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create-answer-cpmm.ts
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create-answer-cpmm.ts
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import * as admin from 'firebase-admin'
import { groupBy, partition, sumBy } from 'lodash'
import { CPMMMultiContract, Contract, add_answers_mode } from 'common/contract'
import { User } from 'common/user'
import { CandidateBet, getBetDownToOneMultiBetInfo } from 'common/new-bet'
import { Answer, getMaximumAnswers } from 'common/answer'
import { APIError, APIHandler } from './helpers/endpoint'
import { ANSWER_COST } from 'common/economy'
import { randomString } from 'common/util/random'
import { getUnfilledBetsAndUserBalances, updateMakers } from './place-bet'
import { FieldValue } from 'firebase-admin/firestore'
import {
addCpmmMultiLiquidityAnswersSumToOne,
getCpmmProbability,
} from 'common/calculate-cpmm'
import { isAdminId } from 'common/envs/constants'
import { Bet } from 'common/bet'
import { floatingEqual } from 'common/util/math'
import { noFees } from 'common/fees'
import { getCpmmInitialLiquidityTxn } from 'common/antes'
import { addUserToContractFollowers } from 'shared/follow-market'
import { log } from 'shared/utils'
import { createNewAnswerOnContractNotification } from 'shared/create-notification'
import { removeUndefinedProps } from 'common/util/object'
import { addHouseSubsidyToAnswer } from 'shared/helpers/add-house-subsidy'
import { runTxn } from 'shared/txn/run-txn'
export const createAnswerCPMM: APIHandler<'market/:contractId/answer'> = async (
props,
auth
) => {
const { contractId, text } = props
return await createAnswerCpmmMain(contractId, text, auth!.uid)
}
export const createAnswerCpmmMain = async (
contractId: string,
text: string,
creatorId: string,
options: {
overrideAddAnswersMode?: add_answers_mode
specialLiquidityPerAnswer?: number
loverUserId?: string
} = {}
) => {
const { overrideAddAnswersMode, specialLiquidityPerAnswer, loverUserId } =
options
log('Received ' + contractId + ' ' + text)
// Run as transaction to prevent race conditions.
const { newAnswerId, contract, user } = await firestore.runTransaction(
async (transaction) => {
const contractDoc = firestore.doc(`contracts/${contractId}`)
const contractSnap = await transaction.get(contractDoc)
if (!contractSnap.exists) throw new APIError(404, 'Contract not found')
const contract = contractSnap.data() as Contract
// TODO if mechanism === 'dpm' call dpm create answer
if (contract.mechanism !== 'cpmm-multi-1')
throw new APIError(403, 'Requires a cpmm multiple choice contract')
if (contract.outcomeType === 'NUMBER')
throw new APIError(
403,
'Cannot create new answers for numeric contracts'
)
const { closeTime, shouldAnswersSumToOne } = contract
if (closeTime && Date.now() > closeTime)
throw new APIError(403, 'Trading is closed')
const addAnswersMode = overrideAddAnswersMode ?? contract.addAnswersMode
if (!addAnswersMode || addAnswersMode === 'DISABLED') {
throw new APIError(400, 'Adding answers is disabled')
}
if (
contract.addAnswersMode === 'ONLY_CREATOR' &&
contract.creatorId !== creatorId &&
!isAdminId(creatorId)
) {
throw new APIError(
403,
'Only the creator or an admin can create an answer'
)
}
const userDoc = firestore.doc(`users/${creatorId}`)
const userSnap = await transaction.get(userDoc)
if (!userSnap.exists)
throw new APIError(401, 'Your account was not found')
const user = userSnap.data() as User
if (user.isBannedFromPosting) throw new APIError(403, 'You are banned')
if (user.balance < ANSWER_COST && !specialLiquidityPerAnswer)
throw new APIError(403, 'Insufficient balance, need M' + ANSWER_COST)
const answersSnap = await transaction.get(
firestore.collection(`contracts/${contractId}/answersCpmm`)
)
const answers = answersSnap.docs.map((doc) => doc.data() as Answer)
