asupersync 0.4.6

//! Durable identity key storage for ATP peers.
//!
//! The store persists NKey user seeds with a small canonical JSON record. All
//! creation and rotation APIs take caller-provided entropy and timestamps so ATP
//! daemon code can keep randomness and clocks capability-explicit.

// The owned NKey codec is staged behind the library test configuration until
// its full text/prefix substrate reaches the terminal N2 gate. Production
// identity operations continue to use the incumbent `nkeys` crate.
#[cfg(test)]
mod nkey_codec;

use nkeys::{KeyPair, KeyPairType};
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use std::collections::BTreeSet;
use std::fmt;
use std::fs::{self, OpenOptions};
use std::io::Write;
use std::path::{Path, PathBuf};
use std::str::FromStr;
use zeroize::Zeroize;

const KEY_STORE_SCHEMA_VERSION: u32 = 1;
const FINGERPRINT_DOMAIN: &[u8] = b"ATP-IDENTITY-KEY-FINGERPRINT-V1\0";
// Seed-entropy sanity thresholds for 32-byte Ed25519 user seeds. Kept in parity
// with the hardened `AuthKey` strength validator (`security::key`: 16/64/192,
// br-asupersync-q3terg) so both identity-key paths reject the same class of
// pathologically-low-entropy material (aasraf). These are a sanity guard, not
// the security boundary — seeds come from a capability-explicit CSPRNG seam.
const MIN_SEED_DISTINCT_BYTES: usize = 16;
const MIN_SEED_HAMMING_WEIGHT: u32 = 64;
const MAX_SEED_HAMMING_WEIGHT: u32 = 192;

/// Stable fingerprint for a public identity key.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct KeyFingerprint([u8; 32]);

impl KeyFingerprint {
    /// Derive the canonical fingerprint from public key material.
    pub fn from_public_key(public_key: &[u8]) -> Result<Self, KeyStoreError> {
        if public_key.is_empty() {
            return Err(KeyStoreError::InvalidPublicKey(
                "public key material is empty".to_string(),
            ));
        }
        if public_key.iter().all(|byte| *byte == 0) {
            return Err(KeyStoreError::InvalidPublicKey(
                "public key material is all zero".to_string(),
            ));
        }
        Ok(Self::from_public_key_unchecked(public_key))
    }

    fn from_public_key_unchecked(public_key: &[u8]) -> Self {
        let mut hasher = Sha256::new();
        hasher.update(FINGERPRINT_DOMAIN);
        hasher.update((public_key.len() as u64).to_be_bytes());
        hasher.update(public_key);
        Self(hasher.finalize().into())
    }

    /// Decode a hex-encoded fingerprint.
    pub fn from_hex(encoded: &str) -> Result<Self, KeyStoreError> {
        let bytes = hex::decode(encoded).map_err(|err| {
            KeyStoreError::InvalidFingerprint(format!("fingerprint is not valid hex: {err}"))
        })?;
        let bytes: [u8; 32] = bytes.try_into().map_err(|bytes: Vec<u8>| {
            KeyStoreError::InvalidFingerprint(format!(
                "fingerprint has {} bytes, expected 32",
                bytes.len()
            ))
        })?;
        Ok(Self(bytes))
    }

    /// Return the canonical fingerprint bytes.
    #[must_use]
    pub const fn as_bytes(self) -> [u8; 32] {
        self.0
    }

    /// Return the full lowercase hex encoding.
    #[must_use]
    pub fn to_hex(self) -> String {
        hex::encode(self.0)
    }

    /// Return a short diagnostic prefix.
    #[must_use]
    pub fn redacted(self) -> String {
        hex::encode(&self.0[..8])
    }
}

impl fmt::Debug for KeyFingerprint {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("KeyFingerprint")
            .field(&self.redacted())
            .finish()
    }
}

impl fmt::Display for KeyFingerprint {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.to_hex())
    }
}

/// Raw byte width of an NKey Ed25519 public key, Ed25519 seed, or X25519 key.
pub const NKEY_KEY_BYTES: usize = 32;
/// Raw byte width of an expanded Ed25519 private key.
pub const NKEY_ED25519_PRIVATE_BYTES: usize = 64;

/// The role carried by a typed Ed25519 NKey.
///
/// Curve/X25519 keys deliberately have a separate owned type and therefore
/// cannot be represented by this enum. Parsing is exact and never falls back
/// to another role for an unknown name.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum NkeyEd25519Kind {
    /// Account identity or explicitly authorized Account signing key.
    Account,
    /// Cluster identity; no NATS JWT hierarchy authority.
    Cluster,
    /// Rust Module extension; no NATS JWT hierarchy authority.
    Module,
    /// Server identity; no Operator/Account/User JWT hierarchy authority.
    Server,
    /// Operator identity or explicitly authorized Operator signing key.
    Operator,
    /// User identity used for server-nonce authentication, never JWT issuance.
    User,
    /// Rust Service extension; no NATS JWT hierarchy authority.
    Service,
}

impl NkeyEd25519Kind {
    /// Return the canonical one-letter public-key symbol.
    #[must_use]
    pub const fn symbol(self) -> char {
        match self {
            Self::Account => 'A',
            Self::Cluster => 'C',
            Self::Module => 'M',
            Self::Server => 'N',
            Self::Operator => 'O',
            Self::User => 'U',
            Self::Service => 'V',
        }
    }

    /// Return the canonical NKey public-prefix byte.
    #[must_use]
    pub const fn prefix_byte(self) -> u8 {
        match self {
            Self::Account => 0,
            Self::Cluster => 16,
            Self::Module => 96,
            Self::Server => 104,
            Self::Operator => 112,
            Self::User => 160,
            Self::Service => 168,
        }
    }
}

impl fmt::Display for NkeyEd25519Kind {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str(match self {
            Self::Account => "Account",
            Self::Cluster => "Cluster",
            Self::Module => "Module",
            Self::Server => "Server",
            Self::Operator => "Operator",
            Self::User => "User",
            Self::Service => "Service",
        })
    }
}

impl FromStr for NkeyEd25519Kind {
    type Err = NkeyOwnedKeyError;

    fn from_str(input: &str) -> Result<Self, Self::Err> {
        match input {
            "A" | "Account" => Ok(Self::Account),
            "C" | "Cluster" => Ok(Self::Cluster),
            "M" | "Module" => Ok(Self::Module),
            "N" | "Server" => Ok(Self::Server),
            "O" | "Operator" => Ok(Self::Operator),
            "U" | "User" => Ok(Self::User),
            "V" | "Service" => Ok(Self::Service),
            _ => Err(NkeyOwnedKeyError::UnknownEd25519Kind {
                actual_len: input.len(),
            }),
        }
    }
}

/// Stable owned-key form used in diagnostics without exposing key material.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum NkeyOwnedKeyForm {
    /// Typed Ed25519 public material.
    Ed25519Public,
    /// Typed Ed25519 seed material.
    Ed25519Seed,
    /// Typed expanded Ed25519 private material.
    Ed25519Private,
    /// Curve/X25519 public material.
    CurvePublic,
    /// Curve/X25519 secret material.
    CurveSecret,
}

impl fmt::Display for NkeyOwnedKeyForm {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str(match self {
            Self::Ed25519Public => "ed25519-public",
            Self::Ed25519Seed => "ed25519-seed",
            Self::Ed25519Private => "ed25519-private",
            Self::CurvePublic => "curve-public",
            Self::CurveSecret => "curve-secret",
        })
    }
}

