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SassMeister-input.scss

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


// Keyed Caesar cipher
// https://en.wikipedia.org/wiki/Caesar_cipher
// http://rumkin.com/tools/cipher/caesar-keyed.php


// Test whether `$value` is containedd between `$min` and `$max`.
// --------
// @param [number] $min: minimum range value
// @param [number] $max: maximum range value
// @param [number] $value: the value to be tested
// --------
// @return [boolean]

@function is-in-range($min, $max, $value) {
  @return ($value >= $min) and ($value <= $max);
}


// Return a charset string.
// --------
// @param [string] $charset: alpha | alphanum | ascii
// --------
// @return [string]

@function charset($charset) {
  @return map-get((
    alpha:
      'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
    alphanum:
      '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
    ascii:
      '!"#$%&' + "'" +
      '()*+,-./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 `$charset`.
// --------
// @param [string] $str
// @param [number] $index
// @param [string] $charset
// --------
// @return [number]

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


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

@function from-char-code($index, $charset: alpha) {
  $chars: if(index((alpha alphanum ascii), $charset), charset($charset), $charset);
  @return char-at($chars, $index);
}


// Return a keyed alphabet.
// --------
// @param [string] $key
// --------
// @return [string]

@function keyed-alpha($key) {
  $alpha: str-slice(charset(alpha), -26);
  $key: to-lower-case($key) + $alpha;
  $result: '';

  @for $i from 1 through str-length($key)  {
    $c: char-at($key, $i);
    @if str-index($alpha, $c) and not str-index($result, $c) {
      $result: $result + $c;
    }
  }

  @return to-upper-case($result) + $result;
}


// Caesar cipher encoder/decoder.
// --------
// @param [string] $message
// @param [number] $shift
// @param [string] $op: encrypt | decrypt
// @param [string] $charset
// --------
// @return [string]

@function caesar(
  $message,
  $shift: 1,
  $op: 'encrypt',
  $charset: alpha
) {
  @if type-of($shift) != number {
    @warn '`$shift` must be a number, type-of($shift) given.';
  }
  @if not is-in-range(0, 26, abs($shift)) {
    @warn '`$shift` must in range [0-26].';
  }

  $result: '';

  @if $op == 'decrypt' {
   $shift: (26 - $shift);
  }

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

    @if $code {
      // Uppercase $col <= 26
      // Lowercase $col > 26
      $start: if($code > 26, 27, 1);
      $match: ((($code - $start) + $shift) % 26) + $start;
      $result: $result + from-char-code($match, $charset);
    }
    @else {
      // Non [A-Za-z] char.
      $result: $result + char-at($message, $i);
    }
  }

  @return $result;
}


// Keyed Caesar cipher encoder/decoder.
// --------
// @param [string] $message
// @param [string] $key
// @param [number] $shift
// @param [string] $op: encrypt | decrypt
// --------
// @return [string]

@function caesar-keyed(
  $message,
  $key,
  $shift: 1,
  $op: 'encrypt'
) {
  $charset: keyed-alpha($key);

  @return caesar($message, $shift, $op, $charset);
}



// Tests
caesar {
  $fixture: (
    ('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz', 'berlin', 13, 'KMOPQSTUVWXYZBERLINACDFGHJkmopqstuvwxyzberlinacdfghj'),
    ('Caesar cipher', 'Amiens', 3, 'Secveu shrgcu'),
    ('Keyed Caesar cipher', 'Cayeux', 6, 'Nhuhg Fbhwbv flskhv')
  );
  
  /* Encrypt */
  $tests: '';
  @each $test in $fixture {
    $pass: caesar-keyed(nth($test, 1), nth($test, 2), nth($test, 3)) == nth($test, 4);
    $tests: $tests + if($pass, '✔ ', 'X ');
  }
  tests: $tests;
  
  /* Decrypt */
  $tests: '';
  @each $test in $fixture {
    $pass: caesar-keyed(nth($test, 4), nth($test, 2), nth($test, 3), 'decrypt') == nth($test, 1);
    $tests: $tests + if($pass, '✔ ', 'X ');
  }
  tests: $tests;
  
  t: caesar-keyed('a', 'b', 3);
  t: caesar-keyed('d', 'b', 3, 'decrypt');
}

SassMeister-output.css

@charset "UTF-8";
caesar {
  /* Encrypt */
  tests: "✔ ✔ ✔ ";
  /* Decrypt */
  tests: "X X X ";
  t: "d";
  t: "b";
}