import { Fraction } from '@uniswap/sdk-core';
import JSBI from 'jsbi';

export const X128 = BigInt(2) ** BigInt(128);

export function ratioX128FromAmounts(t0: bigint, t1: bigint): bigint {
  if (t1 === 0n) return MAX_UINT256;
  return (t0 * X128) / t1;
}

export function ratioX128FromFraction(fr: Fraction): bigint {
  const denom = fr.denominator.toString();
  if (denom === '0') return MAX_UINT256;
  const num = BigInt(fr.numerator.toString());
  return (num * X128) / BigInt(denom);
}

export function absRatioDiffX128(aX128: bigint, bX128: bigint): bigint {
  return aX128 >= bX128 ? aX128 - bX128 : bX128 - aX128;
}

export function compareRatioX128(aX128: bigint, bX128: bigint): number {
  if (aX128 === bX128) return 0;
  return aX128 > bX128 ? 1 : -1;
}

export function withinToleranceByX128(
  heldT0: bigint,
  heldT1: bigint,
  desired: Fraction,
  tol: Fraction,
): boolean {
  const desiredDenom = desired.denominator.toString();
  if (desiredDenom === '0') {
    return heldT1 === 0n;
  }
  const desiredX128 = ratioX128FromFraction(desired);
  const heldX128 = ratioX128FromAmounts(heldT0, heldT1);
  if (heldX128 === MAX_UINT256) return false;
  const diff = absRatioDiffX128(heldX128, desiredX128);
  const tolScaled =
    (desiredX128 * BigInt(tol.numerator.toString())) /
    BigInt(tol.denominator.toString());
  return diff <= tolScaled;
}

export function fractionAbsoluteValue(fraction: Fraction): Fraction {
  const numeratorAbs = JSBI.lessThan(fraction.numerator, JSBI.BigInt(0))
    ? JSBI.unaryMinus(fraction.numerator)
    : fraction.numerator;
  const denominatorAbs = JSBI.lessThan(fraction.denominator, JSBI.BigInt(0))
    ? JSBI.unaryMinus(fraction.denominator)
    : fraction.denominator;
  return new Fraction(numeratorAbs, denominatorAbs);
}

export const MAX_UINT256 = BigInt(
  '0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
);