/// Explicit purpose required before copying secret bytes out of an owned key.
///
/// This enum is an intent marker, not an authorization capability. It makes
/// plaintext export, serialization, and persistence visible at the call site.
/// The returned export guard zeroizes its own copy on drop, but cannot erase
/// caller-created copies, allocator remnants, compiler temporaries, registers,
/// swap, crash dumps, or storage written by the caller.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum NkeySecretDisposition {
    /// Secret remains inside the owned key for a cryptographic operation.
    InProcessOperation,
    /// Caller explicitly requests a transient plaintext copy.
    PlaintextExport,
    /// Caller explicitly requests bytes for plaintext serialization.
    PlaintextSerialization,
    /// Caller explicitly requests bytes for plaintext persistence.
    PlaintextPersistence,
}

impl NkeySecretDisposition {
    const fn permits_export(self) -> bool {
        !matches!(self, Self::InProcessOperation)
    }
}

/// Safe, non-secret diagnostic failures for owned NKey construction/use.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum NkeyOwnedKeyError {
    /// Raw material had the wrong byte length for the selected owned form.
    Length {
        /// Form whose constructor rejected the input.
        form: NkeyOwnedKeyForm,
        /// Observed byte length.
        actual: usize,
        /// Exact required byte length.
        expected: usize,
    },
    /// A textual Ed25519 role was not one of the exact supported names/symbols.
    UnknownEd25519Kind {
        /// Input length only; the untrusted text is deliberately omitted.
        actual_len: usize,
    },
    /// The requested disposition does not permit a plaintext secret copy.
    SecretDisposition {
        /// Rejected disposition intent.
        disposition: NkeySecretDisposition,
    },
}

impl fmt::Display for NkeyOwnedKeyError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Length {
                form,
                actual,
                expected,
            } => write!(
                formatter,
                "{form} key material has {actual} bytes; expected {expected}"
            ),
            Self::UnknownEd25519Kind { actual_len } => write!(
                formatter,
                "unknown Ed25519 NKey kind with {actual_len} input bytes"
            ),
            Self::SecretDisposition { disposition } => write!(
                formatter,
                "secret export is not permitted for disposition {disposition:?}"
            ),
        }
    }
}

impl std::error::Error for NkeyOwnedKeyError {}

struct NkeySecretBytes<const N: usize>([u8; N]);

impl<const N: usize> NkeySecretBytes<N> {
    const fn new(bytes: [u8; N]) -> Self {
        Self(bytes)
    }

    fn export(
        &self,
        disposition: NkeySecretDisposition,
    ) -> Result<NkeySecretExport<N>, NkeyOwnedKeyError> {
        if !disposition.permits_export() {
            return Err(NkeyOwnedKeyError::SecretDisposition { disposition });
        }
        Ok(NkeySecretExport {
            bytes: self.0,
            disposition,
        })
    }
}

impl<const N: usize> Zeroize for NkeySecretBytes<N> {
    fn zeroize(&mut self) {
        self.0.zeroize();
    }
}

impl<const N: usize> Drop for NkeySecretBytes<N> {
    fn drop(&mut self) {
        self.zeroize();
    }
}

/// Explicit transient plaintext copy of secret NKey material.
///
/// This guard is neither `Copy` nor `Clone`, redacts formatting, and zeroizes
/// its own byte array on drop. [`NkeySecretExport::as_bytes`] is intentionally
/// explicit because any caller-created copy is outside this guard's erasure
/// guarantee.
pub struct NkeySecretExport<const N: usize> {
    bytes: [u8; N],
    disposition: NkeySecretDisposition,
}

impl<const N: usize> NkeySecretExport<N> {
    /// Return the explicit disposition that authorized this transient copy.
    #[must_use]
    pub const fn disposition(&self) -> NkeySecretDisposition {
        self.disposition
    }

    /// Borrow the exported plaintext bytes.
    #[must_use]
    pub const fn as_bytes(&self) -> &[u8; N] {
        &self.bytes
    }
}

impl<const N: usize> Zeroize for NkeySecretExport<N> {
    fn zeroize(&mut self) {
        self.bytes.zeroize();
    }
}

impl<const N: usize> Drop for NkeySecretExport<N> {
    fn drop(&mut self) {
        self.zeroize();
    }
}

impl<const N: usize> fmt::Debug for NkeySecretExport<N> {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("NkeySecretExport")
            .field("bytes", &"<redacted>")
            .field("length", &N)
            .field("disposition", &self.disposition)
            .finish()
    }
}

impl<const N: usize> fmt::Display for NkeySecretExport<N> {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(formatter, "<redacted NKey secret: {N} bytes>")
    }
}

fn exact_array<const N: usize>(
    form: NkeyOwnedKeyForm,
    bytes: &[u8],
) -> Result<[u8; N], NkeyOwnedKeyError> {
    bytes.try_into().map_err(|_| NkeyOwnedKeyError::Length {
        form,
        actual: bytes.len(),
        expected: N,
    })
}

/// Owned, typed Ed25519 public verification key.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct NkeyEd25519PublicKey {
    kind: NkeyEd25519Kind,
    bytes: [u8; NKEY_KEY_BYTES],
}

impl NkeyEd25519PublicKey {
    /// Construct from exact raw public bytes and an explicit role.
    #[must_use]
    pub const fn from_bytes(kind: NkeyEd25519Kind, bytes: [u8; NKEY_KEY_BYTES]) -> Self {
        Self { kind, bytes }
    }

    /// Construct from a byte slice, rejecting every non-exact length.
    pub fn try_from_slice(kind: NkeyEd25519Kind, bytes: &[u8]) -> Result<Self, NkeyOwnedKeyError> {
        Ok(Self::from_bytes(
            kind,
            exact_array(NkeyOwnedKeyForm::Ed25519Public, bytes)?,
        ))
    }

    /// Return the explicit Ed25519 role.
    #[must_use]
    pub const fn kind(self) -> NkeyEd25519Kind {
        self.kind
    }

    /// Borrow the public bytes.
    #[must_use]
    pub const fn as_bytes(&self) -> &[u8; NKEY_KEY_BYTES] {
        &self.bytes
    }

    /// Consume the public key and return its non-secret bytes.
    #[must_use]
    pub const fn into_bytes(self) -> [u8; NKEY_KEY_BYTES] {
        self.bytes
    }
}

impl fmt::Debug for NkeyEd25519PublicKey {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("NkeyEd25519PublicKey")
            .field("kind", &self.kind)
            .field("bytes", &self.bytes)
            .finish()
    }
}

/// Owned, typed Ed25519 seed material.
///
/// The type deliberately does not implement `Copy`, `Clone`, equality, or
/// `serde::Serialize`. Plaintext extraction requires an explicit
/// [`NkeySecretDisposition`].
///
/// Drop zeroizes only this value's narrow internal byte array. Construction
/// copies caller-provided bytes; callers remain responsible for erasing their
/// source buffer and any other copies, allocator remnants, compiler
/// temporaries, registers, swap, crash dumps, or persisted representations.
///
/// ```compile_fail
/// use asupersync::security::{NkeyEd25519Kind, NkeyEd25519Seed};
/// let seed = NkeyEd25519Seed::from_bytes(NkeyEd25519Kind::User, [7; 32]);
/// let duplicate = seed.clone();
/// # let _ = duplicate;
/// ```
///
/// ```compile_fail
/// use asupersync::security::NkeyEd25519Seed;
/// fn requires_serialize<T: serde::Serialize>() {}
/// requires_serialize::<NkeyEd25519Seed>();
/// ```
pub struct NkeyEd25519Seed {
    kind: NkeyEd25519Kind,
    secret: NkeySecretBytes<NKEY_KEY_BYTES>,
}

impl NkeyEd25519Seed {
    /// Construct from exact seed bytes and an explicit Ed25519 role.
    #[must_use]
    pub const fn from_bytes(kind: NkeyEd25519Kind, bytes: [u8; NKEY_KEY_BYTES]) -> Self {
        Self {
            kind,
            secret: NkeySecretBytes::new(bytes),
        }
    }

