//#region src/network/ewma.ts
/**
* Exponentially Weighted Moving Average (EWMA)
*
* Pure functional implementation of EWMA calculations.
* Based on Shaka Player's EWMA algorithm.
*/
/**
* Calculate alpha (decay factor) from half-life.
*
* Alpha determines how quickly old data "expires":
* - alpha close to 1 = slow decay (long memory)
* - alpha close to 0 = fast decay (short memory)
*
* @param halfLife - The quantity of prior samples (by weight) that make up
*   half of the new estimate. Must be positive.
* @returns Alpha value between 0 and 1
*
* @example
* const alpha = calculateAlpha(2); // ≈ 0.7071 for 2-second half-life
*/
function calculateAlpha(halfLife) {
	return Math.exp(Math.log(.5) / halfLife);
}
/**
* Calculate exponentially weighted moving average.
*
* Updates an estimate by blending a new value with the previous estimate,
* weighted by the sample duration. Longer samples have more influence.
*
* @param prevEstimate - Previous EWMA estimate
* @param value - New sample value to incorporate
* @param weight - Sample weight (typically duration in seconds)
* @param halfLife - Half-life for decay (typically 2-5 seconds)
* @returns Updated EWMA estimate
*
* @example
* let estimate = 0;
* estimate = calculateEwma(estimate, 1_000_000, 1, 2); // First sample
* estimate = calculateEwma(estimate, 2_000_000, 1, 2); // Second sample
*/
function calculateEwma(prevEstimate, value, weight, halfLife) {
	const adjAlpha = calculateAlpha(halfLife) ** weight;
	return value * (1 - adjAlpha) + adjAlpha * prevEstimate;
}
/**
* Apply zero-factor correction to EWMA estimate.
*
* The zero-factor correction compensates for bias when starting from zero.
* Without this correction, early estimates would be artificially low.
*
* As totalWeight increases, the correction factor approaches 1, meaning
* the estimate becomes more reliable and needs less correction.
*
* @param estimate - Raw EWMA estimate (uncorrected)
* @param totalWeight - Accumulated weight from all samples
* @param halfLife - Half-life used in EWMA calculation
* @returns Corrected estimate, or 0 if totalWeight is 0
*
* @example
* const raw = calculateEwma(0, 1_000_000, 1, 2);
* const corrected = applyZeroFactor(raw, 1, 2); // ≈ 1_000_000
*/
function applyZeroFactor(estimate, totalWeight, halfLife) {
	if (totalWeight === 0) return 0;
	return estimate / (1 - calculateAlpha(halfLife) ** totalWeight);
}
//#endregion
export { applyZeroFactor, calculateAlpha, calculateEwma };

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