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export const MILLISECONDS_PER_SECOND = 1000;
let lastNow = Date.now();
/**
* Returns the time in miliseconds.
* A strictly increasing version of Date.now()
*
* Gives us some minimimal guarentees about user clocks.
*/
export function monotonicNow(): number {
const maybeNow = Date.now();
lastNow = lastNow < maybeNow ? maybeNow : lastNow + 1;
return lastNow;
}
/**
* Timeouts a promise. Returns timeoutValue in event of timeout.
* @param promise The promise to timeout
* @param timeoutMilliseconds The timeout time in milliseconds
*/
export function timeoutPromise< T >(
promise: Promise< T >,
timeoutMilliseconds: number
): Promise< T | null > {
return Promise.race( [
promise,
new Promise< null >( ( _res, rej ) =>
setTimeout(
() => rej( new Error( `Promise has timed-out after ${ timeoutMilliseconds }ms.` ) ),
timeoutMilliseconds
)
),
] );
}
/**
* Wraps an async function so that if it is called multiple times it will just return the same promise - until the promise is fulfilled.
*
* Once the promise has been fulfilled it will reset.
* @param f The function to wrap
*/
export function asyncOneAtATime< T >( f: () => Promise< T > ): () => Promise< T > {
let lastPromise: Promise< T > | null = null;
return () => {
if ( ! lastPromise ) {
lastPromise = f().finally( () => {
lastPromise = null;
} );
}
return lastPromise;
};
}
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