Multiple choice markets (#698)

* multipe choice answers

* create multiple choice cloud function

* multi choice market page

* show outcome '0'

* stats: multi choice type

* update place bet

* answer doc id = outcome

* update resolve market

* prettier

* fix

* fix resolution

common/antes.ts

@@ -5,12 +5,14 @@ import {
   CPMMBinaryContract,
   DPMBinaryContract,
   FreeResponseContract,
+  MultipleChoiceContract,
   NumericContract,
 } from './contract'
 import { User } from './user'
 import { LiquidityProvision } from './liquidity-provision'
 import { noFees } from './fees'
 import { ENV_CONFIG } from './envs/constants'
+import { Answer } from './answer'
 
 export const FIXED_ANTE = ENV_CONFIG.fixedAnte ?? 100
 
@@ -111,6 +113,50 @@ export function getFreeAnswerAnte(
   return anteBet
 }
 
+export function getMultipleChoiceAntes(
+  creator: User,
+  contract: MultipleChoiceContract,
+  answers: string[],
+  betDocIds: string[]
+) {
+  const { totalBets, totalShares } = contract
+  const amount = totalBets['0']
+  const shares = totalShares['0']
+  const p = 1 / answers.length
+
+  const { createdTime } = contract
+
+  const bets: Bet[] = answers.map((answer, i) => ({
+    id: betDocIds[i],
+    userId: creator.id,
+    contractId: contract.id,
+    amount,
+    shares,
+    outcome: i.toString(),
+    probBefore: p,
+    probAfter: p,
+    createdTime,
+    isAnte: true,
+    fees: noFees,
+  }))
+
+  const { username, name, avatarUrl } = creator
+
+  const answerObjects: Answer[] = answers.map((answer, i) => ({
+    id: i.toString(),
+    number: i,
+    contractId: contract.id,
+    createdTime,
+    userId: creator.id,
+    username,
+    name,
+    avatarUrl,
+    text: answer,
+  }))
+
+  return { bets, answerObjects }
+}
+
 export function getNumericAnte(
   anteBettorId: string,
   contract: NumericContract,

common/calculate.ts

@@ -23,6 +23,7 @@ import {
   BinaryContract,
   FreeResponseContract,
   PseudoNumericContract,
+  MultipleChoiceContract,
 } from './contract'
 import { floatingEqual } from './util/math'
 
@@ -200,7 +201,9 @@ export function getContractBetNullMetrics() {
   }
 }
 
-export function getTopAnswer(contract: FreeResponseContract) {
+export function getTopAnswer(
+  contract: FreeResponseContract | MultipleChoiceContract
+) {
   const { answers } = contract
   const top = maxBy(
     answers?.map((answer) => ({

common/contract.ts

@@ -4,13 +4,19 @@ import { JSONContent } from '@tiptap/core'
 import { GroupLink } from 'common/group'
 
 export type AnyMechanism = DPM | CPMM
-export type AnyOutcomeType = Binary | PseudoNumeric | FreeResponse | Numeric
+export type AnyOutcomeType =
+  | Binary
+  | MultipleChoice
+  | PseudoNumeric
+  | FreeResponse
+  | Numeric
 export type AnyContractType =
   | (CPMM & Binary)
   | (CPMM & PseudoNumeric)
   | (DPM & Binary)
   | (DPM & FreeResponse)
   | (DPM & Numeric)
+  | (DPM & MultipleChoice)
 
 export type Contract<T extends AnyContractType = AnyContractType> = {
   id: string
@@ -57,6 +63,7 @@ export type BinaryContract = Contract & Binary
 export type PseudoNumericContract = Contract & PseudoNumeric
 export type NumericContract = Contract & Numeric
 export type FreeResponseContract = Contract & FreeResponse
+export type MultipleChoiceContract = Contract & MultipleChoice
 export type DPMContract = Contract & DPM
 export type CPMMContract = Contract & CPMM
 export type DPMBinaryContract = BinaryContract & DPM
@@ -104,6 +111,13 @@ export type FreeResponse = {
   resolutions?: { [outcome: string]: number } // Used for MKT resolution.
 }
 
