Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.8)
// Compass (v1.0.0.alpha.19)
// ----


// Return a charset string.
// --------
// @param [string] $charset
// --------
// @return [string]

@function charset(
  $charset
) {
  @return map-get((
    numeric:
      '0123456789',
    alphabetic:
      'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
    alphanumeric:
      '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
    ascii:
      '!"#$%&' + "'" +
      '()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~'
  ), $charset);
}


// Get char at `$index` in `$str`.
// --------
// @param [string] $str
// @param [number] $index
// --------
// @return [string]

@function char-at(
  $str,
  $index: 1
) {
  @return str-slice($str, $index, $index);
}


// Get char code from `$str` at `$index` in range `$charset`.
// --------
// @param [string] $str
// @param [number] $index
// @param [string] $charset
// --------
// @return [number]

@function char-code-at(
  $str,
  $index: 1,
  $charset: alphabetic
) {
  $chars: charset($charset);
  @return str-index($chars, char-at($str, $index));
}


// Get char at `$index` in range `$charset`.
// --------
// @param [number] $index
// @param [string] $charset
// --------
// @return [string]

@function from-char-code(
  $index,
  $charset: alphabetic
) {
  $chars: charset($charset) or $charset;
  @return char-at($chars, $index);
}



// Return a filtered string.
// --------
// @param [string] $str
// --------
// @return [string]

@function str-filter(
  $str,
  $charset: alphabetic
) {
  $chars: charset($charset);
  $result: '';

  @for $i from 1 through str-length($str)  {
    $c: char-at($str, $i);
    @if str-index($chars, $c) {
      $result: $result + $c;
    }
  }

  @return $result;
}






// Returns a `key autokey` key.
// --------
// @param [string] $key
// @param [string] $message
// --------
// @return [string]

@function key-autokey(
  $key,
  $message
) {
  $key: str-filter($key);
  $message: str-filter($message);
  $length: str-length($message);
  $result: '';

  @while str-length($result) < $length {
    $result: $result + $key;
  }

  @return str-slice($result, 1, $length);
}


// Returns a `text autokey` key.
// --------
// @param [string] $key
// @param [string] $message
// --------
// @return [string]

@function text-autokey(
  $key,
  $message
) {
  $key: str-filter($key);
  $message: str-filter($message);
  $length: str-length($message);
  $result: $key + $message;

  @return str-slice($result, 1, $length);
}


// Filter and build a numeric key in range [0-25].
// --------
// @param [string] $key
// --------
// @return [list]

@function key(
  $key
) {
  $result: ();

  @for $i from 1 through str-length($key) {
    $c: char-code-at($key, $i);
    @if $c {
      $result: append($result, ($c - 1) % 26);
    }
  }

  @return $result;
}







// Vigenère cipher encoder/decoder.
// --------
// @param [string] $message
// @param [list] $key
// --------
// @return [string]

@function vigenere(
  $message,
  $key
) {
  $length: length($key);
  $result: '';

  $j: 1;
  @for $i from 1 through str-length($message) {
    $col: char-code-at($message, $i);
    $match: '';

    @if $col {
      // Uppercase $col <= 26
      // Lowercase $col > 26
      $pos: if($col > 26, 27, 1);
      $match: (($col - $pos) + nth($key, (($j - 1) % $length + 1))) % 26 + $pos;
      $match: from-char-code($match);
      $j: $j + 1;
    }
    @else {
      // Non [A-Za-z] char.
      $match: str-slice($message, $i, $i);
    }

    $result: $result + $match;
  }

  @return $result;
}


// Encrypt a `$message` with the vigenère cipher based on `$key`.
// --------
// @param [string] $message
// @param [string] $key
// --------
// @return [string]

@function vigenere-encrypt(
  $message,
  $key
) {
  $key: text-autokey($key, $message);
  @return vigenere($message, key($key));
}


// Decrypt a vigenère encrypted `$message` based on `$key`.
// --------
// @param [string] $message
// @param [string] $key
// --------
// @return [string]

@function vigenere-decrypt(
  $message,
  $key
) {
  $result: '';
  
  //$key: text-autokey($key, $message);
  $key: key($key);
  @for $i from 1 through length($key) {
    $key: set-nth($key, $i, (26 - nth($key, $i) % 26));
  }
  
  @for $i from 1 through str-length($message) {
    $c: char-at($message, $i);
    $t: vigenere($c, nth($key, $i));
    $key: append($key, key($t));
    $result: $result + $t;
  }
  
  @return $result;
}




tests {
  t: vigenere-encrypt('amiens', 'gef');
  t: vigenere-decrypt('gqneza', 'gef');
}

SassMeister-output.css

tests {
  t: "gqneza";
  t: "amieli";
}