const unresolvedAnswers = answers.filter((a) => !a.resolution)
const maxAnswers = getMaximumAnswers(contract.shouldAnswersSumToOne)
if (unresolvedAnswers.length >= maxAnswers) {
throw new APIError(
403,
`Cannot add an answer: Maximum number (${maxAnswers}) of open answers reached.`
)
}
let poolYes = ANSWER_COST
let poolNo = ANSWER_COST
let totalLiquidity = ANSWER_COST
let prob = 0.5
if (specialLiquidityPerAnswer) {
if (shouldAnswersSumToOne)
throw new APIError(
500,
"Can't specify specialLiquidityPerAnswer and shouldAnswersSumToOne"
)
prob = 0.02
poolYes = specialLiquidityPerAnswer
poolNo = specialLiquidityPerAnswer / (1 / prob - 1)
totalLiquidity = specialLiquidityPerAnswer
}
const id = randomString()
const n = answers.length
const createdTime = Date.now()
const newAnswer: Answer = removeUndefinedProps({
id,
index: n,
contractId,
createdTime,
userId: user.id,
text,
isOther: false,
poolYes,
poolNo,
prob,
totalLiquidity,
subsidyPool: 0,
probChanges: { day: 0, week: 0, month: 0 },
loverUserId,
})
if (shouldAnswersSumToOne) {
await createAnswerAndSumAnswersToOne(
transaction,
user,
contract,
answers,
newAnswer
)
} else {
const newAnswerDoc = contractDoc
.collection('answersCpmm')
.doc(newAnswer.id)
transaction.create(newAnswerDoc, newAnswer)
}
if (!specialLiquidityPerAnswer) {
transaction.update(userDoc, {
balance: FieldValue.increment(-ANSWER_COST),
totalDeposits: FieldValue.increment(-ANSWER_COST),
})
transaction.update(contractDoc, {
totalLiquidity: FieldValue.increment(ANSWER_COST),
})
const lp = getCpmmInitialLiquidityTxn(
user.id,
contract,
ANSWER_COST,
newAnswer.id
)
await runTxn(transaction, lp)
}
return { newAnswerId: newAnswer.id, contract, user }
}
)
const { shouldAnswersSumToOne, addAnswersMode } = contract
if (shouldAnswersSumToOne && addAnswersMode !== 'DISABLED') {
await convertOtherAnswerShares(contractId, newAnswerId)
}
const continuation = async () => {
await createNewAnswerOnContractNotification(
newAnswerId,
user,
text,
contract
)
await addUserToContractFollowers(contractId, creatorId)
}
return { result: { newAnswerId }, continue: continuation }
}
async function createAnswerAndSumAnswersToOne(
transaction: FirebaseFirestore.Transaction,
user: User,
contract: CPMMMultiContract,
answers: Answer[],
newAnswer: Answer
) {
const [otherAnswers, answersWithoutOther] = partition(
answers,
(a) => a.isOther
)
const otherAnswer = otherAnswers[0]
if (!otherAnswer) {
throw new APIError(
500,
'"Other" answer not found, and is required for adding new answers.'
)
}
const contractDoc = firestore.doc(`contracts/${contract.id}`)
const newAnswerDoc = contractDoc.collection('answersCpmm').doc(newAnswer.id)
// 1. Create a mana budget including ANSWER_COST, and shares from Other.
// 2. Keep track of excess Yes and No shares of Other. Other has been divided
// into three pieces: mana, excessYesShares, excessNoShares.
// 3a. Recreate liquidity for the new answer and other by spending mana.
// 3b. Add excessYesShares to both other and the new answer's pools.
// These Yes shares can be copied because, conceptually, if the new answer is split out of Other,
// then original yes shares in Other should pay out if either it or Other is chosen.
// Note that the new answer has up to ANSWER_COST liquidity, while the remainder of liquidity,
// which could be a lot, is spent on the other answer.
// 4. Convert excess No shares in Other into Yes shares in all the previous answers and add them
// to previous answers' pools.
// 5. Probability sum is now greater than 1. Bet it down equally.
// Proof of >1 prob sum:
// a. If there are excess Yes shares, then old answer probs are unchanged, so
// prob of new answer + prob of other answer must be > than previous prob of other answer. Empirically true...
// b. If there are excess No shares, then new answer & other answer each has 50% prob.