+export type MultipleChoice = {
+  outcomeType: 'MULTIPLE_CHOICE'
+  answers: Answer[]
+  resolution?: string | 'MKT' | 'CANCEL'
+  resolutions?: { [outcome: string]: number } // Used for MKT resolution.
+}
+
 export type Numeric = {
   outcomeType: 'NUMERIC'
   bucketCount: number
@@ -118,6 +132,7 @@ export type resolution = 'YES' | 'NO' | 'MKT' | 'CANCEL'
 export const RESOLUTIONS = ['YES', 'NO', 'MKT', 'CANCEL'] as const
 export const OUTCOME_TYPES = [
   'BINARY',
+  'MULTIPLE_CHOICE',
   'FREE_RESPONSE',
   'PSEUDO_NUMERIC',
   'NUMERIC',

common/new-bet.ts

@@ -18,6 +18,7 @@ import {
   CPMMBinaryContract,
   DPMBinaryContract,
   FreeResponseContract,
+  MultipleChoiceContract,
   NumericContract,
   PseudoNumericContract,
 } from './contract'
@@ -322,7 +323,7 @@ export const getNewBinaryDpmBetInfo = (
 export const getNewMultiBetInfo = (
   outcome: string,
   amount: number,
-  contract: FreeResponseContract,
+  contract: FreeResponseContract | MultipleChoiceContract,
   loanAmount: number
 ) => {
   const { pool, totalShares, totalBets } = contract

common/new-contract.ts

@@ -5,6 +5,7 @@ import {
   CPMM,
   DPM,
   FreeResponse,
+  MultipleChoice,
   Numeric,
   outcomeType,
   PseudoNumeric,
@@ -30,7 +31,10 @@ export function getNewContract(
   bucketCount: number,
   min: number,
   max: number,
-  isLogScale: boolean
+  isLogScale: boolean,
+
+  // for multiple choice
+  answers: string[]
 ) {
   const tags = parseTags(
     [
@@ -48,6 +52,8 @@ export function getNewContract(
       ? getPseudoNumericCpmmProps(initialProb, ante, min, max, isLogScale)
       : outcomeType === 'NUMERIC'
       ? getNumericProps(ante, bucketCount, min, max)
+      : outcomeType === 'MULTIPLE_CHOICE'
+      ? getMultipleChoiceProps(ante, answers)
       : getFreeAnswerProps(ante)
 
   const contract: Contract = removeUndefinedProps({
@@ -151,6 +157,26 @@ const getFreeAnswerProps = (ante: number) => {
   return system
 }
 
+const getMultipleChoiceProps = (ante: number, answers: string[]) => {
+  const numAnswers = answers.length
+  const betAnte = ante / numAnswers
+  const betShares = Math.sqrt(ante ** 2 / numAnswers)
+
+  const defaultValues = (x: any) =>
+    Object.fromEntries(range(0, numAnswers).map((k) => [k, x]))
+
+  const system: DPM & MultipleChoice = {
+    mechanism: 'dpm-2',
+    outcomeType: 'MULTIPLE_CHOICE',
+    pool: defaultValues(betAnte),
+    totalShares: defaultValues(betShares),
+    totalBets: defaultValues(betAnte),
+    answers: [],
+  }
+
+  return system
+}
+
 const getNumericProps = (
   ante: number,
   bucketCount: number,

common/payouts-dpm.ts

@@ -2,7 +2,11 @@ import { sum, groupBy, sumBy, mapValues } from 'lodash'
 
 import { Bet, NumericBet } from './bet'
 import { deductDpmFees, getDpmProbability } from './calculate-dpm'
-import { DPMContract, FreeResponseContract } from './contract'
+import {
+  DPMContract,
+  FreeResponseContract,
+  MultipleChoiceContract,
+} from './contract'
 import { DPM_CREATOR_FEE, DPM_FEES, DPM_PLATFORM_FEE } from './fees'
 import { addObjects } from './util/object'
 
