//! Rivest–Shamir–Adleman (RSA) public keys.

use crate::{
    decoder::{Decode, Decoder},
    encoder::{Encode, Encoder},
    MPInt, Result,
};

/// RSA public key.
///
/// Described in [RFC4253 § 6.6](https://datatracker.ietf.org/doc/html/rfc4253#section-6.6):
#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
pub struct RsaPublicKey {
    /// RSA public exponent.
    pub e: MPInt,

    /// RSA modulus.
    pub n: MPInt,
}

impl RsaPublicKey {
    /// Borrow the bytes used to compute a "checkint" for this key.
    ///
    /// This is a sort of primitive pseudo-MAC used by the OpenSSH key format.
    pub(super) fn checkint_bytes(&self) -> &[u8] {
        self.n.as_bytes()
    }
}

impl Decode for RsaPublicKey {
    fn decode(decoder: &mut impl Decoder) -> Result<Self> {
        let e = MPInt::decode(decoder)?;
        let n = MPInt::decode(decoder)?;
        Ok(Self { e, n })
    }
}

impl Encode for RsaPublicKey {
    fn encoded_len(&self) -> Result<usize> {
        Ok(self.e.encoded_len()? + self.n.encoded_len()?)
    }

    fn encode(&self, encoder: &mut impl Encoder) -> Result<()> {
        self.e.encode(encoder)?;
        self.n.encode(encoder)
    }
}