#![allow(dead_code)] // TODO: remove

use super::SymKey;
use crate::{
    err::{Error, Res},
    hpke::{Aead, Kdf},
};
use hkdf::Hkdf as HkdfImpl;
use log::trace;
use sha2::{Sha256, Sha384, Sha512};

#[derive(Clone, Copy)]
pub enum KeyMechanism {
    Aead(Aead),
    #[allow(dead_code)] // We don't use this one.
    Hkdf,
}

impl KeyMechanism {
    fn len(self) -> usize {
        match self {
            Self::Aead(a) => a.n_k(),
            Self::Hkdf => 0, // Let the underlying module decide.
        }
    }
}

pub enum Hkdf {
    Sha256,
    Sha384,
    Sha512,
}

impl Hkdf {
    pub fn new(kdf: Kdf) -> Self {
        match kdf {
            Kdf::HkdfSha256 => Self::Sha256,
            Kdf::HkdfSha384 => Self::Sha384,
            Kdf::HkdfSha512 => Self::Sha512,
        }
    }

    #[cfg(test)]
    #[allow(clippy::unnecessary_wraps)]
    pub fn import_ikm(ikm: &[u8]) -> Res<SymKey> {
        Ok(SymKey::from(ikm))
    }

    #[allow(clippy::unnecessary_wraps)]
    pub fn extract(&self, salt: &[u8], ikm: &SymKey) -> Res<SymKey> {
        let prk = match self {
            Self::Sha256 => {
                SymKey::from(HkdfImpl::<Sha256>::extract(Some(salt), &ikm.0).0.as_slice())
            }
            Self::Sha384 => {
                SymKey::from(HkdfImpl::<Sha384>::extract(Some(salt), &ikm.0).0.as_slice())
            }
            Self::Sha512 => {
                SymKey::from(HkdfImpl::<Sha512>::extract(Some(salt), &ikm.0).0.as_slice())
            }
        };
        trace!(
            "HKDF extract: salt={} ikm={:?} prk={:?}",
            hex::encode(salt),
            ikm,
            prk
        );
        Ok(prk)
    }

    pub fn expand_key(&self, prk: &SymKey, info: &[u8], key_mech: KeyMechanism) -> Res<SymKey> {
        let okm = SymKey::from(self.expand_data(prk, info, key_mech.len())?);
        trace!(
            "HKDF expand_key: prk={:?} info={} okm={:?}",
            prk,
            hex::encode(info),
            okm,
        );
        Ok(okm)
    }

    pub fn expand_data(&self, prk: &SymKey, info: &[u8], len: usize) -> Res<Vec<u8>> {
        let mut okm = vec![0; len];
        match self {
            Self::Sha256 => {
                let h = HkdfImpl::<Sha256>::from_prk(&prk.0).map_err(|_| Error::Internal)?;
                h.expand(info, &mut okm).map_err(|_| Error::Internal)?;
            }
            Self::Sha384 => {
                let h = HkdfImpl::<Sha384>::from_prk(&prk.0).map_err(|_| Error::Internal)?;
                h.expand(info, &mut okm).map_err(|_| Error::Internal)?;
            }
            Self::Sha512 => {
                let h = HkdfImpl::<Sha512>::from_prk(&prk.0).map_err(|_| Error::Internal)?;
                h.expand(info, &mut okm).map_err(|_| Error::Internal)?;
            }
        }
        trace!(
            "HKDF expand_data: prk={:?} info={} len={} okm={:?}",
            prk,
            hex::encode(info),
            len,
            hex::encode(&okm),
        );
        Ok(okm)
    }
}

#[cfg(test)]
mod test {
    use super::{super::super::hpke::Kdf, Hkdf};
    use crate::init;

    fn sha256_example(
        ikm: &[u8],
        salt: &[u8],
        info: &[u8],
        l: usize,
        expected_prk: &[u8],
        expected_okm: &[u8],
    ) {
        init();
        let hkdf = Hkdf::new(Kdf::HkdfSha256);
        let k_ikm = Hkdf::import_ikm(ikm).unwrap();
        let prk = hkdf.extract(salt, &k_ikm).unwrap();
        let prk_data = prk.key_data().unwrap();
        assert_eq!(prk_data, expected_prk);

        let out = hkdf.expand_data(&prk, info, l).unwrap();
        assert_eq!(&out[..], expected_okm);
    }