@@ -180,7 +184,7 @@ export const getDpmMktPayouts = (
 
 export const getPayoutsMultiOutcome = (
   resolutions: { [outcome: string]: number },
-  contract: FreeResponseContract,
+  contract: FreeResponseContract | MultipleChoiceContract,
   bets: Bet[]
 ) => {
   const poolTotal = sum(Object.values(contract.pool))

common/payouts.ts

@@ -117,6 +117,7 @@ export const getDpmPayouts = (
   resolutionProbability?: number
 ): PayoutInfo => {
   const openBets = bets.filter((b) => !b.isSold && !b.sale)
+  const { outcomeType } = contract
 
   switch (outcome) {
     case 'YES':
@@ -124,7 +125,8 @@ export const getDpmPayouts = (
       return getDpmStandardPayouts(outcome, contract, openBets)
 
     case 'MKT':
-      return contract.outcomeType === 'FREE_RESPONSE' // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      return outcomeType === 'FREE_RESPONSE' ||
+        outcomeType === 'MULTIPLE_CHOICE' // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
         ? getPayoutsMultiOutcome(resolutions!, contract, openBets)
         : getDpmMktPayouts(contract, openBets, resolutionProbability)
     case 'CANCEL':
@@ -132,7 +134,7 @@ export const getDpmPayouts = (
       return getDpmCancelPayouts(contract, openBets)
 
     default:
-      if (contract.outcomeType === 'NUMERIC')
+      if (outcomeType === 'NUMERIC')
         return getNumericDpmPayouts(outcome, contract, openBets as NumericBet[])
 
       // Outcome is a free response answer id.

functions/src/create-contract.ts

@@ -7,6 +7,7 @@ import {
   FreeResponseContract,
   MAX_QUESTION_LENGTH,
   MAX_TAG_LENGTH,
+  MultipleChoiceContract,
   NumericContract,
   OUTCOME_TYPES,
 } from '../../common/contract'
@@ -20,15 +21,18 @@ import {
   FIXED_ANTE,
   getCpmmInitialLiquidity,
   getFreeAnswerAnte,
+  getMultipleChoiceAntes,
   getNumericAnte,
 } from '../../common/antes'
-import { getNoneAnswer } from '../../common/answer'
+import { Answer, getNoneAnswer } from '../../common/answer'
 import { getNewContract } from '../../common/new-contract'
 import { NUMERIC_BUCKET_COUNT } from '../../common/numeric-constants'
 import { User } from '../../common/user'
 import { Group, MAX_ID_LENGTH } from '../../common/group'
 import { getPseudoProbability } from '../../common/pseudo-numeric'
 import { JSONContent } from '@tiptap/core'
+import { zip } from 'lodash'
+import { Bet } from 'common/bet'
 
 const descScehma: z.ZodType<JSONContent> = z.lazy(() =>
   z.intersection(
@@ -79,11 +83,15 @@ const numericSchema = z.object({
   isLogScale: z.boolean().optional(),
 })
 
+const multipleChoiceSchema = z.object({
+  answers: z.string().trim().min(1).array().min(2),
+})
+
 export const createmarket = newEndpoint({}, async (req, auth) => {
   const { question, description, tags, closeTime, outcomeType, groupId } =
     validate(bodySchema, req.body)
 
-  let min, max, initialProb, isLogScale
+  let min, max, initialProb, isLogScale, answers
 
   if (outcomeType === 'PSEUDO_NUMERIC' || outcomeType === 'NUMERIC') {
     let initialValue
@@ -104,10 +112,15 @@ export const createmarket = newEndpoint({}, async (req, auth) => {
         )
       else throw new APIError(400, 'Invalid initial probability.')
   }
+
   if (outcomeType === 'BINARY') {
     ;({ initialProb } = validate(binarySchema, req.body))
   }
 