    /// Construct from a byte slice, rejecting every non-exact length.
    pub fn try_from_slice(kind: NkeyEd25519Kind, bytes: &[u8]) -> Result<Self, NkeyOwnedKeyError> {
        Ok(Self::from_bytes(
            kind,
            exact_array(NkeyOwnedKeyForm::Ed25519Seed, bytes)?,
        ))
    }

    /// Return the explicit Ed25519 role without exposing secret bytes.
    #[must_use]
    pub const fn kind(&self) -> NkeyEd25519Kind {
        self.kind
    }

    /// Create a zeroizing transient plaintext copy for an explicit purpose.
    pub fn export_secret(
        &self,
        disposition: NkeySecretDisposition,
    ) -> Result<NkeySecretExport<NKEY_KEY_BYTES>, NkeyOwnedKeyError> {
        self.secret.export(disposition)
    }
}

impl fmt::Debug for NkeyEd25519Seed {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("NkeyEd25519Seed")
            .field("kind", &self.kind)
            .field("secret", &"<redacted>")
            .finish()
    }
}

impl fmt::Display for NkeyEd25519Seed {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(formatter, "<redacted {} Ed25519 NKey seed>", self.kind)
    }
}

/// Owned, explicitly typed 64-byte expanded Ed25519 private material.
///
/// Drop zeroizes only this value's narrow internal byte array. Construction
/// copies caller-provided bytes; callers remain responsible for erasing their
/// source buffer and any other copies, allocator remnants, compiler
/// temporaries, registers, swap, crash dumps, or persisted representations.
pub struct NkeyEd25519PrivateKey {
    kind: NkeyEd25519Kind,
    secret: NkeySecretBytes<NKEY_ED25519_PRIVATE_BYTES>,
}

impl NkeyEd25519PrivateKey {
    /// Import expanded private material only with an explicit Ed25519 role.
    #[must_use]
    pub const fn from_bytes(
        kind: NkeyEd25519Kind,
        bytes: [u8; NKEY_ED25519_PRIVATE_BYTES],
    ) -> Self {
        Self {
            kind,
            secret: NkeySecretBytes::new(bytes),
        }
    }

    /// Import a byte slice, rejecting every non-exact length.
    pub fn try_from_slice(kind: NkeyEd25519Kind, bytes: &[u8]) -> Result<Self, NkeyOwnedKeyError> {
        Ok(Self::from_bytes(
            kind,
            exact_array(NkeyOwnedKeyForm::Ed25519Private, bytes)?,
        ))
    }

    /// Return the explicit Ed25519 role without exposing secret bytes.
    #[must_use]
    pub const fn kind(&self) -> NkeyEd25519Kind {
        self.kind
    }

    /// Create a zeroizing transient plaintext copy for an explicit purpose.
    pub fn export_secret(
        &self,
        disposition: NkeySecretDisposition,
    ) -> Result<NkeySecretExport<NKEY_ED25519_PRIVATE_BYTES>, NkeyOwnedKeyError> {
        self.secret.export(disposition)
    }
}

impl fmt::Debug for NkeyEd25519PrivateKey {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("NkeyEd25519PrivateKey")
            .field("kind", &self.kind)
            .field("secret", &"<redacted>")
            .finish()
    }
}

impl fmt::Display for NkeyEd25519PrivateKey {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(formatter, "<redacted {} Ed25519 private key>", self.kind)
    }
}

/// Owned Curve/X25519 public key.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct NkeyCurvePublicKey([u8; NKEY_KEY_BYTES]);

impl NkeyCurvePublicKey {
    /// Construct from exact raw X25519 public bytes.
    #[must_use]
    pub const fn from_bytes(bytes: [u8; NKEY_KEY_BYTES]) -> Self {
        Self(bytes)
    }

    /// Construct from a byte slice, rejecting every non-exact length.
    pub fn try_from_slice(bytes: &[u8]) -> Result<Self, NkeyOwnedKeyError> {
        Ok(Self::from_bytes(exact_array(
            NkeyOwnedKeyForm::CurvePublic,
            bytes,
        )?))
    }

    /// Borrow the non-secret public bytes.
    #[must_use]
    pub const fn as_bytes(&self) -> &[u8; NKEY_KEY_BYTES] {
        &self.0
    }

    /// Consume the public key and return its non-secret bytes.
    #[must_use]
    pub const fn into_bytes(self) -> [u8; NKEY_KEY_BYTES] {
        self.0
    }
}

impl fmt::Debug for NkeyCurvePublicKey {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_tuple("NkeyCurvePublicKey")
            .field(&self.0)
            .finish()
    }
}

/// Owned Curve/X25519 secret material.
///
/// This type is separate from every Ed25519 signing form and cannot satisfy
/// [`NkeyEd25519SigningMaterial`].
///
/// Drop zeroizes only this value's narrow internal byte array. Construction
/// copies caller-provided bytes; callers remain responsible for erasing their
/// source buffer and any other copies, allocator remnants, compiler
/// temporaries, registers, swap, crash dumps, or persisted representations.
///
/// ```compile_fail
/// use asupersync::security::{NkeyCurveSecretKey, NkeyEd25519SigningMaterial};
/// fn requires_ed25519<T: NkeyEd25519SigningMaterial>(_: &T) {}
/// let curve = NkeyCurveSecretKey::from_bytes([9; 32]);
/// requires_ed25519(&curve);
/// ```
pub struct NkeyCurveSecretKey(NkeySecretBytes<NKEY_KEY_BYTES>);

impl NkeyCurveSecretKey {
    /// Construct from exact raw X25519 secret bytes.
    #[must_use]
    pub const fn from_bytes(bytes: [u8; NKEY_KEY_BYTES]) -> Self {
        Self(NkeySecretBytes::new(bytes))
    }

    /// Construct from a byte slice, rejecting every non-exact length.
    pub fn try_from_slice(bytes: &[u8]) -> Result<Self, NkeyOwnedKeyError> {
        Ok(Self::from_bytes(exact_array(
            NkeyOwnedKeyForm::CurveSecret,
            bytes,
        )?))
    }

    /// Create a zeroizing transient plaintext copy for an explicit purpose.
    pub fn export_secret(
        &self,
        disposition: NkeySecretDisposition,
    ) -> Result<NkeySecretExport<NKEY_KEY_BYTES>, NkeyOwnedKeyError> {
        self.0.export(disposition)
    }
}

impl fmt::Debug for NkeyCurveSecretKey {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str("NkeyCurveSecretKey(<redacted>)")
    }
}

impl fmt::Display for NkeyCurveSecretKey {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str("<redacted Curve/X25519 secret key>")
    }
}

mod nkey_owned_type_sealed {
    pub trait Sealed {}
}

/// Marker implemented only by owned Ed25519 secret signing material.
///
/// It intentionally has no signing operation yet: N5 owns the audited
/// Ed25519 operation boundary. N3 uses this sealed marker to make Curve keys
/// statically ineligible for future signing APIs.
#[allow(private_bounds)]
pub trait NkeyEd25519SigningMaterial: nkey_owned_type_sealed::Sealed {
    /// Return the explicit signing role without exposing secret bytes.
    fn kind(&self) -> NkeyEd25519Kind;
}

impl nkey_owned_type_sealed::Sealed for NkeyEd25519Seed {}
impl NkeyEd25519SigningMaterial for NkeyEd25519Seed {
    fn kind(&self) -> NkeyEd25519Kind {
        self.kind
    }
}

impl nkey_owned_type_sealed::Sealed for NkeyEd25519PrivateKey {}
impl NkeyEd25519SigningMaterial for NkeyEd25519PrivateKey {
    fn kind(&self) -> NkeyEd25519Kind {
        self.kind
    }
}

