Struct PendingOutbox 

pub struct PendingOutbox {
    pub message_type: Box<str>,
    pub recipient: Box<str>,
    pub payload: Value,
    pub deliver_after: Option<OffsetDateTime>,
    pub payload_schema: Option<Box<str>>,
    pub caused_by_event_index: usize,
}

A lightweight outbox message specification produced by Workflow::handle.

Workflow::handle is a pure function: it cannot know the store-assigned fields (event_id, stream_id, process_id, etc.) of the events it is about to emit. PendingOutbox carries only the information the domain workflow can produce deterministically, without I/O or clock access.

The engine fills in the store-assigned fields after the event append succeeds, converting PendingOutbox into a fully materialised OutboxMessage inside SlateDbStore::append_with_outbox.

Example

// Inside Workflow::handle, when DispatchAperak succeeds:
let outbox = vec![
    PendingOutbox::new("APERAK", &state.sender_party_id().to_string(), aperak_payload)
        .caused_by(0),  // caused by the first event in this batch
];
Ok(WorkflowOutput { events, outbox })

Fields

message_type: Box<str>

EDIFACT or XML message type (e.g. "APERAK", "CONTRL", "REMADV").

recipient: Box<str>

GLN or EIC code of the intended recipient market participant.

payload: Value

Domain-level message payload (JSON).

Typically encodes the intent (e.g. positive/negative APERAK reason) rather than the final EDIFACT bytes. The delivery worker or AS4 gateway is responsible for rendering the final wire format.

deliver_after: Option<OffsetDateTime>

Do not deliver before this time.

None means deliver immediately (as soon as the delivery worker runs). Must not use the wall clock inside handle — derive from domain data only (e.g. a schedule date carried in the command).

payload_schema: Option<Box<str>>

BO4E JSON Schema URL that describes the payload shape.

Set this to the canonical BO4E schema URL when the payload is a BO4E-typed object (e.g. Marktlokation, Messlokation). Leave None for raw EDIFACT or untyped payloads.

Example: "https://raw.githubusercontent.com/BO4E/BO4E-Schemas/v202501.0.0/src/bo4e_schemas/bo/Marktlokation.json"

caused_by_event_index: usize

Zero-based index into the concurrent events batch that caused this outbound message.

Used by the engine to set causation_event_id on the materialised OutboxMessage from the stamped EventEnvelope at the same index. Clamped to events.len() - 1 when out-of-range.

Implementations

impl PendingOutbox

pub fn new( message_type: impl Into<Box<str>>, recipient: impl Into<Box<str>>, payload: Value, ) -> Self

Construct a pending outbox message for immediate delivery.

caused_by_event_index defaults to 0 (first event in the batch). Chain caused_by to change it.

pub fn caused_by(self, index: usize) -> Self

Set the zero-based index of the event that caused this outbox message.

pub fn with_deliver_after(self, deliver_after: OffsetDateTime) -> Self

Set a deferred delivery time (must be derived from domain data, not the wall clock, to preserve Workflow::handle purity).

pub fn with_schema(self, schema_url: &'static str) -> Self

Attach a BO4E JSON Schema URL to the payload.

Use this when the payload is a BO4E-typed object so the ERP adapter can deserialise it into the correct type without inspecting the JSON.

Trait Implementations

impl Clone for PendingOutbox

fn clone(&self) -> PendingOutbox

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PendingOutbox

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.