+  if (outcomeType === 'MULTIPLE_CHOICE') {
+    ;({ answers } = validate(multipleChoiceSchema, req.body))
+  }
+
   const userDoc = await firestore.collection('users').doc(auth.uid).get()
   if (!userDoc.exists) {
     throw new APIError(400, 'No user exists with the authenticated user ID.')
@@ -167,7 +180,8 @@ export const createmarket = newEndpoint({}, async (req, auth) => {
     NUMERIC_BUCKET_COUNT,
     min ?? 0,
     max ?? 0,
-    isLogScale ?? false
+    isLogScale ?? false,
+    answers ?? []
   )
 
   if (ante) await chargeUser(user.id, ante, true)
@@ -189,6 +203,31 @@ export const createmarket = newEndpoint({}, async (req, auth) => {
     )
 
     await liquidityDoc.set(lp)
+  } else if (outcomeType === 'MULTIPLE_CHOICE') {
+    const betCol = firestore.collection(`contracts/${contract.id}/bets`)
+    const betDocs = (answers ?? []).map(() => betCol.doc())
+
+    const answerCol = firestore.collection(`contracts/${contract.id}/answers`)
+    const answerDocs = (answers ?? []).map((_, i) =>
+      answerCol.doc(i.toString())
+    )
+
+    const { bets, answerObjects } = getMultipleChoiceAntes(
+      user,
+      contract as MultipleChoiceContract,
+      answers ?? [],
+      betDocs.map((bd) => bd.id)
+    )
+
+    await Promise.all(
+      zip(bets, betDocs).map(([bet, doc]) => doc?.create(bet as Bet))
+    )
+    await Promise.all(
+      zip(answerObjects, answerDocs).map(([answer, doc]) =>
+        doc?.create(answer as Answer)
+      )
+    )
+    await contractRef.update({ answers: answerObjects })
   } else if (outcomeType === 'FREE_RESPONSE') {
     const noneAnswerDoc = firestore
       .collection(`contracts/${contract.id}/answers`)

functions/src/place-bet.ts

@@ -96,7 +96,10 @@ export const placebet = newEndpoint({}, async (req, auth) => {
           limitProb,
           unfilledBets
         )
-      } else if (outcomeType == 'FREE_RESPONSE' && mechanism == 'dpm-2') {
+      } else if (
+        (outcomeType == 'FREE_RESPONSE' || outcomeType === 'MULTIPLE_CHOICE') &&
+        mechanism == 'dpm-2'
+      ) {
         const { outcome } = validate(freeResponseSchema, req.body)
         const answerDoc = contractDoc.collection('answers').doc(outcome)
         const answerSnap = await trans.get(answerDoc)

functions/src/resolve-market.ts

@@ -5,6 +5,7 @@ import { difference, uniq, mapValues, groupBy, sumBy } from 'lodash'
 import {
   Contract,
   FreeResponseContract,
+  MultipleChoiceContract,
   RESOLUTIONS,
 } from '../../common/contract'
 import { User } from '../../common/user'
@@ -245,7 +246,10 @@ function getResolutionParams(contract: Contract, body: string) {
       ...validate(pseudoNumericSchema, body),
       resolutions: undefined,
     }
-  } else if (outcomeType === 'FREE_RESPONSE') {
+  } else if (
+    outcomeType === 'FREE_RESPONSE' ||
+    outcomeType === 'MULTIPLE_CHOICE'
+  ) {
     const freeResponseParams = validate(freeResponseSchema, body)
     const { outcome } = freeResponseParams
     switch (outcome) {
@@ -292,7 +296,10 @@ function getResolutionParams(contract: Contract, body: string) {
   throw new APIError(500, `Invalid outcome type: ${outcomeType}`)
 }
 
