Sell shares cloud function.

common/calculate-cpmm.ts

@@ -131,7 +131,7 @@ export function calculateCpmmShareValue(
 
 export function calculateCpmmSale(
   contract: FullContract<CPMM, Binary>,
-  bet: Bet
+  bet: { shares: number; outcome: string }
 ) {
   const { shares, outcome } = bet
 

common/sell-bet.ts

@@ -85,21 +85,24 @@ export const getSellBetInfo = (
 
 export const getCpmmSellBetInfo = (
   user: User,
-  bet: Bet,
+  shares: number,
+  outcome: 'YES' | 'NO',
   contract: FullContract<CPMM, Binary>,
   newBetId: string
 ) => {
   const { pool, p } = contract
-  const { id: betId, amount, shares, outcome } = bet
 
-  const { saleValue, newPool, fees } = calculateCpmmSale(contract, bet)
+  const { saleValue, newPool, fees } = calculateCpmmSale(contract, {
+    shares,
+    outcome,
+  })
 
   const probBefore = getCpmmProbability(pool, p)
   const probAfter = getCpmmProbability(newPool, p)
 
   console.log(
     'SELL M$',
-    amount,
+    shares,
     outcome,
     'for M$',
     saleValue,
@@ -117,10 +120,6 @@ export const getCpmmSellBetInfo = (
     probBefore,
     probAfter,
     createdTime: Date.now(),
-    sale: {
-      amount: saleValue,
-      betId,
-    },
     fees,
   }
 

functions/src/index.ts

@@ -7,6 +7,7 @@ export * from './place-bet'
 export * from './resolve-market'
 export * from './stripe'
 export * from './sell-bet'
+export * from './sell-shares'
 export * from './create-contract'
 export * from './create-user'
 export * from './create-fold'

functions/src/sell-bet.ts

@@ -4,7 +4,7 @@ import * as functions from 'firebase-functions'
 import { Contract } from '../../common/contract'
 import { User } from '../../common/user'
 import { Bet } from '../../common/bet'
-import { getCpmmSellBetInfo, getSellBetInfo } from '../../common/sell-bet'
+import { getSellBetInfo } from '../../common/sell-bet'
 import { addObjects, removeUndefinedProps } from '../../common/util/object'
 import { Fees } from '../../common/fees'
 
@@ -34,8 +34,14 @@ export const sellBet = functions.runWith({ minInstances: 1 }).https.onCall(
       if (!contractSnap.exists)
         return { status: 'error', message: 'Invalid contract' }
       const contract = contractSnap.data() as Contract
-
       const { closeTime, mechanism, collectedFees, volume } = contract
+
+      if (mechanism !== 'dpm-2')
+        return {
+          status: 'error',
+          message: 'Sell shares only works with mechanism dpm-2',
+        }
+
       if (closeTime && Date.now() > closeTime)
         return { status: 'error', message: 'Trading is closed' }
 
@@ -57,15 +63,7 @@ export const sellBet = functions.runWith({ minInstances: 1 }).https.onCall(
         newTotalBets,
         newBalance,
         fees,
-      } =
+      } = getSellBetInfo(user, bet, contract, newBetDoc.id)
-        mechanism === 'dpm-2'
-          ? getSellBetInfo(user, bet, contract, newBetDoc.id)
-          : (getCpmmSellBetInfo(
-              user,
-              bet,
-              contract as any,
-              newBetDoc.id
-            ) as any)
 
       if (!isFinite(newBalance)) {
         throw new Error('Invalid user balance for ' + user.username)
@@ -81,7 +79,7 @@ export const sellBet = functions.runWith({ minInstances: 1 }).https.onCall(
           totalShares: newTotalShares,
           totalBets: newTotalBets,
           collectedFees: addObjects<Fees>(fees ?? {}, collectedFees ?? {}),
-          volume: volume + bet.amount,
+          volume: volume + Math.abs(newBet.amount),
         })
       )
 

functions/src/sell-shares.ts

@@ -0,0 +1,78 @@
+import * as admin from 'firebase-admin'
+import * as functions from 'firebase-functions'
+
+import { Binary, CPMM, FullContract } from '../../common/contract'
+import { User } from '../../common/user'
+import { getCpmmSellBetInfo } from '../../common/sell-bet'
+import { addObjects, removeUndefinedProps } from '../../common/util/object'
+
+export const sellShares = functions.runWith({ minInstances: 1 }).https.onCall(
+  async (
+    data: {
+      contractId: string
+      shares: number
+      outcome: 'YES' | 'NO'
+    },
+    context
+  ) => {
+    const userId = context?.auth?.uid
+    if (!userId) return { status: 'error', message: 'Not authorized' }
+
+    const { contractId, shares, outcome } = data
+
+    // Run as transaction to prevent race conditions.
+    return await firestore.runTransaction(async (transaction) => {
+      const userDoc = firestore.doc(`users/${userId}`)
+      const userSnap = await transaction.get(userDoc)
+      if (!userSnap.exists)
+        return { status: 'error', message: 'User not found' }
+      const user = userSnap.data() as User
+
+      const contractDoc = firestore.doc(`contracts/${contractId}`)
+      const contractSnap = await transaction.get(contractDoc)
+      if (!contractSnap.exists)
+        return { status: 'error', message: 'Invalid contract' }
+      const contract = contractSnap.data() as FullContract<CPMM, Binary>
+      const { closeTime, mechanism, collectedFees, volume } = contract
+
+      if (mechanism !== 'cpmm-1')
+        return {
+          status: 'error',
+          message: 'Sell shares only works with mechanism cpmm-1',
+        }
+
+      if (closeTime && Date.now() > closeTime)
+        return { status: 'error', message: 'Trading is closed' }
+
+      const newBetDoc = firestore
+        .collection(`contracts/${contractId}/bets`)
+        .doc()
+
+      const { newBet, newPool, newBalance, fees } = getCpmmSellBetInfo(
+        user,
+        shares,
+        outcome,
+        contract,
+        newBetDoc.id
+      )
+
+      if (!isFinite(newBalance)) {
+        throw new Error('Invalid user balance for ' + user.username)
+      }
+      transaction.update(userDoc, { balance: newBalance })
+      transaction.create(newBetDoc, newBet)
+      transaction.update(
+        contractDoc,
+        removeUndefinedProps({
+          pool: newPool,
+          collectedFees: addObjects(fees ?? {}, collectedFees ?? {}),
+          volume: volume + Math.abs(newBet.amount),
+        })
+      )
+
+      return { status: 'success' }
+    })
+  }
+)
+
+const firestore = admin.firestore()

