Odds Rounding

ODDS_PRECISION = 10 ** 20
ODDS_LADDER_STEP_SIZE = 125  # from GET /metadata

def is_odds_valid(percentage_odds: int) -> bool:
    step = ODDS_LADDER_STEP_SIZE * (10 ** 15)
    return percentage_odds % step == 0

# Valid: 50.250% implied = 50250000000000000000
print(is_odds_valid(50250000000000000000))  # True

# Invalid: 50.200% implied = 50200000000000000000
print(is_odds_valid(50200000000000000000))  # False

const ODDS_PRECISION = 10n ** 20n;
const ODDS_LADDER_STEP_SIZE = 125n; // from GET /metadata

function isOddsValid(percentageOdds) {
  const step = ODDS_LADDER_STEP_SIZE * 10n ** 15n;
  return BigInt(percentageOdds) % step === 0n;
}

// Valid: 50.250% implied
console.log(isOddsValid("50250000000000000000")); // true

// Invalid: 50.200% implied
console.log(isOddsValid("50200000000000000000")); // false

def round_odds_down(percentage_odds: int) -> int:
    """Round odds down to the nearest valid step on the ladder."""
    step = ODDS_LADDER_STEP_SIZE * (10 ** 15)
    return (percentage_odds // step) * step

# 50.200% → 50.125%
raw = 50200000000000000000
rounded = round_odds_down(raw)
print(f"{raw / ODDS_PRECISION:.3%} → {rounded / ODDS_PRECISION:.3%}")
# 50.200% → 50.125%

# 67.800% → 67.750%
raw = 67800000000000000000
rounded = round_odds_down(raw)
print(f"{raw / ODDS_PRECISION:.3%} → {rounded / ODDS_PRECISION:.3%}")
# 67.800% → 67.750%

function roundOddsDown(percentageOdds) {
  const step = ODDS_LADDER_STEP_SIZE * 10n ** 15n;
  const odds = BigInt(percentageOdds);
  return (odds / step) * step;
}

// 50.200% → 50.125%
console.log(roundOddsDown("50200000000000000000").toString());
// "50125000000000000000"

// 67.800% → 67.750%
console.log(roundOddsDown("67800000000000000000").toString());
// "67750000000000000000"

def implied_to_valid_odds(implied: float) -> int:
    """Convert an implied probability to the nearest valid percentageOdds (rounded down)."""
    raw = int(implied * ODDS_PRECISION)
    return round_odds_down(raw)

# Your model says 54.3% implied, you want to post at that price
odds = implied_to_valid_odds(0.543)
print(f"percentageOdds: {odds}")
# 54250000000000000000 (54.250%)

print(f"Implied: {odds / ODDS_PRECISION:.3%}")
# 54.250%

print(f"Valid: {is_odds_valid(odds)}")
# True

function impliedToValidOdds(implied) {
  const raw = BigInt(Math.round(implied * 1e20));
  return roundOddsDown(raw);
}

// Your model says 54.3% implied, you want to post at that price
const odds = impliedToValidOdds(0.543);
console.log(`percentageOdds: ${odds}`);
// 54250000000000000000 (54.250%)

console.log(`Valid: ${isOddsValid(odds)}`);
// true