@hyperlane-xyz/sdk/dist/fee/utils.js

The official SDK for the Hyperlane Network

import { assert } from '@hyperlane-xyz/utils';
export const MAX_BPS = 10000n;
/**
 * Maximum decimal places supported for fractional bps values.
 * The precision scaling in convertToBps/convertFromBps uses 10^MAX_BPS_DECIMALS
 * as a multiplier. Values with more decimal places will be rejected to prevent
 * silent precision loss during bigint arithmetic.
 */
export const MAX_BPS_DECIMALS = 4;
/**
 * Bigint precision multiplier for fractional bps arithmetic.
 * Equals 10^MAX_BPS_DECIMALS = 10_000n.
 */
export const BPS_PRECISION = BigInt(10 ** MAX_BPS_DECIMALS);
/**
 * Returns true if bps has at most MAX_BPS_DECIMALS decimal places.
 * Uses epsilon comparison to avoid IEEE 754 false positives
 * (e.g. 0.3 * 10000 = 2999.9999... which strict equality would wrongly reject).
 */
export function isBpsPrecisionValid(bps) {
    const factor = 10 ** MAX_BPS_DECIMALS;
    const scaled = bps * factor;
    return Math.abs(Math.round(scaled) - scaled) <= 1e-9;
}
/**
 * Validates that a bps value does not exceed MAX_BPS_DECIMALS decimal places.
 * @throws Error if bps has too many decimal places
 */
export function assertBpsPrecision(bps) {
    assert(isBpsPrecisionValid(bps), `bps must have at most ${MAX_BPS_DECIMALS} decimal places, got ${bps}`);
}
/**
 * Assumed maximum transfer amount for zero-supply tokens.
 * 10^36 is astronomically large (10^18 tokens with 18 decimals).
 * This ensures maxFee * amount won't overflow for any realistic transfer
 * in the LinearFee contract's _quoteTransfer calculation.
 */
export const ASSUMED_MAX_AMOUNT_FOR_ZERO_SUPPLY = 10n ** 36n;
/**
 * Converts fee parameters to basis points (BPS)
 * @param maxFee - Maximum fee amount
 * @param halfAmount - Half of the amount at which maxFee is applied
 * @returns Fee in basis points (up to MAX_BPS_DECIMALS decimal places)
 * @throws Error if halfAmount is zero to prevent division by zero
 */
export function convertToBps(maxFee, halfAmount) {
    assert(halfAmount !== 0n, 'halfAmount must be > 0 to prevent division by zero');
    // Use precision scaling to preserve fractional bps (e.g., 1.5)
    // Multiply by BPS_PRECISION before bigint division, then divide back in Number space
    const scaledBps = (maxFee * MAX_BPS * BPS_PRECISION) / (halfAmount * 2n);
    // Round to MAX_BPS_DECIMALS decimal places to prevent floating point drift
    const factor = 10 ** MAX_BPS_DECIMALS;
    return (Math.round((Number(scaledBps) / Number(BPS_PRECISION)) * factor) / factor);
}
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