export default function Base64() {
  // 私钥
  let _keyStr =
    'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
  // 加密
  this.encode = function (input) {
    var output = '';
    var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
    var i = 0;
    input = _utf8_encode(input);
    while (i < input.length) {
      chr1 = input.charCodeAt(i++);
      chr2 = input.charCodeAt(i++);
      chr3 = input.charCodeAt(i++);
      enc1 = chr1 >> 2;
      enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
      enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
      enc4 = chr3 & 63;
      if (isNaN(chr2)) {
        enc3 = enc4 = 64;
      } else if (isNaN(chr3)) {
        enc4 = 64;
      }
      output =
        output +
        _keyStr.charAt(enc1) +
        _keyStr.charAt(enc2) +
        _keyStr.charAt(enc3) +
        _keyStr.charAt(enc4);
    }
    return output;
  };
  // 解密
  this.decode = input => {
    var output = '';
    var chr1, chr2, chr3;
    var enc1, enc2, enc3, enc4;
    var i = 0;
    if (input == undefined || input == null) {
    } else {
      input = input.replace(/[^A-Za-z0-9\+\/\=]/g, '');
      while (i < input.length) {
        enc1 = _keyStr.indexOf(input.charAt(i++));
        enc2 = _keyStr.indexOf(input.charAt(i++));
        enc3 = _keyStr.indexOf(input.charAt(i++));
        enc4 = _keyStr.indexOf(input.charAt(i++));
        chr1 = (enc1 << 2) | (enc2 >> 4);
        chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
        chr3 = ((enc3 & 3) << 6) | enc4;
        output = output + String.fromCharCode(chr1);
        if (enc3 != 64) {
          output = output + String.fromCharCode(chr2);
        }
        if (enc4 != 64) {
          output = output + String.fromCharCode(chr3);
        }
      }
      output = _utf8_decode(output);
      return output;
    }
  };
  // private method for UTF-8 encoding
  let _utf8_encode = string => {
    string = string.replace(/\r\n/g, '\n');
    var utftext = '';
    for (var n = 0; n < string.length; n++) {
      var c = string.charCodeAt(n);
      if (c < 128) {
        utftext += String.fromCharCode(c);
      } else if (c > 127 && c < 2048) {
        utftext += String.fromCharCode((c >> 6) | 192);
        utftext += String.fromCharCode((c & 63) | 128);
      } else {
        utftext += String.fromCharCode((c >> 12) | 224);
        utftext += String.fromCharCode(((c >> 6) & 63) | 128);
        utftext += String.fromCharCode((c & 63) | 128);
      }
    }
    return utftext;
  };
  // private method for UTF-8 decoding
  let _utf8_decode = utftext => {
    var string = '';
    var i = 0;
    var c = (c1 = c2 = 0);
    var c1 = 0;
    var c2 = 0;
    var c3 = 0;
    while (i < utftext.length) {
      c = utftext.charCodeAt(i);
      if (c < 128) {
        string += String.fromCharCode(c);
        i++;
      } else if (c > 191 && c < 224) {
        c2 = utftext.charCodeAt(i + 1);
        string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
        i += 2;
      } else {
        c2 = utftext.charCodeAt(i + 1);
        c3 = utftext.charCodeAt(i + 2);
        string += String.fromCharCode(
          ((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63)
        );
        i += 3;
      }
    }
    return string;
  };
}