/// Public view of an identity key.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PublicIdentityKey {
    /// Monotonic key generation.
    pub generation: u64,
    /// Public NKey value.
    pub public_key: String,
    /// Canonical public-key fingerprint.
    pub fingerprint: KeyFingerprint,
    /// Whether this generation has been revoked.
    pub revoked: bool,
}

/// Platform-specific key-file hardening strategy.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum KeyStorePlatform {
    /// Unix-like hosts use owner-only `0600` key files.
    UnixOwnerOnly,
    /// Windows hosts require ACL hardening by the daemon installer.
    WindowsAclRequired,
    /// Other targets persist records with best-effort process ownership.
    BestEffort,
}

impl KeyStorePlatform {
    /// Return the strategy for the current compilation target.
    #[must_use]
    pub fn current() -> Self {
        if cfg!(unix) {
            Self::UnixOwnerOnly
        } else if cfg!(windows) {
            Self::WindowsAclRequired
        } else {
            Self::BestEffort
        }
    }
}

/// Filesystem-backed ATP identity key store.
#[derive(Debug, Clone)]
pub struct IdentityKeyStore {
    path: PathBuf,
    record: KeyStoreRecord,
}

impl IdentityKeyStore {
    /// Create a new store with an initial active key.
    pub fn create(
        path: impl AsRef<Path>,
        seed_material: [u8; 32],
        created_at_micros: u64,
    ) -> Result<Self, KeyStoreError> {
        let path = path.as_ref().to_path_buf();
        if path.try_exists().map_err(|source| KeyStoreError::Io {
            path: path.clone(),
            source,
        })? {
            return Err(KeyStoreError::StoreAlreadyExists(path));
        }

        let record = KeyStoreRecord {
            schema_version: KEY_STORE_SCHEMA_VERSION,
            active_generation: 1,
            next_generation: 2,
            keys: vec![persisted_key(seed_material, 1, created_at_micros)?],
        };
        persist_record(&path, &record)?;
        Ok(Self { path, record })
    }

    /// Load an existing key store from disk.
    pub fn load(path: impl AsRef<Path>) -> Result<Self, KeyStoreError> {
        let path = path.as_ref().to_path_buf();
        let text = fs::read_to_string(&path).map_err(|source| KeyStoreError::Io {
            path: path.clone(),
            source,
        })?;
        let record: KeyStoreRecord =
            serde_json::from_str(&text).map_err(|source| KeyStoreError::Json {
                path: path.clone(),
                source,
            })?;
        validate_record(&record)?;
        Ok(Self { path, record })
    }

    /// Return the backing store path.
    #[must_use]
    pub fn path(&self) -> &Path {
        &self.path
    }

    /// Return the platform hardening strategy used by this store.
    #[must_use]
    pub fn platform(&self) -> KeyStorePlatform {
        KeyStorePlatform::current()
    }

    /// Return the active generation number.
    #[must_use]
    pub const fn active_generation(&self) -> u64 {
        self.record.active_generation
    }

    /// Export the active public identity key.
    pub fn export_public(&self) -> Result<PublicIdentityKey, KeyStoreError> {
        let active = self.active_key_record()?;
        active.public_view()
    }

    /// Export every public key generation in deterministic order.
    pub fn export_public_history(&self) -> Result<Vec<PublicIdentityKey>, KeyStoreError> {
        self.record
            .keys
            .iter()
            .map(PersistedIdentityKey::public_view)
            .collect()
    }

    /// Return the active NKey key pair for signing.
    pub fn active_key_pair(&self) -> Result<KeyPair, KeyStoreError> {
        self.key_pair_for(self.active_key_record()?)
    }

    /// Rotate to a new active key generation.
    pub fn rotate(
        &mut self,
        seed_material: [u8; 32],
        created_at_micros: u64,
    ) -> Result<PublicIdentityKey, KeyStoreError> {
        let generation = self.record.next_generation;
        let key = persisted_key(seed_material, generation, created_at_micros)?;
        let fingerprint = KeyFingerprint::from_hex(&key.fingerprint)?;
        if self
            .record
            .keys
            .iter()
            .any(|existing| existing.fingerprint == key.fingerprint)
        {
            return Err(KeyStoreError::DuplicateFingerprint(fingerprint));
        }

        self.record.active_generation = generation;
        self.record.next_generation = generation
            .checked_add(1)
            .ok_or(KeyStoreError::GenerationOverflow)?;
        self.record.keys.push(key);
        validate_record(&self.record)?;
        persist_record(&self.path, &self.record)?;
        self.export_public()
    }

    /// Revoke a non-active key by fingerprint.
    pub fn revoke(
        &mut self,
        fingerprint: KeyFingerprint,
        revoked_at_micros: u64,
    ) -> Result<PublicIdentityKey, KeyStoreError> {
        let mut revoked = None;
        for key in &mut self.record.keys {
            if key.fingerprint == fingerprint.to_hex() {
                if key.generation == self.record.active_generation {
                    return Err(KeyStoreError::CannotRevokeActiveKey(fingerprint));
                }
                key.revoked = true;
                key.revoked_at_micros = Some(revoked_at_micros);
                revoked = Some(key.public_view()?);
                break;
            }
        }

        let revoked = revoked.ok_or(KeyStoreError::UnknownFingerprint(fingerprint))?;
        validate_record(&self.record)?;
        persist_record(&self.path, &self.record)?;
        Ok(revoked)
    }

    fn active_key_record(&self) -> Result<&PersistedIdentityKey, KeyStoreError> {
        let active = self
            .record
            .keys
            .iter()
            .find(|key| key.generation == self.record.active_generation)
            .ok_or(KeyStoreError::NoActiveKey)?;
        if active.revoked {
            return Err(KeyStoreError::ActiveKeyRevoked);
        }
        Ok(active)
    }

    fn key_pair_for(&self, key: &PersistedIdentityKey) -> Result<KeyPair, KeyStoreError> {
        let key_pair = KeyPair::from_seed(&key.seed).map_err(|err| {
            KeyStoreError::InvalidSeed(format!(
                "generation {} seed could not be decoded: {err}",
                key.generation
            ))
        })?;
        if key_pair.key_pair_type() != KeyPairType::User {
            return Err(KeyStoreError::InvalidSeed(format!(
                "generation {} is {:?}, expected User",
                key.generation,
                key_pair.key_pair_type()
            )));
        }
        if key_pair.public_key() != key.public_key {
            return Err(KeyStoreError::PublicKeyMismatch {
                generation: key.generation,
            });
        }
        Ok(key_pair)
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
struct KeyStoreRecord {
    schema_version: u32,
    active_generation: u64,
    next_generation: u64,
    keys: Vec<PersistedIdentityKey>,
}

#[derive(Clone, Serialize, Deserialize)]
struct PersistedIdentityKey {
    generation: u64,
    public_key: String,
    seed: String,
    fingerprint: String,
    created_at_micros: u64,
    revoked: bool,
    revoked_at_micros: Option<u64>,
}

impl fmt::Debug for PersistedIdentityKey {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("PersistedIdentityKey")
            .field("generation", &self.generation)
            .field("public_key", &self.public_key)
            .field("seed", &"<redacted>")
            .field("fingerprint", &self.fingerprint)
            .field("created_at_micros", &self.created_at_micros)
            .field("revoked", &self.revoked)
            .field("revoked_at_micros", &self.revoked_at_micros)
            .finish()
    }
}

impl PersistedIdentityKey {
    fn public_view(&self) -> Result<PublicIdentityKey, KeyStoreError> {
        Ok(PublicIdentityKey {
            generation: self.generation,
            public_key: self.public_key.clone(),
            fingerprint: KeyFingerprint::from_hex(&self.fingerprint)?,
            revoked: self.revoked,
        })
    }
}

