File size: 1,493 Bytes
dbb1bf9 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 | interface QueueEntry {
reject: (reason?: unknown) => void;
resolve: (value: unknown) => void;
task: () => Promise<unknown> | unknown;
}
/**
* Small FIFO executor for browser-side async work that must not overlap.
*
* The first task starts synchronously so unload/visibility handlers can begin
* a keepalive fetch before returning. Later tasks wait without allowing a
* rejection to poison the queue.
*/
export class SerializedAsyncQueue {
private active = false;
private readonly entries: QueueEntry[] = [];
get busy(): boolean {
return this.active || this.entries.length > 0;
}
run<T>(task: () => Promise<T> | T): Promise<T> {
return new Promise<T>((resolve, reject) => {
this.entries.push({
task,
resolve: resolve as (value: unknown) => void,
reject,
});
this.startNext();
});
}
private startNext(): void {
if (this.active) return;
const entry = this.entries.shift();
if (!entry) return;
this.active = true;
let result: Promise<unknown> | unknown;
try {
result = entry.task();
} catch (error) {
this.active = false;
this.startNext();
entry.reject(error);
return;
}
void Promise.resolve(result).then(
(value) => {
this.active = false;
this.startNext();
entry.resolve(value);
},
(error) => {
this.active = false;
this.startNext();
entry.reject(error);
},
);
}
}
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