-function validateAnswer(contract: FreeResponseContract, answer: number) {
+function validateAnswer(
+  contract: FreeResponseContract | MultipleChoiceContract,
+  answer: number
+) {
   const validIds = contract.answers.map((a) => a.id)
   if (!validIds.includes(answer.toString())) {
     throw new APIError(400, `${answer} is not a valid answer ID`)

web/components/answers/answer-bet-panel.tsx

@@ -3,7 +3,7 @@ import { useEffect, useRef, useState } from 'react'
 import { XIcon } from '@heroicons/react/solid'
 
 import { Answer } from 'common/answer'
-import { FreeResponseContract } from 'common/contract'
+import { FreeResponseContract, MultipleChoiceContract } from 'common/contract'
 import { BuyAmountInput } from '../amount-input'
 import { Col } from '../layout/col'
 import { APIError, placeBet } from 'web/lib/firebase/api'
@@ -29,7 +29,7 @@ import { isIOS } from 'web/lib/util/device'
 
 export function AnswerBetPanel(props: {
   answer: Answer
-  contract: FreeResponseContract
+  contract: FreeResponseContract | MultipleChoiceContract
   closePanel: () => void
   className?: string
   isModal?: boolean

web/components/answers/answer-item.tsx

@@ -1,7 +1,7 @@
 import clsx from 'clsx'
 
 import { Answer } from 'common/answer'
-import { FreeResponseContract } from 'common/contract'
+import { FreeResponseContract, MultipleChoiceContract } from 'common/contract'
 import { Col } from '../layout/col'
 import { Row } from '../layout/row'
 import { Avatar } from '../avatar'
@@ -13,7 +13,7 @@ import { Linkify } from '../linkify'
 
 export function AnswerItem(props: {
   answer: Answer
-  contract: FreeResponseContract
+  contract: FreeResponseContract | MultipleChoiceContract
   showChoice: 'radio' | 'checkbox' | undefined
   chosenProb: number | undefined
   totalChosenProb?: number

web/components/answers/answer-resolve-panel.tsx

@@ -2,7 +2,7 @@ import clsx from 'clsx'
 import { sum } from 'lodash'
 import { useState } from 'react'
 
-import { Contract, FreeResponse } from 'common/contract'
+import { FreeResponseContract, MultipleChoiceContract } from 'common/contract'
 import { Col } from '../layout/col'
 import { APIError, resolveMarket } from 'web/lib/firebase/api'
 import { Row } from '../layout/row'
@@ -11,7 +11,7 @@ import { ResolveConfirmationButton } from '../confirmation-button'
 import { removeUndefinedProps } from 'common/util/object'
 
 export function AnswerResolvePanel(props: {
-  contract: Contract & FreeResponse
+  contract: FreeResponseContract | MultipleChoiceContract
   resolveOption: 'CHOOSE' | 'CHOOSE_MULTIPLE' | 'CANCEL' | undefined
   setResolveOption: (
     option: 'CHOOSE' | 'CHOOSE_MULTIPLE' | 'CANCEL' | undefined

web/components/answers/answers-graph.tsx

@@ -5,14 +5,14 @@ import { groupBy, sortBy, sumBy } from 'lodash'
 import { memo } from 'react'
 
 import { Bet } from 'common/bet'
-import { FreeResponseContract } from 'common/contract'
+import { FreeResponseContract, MultipleChoiceContract } from 'common/contract'
 import { getOutcomeProbability } from 'common/calculate'
 import { useWindowSize } from 'web/hooks/use-window-size'
 
 const NUM_LINES = 6
 
 export const AnswersGraph = memo(function AnswersGraph(props: {
-  contract: FreeResponseContract
+  contract: FreeResponseContract | MultipleChoiceContract
   bets: Bet[]
   height?: number
 }) {
@@ -178,15 +178,22 @@ function formatTime(
   return d.format(format)
 }
 
