use crate::util;

pub struct AtabashChipher {
    alphabet: Vec<char>,
}

impl AtabashChipher {
    pub fn new(alphabet: impl Into<Vec<char>>) -> anyhow::Result<Self> {
        let alphabet = alphabet.into();

        util::verify_alphabet(&alphabet)?;

        Ok(Self { alphabet })
    }

    pub fn encode(&self, input: &str) -> anyhow::Result<String> {
        let mut output = String::with_capacity(input.len());

        for c in input.chars() {
            let index = self
                .alphabet
                .iter()
                .position(|&x| x == c)
                .ok_or(anyhow::anyhow!("cannot encode character {:?}", c))?;
            output.push(self.alphabet[self.alphabet.len() - index - 1]);
        }

        Ok(output)
    }

    pub fn decode(&self, input: &str) -> anyhow::Result<String> {
        self.encode(input)
    }
}