diff --git a/common/calculate-multi.ts b/common/calculate-multi.ts
new file mode 100644
index 00000000..5ff23cdb
--- /dev/null
+++ b/common/calculate-multi.ts
@@ -0,0 +1,27 @@
+import * as _ from 'lodash'
+
+export function getMultiProbability(
+ totalShares: {
+ [answerId: string]: number
+ },
+ answerId: string
+) {
+ const squareSum = _.sumBy(Object.values(totalShares), (shares) => shares ** 2)
+ const shares = totalShares[answerId] ?? 0
+ return shares ** 2 / squareSum
+}
+
+export function calculateMultiShares(
+ totalShares: {
+ [answerId: string]: number
+ },
+ bet: number,
+ betChoice: string
+) {
+ const squareSum = _.sumBy(Object.values(totalShares), (shares) => shares ** 2)
+ const shares = totalShares[betChoice] ?? 0
+
+ const c = 2 * bet * Math.sqrt(squareSum)
+
+ return Math.sqrt(bet ** 2 + shares ** 2 + c) - shares
+}
diff --git a/common/new-bet.ts b/common/new-bet.ts
index 61c72015..5b23c84e 100644
--- a/common/new-bet.ts
+++ b/common/new-bet.ts
@@ -1,9 +1,10 @@
import { Bet } from './bet'
import { calculateShares, getProbability } from './calculate'
+import { calculateMultiShares, getMultiProbability } from './calculate-multi'
import { Contract } from './contract'
import { User } from './user'
-export const getNewBetInfo = (
+export const getNewBinaryBetInfo = (
user: User,
outcome: 'YES' | 'NO',
amount: number,
@@ -52,3 +53,43 @@ export const getNewBetInfo = (
return { newBet, newPool, newTotalShares, newTotalBets, newBalance }
}
+
+export const getNewMultiBetInfo = (
+ user: User,
+ outcome: string,
+ amount: number,
+ contract: Contract<'MULTI'>,
+ newBetId: string
+) => {
+ const { pool, totalShares, totalBets } = contract
+
+ const prevOutcomePool = pool[outcome] ?? 0
+ const newPool = { ...pool, outcome: prevOutcomePool + amount }
+
+ const shares = calculateMultiShares(contract.totalShares, amount, outcome)
+
+ const prevShares = totalShares[outcome] ?? 0
+ const newTotalShares = { ...totalShares, outcome: prevShares + shares }
+
+ const prevTotalBets = totalBets[outcome] ?? 0
+ const newTotalBets = { ...totalBets, outcome: prevTotalBets + amount }
+
+ const probBefore = getMultiProbability(totalShares, outcome)
+ const probAfter = getMultiProbability(newTotalShares, outcome)
+
+ const newBet: Bet<'MULTI'> = {
+ id: newBetId,
+ userId: user.id,
+ contractId: contract.id,
+ amount,
+ shares,
+ outcome,
+ probBefore,
+ probAfter,
+ createdTime: Date.now(),
+ }
+
+ const newBalance = user.balance - amount
+
+ return { newBet, newPool, newTotalShares, newTotalBets, newBalance }
+}
diff --git a/firestore.rules b/firestore.rules
index 253d57f5..a48e23c9 100644
--- a/firestore.rules
+++ b/firestore.rules
@@ -44,6 +44,14 @@ service cloud.firestore {
allow read;
}
+ match /contracts/{contractId}/answers/{answerId} {
+ allow read;
+ }
+
+ match /{somePath=**}/answers/{answerId} {
+ allow read;
+ }
+
match /folds/{foldId} {
allow read;
allow update, delete: if request.auth.uid == resource.data.curatorId;
diff --git a/functions/src/create-answer.ts b/functions/src/create-answer.ts
new file mode 100644
index 00000000..230c12a3
--- /dev/null
+++ b/functions/src/create-answer.ts
@@ -0,0 +1,98 @@
+import * as functions from 'firebase-functions'
+import * as admin from 'firebase-admin'
+
+import { Contract } from '../../common/contract'
+import { User } from '../../common/user'
+import { getNewMultiBetInfo } from '../../common/new-bet'
+import { Answer } from '../../common/answer'
+
+export const createAnswer = functions.runWith({ minInstances: 1 }).https.onCall(
+ async (
+ data: {
+ contractId: string
+ amount: number
+ text: string
+ },
+ context
+ ) => {
+ const userId = context?.auth?.uid
+ if (!userId) return { status: 'error', message: 'Not authorized' }
+
+ const { contractId, amount, text } = data
+
+ if (amount <= 0 || isNaN(amount) || !isFinite(amount))
+ return { status: 'error', message: 'Invalid amount' }
+
+ if (!text || typeof text !== 'string' || text.length > 1000)
+ return { status: 'error', message: 'Invalid text' }
+
+ // Run as transaction to prevent race conditions.
