SseWriter

SUPPORT · interface · Type contract

Destination that reports backpressure instead of buffering without bound.

Import

TypeScript

import type { SseWriter } from '@jangts/agent-core/sse';

JavaScript

/** @typedef {import('@jangts/agent-core/sse').SseWriter} SseWriter */

Other public entry points:@jangts/agent-core, @jangts/agent-core/types, @jangts/agent-core/structs, @jangts/agent-core/sse, @jangts/agent-core/support.

Definition

interface SseWriter

Field structure

Field	Type	Required	Description
write	(frame: string) => boolean	Required	Writes one encoded frame; returns false when the consumer needs a drain wait.
waitForDrain	(signal?: AbortSignal) => Promise<unknown>	Required	Resolves once the destination can accept more data, or rejects when signal aborts.

Member index

Member	Purpose
write	Writes one encoded frame; returns false when the consumer needs a drain wait.
waitForDrain	Resolves once the destination can accept more data, or rejects when signal aborts.

Member details

write

Writes one encoded frame; returns false when the consumer needs a drain wait.

SseWriter.write(frame: string): boolean

Writes one encoded frame; returns false when the consumer needs a drain wait.

Parameter	Type	Passing	Description
frame	string	Required	—

Returns: boolean.

waitForDrain

Resolves once the destination can accept more data, or rejects when signal aborts.

SseWriter.waitForDrain(signal?: AbortSignal): Promise<unknown>

Resolves once the destination can accept more data, or rejects when signal aborts.

Parameter	Type	Passing	Description
signal	AbortSignal | undefined	Optional	—

Returns: Promise<unknown>.

Awaited value: unknown.

Examples

• SSE, JSON frames, and bounded event streams: Reuse transport mechanics while preserving cancellation and backpressure; protocol parsing and business validation remain separate.

Parse one SSE frame locally

Beginner · Node.js

TypeScript

import { Support } from '@jangts/agent-core';
const frame = Support.encodeSseEvent({ event: 'status', data: JSON.stringify({ phase: 'thinking' }) });
const body = new Response(frame).body!;
for await (const event of Support.readSse(body)) console.log(event.event, event.data);

JavaScript

import { Support } from '@jangts/agent-core';
const frame = Support.encodeSseEvent({ event: 'status', data: JSON.stringify({ phase: 'thinking' }) });
const body = new Response(frame).body;
for await (const event of Support.readSse(body))
    console.log(event.event, event.data);

Producer waits for each event delivery

Configuration · Node.js

TypeScript

import { Support } from '@jangts/agent-core';
const signal = new AbortController().signal;
const stream = Support.streamEvents<{ phase: string }>(async emit => {
  await emit({ phase: 'preparing' });
  await emit({ phase: 'complete' });
}, { signal });
for await (const event of stream) console.log(event.phase);

JavaScript

import { Support } from '@jangts/agent-core';
const signal = new AbortController().signal;
const stream = Support.streamEvents(async (emit) => {
    await emit({ phase: 'preparing' });
    await emit({ phase: 'complete' });
}, { signal });
for await (const event of stream)
    console.log(event.phase);

Related policy source

• Single-slot handoff and backpressure in event streams