//! Pseudo Random Functions (PRFs) with a tree-like label scheme which
//! ensures their uniqueness

use {
    crate::{prftree::PrfTree, sodium::KEY_SIZE},
    anyhow::Result,
};

pub fn protocol() -> Result<PrfTree> {
    PrfTree::zero().mix("Rosenpass v1 mceliece460896 Kyber512 ChaChaPoly1305 BLAKE2s".as_bytes())
}

// TODO Use labels that can serve as identifiers
macro_rules! prflabel {
    ($base:ident, $name:ident, $($lbl:expr),* ) => {
        pub fn $name() -> Result<PrfTree> {
            let t = $base()?;
            $( let t = t.mix($lbl.as_bytes())?; )*
            Ok(t)
        }
    }
}

prflabel!(protocol, mac,        "mac");
prflabel!(protocol, cookie,     "cookie");
prflabel!(protocol, peerid,     "peer id");
prflabel!(protocol, biscuit_ad, "biscuit additional data");
prflabel!(protocol, ckinit,     "chaining key init");
prflabel!(protocol, _ckextract,  "chaining key extract");

macro_rules! prflabel_leaf {
    ($base:ident, $name:ident, $($lbl:expr),* ) => {
        pub fn $name() -> Result<[u8; KEY_SIZE]> {
            let t = $base()?;
            $( let t = t.mix($lbl.as_bytes())?; )*
            Ok(t.into_value())
        }
    }
}

prflabel_leaf!(_ckextract, mix,        "mix");
prflabel_leaf!(_ckextract, hs_enc,     "handshake encryption");
prflabel_leaf!(_ckextract, ini_enc,    "initiator handshake encryption");
prflabel_leaf!(_ckextract, res_enc,    "responder handshake encryption");

prflabel!(_ckextract, _user, "user");
prflabel!(_user, _rp, "rosenpass.eu");
prflabel_leaf!(_rp, osk, "wireguard psk");