/// Durable key-store failures.
#[derive(Debug, thiserror::Error)]
pub enum KeyStoreError {
    /// Filesystem operation failed.
    #[error("key store I/O failed for {}: {source}", path.display())]
    Io {
        /// Path involved in the failed operation.
        path: PathBuf,
        /// Underlying I/O error.
        #[source]
        source: std::io::Error,
    },
    /// JSON parsing or serialization failed.
    #[error("key store JSON failed for {}: {source}", path.display())]
    Json {
        /// Path involved in the failed operation.
        path: PathBuf,
        /// Underlying JSON error.
        #[source]
        source: serde_json::Error,
    },
    /// Store creation would overwrite an existing record.
    #[error("key store already exists: {}", .0.display())]
    StoreAlreadyExists(PathBuf),
    /// Store path has no valid file name.
    #[error("invalid key store path: {}", .0.display())]
    InvalidStorePath(PathBuf),
    /// Persistent schema version is unsupported.
    #[error("unsupported key store schema version: {0}")]
    UnsupportedSchema(u32),
    /// Store contains no key generations.
    #[error("key store contains no key generations")]
    EmptyStore,
    /// Store has no usable active key.
    #[error("key store has no active key")]
    NoActiveKey,
    /// Active key was marked revoked.
    #[error("active key generation is revoked")]
    ActiveKeyRevoked,
    /// Active key cannot be revoked before rotation.
    #[error("cannot revoke active key {0}")]
    CannotRevokeActiveKey(KeyFingerprint),
    /// Requested fingerprint is not present.
    #[error("unknown key fingerprint: {0}")]
    UnknownFingerprint(KeyFingerprint),
    /// Rotation would reuse an existing key.
    #[error("duplicate key fingerprint: {0}")]
    DuplicateFingerprint(KeyFingerprint),
    /// Generation counter overflowed.
    #[error("key generation overflow")]
    GenerationOverflow,
    /// Caller-provided seed material was weak.
    #[error("weak identity seed: {0}")]
    WeakSeed(&'static str),
    /// Encoded seed was invalid.
    #[error("invalid identity seed: {0}")]
    InvalidSeed(String),
    /// Public key material was invalid.
    #[error("invalid public identity key: {0}")]
    InvalidPublicKey(String),
    /// Fingerprint encoding was invalid.
    #[error("invalid key fingerprint: {0}")]
    InvalidFingerprint(String),
    /// Stored public key did not match the stored seed.
    #[error("stored public key does not match seed for generation {generation}")]
    PublicKeyMismatch {
        /// Generation that failed validation.
        generation: u64,
    },
    /// Stored fingerprint did not match the public key.
    #[error("stored fingerprint does not match public key for generation {generation}")]
    FingerprintMismatch {
        /// Generation that failed validation.
        generation: u64,
    },
    /// Store has duplicate generations or fingerprints.
    #[error("duplicate key-store field: {0}")]
    DuplicateRecordField(&'static str),
}

fn persisted_key(
    seed_material: [u8; 32],
    generation: u64,
    created_at_micros: u64,
) -> Result<PersistedIdentityKey, KeyStoreError> {
    validate_seed_material(&seed_material)?;
    let key_pair = KeyPair::new_from_raw(KeyPairType::User, seed_material)
        .map_err(|err| KeyStoreError::InvalidSeed(err.to_string()))?;
    let seed = key_pair
        .seed()
        .map_err(|err| KeyStoreError::InvalidSeed(err.to_string()))?;
    let public_key = key_pair.public_key();
    validate_public_key(&public_key, generation)?;
    let fingerprint = KeyFingerprint::from_public_key(public_key.as_bytes())?.to_hex();

    Ok(PersistedIdentityKey {
        generation,
        public_key,
        seed,
        fingerprint,
        created_at_micros,
        revoked: false,
        revoked_at_micros: None,
    })
}

fn validate_seed_material(seed: &[u8; 32]) -> Result<(), KeyStoreError> {
    if seed.iter().all(|byte| *byte == 0) {
        return Err(KeyStoreError::WeakSeed("all-zero seed"));
    }

    let mut seen = [false; 256];
    let mut distinct = 0usize;
    for &byte in seed {
        let idx = byte as usize;
        if !seen[idx] {
            seen[idx] = true;
            distinct += 1;
        }
    }
    if distinct < MIN_SEED_DISTINCT_BYTES {
        return Err(KeyStoreError::WeakSeed("insufficient byte diversity"));
    }

    let hamming_weight: u32 = seed.iter().map(|byte| byte.count_ones()).sum();
    if !(MIN_SEED_HAMMING_WEIGHT..=MAX_SEED_HAMMING_WEIGHT).contains(&hamming_weight) {
        return Err(KeyStoreError::WeakSeed("extreme hamming weight"));
    }

    Ok(())
}

fn validate_record(record: &KeyStoreRecord) -> Result<(), KeyStoreError> {
    if record.schema_version != KEY_STORE_SCHEMA_VERSION {
        return Err(KeyStoreError::UnsupportedSchema(record.schema_version));
    }
    if record.keys.is_empty() {
        return Err(KeyStoreError::EmptyStore);
    }
    if record.next_generation <= record.active_generation {
        return Err(KeyStoreError::GenerationOverflow);
    }

    let mut generations = BTreeSet::new();
    let mut fingerprints = BTreeSet::new();
    let mut has_active = false;
    for key in &record.keys {
        if !generations.insert(key.generation) {
            return Err(KeyStoreError::DuplicateRecordField("generation"));
        }
        if !fingerprints.insert(key.fingerprint.clone()) {
            return Err(KeyStoreError::DuplicateRecordField("fingerprint"));
        }
        validate_public_key(&key.public_key, key.generation)?;
        let fingerprint = KeyFingerprint::from_public_key(key.public_key.as_bytes())?;
        if key.fingerprint != fingerprint.to_hex() {
            return Err(KeyStoreError::FingerprintMismatch {
                generation: key.generation,
            });
        }
        if key.generation == record.active_generation {
            has_active = true;
            if key.revoked {
                return Err(KeyStoreError::ActiveKeyRevoked);
            }
        }
        let key_pair = KeyPair::from_seed(&key.seed).map_err(|err| {
            KeyStoreError::InvalidSeed(format!(
                "generation {} seed could not be decoded: {err}",
                key.generation
            ))
        })?;
        if key_pair.key_pair_type() != KeyPairType::User {
            return Err(KeyStoreError::InvalidSeed(format!(
                "generation {} is {:?}, expected User",
                key.generation,
                key_pair.key_pair_type()
            )));
        }
        if key_pair.public_key() != key.public_key {
            return Err(KeyStoreError::PublicKeyMismatch {
                generation: key.generation,
            });
        }
    }

    if has_active {
        Ok(())
    } else {
        Err(KeyStoreError::NoActiveKey)
    }
}

fn validate_public_key(public_key: &str, generation: u64) -> Result<(), KeyStoreError> {
    KeyPair::from_public_key(public_key).map_err(|err| {
        KeyStoreError::InvalidPublicKey(format!(
            "generation {generation} public key could not be decoded: {err}"
        ))
    })?;
    KeyFingerprint::from_public_key(public_key.as_bytes())?;
    Ok(())
}

fn persist_record(path: &Path, record: &KeyStoreRecord) -> Result<(), KeyStoreError> {
    let parent = path.parent();
    if let Some(parent) = parent {
        fs::create_dir_all(parent).map_err(|source| KeyStoreError::Io {
            path: parent.to_path_buf(),
            source,
        })?;
    }

