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mod r5_cpa_kem;

use crate::parameters::Parameters;
use crate::kem::r5_cpa_kem::{r5_cpa_kem_keygen, r5_cpa_kem_encapsulate, r5_cpa_kem_decapsulate};
use crate::types::Random;
#[cfg(feature="support-snow")]
use crate::types::Kem;


pub struct R5Kem {
    params: Parameters,
    pk: Option<Vec<u8>>,
    sk: Option<Vec<u8>>
}

impl R5Kem {
    pub fn new(params: Parameters) -> R5Kem {
        R5Kem { params, pk: None, sk: None }
    }

    pub fn default() -> R5Kem {
        let params = Parameters::r5n1_1_kem_0d();
        R5Kem { params, pk: None, sk: None }
    }

    pub fn public(&self) -> &[u8] {
        self.pk.as_ref().expect("You should call .keypair() before you take the pubkey")
    }

    pub fn keypair(&mut self, rng: &mut dyn Random) {
        self.pk = Some(vec![0u8; self.params.c_pk]);
        self.sk = Some(vec![0u8; self.params.c_sk]);
        r5_cpa_kem_keygen(self.pk.as_mut().unwrap(), self.sk.as_mut().unwrap(), rng, &self.params);
    }
    
    pub fn enc(&self, pubkey: &[u8], rng: &mut dyn Random) -> (Vec<u8>, Vec<u8>) {
        r5_cpa_kem_encapsulate(pubkey, rng, &self.params)
    }

    pub fn dec(&self, ciphertext: &[u8]) -> Vec<u8> {
        r5_cpa_kem_decapsulate(ciphertext, self.sk.as_ref().unwrap(), &self.params)
    }

}

#[cfg(feature = "support-snow")]
impl Kem for R5Kem {
    fn name(&self) -> &'static str {
        self.params.name
    }

    fn pub_len(&self) -> usize {
        self.params.pk_size as usize
    }

    fn ciphertext_len(&self) -> usize {
        self.params.ct_size as usize
    }

    fn shared_secret_len(&self) -> usize {
        self.params.c_b
    }

    fn generate(&mut self, rng: &mut dyn Random) {
        self.keypair(rng);
    }

    fn pubkey(&self) -> &[u8] {
        self.public()
    }

    fn encapsulate(
        &self,
        pubkey: &[u8],
        shared_secret_out: &mut [u8],
        ciphertext_out: &mut [u8],
        rng: &mut dyn Random
    ) -> Result<(usize, usize), ()> {
        let (shared_secret, ciphertext) = self.enc(pubkey, rng);
        shared_secret_out.copy_from_slice(shared_secret.as_slice());
        ciphertext_out.copy_from_slice(ciphertext.as_slice());
        Ok((shared_secret.len(), ciphertext.len()))
    }

    fn decapsulate(&self, ciphertext: &[u8], shared_secret_out: &mut [u8]) -> Result<usize, ()> {
        let shared_secret = self.dec(ciphertext);
        shared_secret_out.copy_from_slice(shared_secret.as_slice());
        Ok(shared_secret.len())
    }
}