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use common::ALPHABET;
/// Substitution Cipher
///
/// The struct is generated through the new() function.
///
pub struct Substitution {
key: &'static str,
}
impl Substitution {
/// Initializes a substitution cipher with a supplied substitute alphabet.
///
/// # Examples
///
/// ```
/// use kryptos::ciphers::substitution::Substitution;
///
/// let s = Substitution::new("RBQIZDJCFMELOPAVNHYGWKTUXS").unwrap();
/// ```
///
/// # Errors
///
/// Will return Err() if the alphabet is not 26 unique alphabetic characters.
///
pub fn new(key: &'static str) -> Result<Self, String> {
if key.chars().count() != 26 {
return Err(String::from("Key is not the correct length"));
}
let mut alphabet_check = String::new();
for c in key.chars() {
if c.is_alphabetic() {
if alphabet_check.contains(c) {
return Err(String::from("Key alphabet must be unique"));
}
alphabet_check.push(c);
continue;
} else {
return Err(String::from("Key must be alphabetic"));
}
}
Ok(Substitution { key })
}
/// Enciphers a message with a substitution cipher.
///
/// # Examples
///
/// ```
/// use kryptos::ciphers::substitution::*;
///
/// let s = Substitution::new("NAKYQRTXBZPFIVEJSDCHGOUMWL").unwrap();
/// assert_eq!(
/// "Ye weg fbpq cqkdqh iqccntqc",
/// s.encipher("Do you like secret messages").unwrap()
/// );
/// ```
///
/// # Panics
///
/// Will panic if there is a missing character or invalid character.
///
pub fn encipher(&self, plaintext: &str) -> Result<String, &'static str> {
Ok(plaintext
.chars()
.map(|c| match c as u8 {
65..=90 => {
let index = ALPHABET.chars().position(|i| i == c).unwrap();
self.key
.chars()
.nth(index)
.expect("Something is wrong with the key alphabet")
}
97..=122 => {
let index = ALPHABET
.chars()
.position(|i| i == char::from(c as u8 - 97 + 65))
.unwrap();
(self
.key
.chars()
.nth(index)
.expect("Something is wrong with the key alphabet")
as u8
- 65
+ 97) as char
}
_ => c,
})
.collect::<String>())
}
/// Deciphers a message with a substitution cipher.
///
/// # Examples
///
/// ```
/// use kryptos::ciphers::substitution::*;
///
/// let s = Substitution::new("NAKYQRTXBZPFIVEJSDCHGOUMWL").unwrap();
/// assert_eq!(
/// "Do you like secret messages",
/// s.decipher("Ye weg fbpq cqkdqh iqccntqc").unwrap()
/// );
/// ```
///
/// # Panics
///
/// Will panic if there is a missing character or invalid character.
///
pub fn decipher(&self, plaintext: &str) -> Result<String, &'static str> {
Ok(plaintext
.chars()
.map(|c| match c as u8 {
65..=90 => {
let index = self.key.chars().position(|i| i == c).unwrap();
ALPHABET
.chars()
.nth(index)
.expect("Something is wrong with the key alphabet")
}
97..=122 => {
let index = self
.key
.chars()
.position(|i| i == char::from(c as u8 - 97 + 65))
.unwrap();
(ALPHABET
.chars()
.nth(index)
.expect("Something is wrong with the key alphabet")
as u8
- 65
+ 97) as char
}
_ => c,
})
.collect::<String>())
}
}
#[cfg(test)]
mod tests {
use super::Substitution;
#[test]
fn unique_alphabet() {
assert!(Substitution::new("RBQIZDJCFMELOPAVNHYGWKTUXS").is_ok());
}
#[test]
fn non_unique_alphabet() {
assert!(Substitution::new("ABCDEFGHIJKLMNOPQRSTUVWXAZ").is_err());
}
#[test]
fn non_alphabetic() {
assert!(Substitution::new("RBQI1DJCFMELOPAVNHYGWKTUXS").is_err());
}
#[test]
fn too_small_alphabet() {
assert!(Substitution::new("ABC").is_err());
}
#[test]
fn too_large_alphabet() {
assert!(Substitution::new("ABCDEFGHIJKLMNOPQRSTUVWXYZA").is_err());
}
#[test]
fn encipher() {
let s = Substitution::new("NAKYQRTXBZPFIVEJSDCHGOUMWL").unwrap();
assert_eq!(
"Ye weg fbpq cqkdqh iqccntqc",
s.encipher("Do you like secret messages").unwrap()
);
}
#[test]
fn with_punctuation() {
let s = Substitution::new("NAKYQRTXBZPFIVEJSDCHGOUMWL").unwrap();
assert_eq!(
"Ye weg fbpq cqkdqh iqccntqc?",
s.encipher("Do you like secret messages?").unwrap()
);
}
#[test]
fn with_unicode() {
let s = Substitution::new("NAKYQRTXBZPFIVEJSDCHGOUMWL").unwrap();
assert_eq!(
"Ye weg fbpq cqkdqh 🖤 iqccntqc",
s.encipher("Do you like secret 🖤 messages").unwrap()
);
}
#[test]
fn decipher() {
let s = Substitution::new("NAKYQRTXBZPFIVEJSDCHGOUMWL").unwrap();
assert_eq!(
"Do you like secret messages",
s.decipher("Ye weg fbpq cqkdqh iqccntqc").unwrap()
);
}
}