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import * as utils from './utils.js';
/**
* Convert a `Response` body containing Server Sent Events (SSE) into an Async Iterator that yields {@linkcode ServerSentEventMessage} objects.
*
* @see {@link https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events}
*
* @example
* ```js
* // Optional
* let abort = new AbortController;
*
* // Manually fetch a Response
* let res = await fetch('https://...', {
* method: 'POST',
* signal: abort.signal,
* headers: {
* 'api-key': 'token <value>',
* 'content-type': 'application/json',
* },
* body: JSON.stringify({
* stream: true, // <- hypothetical
* // ...
* })
* });
*
* if (res.ok) {
* let stream = events(res, abort.signal);
* for await (let event of stream) {
* console.log('<<', event.data);
* }
* }
* ```
*/
export async function* events(res, signal) {
// TODO: throw error?
if (!res.body)
return;
let iter = utils.stream(res.body);
let line, reader = iter.getReader();
let event;
for (;;) {
if (signal && signal.aborted) {
return reader.cancel();
}
line = await reader.read();
if (line.done)
return;
if (!line.value) {
if (event)
yield event;
event = undefined;
continue;
}
let [field, value] = utils.split(line.value) || [];
if (!field)
continue; // comment or invalid
if (field === 'data') {
event ||= {};
event[field] = event[field] ? (event[field] + '\n' + value) : value;
}
else if (field === 'event') {
event ||= {};
event[field] = value;
}
else if (field === 'id') {
event ||= {};
event[field] = +value || value;
}
else if (field === 'retry') {
event ||= {};
event[field] = +value || undefined;
}
}
}
/**
* Convenience function that will `fetch` with the given arguments and, if ok, will return the {@linkcode events} async iterator.
*
* If the response is not ok (status 200-299), the `Response` is thrown.
*
* @example
* ```js
* // NOTE: throws `Response` if not 2xx status
* let events = await stream('https://api.openai.com/...', {
* method: 'POST',
* headers: {
* 'Authorization': 'Bearer <token>',
* 'Content-Type': 'application/json',
* },
* body: JSON.stringify({
* stream: true,
* // ...
* })
* });
*
* for await (let event of events) {
* console.log('<<', JSON.parse(event.data));
* }
* ```
*/
export async function stream(input, init) {
let req = new Request(input, init);
utils.fallback(req.headers, 'Accept', 'text/event-stream');
utils.fallback(req.headers, 'Content-Type', 'application/json');
let r = await fetch(req);
if (!r.ok)
throw r;
return events(r, req.signal);
}
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