148 lines
3.6 KiB
TypeScript
148 lines
3.6 KiB
TypeScript
import { Bet } from './bet'
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import { getProbability } from './calculate'
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import { Contract, outcome } from './contract'
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import { CREATOR_FEE, FEES } from './fees'
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export const getCancelPayouts = (contract: Contract, bets: Bet[]) => {
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const { pool } = contract
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const poolTotal = pool.YES + pool.NO
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console.log('resolved N/A, pool M$', poolTotal)
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const betSum = sumBy(bets, (b) => b.amount)
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return bets.map((bet) => ({
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userId: bet.userId,
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payout: (bet.amount / betSum) * poolTotal,
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}))
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}
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export const getStandardPayouts = (
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outcome: 'YES' | 'NO',
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contract: Contract,
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bets: Bet[]
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) => {
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const [yesBets, noBets] = partition(bets, (bet) => bet.outcome === 'YES')
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const winningBets = outcome === 'YES' ? yesBets : noBets
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const betSum = sumBy(winningBets, (b) => b.amount)
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const poolTotal = contract.pool.YES + contract.pool.NO
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if (betSum >= poolTotal) return getCancelPayouts(contract, winningBets)
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const shareDifferenceSum = sumBy(winningBets, (b) => b.shares - b.amount)
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const winningsPool = poolTotal - betSum
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const winnerPayouts = winningBets.map((bet) => ({
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userId: bet.userId,
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payout:
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bet.amount +
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(1 - 2 * FEES) *
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((bet.shares - bet.amount) / shareDifferenceSum) *
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winningsPool,
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}))
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const creatorPayout = 2 * CREATOR_FEE * winningsPool
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console.log(
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'resolved',
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outcome,
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'pool: M$',
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poolTotal,
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'creator fee: M$',
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creatorPayout
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)
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return winnerPayouts.concat([
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{ userId: contract.creatorId, payout: creatorPayout },
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]) // add creator fee
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}
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export const getMktPayouts = (contract: Contract, bets: Bet[]) => {
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const p = getProbability(contract.totalShares)
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const poolTotal = contract.pool.YES + contract.pool.NO
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console.log('Resolved MKT at p=', p, 'pool: $M', poolTotal)
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const [yesBets, noBets] = partition(bets, (bet) => bet.outcome === 'YES')
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const weightedBetTotal =
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p * sumBy(yesBets, (b) => b.amount) +
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(1 - p) * sumBy(noBets, (b) => b.amount)
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if (weightedBetTotal >= poolTotal) {
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return bets.map((bet) => ({
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userId: bet.userId,
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payout:
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(((bet.outcome === 'YES' ? p : 1 - p) * bet.amount) /
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weightedBetTotal) *
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poolTotal,
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}))
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}
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const winningsPool = poolTotal - weightedBetTotal
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const weightedShareTotal =
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p * sumBy(yesBets, (b) => b.shares - b.amount) +
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(1 - p) * sumBy(noBets, (b) => b.shares - b.amount)
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const yesPayouts = yesBets.map((bet) => ({
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userId: bet.userId,
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payout:
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p * bet.amount +
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(1 - 2 * FEES) *
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((p * (bet.shares - bet.amount)) / weightedShareTotal) *
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winningsPool,
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}))
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const noPayouts = noBets.map((bet) => ({
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userId: bet.userId,
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payout:
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(1 - p) * bet.amount +
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(1 - 2 * FEES) *
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(((1 - p) * (bet.shares - bet.amount)) / weightedShareTotal) *
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winningsPool,
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}))
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const creatorPayout = 2 * CREATOR_FEE * winningsPool
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return [
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...yesPayouts,
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...noPayouts,
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{ userId: contract.creatorId, payout: creatorPayout },
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]
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}
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export const getPayouts = (
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outcome: outcome,
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contract: Contract,
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bets: Bet[]
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) => {
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switch (outcome) {
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case 'YES':
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case 'NO':
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return getStandardPayouts(outcome, contract, bets)
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case 'MKT':
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return getMktPayouts(contract, bets)
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case 'CANCEL':
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return getCancelPayouts(contract, bets)
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}
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}
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const partition = <T>(array: T[], f: (t: T) => boolean) => {
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const yes = []
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const no = []
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for (let t of array) {
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if (f(t)) yes.push(t)
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else no.push(t)
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}
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return [yes, no] as [T[], T[]]
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}
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const sumBy = <T>(array: T[], f: (t: T) => number) => {
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const values = array.map(f)
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return values.reduce((prev, cur) => prev + cur, 0)
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}
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