+ return await firestore.runTransaction(async (transaction) => {
+ const userDoc = firestore.doc(`users/${userId}`)
+ const userSnap = await transaction.get(userDoc)
+ if (!userSnap.exists)
+ return { status: 'error', message: 'User not found' }
+ const user = userSnap.data() as User
+
+ if (user.balance < amount)
+ return { status: 'error', message: 'Insufficient balance' }
+
+ const contractDoc = firestore.doc(`contracts/${contractId}`)
+ const contractSnap = await transaction.get(contractDoc)
+ if (!contractSnap.exists)
+ return { status: 'error', message: 'Invalid contract' }
+ const contract = contractSnap.data() as Contract<'MULTI'>
+
+ if (
+ contract.outcomeType !== 'MULTI' ||
+ contract.outcomes !== 'FREE_ANSWER'
+ )
+ return {
+ status: 'error',
+ message: 'Requires a multi, free answer contract',
+ }
+
+ const { closeTime } = contract
+ if (closeTime && Date.now() > closeTime)
+ return { status: 'error', message: 'Trading is closed' }
+
+ const newAnswerDoc = firestore
+ .collection(`contracts/${contractId}/answers`)
+ .doc()
+
+ const answerId = newAnswerDoc.id
+ const { username, name, avatarUrl } = user
+
+ const answer: Answer = {
+ id: answerId,
+ contractId,
+ createdTime: Date.now(),
+ userId: user.id,
+ username,
+ name,
+ avatarUrl,
+ text,
+ }
+ transaction.create(newAnswerDoc, answer)
+
+ const newBetDoc = firestore
+ .collection(`contracts/${contractId}/bets`)
+ .doc()
+
+ const { newBet, newPool, newTotalShares, newTotalBets, newBalance } =
+ getNewMultiBetInfo(user, answerId, amount, contract, newBetDoc.id)
+
+ transaction.create(newBetDoc, newBet)
+ transaction.update(contractDoc, {
+ pool: newPool,
+ totalShares: newTotalShares,
+ totalBets: newTotalBets,
+ })
+ transaction.update(userDoc, { balance: newBalance })
+
+ return { status: 'success', answerId, betId: newBetDoc.id }
+ })
+ }
+)
+
+const firestore = admin.firestore()
diff --git a/functions/src/index.ts b/functions/src/index.ts
index f46e72a8..7af5b4f4 100644
--- a/functions/src/index.ts
+++ b/functions/src/index.ts
@@ -11,6 +11,7 @@ export * from './sell-bet'
export * from './create-contract'
export * from './create-user'
export * from './create-fold'
+export * from './create-answer'
export * from './on-fold-follow'
export * from './on-fold-delete'
export * from './unsubscribe'
diff --git a/functions/src/place-bet.ts b/functions/src/place-bet.ts
index dee470d6..333928d8 100644
--- a/functions/src/place-bet.ts
+++ b/functions/src/place-bet.ts
@@ -3,7 +3,7 @@ import * as admin from 'firebase-admin'
import { Contract } from '../../common/contract'
import { User } from '../../common/user'
-import { getNewBetInfo } from '../../common/new-bet'
+import { getNewBinaryBetInfo } from '../../common/new-bet'
export const placeBet = functions.runWith({ minInstances: 1 }).https.onCall(
async (
@@ -51,7 +51,7 @@ export const placeBet = functions.runWith({ minInstances: 1 }).https.onCall(
.doc()
const { newBet, newPool, newTotalShares, newTotalBets, newBalance } =
- getNewBetInfo(user, outcome, amount, contract, newBetDoc.id)
+ getNewBinaryBetInfo(user, outcome, amount, contract, newBetDoc.id)
transaction.create(newBetDoc, newBet)
transaction.update(contractDoc, {
diff --git a/web/components/answers-panel.tsx b/web/components/answers-panel.tsx
new file mode 100644
index 00000000..ccc3a65b
--- /dev/null
+++ b/web/components/answers-panel.tsx
@@ -0,0 +1,95 @@
+import clsx from 'clsx'
+import { useState } from 'react'
+import Textarea from 'react-expanding-textarea'
+
+import { Answer } from '../../common/answer'
+import { Contract } from '../../common/contract'
+import { AmountInput } from './amount-input'
+import { Col } from './layout/col'
+import { createAnswer } from '../lib/firebase/api-call'
+
+export function AnswersPanel(props: {
+ contract: Contract<'MULTI'>
+ answers: Answer[]
+}) {
+ const { contract, answers } = props
+
+ return (
+
+
+ {answers.map((answer) => (
+ {answer.text}
+ ))}
+
+ )
+}
+
+function CreateAnswerInput(props: { contract: Contract<'MULTI'> }) {
+ const { contract } = props
+ const [text, setText] = useState('')
+ const [betAmount, setBetAmount] = useState(10)
+ const [amountError, setAmountError] = useState()
+ const [isSubmitting, setIsSubmitting] = useState(false)
+
+ const canSubmit = text && betAmount && !amountError && !isSubmitting
+
+ const submitAnswer = async () => {
+ if (canSubmit) {
+ setIsSubmitting(true)
+ console.log('submitting', { text, betAmount })
+ const result = await createAnswer({
+ contractId: contract.id,
+ text,
+ amount: betAmount,
+ }).then((r) => r.data)
+
+ console.log('submit complte', result)
+ setIsSubmitting(false)
+
+ if (result.status === 'success') {
+ setText('')
+ setBetAmount(10)
+ setAmountError(undefined)
+ }
+ }
+ }
+
+ return (
+
+ Add your answer
+