Create answer

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
+}

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 }
+}

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;

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()

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'

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, {

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 (
+    <Col>
+      <CreateAnswerInput contract={contract} />
+      {answers.map((answer) => (
+        <div>{answer.text}</div>
+      ))}
+    </Col>
+  )
+}
+
+function CreateAnswerInput(props: { contract: Contract<'MULTI'> }) {
+  const { contract } = props
+  const [text, setText] = useState('')
+  const [betAmount, setBetAmount] = useState<number | undefined>(10)
+  const [amountError, setAmountError] = useState<string | undefined>()
+  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 (
+    <Col className="gap-4">
+      <div className="text-xl text-indigo-700">Add your answer</div>
+      <Textarea
+        value={text}
+        onChange={(e) => setText(e.target.value)}
+        className="textarea textarea-bordered w-full"
+        placeholder="Type your answer..."
+        rows={1}
+        maxLength={10000}
+      />
+      <Col className="gap-2 justify-between self-end sm:flex-row">
+        {text && (
+          <Col className="gap-2">
+            <div className="text-gray-500 text-sm">Bet amount</div>
+            <AmountInput
+              amount={betAmount}
+              onChange={setBetAmount}
+              error={amountError}
+              setError={setAmountError}
+              minimumAmount={10}
+              disabled={isSubmitting}
+            />
+          </Col>
+        )}
+        <button
+          className={clsx(
+            'btn btn-sm self-start',
+            canSubmit ? 'btn-outline' : 'btn-disabled'
+          )}
+          disabled={!canSubmit}
+          onClick={submitAnswer}
+        >
+          Submit answer
+        </button>
+      </Col>
+    </Col>
+  )
+}

web/components/contract-feed.tsx

@@ -12,6 +12,7 @@ import {
 } from '@heroicons/react/solid'
 import dayjs from 'dayjs'
 import clsx from 'clsx'
+import Textarea from 'react-expanding-textarea'
 
 import { OutcomeLabel } from './outcome-label'
 import {
@@ -37,7 +38,6 @@ import { useBetsWithoutAntes } from '../hooks/use-bets'
 import { Bet } from '../lib/firebase/bets'
 import { Comment, mapCommentsByBetId } from '../lib/firebase/comments'
 import { JoinSpans } from './join-spans'
-import Textarea from 'react-expanding-textarea'
 import { outcome } from '../../common/contract'
 import { fromNow } from '../lib/util/time'
 import BetRow from './bet-row'
@@ -204,7 +204,7 @@ function EditContract(props: {
   ) : (
     <Row>
       <button
-        className="btn btn-neutral btn-outline btn-sm mt-4"
+        className="btn btn-neutral btn-outline btn-xs mt-4"
         onClick={() => setEditing(true)}
       >
         {props.buttonText}

web/lib/firebase/api-call.ts

@@ -18,6 +18,16 @@ export const createFold = cloudFunction<
 
 export const placeBet = cloudFunction('placeBet')
 
+export const createAnswer = cloudFunction<
+  { contractId: string; text: string; amount: number },
+  {
+    status: 'error' | 'success'
+    message?: string
+    answerId?: string
+    betId?: string
+  }
+>('createAnswer')
+
 export const resolveMarket = cloudFunction('resolveMarket')
 
 export const sellBet = cloudFunction('sellBet')

web/lib/firebase/contracts.ts

@@ -49,7 +49,7 @@ export function getBinaryProbPercent(contract: Contract) {
   return probPercent
 }
 
-export function tradingAllowed(contract: Contract) {
+export function tradingAllowed(contract: Contract<'BINARY' | 'MULTI'>) {
   return (
     !contract.isResolved &&
     (!contract.closeTime || contract.closeTime > Date.now())
@@ -84,7 +84,9 @@ export async function getContractFromSlug(slug: string) {
   const q = query(contractCollection, where('slug', '==', slug))
   const snapshot = await getDocs(q)
 
-  return snapshot.empty ? undefined : (snapshot.docs[0].data() as Contract)
+  return snapshot.empty
+    ? undefined
+    : (snapshot.docs[0].data() as Contract<'BINARY' | 'MULTI'>)
 }
 
 export async function deleteContract(contractId: string) {

web/pages/[username]/[contractSlug].tsx

@@ -26,6 +26,9 @@ import Custom404 from '../404'
 import { getFoldsByTags } from '../../lib/firebase/folds'
 import { Fold } from '../../../common/fold'
 import { useFoldsWithTags } from '../../hooks/use-fold'
+import { listAllAnswers } from '../../lib/firebase/answers'
+import { Answer } from '../../../common/answer'
+import { AnswersPanel } from '../../components/answers-panel'
 
 export async function getStaticProps(props: {
   params: { username: string; contractSlug: string }
@@ -36,9 +39,12 @@ export async function getStaticProps(props: {
 
   const foldsPromise = getFoldsByTags(contract?.tags ?? [])
 
-  const [bets, comments] = await Promise.all([
+  const [bets, comments, answers] = await Promise.all([
     contractId ? listAllBets(contractId) : [],
     contractId ? listAllComments(contractId) : [],
+    contractId && contract.outcomes === 'FREE_ANSWER'
+      ? listAllAnswers(contractId)
+      : [],
   ])
 
   const folds = await foldsPromise
@@ -50,6 +56,7 @@ export async function getStaticProps(props: {
       slug: contractSlug,
       bets,
       comments,
+      answers,
       folds,
     },
 
@@ -66,6 +73,7 @@ export default function ContractPage(props: {
   username: string
   bets: Bet[]
   comments: Comment[]
+  answers: Answer[]
   slug: string
   folds: Fold[]
 }) {
@@ -112,6 +120,10 @@ export default function ContractPage(props: {
             comments={comments ?? []}
             folds={folds}
           />
+
+          {contract.outcomes === 'FREE_ANSWER' && (
+            <AnswersPanel contract={contract as any} answers={props.answers} />
+          )}
           <BetsSection contract={contract} user={user ?? null} bets={bets} />
         </div>
 
@@ -140,6 +152,7 @@ function BetsSection(props: {
   bets: Bet[]
 }) {
   const { contract, user } = props
+  const isBinary = contract.outcomeType === 'BINARY'
   const bets = useBets(contract.id) ?? props.bets
 
   // Decending creation time.
@@ -152,6 +165,8 @@ function BetsSection(props: {
   return (
     <div>
       <Title className="px-2" text="Your trades" />
+      {isBinary && (
+        <>
           <MyBetsSummary
             className="px-2"
             contract={contract}
@@ -159,6 +174,8 @@ function BetsSection(props: {
             showMKT
           />
           <Spacer h={6} />
+        </>
+      )}
       <ContractBetsTable contract={contract} bets={userBets} />
       <Spacer h={12} />
     </div>