//! Shard engine for erasure-coded block distribution and reconstruction.
//!
//! # Overview
//!
//! The shards subsystem distributes erasure-coded blocks, validates shard authenticity, and
//! reconstructs blocks on demand. It ensures every validator contributes bandwidth proportional
//! to a single shard while allowing any node to recover the entire [`super::types::CodedBlock`]
//! once enough shards are available.
//!
//! # Responsibilities
//!
//! - [`Engine`] accepts commands over [`Mailbox`] to broadcast proposer shards, validate and
//!   reshare received shards, and serve reconstruction requests.
//! - Maintains an ephemeral cache of reconstructed blocks, evicted when marshal signals
//!   durability.
//! - Tracks subscriptions for shard arrival and block reconstruction, notifying waiters when
//!   data becomes available.

mod mailbox;
pub use mailbox::{Mailbox, Message};

mod metrics;

mod engine;
pub use engine::{Config, Engine, Error};