Module traits 

Trait boundary between engine-core and the runtime.

This module defines the traits that separate the pure engine logic from the runtime (tokio, channels, WAL, NATS, persistence). The engine emits events and journal entries through these traits without knowing anything about the transport or storage backend.

The hypercall crate provides production implementations backed by:

• tokio::sync::broadcast channels for EventSink
• WAL files with CRC validation for JournalWriter
• NATS for CommandPublisher

In tests, these can be stubbed with simple in-memory implementations (e.g., a Vec<EngineEvent> behind a mutex).

This module also defines the data types that flow through these traits: EngineEvent, JournalEntry, and JournalError.

Structs

JournalEntry

A journal entry representing a single command for WAL persistence.

Enums

EngineEvent

Events emitted by the engine after command processing.

JournalError

Error type for journal write failures.

Traits

CommandPublisher

Publisher for command replication to standby instances.

EventSink

Sink for engine events emitted after command processing.

JournalWriter

Durable journal writer for crash recovery.