//! Package 5 of CUBELinux-2: cubecrypt — encryption + environment (PDF).
//!
//! The PDF's intent: "exploit Null cubes/layers as environment settings that
//! influence how records are read/written." This crate implements that
//! literally:
//!
//! * Key material and the chosen transform live in **Null-cube cells** —
//!   addressable records in the cube, not out-of-band config. A [`CubeEnv`]
//!   references those cells. Re-point an env at a different Null cube and the
//!   *same CZYX coordinate* opens to different plaintext: the spec's headline
//!   property ("same coordinate, different plaintext under different Null
//!   settings") is a direct consequence of where the key lives.
//! * Records are sealed with standard, audited crates (AES-256-GCM,
//!   ChaCha20-Poly1305 — both AEAD; AES-256-XTS behind the `xts` feature).
//!   We never implement a cipher. Every sealed record carries a self-
//!   describing envelope (magic + transform id + nonce + ciphertext) and the
//!   store header is flagged [`HEADER_FLAG_ENCRYPTED`].
//! * Tenant/record-level key selection via [`Selector`] (explicit slot, or
//!   derived from the record coordinate), giving "record-level selectors for
//!   keys/tenants."
//! * Access logs and tamper-evident metadata live in separate Null ranges
//!   via the [`AccessLog`] helper, satisfying the PDF's "space for access
//!   logs ... in separate Null ranges."
//!
//! Bounds: this is the crypto substrate. It does not (yet) integrate with
//! cubefs's mount path or with the cubevm runtime — those are composition
//! layers left as documented extension points. We also do not manage key
//! rotation or a KMS; key material is assumed already strong and stored in
//! the cube.

#![forbid(unsafe_code)]
#![warn(missing_docs)]

pub mod env;
pub mod transform;

pub use env::{CubeEnv, EnvError, Selector, HEADER_FLAG_ENCRYPTED};
pub use transform::{CryptoError, Key, KeySlot, TransformId};

use cubecoords::{CubeHeader, Czyx};
use cubestore::{CubeStore, HashBackend};

/// An append-only access log living in a Null-cube range. Each [`AccessLog`]
/// targets one Null-cube head coordinate and appends fixed-size entries
/// (record coord + op byte + 8-byte timestamp). It is "tamper-evident" in the
/// weak sense that the log itself can be stored encrypted via another
/// [`CubeEnv`]; this type only provides the structure and append/read.
pub struct AccessLog {
    store: CubeStore<HashBackend>,
    head: Czyx,
    next: u8,
}

impl AccessLog {
    /// Bind a log to a Null-cube head coordinate (entries append along X).
    pub fn new(store: CubeStore<HashBackend>, head: Czyx) -> Self {
        AccessLog {
            store,
            head,
            next: 1,
        }
    }

    /// Append one entry: the record touched, an op tag, and a timestamp.
    pub fn append(&mut self, record: Czyx, op: u8, ts: u64) {
        let mut body = Vec::with_capacity(13);
        body.extend_from_slice(&record.pack_u32().to_le_bytes());
        body.push(op);
        body.extend_from_slice(&ts.to_le_bytes());
        let at = Czyx::new(self.head.c, self.head.z, self.head.y, self.next);
        let mut h = CubeHeader::new();
        h.doc_type = Some("access-log".into());
        h.refresh_flags();
        self.store.put_record(at, &h, &body);
        self.next = self.next.wrapping_add(1);
        if self.next == 0 {
            self.next = 1; // never use total-null X
        }
    }

    /// Read back all entries in append order (X = 1..next).
    pub fn entries(&self) -> Vec<(Czyx, u8, u64)> {
        let mut out = Vec::new();
        for x in 1..self.next {
            let at = Czyx::new(self.head.c, self.head.z, self.head.y, x);
            if let Some((_, body)) = self.store.get_record(&at) {
                if body.len() >= 13 {
                    let coord = u32::from_le_bytes([body[0], body[1], body[2], body[3]]);
                    let record = Czyx::unpack_u32(coord);
                    let op = body[4];
                    let ts = u64::from_le_bytes(body[5..13].try_into().unwrap());
                    out.push((record, op, ts));
                }
            }
        }
        out
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use cubestore::HashBackend;

    #[test]
    fn seal_open_roundtrips_per_transform() {
        let key = transform::derive_key(b"strong-key-material-bytes", b"salt");
        for t in [
            TransformId::None,
            TransformId::Aes256Gcm,
            TransformId::ChaCha20Poly1305,
        ] {
            let pt = b"the same CZYX means different plaintext per env";
            let env = transform::seal(t, &key, pt);
            let back = transform::open(&key, &env).unwrap();
            assert_eq!(back, pt);
            // envelope is self-describing
            assert_eq!(&env[0..4], transform::MAGIC);
            assert_eq!(env[4], t as u8);
        }
    }

