manifold/common/payouts.ts

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