-const computeProbsByOutcome = (bets: Bet[], contract: FreeResponseContract) => {
-  const { totalBets } = contract
+const computeProbsByOutcome = (
+  bets: Bet[],
+  contract: FreeResponseContract | MultipleChoiceContract
+) => {
+  const { totalBets, outcomeType } = contract
 
   const betsByOutcome = groupBy(bets, (bet) => bet.outcome)
   const outcomes = Object.keys(betsByOutcome).filter((outcome) => {
     const maxProb = Math.max(
       ...betsByOutcome[outcome].map((bet) => bet.probAfter)
     )
-    return outcome !== '0' && maxProb > 0.02 && totalBets[outcome] > 0.000000001
+    return (
+      (outcome !== '0' || outcomeType === 'MULTIPLE_CHOICE') &&
+      maxProb > 0.02 &&
+      totalBets[outcome] > 0.000000001
+    )
   })
 
   const trackedOutcomes = sortBy(

web/components/answers/answers-panel.tsx

@@ -1,7 +1,7 @@
 import { sortBy, partition, sum, uniq } from 'lodash'
 import { useEffect, useState } from 'react'
 
-import { FreeResponseContract } from 'common/contract'
+import { FreeResponseContract, MultipleChoiceContract } from 'common/contract'
 import { Col } from '../layout/col'
 import { useUser } from 'web/hooks/use-user'
 import { getDpmOutcomeProbability } from 'common/calculate-dpm'
@@ -25,14 +25,19 @@ import { UserLink } from 'web/components/user-page'
 import { Linkify } from 'web/components/linkify'
 import { BuyButton } from 'web/components/yes-no-selector'
 
-export function AnswersPanel(props: { contract: FreeResponseContract }) {
+export function AnswersPanel(props: {
+  contract: FreeResponseContract | MultipleChoiceContract
+}) {
   const { contract } = props
-  const { creatorId, resolution, resolutions, totalBets } = contract
+  const { creatorId, resolution, resolutions, totalBets, outcomeType } =
+    contract
 
   const answers = useAnswers(contract.id) ?? contract.answers
   const [winningAnswers, losingAnswers] = partition(
     answers.filter(
-      (answer) => answer.id !== '0' && totalBets[answer.id] > 0.000000001
+      (answer) =>
+        (answer.id !== '0' || outcomeType === 'MULTIPLE_CHOICE') &&
+        totalBets[answer.id] > 0.000000001
     ),
     (answer) =>
       answer.id === resolution || (resolutions && resolutions[answer.id])
@@ -131,7 +136,8 @@ export function AnswersPanel(props: { contract: FreeResponseContract }) {
         <div className="pb-4 text-gray-500">No answers yet...</div>
       )}
 
-      {tradingAllowed(contract) &&
+      {outcomeType === 'FREE_RESPONSE' &&
+        tradingAllowed(contract) &&
         (!resolveOption || resolveOption === 'CANCEL') && (
           <CreateAnswerPanel contract={contract} />
         )}
@@ -152,7 +158,7 @@ export function AnswersPanel(props: { contract: FreeResponseContract }) {
 }
 
 function getAnswerItems(
-  contract: FreeResponseContract,
+  contract: FreeResponseContract | MultipleChoiceContract,
   answers: Answer[],
   user: User | undefined | null
 ) {
@@ -178,7 +184,7 @@ function getAnswerItems(
 }
 
 function OpenAnswer(props: {
-  contract: FreeResponseContract
+  contract: FreeResponseContract | MultipleChoiceContract
   answer: Answer
   items: ActivityItem[]
   type: string