    let tmp_path = pending_path(path)?;
    let bytes = serde_json::to_vec_pretty(record).map_err(|source| KeyStoreError::Json {
        path: path.to_path_buf(),
        source,
    })?;
    write_key_file(&tmp_path, &bytes)?;
    fs::rename(&tmp_path, path).map_err(|source| KeyStoreError::Io {
        path: path.to_path_buf(),
        source,
    })?;
    harden_key_file(path)?;
    sync_parent_dir(parent);
    Ok(())
}

fn write_key_file(path: &Path, bytes: &[u8]) -> Result<(), KeyStoreError> {
    let mut options = OpenOptions::new();
    // The pending path is security-sensitive. Exclusive creation prevents
    // following an attacker-controlled stale symlink or truncating a real file.
    options.create_new(true).write(true);
    #[cfg(unix)]
    {
        use std::os::unix::fs::OpenOptionsExt;
        options.mode(0o600);
    }

    let mut file = options.open(path).map_err(|source| KeyStoreError::Io {
        path: path.to_path_buf(),
        source,
    })?;
    file.write_all(bytes).map_err(|source| KeyStoreError::Io {
        path: path.to_path_buf(),
        source,
    })?;
    file.write_all(b"\n").map_err(|source| KeyStoreError::Io {
        path: path.to_path_buf(),
        source,
    })?;
    file.sync_all().map_err(|source| KeyStoreError::Io {
        path: path.to_path_buf(),
        source,
    })?;
    harden_key_file(path)
}

fn pending_path(path: &Path) -> Result<PathBuf, KeyStoreError> {
    let file_name = path
        .file_name()
        .ok_or_else(|| KeyStoreError::InvalidStorePath(path.to_path_buf()))?;
    let mut pending_name = file_name.to_os_string();
    pending_name.push(".pending");
    Ok(path.with_file_name(pending_name))
}

fn harden_key_file(path: &Path) -> Result<(), KeyStoreError> {
    #[cfg(unix)]
    {
        use std::os::unix::fs::PermissionsExt;
        let permissions = fs::Permissions::from_mode(0o600);
        fs::set_permissions(path, permissions).map_err(|source| KeyStoreError::Io {
            path: path.to_path_buf(),
            source,
        })?;
    }
    #[cfg(not(unix))]
    let _ = path;
    Ok(())
}

fn sync_parent_dir(parent: Option<&Path>) {
    if let Some(parent) = parent {
        if let Ok(dir) = fs::File::open(parent) {
            let _ = dir.sync_all();
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::mem;
    use tempfile::tempdir;

    fn strong_seed(tag: u8) -> [u8; 32] {
        let mut hasher = Sha256::new();
        hasher.update(b"asupersync::security::keys::tests");
        hasher.update([tag]);
        hasher.finalize().into()
    }

    #[test]
    fn owned_nkey_kinds_are_exact_and_never_fallback() {
        for (name, symbol, kind, prefix) in [
            ("Account", "A", NkeyEd25519Kind::Account, 0),
            ("Cluster", "C", NkeyEd25519Kind::Cluster, 16),
            ("Module", "M", NkeyEd25519Kind::Module, 96),
            ("Server", "N", NkeyEd25519Kind::Server, 104),
            ("Operator", "O", NkeyEd25519Kind::Operator, 112),
            ("User", "U", NkeyEd25519Kind::User, 160),
            ("Service", "V", NkeyEd25519Kind::Service, 168),
        ] {
            assert_eq!(name.parse(), Ok(kind));
            assert_eq!(symbol.parse(), Ok(kind));
            assert_eq!(kind.to_string(), name);
            assert_eq!(kind.symbol().to_string(), symbol);
            assert_eq!(kind.prefix_byte(), prefix);
        }

        for unknown in ["", "Curve", "X", "Unknown", "user", " User"] {
            assert_eq!(
                unknown.parse::<NkeyEd25519Kind>(),
                Err(NkeyOwnedKeyError::UnknownEd25519Kind {
                    actual_len: unknown.len(),
                })
            );
        }
    }

    #[test]
    fn owned_public_forms_are_copyable_comparable_and_type_separated() {
        fn assert_send_sync<T: Send + Sync>() {}
        fn assert_copy<T: Copy>() {}

        assert_send_sync::<NkeyEd25519PublicKey>();
        assert_send_sync::<NkeyCurvePublicKey>();
        assert_copy::<NkeyEd25519PublicKey>();
        assert_copy::<NkeyCurvePublicKey>();

        let user = NkeyEd25519PublicKey::from_bytes(NkeyEd25519Kind::User, [0x11; 32]);
        let account = NkeyEd25519PublicKey::from_bytes(NkeyEd25519Kind::Account, [0x11; 32]);
        let curve = NkeyCurvePublicKey::from_bytes([0x11; 32]);
        assert_ne!(user, account, "the Ed25519 role is part of identity");
        assert_eq!(user.kind(), NkeyEd25519Kind::User);
        assert_eq!(user.into_bytes(), [0x11; 32]);
        assert_eq!(curve.into_bytes(), [0x11; 32]);
        assert_eq!(
            NkeyEd25519PublicKey::try_from_slice(NkeyEd25519Kind::User, &[0x11; 32]),
            Ok(user)
        );
        assert_eq!(NkeyCurvePublicKey::try_from_slice(&[0x11; 32]), Ok(curve));
    }

    #[test]
    fn owned_secret_forms_require_explicit_disposition_and_zeroize_exports() {
        fn assert_send_sync<T: Send + Sync>() {}
        fn assert_signer<T: NkeyEd25519SigningMaterial>(value: &T, expected: NkeyEd25519Kind) {
            assert_eq!(value.kind(), expected);
        }

        assert_send_sync::<NkeyEd25519Seed>();
        assert_send_sync::<NkeyEd25519PrivateKey>();
        assert_send_sync::<NkeyCurveSecretKey>();
        assert!(mem::needs_drop::<NkeyEd25519Seed>());
        assert!(mem::needs_drop::<NkeyEd25519PrivateKey>());
        assert!(mem::needs_drop::<NkeyCurveSecretKey>());
        assert!(mem::needs_drop::<NkeySecretExport<32>>());

        let seed = NkeyEd25519Seed::from_bytes(NkeyEd25519Kind::User, [0x21; 32]);
        let private = NkeyEd25519PrivateKey::from_bytes(NkeyEd25519Kind::Operator, [0x42; 64]);
        let curve = NkeyCurveSecretKey::from_bytes([0x63; 32]);
        assert_signer(&seed, NkeyEd25519Kind::User);
        assert_signer(&private, NkeyEd25519Kind::Operator);

        assert!(matches!(
            seed.export_secret(NkeySecretDisposition::InProcessOperation),
            Err(NkeyOwnedKeyError::SecretDisposition {
                disposition: NkeySecretDisposition::InProcessOperation
            })
        ));

        let mut seed_export = seed
            .export_secret(NkeySecretDisposition::PlaintextSerialization)
            .expect("serialization requires an explicit export guard");
        assert_eq!(
            seed_export.disposition(),
            NkeySecretDisposition::PlaintextSerialization
        );
        assert_eq!(seed_export.as_bytes(), &[0x21; 32]);
        seed_export.zeroize();
        assert_eq!(seed_export.as_bytes(), &[0; 32]);

        let private_export = private
            .export_secret(NkeySecretDisposition::PlaintextPersistence)
            .expect("persistence requires an explicit export guard");
        assert_eq!(private_export.as_bytes(), &[0x42; 64]);

        let curve_export = curve
            .export_secret(NkeySecretDisposition::PlaintextExport)
            .expect("Curve secret export is explicit and zeroizing");
        assert_eq!(curve_export.as_bytes(), &[0x63; 32]);
    }

