elastik-core 8.2.0

//! # Elastik — Audi-ted L5 Storage Engine
//!
//! `elastik-core` is a protocol-neutral storage engine: canonical paths, opaque
//! bytes, content-addressed versioning, an HMAC-chained audit log, and a
//! four-tier access model. **SQLite for files.**
//!
//! ## Quick start
//!
//! ```no_run
//! # #[cfg(feature = "unstable-engine")]
//! # async fn run() {
//! use elastik_core::{
//!     AccessTier, Engine, Preconditions, Representation, SecretBytes, ValidatedWorldPath,
//! };
//! use bytes::Bytes;
//!
//! let engine = Engine::builder()
//!     .data_root("./data")
//!     .key(SecretBytes::new(b"shared-hmac-secret".to_vec()).expect("hmac key"))
//!     .build()
//!     .expect("engine builds");
//!
//! let world = ValidatedWorldPath::new("home/hello").expect("canonical path");
//!
//! // Store bytes at a path.
//! engine
//!     .replace(
//!         &world,
//!         Representation::new(Bytes::from_static(b"hi"), "text/plain", Vec::new()),
//!         Preconditions::none(),
//!         AccessTier::Write,
//!     )
//!     .await
//!     .expect("write succeeds");
//!
//! // Retrieve bytes by path.
//! let read = engine.read(&world, AccessTier::Read).expect("read succeeds");
//! assert!(read.is_some());
//! # }
//! ```
//!
//! ## What the library does
//!
//! - **Bytes at paths.** Canonical `home/`, `tmp/`, `dev/`, `sys/`, `etc/`,
//!   `lib/`, `boot/`, `usr/`, `var/` namespaces decide durable-vs-transient
//!   without per-call configuration.
//! - **Versions everything.** Every successful write returns an ETag; reads,
//!   replaces, and appends honour `Preconditions::if_match` / `if_none_match`.
//! - **Audits everything.** HMAC-chained ledger; `Engine::verify_audit`
//!   returns a typed [`AuditVerify`] result and refuses to start when an
//!   existing chain is corrupted.
//! - **Authenticates everything.** [`AccessTier`] (Anon / Read / Write /
//!   Approve) plus token-bytes verification via [`Engine::verify_token`].
//! - **Subscribes to changes.** [`Engine::subscribe`] returns an
//!   [`EngineSubscription`] with replay-then-live ordering.
//!
//! ## What the library does *not* do
//!
//! No protocol adapters and no server runtime. Those live in the `elastik-bin`
//! package's `elastik-core` binary and consume this library through the
//! unstable public [`Engine`] API. In a minimal library-only build, the library
//! does not read environment variables, does not bind sockets, and does not
//! depend on protocol-adapter transport crates.
//!
//! ## Feature flags
//!
//! - `bundled-sqlite` *(default)* — link a bundled SQLite via `rusqlite/bundled`.
//! - `unstable-engine` — expose the public [`Engine`] facade. **The API shape
//!   is allowed to change between minor versions while this gate stays.**
//!
//! Binary adapter features such as `coap`, `mqtt`, and `multi-thread` live in
//! `bin/Cargo.toml`, not in this library package.
//!
//! Minimal library-only build from the repository root:
//! `cargo build --manifest-path core/Cargo.toml --lib --no-default-features
//! --features bundled-sqlite,unstable-engine`.
mod audit;
mod auth;
mod data_lock;
mod defaults;
mod delete_ops;
mod engine;
mod engine_introspection;
mod engine_ops;
mod engine_trace;
mod engine_types;
mod etag;
mod event;
mod ledger;
mod path;
mod read_cache;
mod state;
mod storage_class;
mod store;
#[cfg(test)]
mod test_support;
mod world;
mod world_ops;

