68 lines
1.8 KiB
TypeScript
68 lines
1.8 KiB
TypeScript
import { Bet } from '../firebase/bets'
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import { Contract } from '../firebase/contracts'
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const fees = 0.02
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export function getProbability(pot: { YES: number; NO: number }) {
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const [yesPot, noPot] = [pot.YES, pot.NO]
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const numerator = Math.pow(yesPot, 2)
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const denominator = Math.pow(yesPot, 2) + Math.pow(noPot, 2)
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return numerator / denominator
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}
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export function getProbabilityAfterBet(
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pot: { YES: number; NO: number },
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outcome: 'YES' | 'NO',
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bet: number
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) {
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const [YES, NO] = [
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pot.YES + (outcome === 'YES' ? bet : 0),
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pot.NO + (outcome === 'NO' ? bet : 0),
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]
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return getProbability({ YES, NO })
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}
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export function getDpmWeight(
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pot: { YES: number; NO: number },
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bet: number,
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betChoice: 'YES' | 'NO'
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) {
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const [yesPot, noPot] = [pot.YES, pot.NO]
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return betChoice === 'YES'
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? (bet * Math.pow(noPot, 2)) / (Math.pow(yesPot, 2) + bet * yesPot)
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: (bet * Math.pow(yesPot, 2)) / (Math.pow(noPot, 2) + bet * noPot)
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}
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export function calculateWinnings(
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contract: Contract,
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bet: Bet,
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outcome: 'YES' | 'NO' | 'CANCEL'
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) {
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const { amount, outcome: betOutcome, dpmWeight } = bet
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if (outcome === 'CANCEL') return amount
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if (betOutcome !== outcome) return 0
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let { dpmWeights, pot, seedAmounts } = contract
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// Fake data if not set.
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if (!dpmWeights) dpmWeights = { YES: 100, NO: 100 }
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// Fake data if not set.
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if (!pot) pot = { YES: 100, NO: 100 }
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const otherOutcome = outcome === 'YES' ? 'NO' : 'YES'
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const potSize = pot[otherOutcome] - seedAmounts[otherOutcome]
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return (1 - fees) * (dpmWeight / dpmWeights[outcome]) * potSize + amount
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}
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export function currentValue(contract: Contract, bet: Bet) {
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const prob = getProbability(contract.pot)
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const yesWinnings = calculateWinnings(contract, bet, 'YES')
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const noWinnings = calculateWinnings(contract, bet, 'NO')
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return prob * yesWinnings + (1 - prob) * noWinnings
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}
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