web/components/answers/multiple-choice-answers.tsx

@@ -0,0 +1,65 @@
+import { MAX_ANSWER_LENGTH } from 'common/answer'
+import { useState } from 'react'
+import Textarea from 'react-expanding-textarea'
+import { XIcon } from '@heroicons/react/solid'
+
+import { Col } from '../layout/col'
+import { Row } from '../layout/row'
+
+export function MultipleChoiceAnswers(props: {
+  setAnswers: (answers: string[]) => void
+}) {
+  const [answers, setInternalAnswers] = useState(['', '', ''])
+
+  const setAnswer = (i: number, answer: string) => {
+    const newAnswers = setElement(answers, i, answer)
+    setInternalAnswers(newAnswers)
+    props.setAnswers(newAnswers)
+  }
+
+  const removeAnswer = (i: number) => {
+    const newAnswers = answers.slice(0, i).concat(answers.slice(i + 1))
+    setInternalAnswers(newAnswers)
+    props.setAnswers(newAnswers)
+  }
+
+  const addAnswer = () => setAnswer(answers.length, '')
+
+  return (
+    <Col>
+      {answers.map((answer, i) => (
+        <Row className="mb-2 items-center align-middle">
+          {i + 1}.{' '}
+          <Textarea
+            value={answer}
+            onChange={(e) => setAnswer(i, e.target.value)}
+            className="textarea textarea-bordered ml-2 w-full resize-none"
+            placeholder="Type your answer..."
+            rows={1}
+            maxLength={MAX_ANSWER_LENGTH}
+          />
+          {answers.length > 2 && (
+            <button
+              className="btn btn-xs btn-outline ml-2"
+              onClick={() => removeAnswer(i)}
+            >
+              <XIcon className="h-4 w-4 flex-shrink-0" />
+            </button>
+          )}
+        </Row>
+      ))}
+
+      <Row className="justify-end">
+        <button className="btn btn-outline btn-xs" onClick={addAnswer}>
+          Add answer
+        </button>
+      </Row>
+    </Col>
+  )
+}
+
+const setElement = <T,>(array: T[], i: number, elem: T) => {
+  const newArray = array.concat()
+  newArray[i] = elem
+  return newArray
+}

web/components/contract/contract-card.tsx

@@ -8,6 +8,7 @@ import {
   BinaryContract,
   Contract,
   FreeResponseContract,
+  MultipleChoiceContract,
   NumericContract,
   PseudoNumericContract,
 } from 'common/contract'
@@ -227,7 +228,7 @@ function FreeResponseTopAnswer(props: {
 }
 
 export function FreeResponseResolutionOrChance(props: {
-  contract: FreeResponseContract
+  contract: FreeResponseContract | MultipleChoiceContract
   truncate: 'short' | 'long' | 'none'
   className?: string
 }) {

web/components/contract/contract-info-dialog.tsx

@@ -41,6 +41,8 @@ export function ContractInfoDialog(props: { contract: Contract; bets: Bet[] }) {
       ? 'YES / NO'
       : outcomeType === 'FREE_RESPONSE'
       ? 'Free response'
+      : outcomeType === 'MULTIPLE_CHOICE'
+      ? 'Multiple choice'
       : 'Numeric'
 
   return (

web/components/contract/contract-overview.tsx

@@ -85,7 +85,8 @@ export const ContractOverview = (props: {
             {tradingAllowed(contract) && <BetRow contract={contract} />}
           </Row>
         ) : (
-          outcomeType === 'FREE_RESPONSE' &&
+          (outcomeType === 'FREE_RESPONSE' ||
+            outcomeType === 'MULTIPLE_CHOICE') &&
           resolution && (
             <FreeResponseResolutionOrChance
               contract={contract}
@@ -110,7 +111,8 @@ export const ContractOverview = (props: {
       {(isBinary || isPseudoNumeric) && (
         <ContractProbGraph contract={contract} bets={bets} />
       )}{' '}
-      {outcomeType === 'FREE_RESPONSE' && (
+      {(outcomeType === 'FREE_RESPONSE' ||
+        outcomeType === 'MULTIPLE_CHOICE') && (
         <AnswersGraph contract={contract} bets={bets} />
       )}
       {outcomeType === 'NUMERIC' && <NumericGraph contract={contract} />}

