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/**
* Creates a function that samples calls at regular intervals and captures trailing calls.
* - Drops calls that occur between sampling intervals
* - Takes one call per sampling interval if available
* - Captures the last call if no call was made during the interval
*
* @param fn The function to sample
* @param sampleInterval How often to sample calls (in ms)
* @returns The sampled function
*/
export function createSampler<T extends (...args: any[]) => any>(fn: T, sampleInterval: number): T {
let lastArgs: Parameters<T> | null = null;
let lastTime = 0;
let timeout: NodeJS.Timeout | null = null;
// Create a function with the same type as the input function
const sampled = function (this: any, ...args: Parameters<T>) {
const now = Date.now();
lastArgs = args;
// If we're within the sample interval, just store the args
if (now - lastTime < sampleInterval) {
// Set up trailing call if not already set
if (!timeout) {
timeout = setTimeout(
() => {
timeout = null;
lastTime = Date.now();
if (lastArgs) {
fn.apply(this, lastArgs);
lastArgs = null;
}
},
sampleInterval - (now - lastTime),
);
}
return;
}
// If we're outside the interval, execute immediately
lastTime = now;
fn.apply(this, args);
lastArgs = null;
} as T;
return sampled;
}
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