create multiple choice cloud function

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/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,

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 +203,29 @@ 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(() => answerCol.doc())
+
+    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`)