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export class PubSub {
#target = new EventTarget();
publish(trigger: string, payload: unknown): Promise<void> {
this.#target.dispatchEvent(new CustomEvent(trigger, { detail: payload }));
return Promise.resolve();
}
asyncIterator<T>(triggers: string | string[]): AsyncIterableIterator<T> {
const names = Array.isArray(triggers) ? triggers : [triggers];
const pulls: Array<(result: IteratorResult<T>) => void> = [];
const pushes: T[] = [];
let done = false;
const listener = (event: Event) => {
const value = (event as CustomEvent<T>).detail;
const pull = pulls.shift();
if (pull)
pull({ done: false, value });
else
pushes.push(value);
};
for (const name of names)
this.#target.addEventListener(name, listener);
const close = (): Promise<IteratorResult<T>> => {
if (!done) {
done = true;
for (const name of names)
this.#target.removeEventListener(name, listener);
for (const pull of pulls.splice(0))
pull({ done: true, value: undefined });
pushes.length = 0;
}
return Promise.resolve({ done: true, value: undefined });
};
return {
next: () => {
if (done)
return Promise.resolve({ done: true, value: undefined });
if (pushes.length > 0)
return Promise.resolve({ done: false, value: pushes.shift() as T });
return new Promise((resolve) => pulls.push(resolve));
},
return: close,
throw: (error: unknown) => {
close();
return Promise.reject(error);
},
[Symbol.asyncIterator]() {
return this;
}
};
}
}
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