    #[test]
    fn owned_key_constructors_reject_every_wrong_length_without_echoing_bytes() {
        for actual in [0, 1, 31, 33, 63, 65] {
            let bytes = vec![0xa5; actual];
            let seed_error = NkeyEd25519Seed::try_from_slice(NkeyEd25519Kind::User, &bytes)
                .expect_err("all non-32-byte seed lengths fail");
            assert_eq!(
                seed_error,
                NkeyOwnedKeyError::Length {
                    form: NkeyOwnedKeyForm::Ed25519Seed,
                    actual,
                    expected: 32,
                }
            );
            assert!(!seed_error.to_string().contains("a5"));
        }

        for actual in [0, 1, 32, 63, 65] {
            let bytes = vec![0x5a; actual];
            assert_eq!(
                NkeyEd25519PrivateKey::try_from_slice(NkeyEd25519Kind::Account, &bytes)
                    .expect_err("all non-64-byte private lengths fail"),
                NkeyOwnedKeyError::Length {
                    form: NkeyOwnedKeyForm::Ed25519Private,
                    actual,
                    expected: 64,
                }
            );
        }

        assert_eq!(
            NkeyCurvePublicKey::try_from_slice(&[0; 31]),
            Err(NkeyOwnedKeyError::Length {
                form: NkeyOwnedKeyForm::CurvePublic,
                actual: 31,
                expected: 32,
            })
        );
        assert!(matches!(
            NkeyCurveSecretKey::try_from_slice(&[0; 33]),
            Err(NkeyOwnedKeyError::Length {
                form: NkeyOwnedKeyForm::CurveSecret,
                actual: 33,
                expected: 32,
            })
        ));
    }

    #[test]
    fn owned_secret_canary_is_redacted_from_formatting_errors_and_panics() {
        #[derive(Clone)]
        struct TraceBuffer(std::sync::Arc<std::sync::Mutex<Vec<u8>>>);

        impl std::io::Write for TraceBuffer {
            fn write(&mut self, bytes: &[u8]) -> std::io::Result<usize> {
                self.0
                    .lock()
                    .expect("trace buffer lock")
                    .extend_from_slice(bytes);
                Ok(bytes.len())
            }

            fn flush(&mut self) -> std::io::Result<()> {
                Ok(())
            }
        }

        const CANARY: &[u8; 32] = b"NKEY-SECRET-CANARY-0123456789ABC";
        let canary_text = std::str::from_utf8(CANARY).expect("ASCII canary");
        let seed = NkeyEd25519Seed::from_bytes(NkeyEd25519Kind::User, *CANARY);
        let curve = NkeyCurveSecretKey::from_bytes(*CANARY);
        let export = seed
            .export_secret(NkeySecretDisposition::PlaintextExport)
            .expect("explicit canary export");

        for rendered in [
            format!("{seed:?}"),
            seed.to_string(),
            format!("{curve:?}"),
            curve.to_string(),
            format!("{export:?}"),
            export.to_string(),
            NkeyOwnedKeyError::SecretDisposition {
                disposition: NkeySecretDisposition::InProcessOperation,
            }
            .to_string(),
        ] {
            assert!(!rendered.contains(canary_text));
            assert!(
                rendered.to_ascii_lowercase().contains("redacted")
                    || rendered.contains("not permitted")
            );
        }

        let panic = std::panic::catch_unwind(|| panic!("{seed:?}"))
            .expect_err("redacted debug panic is captured");
        let panic_text = panic
            .downcast_ref::<String>()
            .map(String::as_str)
            .or_else(|| panic.downcast_ref::<&str>().copied())
            .expect("panic text");
        assert!(!panic_text.contains(canary_text));
        assert!(panic_text.contains("<redacted>"));

        let trace_bytes = std::sync::Arc::new(std::sync::Mutex::new(Vec::new()));
        let writer_bytes = std::sync::Arc::clone(&trace_bytes);
        let disposition_error = NkeyOwnedKeyError::SecretDisposition {
            disposition: NkeySecretDisposition::InProcessOperation,
        };
        let subscriber = tracing_subscriber::fmt()
            .without_time()
            .with_ansi(false)
            .with_writer(move || TraceBuffer(std::sync::Arc::clone(&writer_bytes)))
            .finish();
        tracing::subscriber::with_default(subscriber, || {
            tracing::info!(
                seed = ?seed,
                curve = ?curve,
                export = ?export,
                error = ?disposition_error,
                "NKey secret redaction canary"
            );
        });
        let trace = String::from_utf8(trace_bytes.lock().expect("trace buffer lock").clone())
            .expect("trace output is UTF-8");
        assert!(!trace.contains(canary_text));
        assert!(trace.contains("<redacted>"));
    }

    #[test]
    fn ver_a1_asupersync_dep_p4_nkeys_poc60v_1_3_5e81559b363d_local_invariants() {
        fn assert_send_sync<T: Send + Sync>() {}
        fn assert_copy<T: Copy>() {}

        assert_copy::<NkeyEd25519PublicKey>();
        assert_copy::<NkeyCurvePublicKey>();
        assert_send_sync::<NkeyEd25519Seed>();
        assert_send_sync::<NkeyEd25519PrivateKey>();
        assert_send_sync::<NkeyCurveSecretKey>();
        assert!(mem::needs_drop::<NkeyEd25519Seed>());
        assert!(mem::needs_drop::<NkeyEd25519PrivateKey>());
        assert!(mem::needs_drop::<NkeyCurveSecretKey>());

        let user = NkeyEd25519PublicKey::from_bytes(NkeyEd25519Kind::User, [0x41; 32]);
        let curve = NkeyCurvePublicKey::from_bytes([0x41; 32]);
        assert_eq!(user.kind(), NkeyEd25519Kind::User);
        assert_eq!(user.as_bytes(), &[0x41; 32]);
        assert_eq!(curve.as_bytes(), &[0x41; 32]);
        assert_ne!(format!("{user:?}"), format!("{curve:?}"));

        let seed = NkeyEd25519Seed::from_bytes(NkeyEd25519Kind::User, [0x51; 32]);
        assert!(matches!(
            seed.export_secret(NkeySecretDisposition::InProcessOperation),
            Err(NkeyOwnedKeyError::SecretDisposition {
                disposition: NkeySecretDisposition::InProcessOperation
            })
        ));
    }

    #[test]
    fn ver_a1_asupersync_dep_p4_nkeys_poc60v_1_3_5e81559b363d_property_matrix() {
        const KINDS: [NkeyEd25519Kind; 7] = [
            NkeyEd25519Kind::Account,
            NkeyEd25519Kind::Cluster,
            NkeyEd25519Kind::Module,
            NkeyEd25519Kind::Server,
            NkeyEd25519Kind::Operator,
            NkeyEd25519Kind::User,
            NkeyEd25519Kind::Service,
        ];

        for case in 0u8..64 {
            let kind = KINDS[usize::from(case) % KINDS.len()];
            let bytes = [case; NKEY_KEY_BYTES];
            let public = NkeyEd25519PublicKey::try_from_slice(kind, &bytes)
                .expect("every exact-width public key is retained exactly");
            let curve_public = NkeyCurvePublicKey::try_from_slice(&bytes)
                .expect("every exact-width Curve public key is retained exactly");
            let seed = NkeyEd25519Seed::try_from_slice(kind, &bytes)
                .expect("every exact-width seed is retained exactly");
            let curve_secret = NkeyCurveSecretKey::try_from_slice(&bytes)
                .expect("every exact-width Curve secret is retained exactly");

            assert_eq!(public.kind(), kind);
            assert_eq!(public.as_bytes(), &bytes);
            assert_eq!(curve_public.as_bytes(), &bytes);

            let seed_export = seed
                .export_secret(NkeySecretDisposition::PlaintextSerialization)
                .expect("explicit serialization disposition permits a guarded export");
            let curve_export = curve_secret
                .export_secret(NkeySecretDisposition::PlaintextExport)
                .expect("explicit export disposition permits a guarded export");
            assert_eq!(seed_export.as_bytes(), &bytes);
            assert_eq!(curve_export.as_bytes(), &bytes);
            assert_eq!(
                seed_export.disposition(),
                NkeySecretDisposition::PlaintextSerialization
            );
            assert_eq!(
                curve_export.disposition(),
                NkeySecretDisposition::PlaintextExport
            );
        }
    }

