 0x03) << 4) + (bytes[i + 1] >> 4)];
    result += chrTable[((bytes[i + 1] & 0x0f) << 2) + (bytes[i + 2] >> 6)];
    result += chrTable[bytes[i + 2] & 0x3f];
  }

  // Convert the remaining 1 or 2 bytes, pad out to 4 characters.
  if (length % 3) {
    i = length - (length % 3);
    result += chrTable[bytes[i] >> 2];
    if ((length % 3) === 2) {
      result += chrTable[((bytes[i] & 0x03) << 4) + (bytes[i + 1] >> 4)];
      result += chrTable[(bytes[i + 1] & 0x0f) << 2];
      result += padding;
    } else {
      result += chrTable[(bytes[i] & 0x03) << 4];
      result += padding + padding;
    }
  }

  return result;
}

function decode(data) {
  var value, code, idx = 0,
      bytes = [],
      leftbits = 0, // number of bits decoded, but yet to be appended
      leftdata = 0; // bits decoded, but yet to be appended

  // Convert one by one.
  for (idx = 0; idx < data.length; idx += 1) {
    code = data.charCodeAt(idx);
    value = binTable[code & 0x7F];

    if (value === -1) {
      // Skip illegal characters and whitespace
      logger.warn('Illegal characters (code=' + code + ') in position ' + idx);
    } else {
      // Collect data into leftdata, update bitcount
      leftdata = (leftdata << 6) | value;
      leftbits += 6;

      // If we have 8 or more bits, append 8 bits to the result
      if (leftbits >= 8) {
        leftbits -= 8;
        // Append if not padding.
        if (padding !== data.charAt(idx)) {
          bytes.push((leftdata >> leftbits) & 0xFF);
        }
        leftdata &= (1 << leftbits) - 1;
      }
    }
  }

  // If there are any bits left, the base64 string was corrupted
  if (leftbits) {
    logger.error('Corrupted base64 string');
    return null;
  }

  return utf8Decode(bytes);
}

exports.encode = encode;
exports.decode = decode;