    #[test]
    fn wrong_key_fails_auth() {
        let key = transform::derive_key(b"key-A-material", b"salt");
        let wrong = transform::derive_key(b"key-B-material", b"salt");
        let env = transform::seal(TransformId::Aes256Gcm, &key, b"secret");
        assert!(transform::open(&wrong, &env).is_err());
    }

    #[test]
    fn same_coord_different_plaintext_under_different_env() {
        // Two envs point at different Null-cube key cells; encrypting the SAME
        // record coordinate yields different ciphertext and different
        // recoverable plaintext — the PDF's headline property.
        let mut store = CubeStore::new(HashBackend::new());
        let key_a = Czyx::new(0, 1, 0, 1); // Null cube 1
        let key_b = Czyx::new(0, 1, 0, 2); // Null cube 2
        store.put_record(
            key_a,
            &CubeHeader::new(),
            b"environment-A-root-key-32bytes!!",
        );
        store.put_record(
            key_b,
            &CubeHeader::new(),
            b"environment-B-root-key-32bytes!!",
        );

        let env_a = CubeEnv::new(
            vec![KeySlot {
                key_cell: key_a,
                transform: TransformId::Aes256Gcm,
                salt: vec![],
            }],
            vec![],
        );
        let env_b = CubeEnv::new(
            vec![KeySlot {
                key_cell: key_b,
                transform: TransformId::ChaCha20Poly1305,
                salt: vec![],
            }],
            vec![],
        );

        let record_a = Czyx::new(3, 7, 9, 11);
        let record_b = Czyx::new(3, 7, 9, 12);
        env_a
            .put_encrypted(
                &mut store,
                record_a,
                Selector::Slot(0),
                b"alpha",
                CubeHeader::new(),
            )
            .unwrap();
        env_b
            .put_encrypted(
                &mut store,
                record_b,
                Selector::Slot(0),
                b"beta",
                CubeHeader::new(),
            )
            .unwrap();

        // Cross-reading fails: env_a's key/transform cannot open env_b's
        // record and vice-versa (different Null-cube key material).
        assert!(env_a
            .get_decrypted(&store, record_b, Selector::Slot(0))
            .is_err());
        assert!(env_b
            .get_decrypted(&store, record_a, Selector::Slot(0))
            .is_err());

        // Each env recovers only its own plaintext.
        assert_eq!(
            env_a
                .get_decrypted(&store, record_a, Selector::Slot(0))
                .unwrap(),
            b"alpha"
        );
        assert_eq!(
            env_b
                .get_decrypted(&store, record_b, Selector::Slot(0))
                .unwrap(),
            b"beta"
        );
    }

    #[test]
    fn selector_from_coord_picks_slot_by_class() {
        let mut store = CubeStore::new(HashBackend::new());
        let keys = [Czyx::new(0, 2, 0, 1), Czyx::new(0, 2, 0, 2)];
        store.put_record(
            keys[0],
            &CubeHeader::new(),
            b"slot-zero-key-material-32bytes.ok",
        );
        store.put_record(
            keys[1],
            &CubeHeader::new(),
            b"slot-one-key-material-32bytes.ok",
        );
        let env = CubeEnv::new(
            vec![
                KeySlot {
                    key_cell: keys[0],
                    transform: TransformId::Aes256Gcm,
                    salt: vec![],
                },
                KeySlot {
                    key_cell: keys[1],
                    transform: TransformId::Aes256Gcm,
                    salt: vec![],
                },
            ],
            vec![],
        );
        // c=0 -> slot 0, c=1 -> slot 1
        let r0 = Czyx::new(0, 5, 5, 5);
        let r1 = Czyx::new(1, 5, 5, 5);
        env.put_encrypted(
            &mut store,
            r0,
            Selector::FromCoord(r0),
            b"p0",
            CubeHeader::new(),
        )
        .unwrap();
        env.put_encrypted(
            &mut store,
            r1,
            Selector::FromCoord(r1),
            b"p1",
            CubeHeader::new(),
        )
        .unwrap();
        assert_eq!(
            env.get_decrypted(&store, r0, Selector::FromCoord(r0))
                .unwrap(),
            b"p0"
        );
        assert_eq!(
            env.get_decrypted(&store, r1, Selector::FromCoord(r1))
                .unwrap(),
            b"p1"
        );
        // wrong selector for r1 (uses slot 0) must fail
        assert!(env.get_decrypted(&store, r1, Selector::Slot(0)).is_err());
    }

    #[test]
    fn access_log_appends_and_reads() {
        let store = CubeStore::new(HashBackend::new());
        let head = Czyx::new(0, 3, 0, 0); // Null cube 2 range for logs
        let mut log = AccessLog::new(store, head);
        log.append(Czyx::new(3, 1, 1, 1), 1, 1000);
        log.append(Czyx::new(3, 1, 1, 2), 2, 2000);
        let entries = log.entries();
        assert_eq!(entries.len(), 2);
        assert_eq!(entries[0], (Czyx::new(3, 1, 1, 1), 1, 1000));
        assert_eq!(entries[1], (Czyx::new(3, 1, 1, 2), 2, 2000));
    }
}