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EventStream.ts
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EventStream.ts
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import { APIUserAbortError, OpenAIError } from "../error.ts";
export class EventStream<EventTypes extends BaseEvents> {
controller: AbortController = new AbortController();
#connectedPromise: Promise<void>;
#resolveConnectedPromise: () => void = () => {};
#rejectConnectedPromise: (error: OpenAIError) => void = () => {};
#endPromise: Promise<void>;
#resolveEndPromise: () => void = () => {};
#rejectEndPromise: (error: OpenAIError) => void = () => {};
#listeners: {
[Event in keyof EventTypes]?: EventListeners<EventTypes, Event>;
} = {};
#ended = false;
#errored = false;
#aborted = false;
#catchingPromiseCreated = false;
constructor() {
this.#connectedPromise = new Promise<void>((resolve, reject) => {
this.#resolveConnectedPromise = resolve;
this.#rejectConnectedPromise = reject;
});
this.#endPromise = new Promise<void>((resolve, reject) => {
this.#resolveEndPromise = resolve;
this.#rejectEndPromise = reject;
});
// Don't let these promises cause unhandled rejection errors.
// we will manually cause an unhandled rejection error later
// if the user hasn't registered any error listener or called
// any promise-returning method.
this.#connectedPromise.catch(() => {});
this.#endPromise.catch(() => {});
}
protected _run(this: EventStream<EventTypes>, executor: () => Promise<any>) {
// Unfortunately if we call `executor()` immediately we get runtime errors about
// references to `this` before the `super()` constructor call returns.
setTimeout(() => {
executor().then(() => {
this._emitFinal();
this._emit("end");
}, this.#handleError.bind(this));
}, 0);
}
protected _connected(this: EventStream<EventTypes>) {
if (this.ended) return;
this.#resolveConnectedPromise();
this._emit("connect");
}
get ended(): boolean {
return this.#ended;
}
get errored(): boolean {
return this.#errored;
}
get aborted(): boolean {
return this.#aborted;
}
abort() {
this.controller.abort();
}
/**
* Adds the listener function to the end of the listeners array for the event.
* No checks are made to see if the listener has already been added. Multiple calls passing
* the same combination of event and listener will result in the listener being added, and
* called, multiple times.
* @returns this ChatCompletionStream, so that calls can be chained
*/
on<Event extends keyof EventTypes>(
event: Event,
listener: EventListener<EventTypes, Event>,
): this {
const listeners: EventListeners<EventTypes, Event> =
this.#listeners[event] || (this.#listeners[event] = []);
listeners.push({ listener });
return this;
}
/**
* Removes the specified listener from the listener array for the event.
* off() will remove, at most, one instance of a listener from the listener array. If any single
* listener has been added multiple times to the listener array for the specified event, then
* off() must be called multiple times to remove each instance.
* @returns this ChatCompletionStream, so that calls can be chained
*/
off<Event extends keyof EventTypes>(
event: Event,
listener: EventListener<EventTypes, Event>,
): this {
const listeners = this.#listeners[event];
if (!listeners) return this;
const index = listeners.findIndex((l) => l.listener === listener);
if (index >= 0) listeners.splice(index, 1);
return this;
}
/**
* Adds a one-time listener function for the event. The next time the event is triggered,
* this listener is removed and then invoked.
* @returns this ChatCompletionStream, so that calls can be chained
*/
once<Event extends keyof EventTypes>(
event: Event,
listener: EventListener<EventTypes, Event>,
): this {
const listeners: EventListeners<EventTypes, Event> =
this.#listeners[event] || (this.#listeners[event] = []);
listeners.push({ listener, once: true });
return this;
}
/**
* This is similar to `.once()`, but returns a Promise that resolves the next time
* the event is triggered, instead of calling a listener callback.
* @returns a Promise that resolves the next time given event is triggered,
* or rejects if an error is emitted. (If you request the 'error' event,
* returns a promise that resolves with the error).
*
* Example:
*
* const message = await stream.emitted('message') // rejects if the stream errors
*/
emitted<Event extends keyof EventTypes>(
event: Event,
): Promise<
EventParameters<EventTypes, Event> extends [infer Param] ? Param
: EventParameters<EventTypes, Event> extends [] ? void
: EventParameters<EventTypes, Event>
> {
return new Promise((resolve, reject) => {
this.#catchingPromiseCreated = true;
if (event !== "error") this.once("error", reject);
this.once(event, resolve as any);
});
}
async done(): Promise<void> {
this.#catchingPromiseCreated = true;
await this.#endPromise;
}
#handleError(this: EventStream<EventTypes>, error: unknown) {
this.#errored = true;
if (error instanceof Error && error.name === "AbortError") {
error = new APIUserAbortError();
}
if (error instanceof APIUserAbortError) {
this.#aborted = true;
return this._emit("abort", error);
}
if (error instanceof OpenAIError) {
return this._emit("error", error);
}
if (error instanceof Error) {
const openAIError: OpenAIError = new OpenAIError(error.message);
// @ts-ignore
openAIError.cause = error;
return this._emit("error", openAIError);
}
return this._emit("error", new OpenAIError(String(error)));
}
_emit<Event extends keyof BaseEvents>(
event: Event,
...args: EventParameters<BaseEvents, Event>
): void;
_emit<Event extends keyof EventTypes>(
event: Event,
...args: EventParameters<EventTypes, Event>
): void;
_emit<Event extends keyof EventTypes>(
this: EventStream<EventTypes>,
event: Event,
...args: EventParameters<EventTypes, Event>
) {
// make sure we don't emit any events after end
if (this.#ended) {
return;
}
if (event === "end") {
this.#ended = true;
this.#resolveEndPromise();
}
const listeners: EventListeners<EventTypes, Event> | undefined =
this.#listeners[event];
if (listeners) {
this.#listeners[event] = listeners.filter((l) => !l.once) as any;
listeners.forEach(({ listener }: any) => listener(...(args as any)));
}
if (event === "abort") {
const error = args[0] as APIUserAbortError;
if (!this.#catchingPromiseCreated && !listeners?.length) {
Promise.reject(error);
}
this.#rejectConnectedPromise(error);
this.#rejectEndPromise(error);
this._emit("end");
return;
}
if (event === "error") {
// NOTE: _emit('error', error) should only be called from #handleError().
const error = args[0] as OpenAIError;
if (!this.#catchingPromiseCreated && !listeners?.length) {
// Trigger an unhandled rejection if the user hasn't registered any error handlers.
// If you are seeing stack traces here, make sure to handle errors via either:
// - runner.on('error', () => ...)
// - await runner.done()
// - await runner.finalChatCompletion()
// - etc.
Promise.reject(error);
}
this.#rejectConnectedPromise(error);
this.#rejectEndPromise(error);
this._emit("end");
}
}
protected _emitFinal(): void {}
}
type EventListener<Events, EventType extends keyof Events> = Events[EventType];
type EventListeners<Events, EventType extends keyof Events> = Array<{
listener: EventListener<Events, EventType>;
once?: boolean;
}>;
export type EventParameters<Events, EventType extends keyof Events> = {
[Event in EventType]: EventListener<Events, EventType> extends
(...args: infer P) => any ? P : never;
}[EventType];
export interface BaseEvents {
connect: () => void;
error: (error: OpenAIError) => void;
abort: (error: APIUserAbortError) => void;
end: () => void;
}