// Re-export protocol-neutral helpers at the crate root.
pub(crate) use crate::state::*;
pub(crate) use crate::storage_class::*;
#[cfg(not(feature = "unstable-engine"))]
pub(crate) use auth::AuthGate;
#[cfg(feature = "unstable-engine")]
pub use auth::{is_valid_token, AuthGate};
pub(crate) use data_lock::acquire_data_root_writer_lock;
#[cfg(feature = "unstable-engine")]
pub use defaults::{
    DEFAULT_LISTEN_REPLAY_MAX, DEFAULT_MAX_LISTEN_CONNECTIONS, DEFAULT_MAX_MEMORY_BYTES,
    DEFAULT_MAX_WORLD_BYTES, DEFAULT_READ_CACHE_MAX_ENTRIES,
};
#[cfg(feature = "unstable-engine")]
#[doc(hidden)]
pub use engine::ShutdownToken;
#[cfg(feature = "unstable-engine")]
pub use engine::{Engine, EngineBuildError, EngineBuilder, EngineError};
#[cfg(feature = "unstable-engine")]
pub use engine_introspection::{
    AuditBroken, AuditValid, AuditVerify, DfSnapshot, InvalidProcPath, PoolSnapshot, ProcEndpoint,
    ValidatedProcPath, WorldUsage,
};
#[cfg(feature = "unstable-engine")]
pub use engine_trace::{DeleteMetadata, EngineDeleteTraceHooks, EngineWriteTraceHooks};
#[cfg(feature = "unstable-engine")]
pub use engine_types::{
    parse_etag_matchers, AccessTier, ChangeEvent, ChangeVerb, EmptyKeyError, EngineSubscription,
    EtagMatcher, InvalidWorldPath, Preconditions, ReadResult, Representation, SecretBytes,
    SubscribePattern, SubscriptionRecvError, ValidatedWorldPath, WriteKind, WriteResult,
};
#[cfg(feature = "unstable-engine")]
pub use path::{validate_world_name, NAMESPACE_PREFIXES};

// ─── helpers ────────────────────────────────────────────────────────

pub(crate) fn can_write(world_name: &str, tier: auth::Tier) -> bool {
    // Harvard gate: /lib/, /etc/, /boot/, /usr/, and audit logs
    // require approve. /home/, /tmp/, /dev/, /sys/, and non-log
    // /var/ worlds accept the normal token. Anon refused.
    let needs_approve = needs_write_approve(world_name);
    match tier {
        auth::Tier::Anon => false,
        auth::Tier::Read => false,
        auth::Tier::Write => !needs_approve,
        auth::Tier::Approve => true,
    }
}

/// Mirrors the harvard-gate decision in `can_write`. Lifted out so
/// `handler::execute_put` / `execute_post` can classify a rejected
/// write as `Auth(Write)` vs `Auth(WriteApprove)` for the FSM trace
/// without re-deriving the predicate.
pub(crate) fn needs_write_approve(world_name: &str) -> bool {
    exact_or_child(world_name, "lib")
        || exact_or_child(world_name, "etc")
        || exact_or_child(world_name, "boot")
        || exact_or_child(world_name, "usr")
        || exact_or_child(world_name, "var/log")
}

pub(crate) fn can_delete(tier: auth::Tier) -> bool {
    matches!(tier, auth::Tier::Approve)
}

// (memory_write_projected_bytes / memory_append_projected_bytes were
// removed: the snapshot-based projection they computed could be observed
// by two concurrent writers before either had committed, letting them
// both pass and overshoot max_memory_bytes once the global write_lock was
// gone. Quota is now enforced inside MemoryStore::write_with_quota /
// append_with_quota, atomically with the write itself.)

// `require_read` (auth gate for proc handlers) lives in proc.rs now,
// next to its only callers.

pub(crate) fn exact_or_child(world_name: &str, prefix: &str) -> bool {
    world_name == prefix
        || world_name
            .strip_prefix(prefix)
            .is_some_and(|rest| rest.starts_with('/'))
}

pub(crate) fn can_read(core: &Core, tier: auth::Tier) -> bool {
    !core.tokens.read_required()
        || matches!(
            tier,
            auth::Tier::Read | auth::Tier::Write | auth::Tier::Approve
        )
}