    /// Example 1 from <https://tools.ietf.org/html/rfc5869#appendix-A.1>
    #[test]
    fn example1() {
        const IKM: &[u8] = &[
            0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
            0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
        ];
        const SALT: &[u8] = &[
            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c,
        ];
        const INFO: &[u8] = &[0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9];
        const L: usize = 42;
        const PRK: &[u8] = &[
            0x07, 0x77, 0x09, 0x36, 0x2c, 0x2e, 0x32, 0xdf, 0x0d, 0xdc, 0x3f, 0x0d, 0xc4, 0x7b,
            0xba, 0x63, 0x90, 0xb6, 0xc7, 0x3b, 0xb5, 0x0f, 0x9c, 0x31, 0x22, 0xec, 0x84, 0x4a,
            0xd7, 0xc2, 0xb3, 0xe5,
        ];
        const OKM: &[u8] = &[
            0x3c, 0xb2, 0x5f, 0x25, 0xfa, 0xac, 0xd5, 0x7a, 0x90, 0x43, 0x4f, 0x64, 0xd0, 0x36,
            0x2f, 0x2a, 0x2d, 0x2d, 0x0a, 0x90, 0xcf, 0x1a, 0x5a, 0x4c, 0x5d, 0xb0, 0x2d, 0x56,
            0xec, 0xc4, 0xc5, 0xbf, 0x34, 0x00, 0x72, 0x08, 0xd5, 0xb8, 0x87, 0x18, 0x58, 0x65,
        ];
        sha256_example(IKM, SALT, INFO, L, PRK, OKM);
    }

    /// Example 2 from <https://tools.ietf.org/html/rfc5869#appendix-A.2>
    #[test]
    fn example2() {
        const IKM: &[u8] = &[
            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d,
            0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b,
            0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29,
            0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
            0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45,
            0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
        ];
        const SALT: &[u8] = &[
            0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d,
            0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x7b,
            0x7c, 0x7d, 0x7e, 0x7f, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
            0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
            0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5,
            0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
        ];
        const INFO: &[u8] = &[
            0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd,
            0xbe, 0xbf, 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xcb,
            0xcc, 0xcd, 0xce, 0xcf, 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9,
            0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf, 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
            0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5,
            0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
        ];
        const L: usize = 82;
        const PRK: &[u8] = &[
            0x06, 0xa6, 0xb8, 0x8c, 0x58, 0x53, 0x36, 0x1a, 0x06, 0x10, 0x4c, 0x9c, 0xeb, 0x35,
            0xb4, 0x5c, 0xef, 0x76, 0x00, 0x14, 0x90, 0x46, 0x71, 0x01, 0x4a, 0x19, 0x3f, 0x40,
            0xc1, 0x5f, 0xc2, 0x44,
        ];
        const OKM: &[u8] = &[
            0xb1, 0x1e, 0x39, 0x8d, 0xc8, 0x03, 0x27, 0xa1, 0xc8, 0xe7, 0xf7, 0x8c, 0x59, 0x6a,
            0x49, 0x34, 0x4f, 0x01, 0x2e, 0xda, 0x2d, 0x4e, 0xfa, 0xd8, 0xa0, 0x50, 0xcc, 0x4c,
            0x19, 0xaf, 0xa9, 0x7c, 0x59, 0x04, 0x5a, 0x99, 0xca, 0xc7, 0x82, 0x72, 0x71, 0xcb,
            0x41, 0xc6, 0x5e, 0x59, 0x0e, 0x09, 0xda, 0x32, 0x75, 0x60, 0x0c, 0x2f, 0x09, 0xb8,
            0x36, 0x77, 0x93, 0xa9, 0xac, 0xa3, 0xdb, 0x71, 0xcc, 0x30, 0xc5, 0x81, 0x79, 0xec,
            0x3e, 0x87, 0xc1, 0x4c, 0x01, 0xd5, 0xc1, 0xf3, 0x43, 0x4f, 0x1d, 0x87,
        ];
        sha256_example(IKM, SALT, INFO, L, PRK, OKM);
    }

    /// Example 3 from <https://tools.ietf.org/html/rfc5869#appendix-A.3>
    #[test]
    fn example3() {
        const IKM: &[u8] = &[
            0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
            0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
        ];
        const SALT: &[u8] = &[];
        const INFO: &[u8] = &[];
        const L: usize = 42;
        const PRK: &[u8] = &[
            0x19, 0xef, 0x24, 0xa3, 0x2c, 0x71, 0x7b, 0x16, 0x7f, 0x33, 0xa9, 0x1d, 0x6f, 0x64,
            0x8b, 0xdf, 0x96, 0x59, 0x67, 0x76, 0xaf, 0xdb, 0x63, 0x77, 0xac, 0x43, 0x4c, 0x1c,
            0x29, 0x3c, 0xcb, 0x04,
        ];
        const OKM: &[u8] = &[
            0x8d, 0xa4, 0xe7, 0x75, 0xa5, 0x63, 0xc1, 0x8f, 0x71, 0x5f, 0x80, 0x2a, 0x06, 0x3c,
            0x5a, 0x31, 0xb8, 0xa1, 0x1f, 0x5c, 0x5e, 0xe1, 0x87, 0x9e, 0xc3, 0x45, 0x4e, 0x5f,
            0x3c, 0x73, 0x8d, 0x2d, 0x9d, 0x20, 0x13, 0x95, 0xfa, 0xa4, 0xb6, 0x1a, 0x96, 0xc8,
        ];
        sha256_example(IKM, SALT, INFO, L, PRK, OKM);
    }
}