    #[test]
    fn ver_a1_asupersync_dep_p4_nkeys_poc60v_1_3_5e81559b363d_lab_lifecycle() {
        use std::sync::Arc;
        use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};

        struct SecretDropProbe {
            _secret: NkeyCurveSecretKey,
            drops: Arc<AtomicUsize>,
        }

        impl Drop for SecretDropProbe {
            fn drop(&mut self) {
                self.drops.fetch_add(1, Ordering::SeqCst);
            }
        }

        let entered = Arc::new(AtomicBool::new(false));
        let drops = Arc::new(AtomicUsize::new(0));
        let task_entered = Arc::clone(&entered);
        let task_drops = Arc::clone(&drops);
        let probe = SecretDropProbe {
            _secret: NkeyCurveSecretKey::from_bytes([0x73; NKEY_KEY_BYTES]),
            drops: task_drops,
        };

        let mut runtime = crate::lab::runtime::LabRuntime::new(
            crate::lab::config::LabConfig::new(37)
                .max_steps(128)
                .panic_on_leak(false),
        );
        let root = runtime.state.create_root_region(crate::Budget::INFINITE);
        let (task_id, _handle) = runtime
            .state
            .create_task(root, crate::Budget::INFINITE, async move {
                let _probe = probe;
                task_entered.store(true, Ordering::SeqCst);
                loop {
                    crate::runtime::yield_now::yield_now().await;
                    if crate::cx::Cx::with_current(|cx| cx.checkpoint().is_err())
                        .expect("lab task installs a current Cx")
                    {
                        break;
                    }
                }
            })
            .expect("create secret-owning task");
        runtime
            .scheduler
            .lock()
            .schedule(task_id, crate::Budget::INFINITE.priority);
        runtime.step_for_test();

        assert!(
            entered.load(Ordering::SeqCst),
            "task reached secret-owning state"
        );
        assert_eq!(
            drops.load(Ordering::SeqCst),
            0,
            "secret remains owned before cancellation"
        );

        let reason = crate::CancelReason::user("NKey secret lifecycle test");
        let effects = runtime.state.cancel_task(task_id, &reason);
        let (cancelled, wake_effects) = effects.into_parts();
        assert!(cancelled, "cancellation is recorded for the live task");
        runtime
            .scheduler
            .lock()
            .schedule_cancel(task_id, reason.cleanup_budget().priority);
        wake_effects.dispatch();
        runtime.run_until_quiescent();

        assert_eq!(
            drops.load(Ordering::SeqCst),
            1,
            "secret owner drops exactly once"
        );
        assert_eq!(
            runtime.state.live_task_count(),
            0,
            "cancelled task is retired"
        );
        assert_eq!(
            runtime.state.pending_obligation_count(),
            0,
            "secret lifecycle leaves no pending obligations"
        );
    }

    #[test]
    fn create_load_and_export_public_identity_key() {
        let dir = tempdir().expect("tempdir");
        let path = dir.path().join("identity.json");
        let store = IdentityKeyStore::create(&path, strong_seed(1), 100).expect("create store");
        let exported = store.export_public().expect("export public");

        assert_eq!(exported.generation, 1);
        assert!(!exported.revoked);
        assert_eq!(
            exported.fingerprint,
            KeyFingerprint::from_public_key(exported.public_key.as_bytes()).expect("fingerprint")
        );

        let loaded = IdentityKeyStore::load(&path).expect("load store");
        assert_eq!(loaded.export_public().unwrap(), exported);
        assert_eq!(loaded.platform(), KeyStorePlatform::current());
    }

    #[test]
    fn debug_redacts_persisted_seed_material() {
        let dir = tempdir().expect("tempdir");
        let path = dir.path().join("identity.json");
        let store = IdentityKeyStore::create(&path, strong_seed(4), 100).expect("create store");
        let persisted_seed = store.record.keys[0].seed.clone();

        let store_debug = format!("{store:?}");
        assert!(
            !store_debug.contains(&persisted_seed),
            "IdentityKeyStore Debug must not expose persisted NKey seed"
        );
        assert!(
            store_debug.contains("seed: \"<redacted>\""),
            "IdentityKeyStore Debug should show that seed material was redacted"
        );

        let key_debug = format!("{:?}", store.record.keys[0]);
        assert!(
            !key_debug.contains(&persisted_seed),
            "PersistedIdentityKey Debug must not expose persisted NKey seed"
        );
        assert!(
            key_debug.contains("seed: \"<redacted>\""),
            "PersistedIdentityKey Debug should show that seed material was redacted"
        );
    }

    #[test]
    fn rotate_then_revoke_retired_generation() {
        let dir = tempdir().expect("tempdir");
        let path = dir.path().join("identity.json");
        let mut store = IdentityKeyStore::create(&path, strong_seed(2), 100).expect("create store");
        let old = store.export_public().expect("old public");
        let new = store.rotate(strong_seed(3), 200).expect("rotate");

        assert_eq!(new.generation, 2);
        assert_ne!(old.fingerprint, new.fingerprint);
        assert_eq!(store.active_generation(), 2);

        let revoked = store.revoke(old.fingerprint, 300).expect("revoke old");
        assert!(revoked.revoked);
        assert_eq!(
            store.revoke(new.fingerprint, 400).unwrap_err().to_string(),
            format!("cannot revoke active key {}", new.fingerprint)
        );

        let loaded = IdentityKeyStore::load(&path).expect("load rotated store");
        let history = loaded.export_public_history().expect("history");
        assert_eq!(history.len(), 2);
        assert!(history[0].revoked);
        assert!(!history[1].revoked);
    }

    #[test]
    fn rejects_weak_seed_and_bad_public_key_material() {
        let dir = tempdir().expect("tempdir");
        let path = dir.path().join("identity.json");
        assert!(matches!(
            IdentityKeyStore::create(&path, [0; 32], 100),
            Err(KeyStoreError::WeakSeed("all-zero seed"))
        ));
        assert!(matches!(
            KeyFingerprint::from_public_key(&[]),
            Err(KeyStoreError::InvalidPublicKey(_))
        ));
    }

    #[cfg(unix)]
    #[test]
    fn pending_symlink_does_not_redirect_key_store_write() {
        use std::io::ErrorKind;
        use std::os::unix::fs::symlink;

        let dir = tempdir().expect("tempdir");
        let path = dir.path().join("identity.json");
        let pending = pending_path(&path).expect("pending path");
        let sentinel = dir.path().join("sentinel");
        fs::write(&sentinel, b"do-not-touch").expect("write sentinel");
        symlink(&sentinel, &pending).expect("create pending symlink");

        let err = IdentityKeyStore::create(&path, strong_seed(5), 100).unwrap_err();
        match err {
            KeyStoreError::Io {
                path: failed_path,
                source,
            } => {
                assert_eq!(failed_path, pending);
                assert_eq!(source.kind(), ErrorKind::AlreadyExists);
            }
            other => panic!("unexpected key-store error: {other}"),
        }
        assert_eq!(fs::read(&sentinel).expect("read sentinel"), b"do-not-touch");
        assert!(matches!(
            fs::symlink_metadata(&path),
            Err(error) if error.kind() == ErrorKind::NotFound
        ));
    }
}