use anyhow::Result;
use clap::Subcommand;
#[derive(Subcommand)]
pub enum GronsfeldAction {
#[command(about = "Encrypt with Gronsfeld cipher")]
Encrypt {
#[arg(help = "Input text")]
input: String,
#[arg(short, long, help = "Numeric key (digits only, e.g., \"31415\")")]
key: String,
},
#[command(about = "Decrypt Gronsfeld cipher")]
Decrypt {
#[arg(help = "Encrypted text")]
input: String,
#[arg(short, long, help = "Numeric key (digits only, e.g., \"31415\")")]
key: String,
},
}
pub fn run(action: GronsfeldAction) -> Result<()> {
match action {
GronsfeldAction::Encrypt { input, key } => {
println!("{}", encrypt(&input, &key)?);
}
GronsfeldAction::Decrypt { input, key } => {
println!("{}", decrypt(&input, &key)?);
}
}
Ok(())
}
fn validate_key(key: &str) -> Result<Vec<u8>> {
if key.is_empty() {
anyhow::bail!("Key must be non-empty");
}
if !key.chars().all(|c| c.is_ascii_digit()) {
anyhow::bail!("Key must contain only digits (0-9)");
}
Ok(key.bytes().map(|b| b - b'0').collect())
}
pub fn encrypt(input: &str, key: &str) -> Result<String> {
let shifts = validate_key(key)?;
let mut key_index = 0;
Ok(input
.chars()
.map(|c| {
if c.is_ascii_alphabetic() {
let base = if c.is_ascii_uppercase() { b'A' } else { b'a' };
let shift = shifts[key_index % shifts.len()];
key_index += 1;
((c as u8 - base + shift) % 26 + base) as char
} else {
c
}
})
.collect())
}
pub fn decrypt(input: &str, key: &str) -> Result<String> {
let shifts = validate_key(key)?;
let mut key_index = 0;
Ok(input
.chars()
.map(|c| {
if c.is_ascii_alphabetic() {
let base = if c.is_ascii_uppercase() { b'A' } else { b'a' };
let shift = shifts[key_index % shifts.len()];
key_index += 1;
((c as u8 - base + 26 - shift) % 26 + base) as char
} else {
c
}
})
.collect())
}