web/components/outcome-label.tsx

@@ -7,6 +7,7 @@ import {
   BinaryContract,
   Contract,
   FreeResponseContract,
+  MultipleChoiceContract,
   resolution,
 } from 'common/contract'
 import { formatLargeNumber, formatPercent } from 'common/util/format'
@@ -77,7 +78,7 @@ export function BinaryContractOutcomeLabel(props: {
 }
 
 export function FreeResponseOutcomeLabel(props: {
-  contract: FreeResponseContract
+  contract: FreeResponseContract | MultipleChoiceContract
   resolution: string | 'CANCEL' | 'MKT'
   truncate: 'short' | 'long' | 'none'
   answerClassName?: string

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

@@ -217,7 +217,8 @@ export function ContractPageContent(
           />
         )}
 
-        {outcomeType === 'FREE_RESPONSE' && (
+        {(outcomeType === 'FREE_RESPONSE' ||
+          outcomeType === 'MULTIPLE_CHOICE') && (
           <>
             <Spacer h={4} />
             <AnswersPanel contract={contract} />

web/pages/create.tsx

@@ -31,6 +31,7 @@ import { Checkbox } from 'web/components/checkbox'
 import { redirectIfLoggedOut } from 'web/lib/firebase/server-auth'
 import { Title } from 'web/components/title'
 import { SEO } from 'web/components/SEO'
+import { MultipleChoiceAnswers } from 'web/components/answers/multiple-choice-answers'
 
 export const getServerSideProps = redirectIfLoggedOut('/')
 
@@ -116,6 +117,8 @@ export function NewContract(props: {
   const [isLogScale, setIsLogScale] = useState<boolean>(!!params?.isLogScale)
   const [initialValueString, setInitialValueString] = useState(initValue)
 
+  const [answers, setAnswers] = useState<string[]>([]) // for multiple choice
+
   useEffect(() => {
     if (groupId && creator)
       getGroup(groupId).then((group) => {
@@ -160,6 +163,10 @@ export function NewContract(props: {
   // get days from today until the end of this year:
   const daysLeftInTheYear = dayjs().endOf('year').diff(dayjs(), 'day')
 
+  const isValidMultipleChoice = answers.every(
+    (answer) => answer.trim().length > 0
+  )
+
   const isValid =
     (outcomeType === 'BINARY' ? initialProb >= 5 && initialProb <= 95 : true) &&
     question.length > 0 &&
@@ -178,7 +185,8 @@ export function NewContract(props: {
         min < max &&
         max - min > 0.01 &&
         min < initialValue &&
-        initialValue < max))
+        initialValue < max)) &&
+    (outcomeType !== 'MULTIPLE_CHOICE' || isValidMultipleChoice)
 
   const [errorText, setErrorText] = useState<string>('')
   useEffect(() => {
@@ -221,6 +229,7 @@ export function NewContract(props: {
           max,
           initialValue,
           isLogScale,
+          answers,
           groupId: selectedGroup?.id,
         })
       )
@@ -259,10 +268,11 @@ export function NewContract(props: {
               'Users can submit their own answers to this market.'
             )
           else setMarketInfoText('')
-          setOutcomeType(choice as 'BINARY' | 'FREE_RESPONSE')
+          setOutcomeType(choice as outcomeType)
         }}
         choicesMap={{
           'Yes / No': 'BINARY',
+          'Multiple choice': 'MULTIPLE_CHOICE',
           'Free response': 'FREE_RESPONSE',
           Numeric: 'PSEUDO_NUMERIC',
         }}
@@ -277,6 +287,10 @@ export function NewContract(props: {
 
       <Spacer h={6} />
 
+      {outcomeType === 'MULTIPLE_CHOICE' && (
+        <MultipleChoiceAnswers setAnswers={setAnswers} />
+      )}
+
       {outcomeType === 'PSEUDO_NUMERIC' && (
         <>
           <div className="form-control mb-2 items-start">