web/components/amount-input.tsx

@@ -212,12 +212,12 @@ export function SellAmountInput(props: {
   const prevLoanAmount = _.sumBy(openUserBets, (bet) => bet.loanAmount ?? 0)
 
   const sharesSold = Math.min(amount ?? 0, yesShares || noShares)
-  const sellAmount = calculateCpmmSale(contract, {
+  const { saleValue } = calculateCpmmSale(contract, {
     shares: sharesSold,
-    outcome: sellOutcome,
+    outcome: sellOutcome as 'YES' | 'NO',
-  } as Bet).saleValue
+  })
 
-  const loanRepaid = Math.min(prevLoanAmount, sellAmount)
+  const loanRepaid = Math.min(prevLoanAmount, saleValue)
 
   const onAmountChange = (amount: number | undefined) => {
     onChange(amount)
@@ -248,7 +248,7 @@ export function SellAmountInput(props: {
         <Col className="gap-3 text-sm">
           <Row className="items-center justify-between gap-2 text-gray-500">
             Sale proceeds{' '}
-            <span className="text-neutral">{formatMoney(sellAmount)}</span>
+            <span className="text-neutral">{formatMoney(saleValue)}</span>
           </Row>
           {prevLoanAmount && (
             <Row className="items-center justify-between gap-2 text-gray-500">

web/components/bet-panel.tsx

@@ -16,7 +16,7 @@ import {
 import { Title } from './title'
 import { firebaseLogin, User } from '../lib/firebase/users'
 import { Bet } from '../../common/bet'
-import { placeBet } from '../lib/firebase/api-call'
+import { placeBet, sellShares } from '../lib/firebase/api-call'
 import { BuyAmountInput, SellAmountInput } from './amount-input'
 import { InfoTooltip } from './info-tooltip'
 import { OutcomeLabel } from './outcome-label'
@@ -196,7 +196,7 @@ function BuyPanel(props: {
       setBetAmount(undefined)
       if (onBuySuccess) onBuySuccess()
     } else {
-      setError(result?.error || 'Error placing bet')
+      setError(result?.message || 'Error placing bet')
       setIsSubmitting(false)
     }
   }
@@ -339,13 +339,13 @@ function SellPanel(props: {
     setError(undefined)
     setIsSubmitting(true)
 
-    const result = await placeBet({
+    const result = await sellShares({
       shares: amount,
       outcome: sharesOutcome,
       contractId: contract.id,
-    }).then((r) => r.data as any)
+    }).then((r) => r.data)
 
-    console.log('placed bet. Result:', result)
+    console.log('Sold shares. Result:', result)
 
     if (result?.status === 'success') {
       setIsSubmitting(false)
@@ -353,7 +353,7 @@ function SellPanel(props: {
       setAmount(undefined)
       if (onSellSuccess) onSellSuccess()
     } else {
-      setError(result?.error || 'Error selling')
+      setError(result?.message || 'Error selling')
       setIsSubmitting(false)
     }
   }
@@ -362,7 +362,7 @@ function SellPanel(props: {
   const { newPool } = calculateCpmmSale(contract, {
     shares: amount ?? 0,
     outcome: sharesOutcome,
-  } as Bet)
+  })
   const resultProb = getCpmmProbability(newPool, contract.p)
 
   return (

web/lib/firebase/api-call.ts

@@ -18,6 +18,13 @@ export const createFold = cloudFunction<
 
 export const placeBet = cloudFunction('placeBet')
 
+export const sellBet = cloudFunction('sellBet')
+
+export const sellShares = cloudFunction<
+  { contractId: string; shares: number; outcome: 'YES' | 'NO' },
+  { status: 'error' | 'success'; message?: string }
+>('sellShares')
+
 export const createAnswer = cloudFunction<
   { contractId: string; text: string; amount: number },
   {
@@ -38,8 +45,6 @@ export const resolveMarket = cloudFunction<
   { status: 'error' | 'success'; message?: string }
 >('resolveMarket')
 
-export const sellBet = cloudFunction('sellBet')
-
 export const createUser: () => Promise<User | null> = () => {
   let deviceToken = window.localStorage.getItem('device-token')
   if (!deviceToken) {