export default class Base64 {
  // private property
  static _keyStr: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='

  // public method for encoding
  public encode = (input: string) => {
    let output = ''
    let chr1, chr2, chr3, enc1, enc2, enc3, enc4
    let i = 0
    input = this._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 +
        Base64._keyStr.charAt(enc1) +
        Base64._keyStr.charAt(enc2) +
        Base64._keyStr.charAt(enc3) +
        Base64._keyStr.charAt(enc4)
    }
    return output
  }

  // public method for decoding
  public decode = (input: string) => {
    let output = ''
    let chr1, chr2, chr3
    let enc1, enc2, enc3, enc4
    let i = 0
    input = input.replace(/[^A-Za-z0-9+/=]/g, '')
    while (i < input.length) {
      enc1 = Base64._keyStr.indexOf(input.charAt(i++))
      enc2 = Base64._keyStr.indexOf(input.charAt(i++))
      enc3 = Base64._keyStr.indexOf(input.charAt(i++))
      enc4 = Base64._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 = this._utf8_decode(output)
    return output
  }

  // private method for UTF-8 encoding
  private _utf8_encode = (str: string) => {
    str = str.replace(/rn/g, 'n')
    let utftext = ''
    for (let n = 0; n < str.length; n++) {
      const c = str.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
  private _utf8_decode = (utftext: string) => {
    let string = ''
    let i = 0
    let c1, c2, c3
    let c = (c1 = c2 = 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
  }
}