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mod error;
mod field;
mod shamir;
mod util;

pub use error::Error;

pub fn split_secret(
    threshold: u8,
    share_count: u8,
    shared_secret: &[u8],
) -> Result<Vec<Vec<u8>>, error::Error> {
    let splitter = shamir::Splitter::new(None);
    let proto_share = shamir::Share::new()?;
    let shares = splitter
        .split_secret(&proto_share, threshold, share_count, shared_secret)?
        .into_iter()
        .map(|s| s.to_u8_vec())
        .collect::<Result<Vec<_>, _>>()?;

    Ok(shares)
}

pub fn recover_secret<'a, I>(shares: I) -> Result<Vec<u8>, error::Error>
where
    I: IntoIterator<Item = &'a [u8]>,
{
    let shares = shares
        .into_iter()
        .map(shamir::Share::from_u8_vec)
        .collect::<Result<Vec<_>, _>>()?;

    let splitter = shamir::Splitter::new(None);
    let secret = splitter.recover_secret(&shares)?;

    Ok(secret)
}

#[cfg(test)]
mod tests {
    use super::*;
    use rand::{prelude::SliceRandom, thread_rng};

    #[test]
    fn split_recover() -> Result<(), error::Error> {
        let secret = util::fill_vec_rand(100);
        let shares = split_secret(5, 10, &secret)?;
        let mut subset = shares.clone();
        subset.shuffle(&mut thread_rng());
        subset.truncate(5);
        let recovered = recover_secret(subset.iter().map(|s| s.as_slice()))?;
        assert_eq!(secret, recovered);
        Ok(())
    }
}