// 6. Betting it down to 1 produces mana, which we then insert as subsidy.
const mana = ANSWER_COST + Math.min(otherAnswer.poolYes, otherAnswer.poolNo)
const excessYesShares = Math.max(0, otherAnswer.poolYes - otherAnswer.poolNo)
const excessNoShares = Math.max(0, otherAnswer.poolNo - otherAnswer.poolYes)
const answerCostOrHalf = Math.min(ANSWER_COST, mana / 2)
const newAnswerPool = {
YES: answerCostOrHalf + excessYesShares,
NO: answerCostOrHalf,
}
const newOtherPool = {
YES: mana - answerCostOrHalf + excessYesShares,
NO: mana - answerCostOrHalf,
}
const newAnswerProb = getCpmmProbability(newAnswerPool, 0.5)
const otherProb = getCpmmProbability(newOtherPool, 0.5)
const n = answers.length
newAnswer = {
...newAnswer,
index: n - 1,
poolYes: newAnswerPool.YES,
poolNo: newAnswerPool.NO,
prob: newAnswerProb,
totalLiquidity: answerCostOrHalf,
}
const updatedOtherAnswerProps = {
totalLiquidity: newOtherPool.NO,
index: n,
}
const updatedOtherAnswer = {
...otherAnswer,
...updatedOtherAnswerProps,
poolYes: newOtherPool.YES,
poolNo: newOtherPool.NO,
prob: otherProb,
}
const updatedPreviousAnswers = answersWithoutOther.map((a) => ({
...a,
poolYes: a.poolYes + excessNoShares,
}))
const answersWithNewAnswer = [
...updatedPreviousAnswers,
newAnswer,
updatedOtherAnswer,
]
const { unfilledBets, balanceByUserId } =
await getUnfilledBetsAndUserBalances(transaction, contractDoc)
// Cancel limit orders on Other answer.
const [unfilledBetsOnOther, unfilledBetsExcludingOther] = partition(
unfilledBets,
(b) => b.answerId === otherAnswer.id
)
const { betResults, extraMana } = getBetDownToOneMultiBetInfo(
contract,
answersWithNewAnswer,
unfilledBetsExcludingOther,
balanceByUserId
)
log('New answer', { newAnswer })
log('Other answer', { updatedOtherAnswer })
log('extraMana ' + extraMana)
log('bet amounts', {
amounts: betResults.map((r) =>
sumBy(r.takers.slice(0, r.takers.length - 1), (t) => t.amount)
),
shares: betResults.map((r) =>
sumBy(r.takers.slice(0, r.takers.length - 1), (t) => t.shares)
),
})
transaction.create(newAnswerDoc, newAnswer)
transaction.update(
contractDoc.collection('answersCpmm').doc(otherAnswer.id),
updatedOtherAnswerProps
)
const poolsByAnswer = Object.fromEntries(
betResults.map((r) => [
r.answer.id,
r.cpmmState.pool as { YES: number; NO: number },
])
)
for (const [answerId, pool] of Object.entries(poolsByAnswer)) {
const { YES: poolYes, NO: poolNo } = pool
const prob = poolNo / (poolYes + poolNo)
log('After arbitrage answer ', {
answerText: newAnswer.text,
answerId,
poolYes,
poolNo,
prob,
})
}
const newPoolsByAnswer = addCpmmMultiLiquidityAnswersSumToOne(
poolsByAnswer,
extraMana
)
for (const result of betResults) {
const { answer, bet, makers, ordersToCancel } = result
const betDoc = contractDoc.collection('bets').doc()
transaction.create(betDoc, {
id: betDoc.id,
userId: user.id,
userAvatarUrl: user.avatarUrl,
userUsername: user.username,
userName: user.name,
isApi: false,
...bet,
})
const pool = newPoolsByAnswer[answer.id]
const { YES: poolYes, NO: poolNo } = pool
const prob = getCpmmProbability(pool, 0.5)
log('Updating answer ', {
answerText: answer.text,
poolYes,
poolNo,
prob,
})
transaction.update(contractDoc.collection('answersCpmm').doc(answer.id), {
poolYes,
poolNo,
prob,
})
updateMakers(makers, betDoc.id, contractDoc, transaction)
for (const bet of ordersToCancel) {
transaction.update(contractDoc.collection('bets').doc(bet.id), {
isCancelled: true,
})
}
}
for (const bet of unfilledBetsOnOther) {
transaction.update(contractDoc.collection('bets').doc(bet.id), {
isCancelled: true,
})
}
}
const firestore = admin.firestore()
async function convertOtherAnswerShares(
contractId: string,
newAnswerId: string
) {
// Run as transaction to prevent race conditions.
