//! Golden vectors produced by the C++ implementation (CryptoPP + cereal)
//! in `omnivox-ref/cppgen.cpp`. The Rust leaves must reproduce these bytes.

use omnivox::{AeadPacket, Cereal, decrypt, derive_encrypt_key, encrypt_with_nonce};

fn vectors() -> Vec<(String, String)> {
    include_str!("vectors.txt")
        .lines()
        .filter_map(|l| l.split_once('='))
        .map(|(k, v)| (k.to_owned(), v.to_owned()))
        .collect()
}

fn get<'a>(vs: &'a [(String, String)], key: &str) -> &'a str {
    vs.iter()
        .find(|(k, _)| k == key)
        .unwrap_or_else(|| panic!("missing vector {key}"))
        .1
        .as_str()
}

fn unhex(s: &str) -> Vec<u8> {
    (0..s.len())
        .step_by(2)
        .map(|i| u8::from_str_radix(&s[i..i + 2], 16).unwrap())
        .collect()
}

#[test]
fn scrypt_key_matches_cpp_default_params() {
    let vs = vectors();
    let pw = b"SecurePassword123";
    let salt: Vec<u8> = (1u8..=8).collect();
    let key = derive_encrypt_key(pw, &salt, 17, 8, 1).expect("scrypt");
    assert_eq!(hex(key), get(&vs, "scrypt_key"));
}

#[test]
fn scrypt_key_matches_cpp_short_inputs() {
    let vs = vectors();
    let key = derive_encrypt_key(b"pass", b"salt", 17, 8, 1).expect("scrypt");
    assert_eq!(hex(key), get(&vs, "scrypt_key2"));
}

#[test]
fn empty_inputs_rejected_like_cpp_invalid_argument() {
    assert!(derive_encrypt_key(b"", b"salt", 17, 8, 1).is_err());
    assert!(derive_encrypt_key(b"pw", b"", 17, 8, 1).is_err());
}

#[test]
fn datagram_payload_layout_matches_cereal() {
    struct DatagramPayload {
        id: u16,
        v1: u64,
        payload: Vec<u8>,
    }
    impl Cereal for DatagramPayload {
        fn encode(&self, out: &mut Vec<u8>) {
            out.extend_from_slice(&self.id.to_le_bytes());
            out.extend_from_slice(&self.v1.to_le_bytes());
            omnivox::write_byte_vec(out, &self.payload);
        }
        fn decode(bytes: &[u8]) -> Result<Self, omnivox::CodecError> {
            let mut r = omnivox::Reader::new(bytes);
            Ok(Self {
                id: r.u16()?,
                v1: r.u64()?,
                payload: r.byte_vec()?,
            })
        }
    }

    let vs = vectors();
    let dp = DatagramPayload {
        id: 0x1234,
        v1: 0x1122334455667788,
        payload: b"Hello".to_vec(),
    };
    let mut out = Vec::new();
    dp.encode(&mut out);
    assert_eq!(hex(&out), get(&vs, "cereal_datagram"));
    let back = DatagramPayload::decode(&out).unwrap();
    assert_eq!(
        (back.id, back.v1, back.payload),
        (0x1234, 0x1122334455667788, b"Hello".to_vec())
    );

    let mut zeroed = Vec::new();
    DatagramPayload {
        id: 0,
        v1: 0,
        payload: vec![],
    }
    .encode(&mut zeroed);
    assert_eq!(hex(zeroed), get(&vs, "cereal_datagram_default"));
}

#[test]
fn aead_packet_layout_matches_cereal() {
    let vs = vectors();
    let pkt = AeadPacket {
        nonce: std::array::from_fn(|i| i as u8),
        tag: std::array::from_fn(|i| 0xA0 + i as u8),
        payload: vec![0xDE, 0xAD, 0xBE, 0xEF],
    };
    let mut out = Vec::new();
    pkt.encode(&mut out);
    assert_eq!(hex(&out), get(&vs, "cereal_aead"));
    assert_eq!(AeadPacket::decode(&out).unwrap(), pkt);

    let empty = AeadPacket {
        nonce: [0; 12],
        tag: [0; 16],
        payload: vec![],
    };
    let mut out = Vec::new();
    empty.encode(&mut out);
    assert_eq!(hex(out), get(&vs, "cereal_aead_empty"));
}

#[test]
fn aead_matches_cryptopp_output() {
    let vs = vectors();
    let key: [u8; 32] = unhex(get(&vs, "scrypt_key")).try_into().unwrap();
    let nonce: [u8; 12] = std::array::from_fn(|i| i as u8);

    let pkt = encrypt_with_nonce(&key, &nonce, b"Hello");
    assert_eq!(hex(&pkt.payload), get(&vs, "aead_ct"));
    assert_eq!(hex(pkt.tag), get(&vs, "aead_tag"));
    assert_eq!(decrypt(&key, &pkt).unwrap(), b"Hello");

    let empty = encrypt_with_nonce(&key, &nonce, b"");
    assert_eq!(hex(empty.tag), get(&vs, "aead_empty_tag"));
    assert_eq!(decrypt(&key, &empty).unwrap(), b"");
}

#[test]
fn tampered_packet_fails_authentication() {
    let key = [3u8; 32];
    let mut pkt = omnivox::encrypt(&key, b"important");
    pkt.payload[0] ^= 0x01;
    let err = decrypt(&key, &pkt).unwrap_err();
    assert!(err.to_string().contains("tampered"));
}

fn hex(bytes: impl AsRef<[u8]>) -> String {
    bytes.as_ref().iter().map(|b| format!("{b:02x}")).collect()
}