const { answers, betsByUserId, newAnswer, otherAnswer } =
await firestore.runTransaction(async (transaction) => {
const now = Date.now()
const contractDoc = firestore.doc(`contracts/${contractId}`)
const answersSnap = await transaction.get(
contractDoc.collection('answersCpmm').orderBy('index')
)
const answers = answersSnap.docs.map((doc) => doc.data() as Answer)
const newAnswer = answers.find((a) => a.id === newAnswerId)!
const otherAnswer = answers.find((a) => a.isOther)!
const betsSnap = await transaction.get(
contractDoc.collection('bets').where('answerId', '==', otherAnswer.id)
)
const bets = betsSnap.docs.map((doc) => doc.data() as Bet)
const betsByUserId = groupBy(bets, (b) => b.userId)
// Gain YES shares in new answer for each YES share in Other.
for (const [userId, bets] of Object.entries(betsByUserId)) {
const position = sumBy(
bets,
(b) => b.shares * (b.outcome === 'YES' ? 1 : -1)
)
if (!floatingEqual(position, 0) && position > 0) {
const betDoc = contractDoc.collection('bets').doc()
const freeYesSharesBet: CandidateBet & {
id: string
userId: string
} = {
id: betDoc.id,
contractId,
userId,
answerId: newAnswer.id,
outcome: 'YES',
shares: position,
amount: 0,
isCancelled: false,
isFilled: true,
loanAmount: 0,
probBefore: newAnswer.prob,
probAfter: newAnswer.prob,
createdTime: now,
fees: noFees,
isAnte: false,
isRedemption: true,
isChallenge: false,
visibility: bets[0].visibility,
isApi: false,
}
transaction.create(betDoc, freeYesSharesBet)
}
}
return { answers, betsByUserId, newAnswer, otherAnswer }
})
await Promise.all(
// Convert NO shares in Other answer to YES shares in all other answers (excluding new answer).
Object.entries(betsByUserId).map(async ([userId, bets]) => {
// Run each in a separate transaction so we don't hit 500 doc limit.
await firestore.runTransaction(async (transaction) => {
const now = Date.now()
const contractDoc = firestore.doc(`contracts/${contractId}`)
const noPosition = sumBy(
bets,
(b) => b.shares * (b.outcome === 'YES' ? -1 : 1)
)
if (!floatingEqual(noPosition, 0) && noPosition > 0) {
const betDoc = contractDoc.collection('bets').doc()
const convertNoSharesBet: CandidateBet & {
id: string
userId: string
} = {
id: betDoc.id,
contractId,
userId,
answerId: otherAnswer.id,
outcome: 'NO',
shares: -noPosition,
amount: 0,
isCancelled: false,
isFilled: true,
loanAmount: 0,
probBefore: otherAnswer.prob,
probAfter: otherAnswer.prob,
createdTime: now,
fees: noFees,
isAnte: false,
isRedemption: true,
isChallenge: false,
visibility: bets[0].visibility,
isApi: false,
}
transaction.create(betDoc, convertNoSharesBet)
const previousAnswers = answers.filter(
(a) => a.id !== newAnswer.id && a.id !== otherAnswer.id
)
for (const answer of previousAnswers) {
const betDoc = contractDoc.collection('bets').doc()
const gainYesSharesBet: CandidateBet & {
id: string
userId: string
} = {
id: betDoc.id,
contractId,
userId,
answerId: answer.id,
outcome: 'YES',
shares: noPosition,
amount: 0,
isCancelled: false,
isFilled: true,
loanAmount: 0,
probBefore: answer.prob,
probAfter: answer.prob,
createdTime: now,
fees: noFees,
isAnte: false,
isRedemption: true,
isChallenge: false,
visibility: bets[0].visibility,
isApi: false,
}
transaction.create(betDoc, gainYesSharesBet)
}
}
})
})
)
return answers
}