placeBet

functions/package.json

@@ -13,12 +13,12 @@
   },
   "main": "lib/index.js",
   "dependencies": {
-    "firebase-admin": "9.8.0",
-    "firebase-functions": "3.14.1"
+    "firebase-admin": "10.0.0",
+    "firebase-functions": "3.16.0"
   },
   "devDependencies": {
-    "firebase-functions-test": "0.2.0",
-    "typescript": "3.8.0"
+    "firebase-functions-test": "0.3.3",
+    "typescript": "4.5.3"
   },
   "private": true
 }

functions/src/index.ts

@@ -1,6 +1,5 @@
-import * as functions from "firebase-functions"
+import * as admin from 'firebase-admin'
 
-export const helloWorld = functions.https.onRequest((request, response) => {
-  functions.logger.info("Hello logs!", { structuredData: true })
-  response.send("Hello from Firebase!")
-})
+admin.initializeApp()
+
+export * from './place-bet'

functions/src/place-bet.ts

@@ -0,0 +1,75 @@
+import * as functions from 'firebase-functions'
+import * as admin from 'firebase-admin'
+
+import { Contract } from './types/contract'
+import { User } from './types/user'
+import { Bet } from './types/bet'
+
+export const placeBet = functions.https.onCall(async (data: {
+  amount: number
+  outcome: string
+  contractId: string
+}, context) => {
+  const userId = context?.auth?.uid
+  if (!userId)
+    return { status: 'error', message: 'Not authorized' }
+
+  const { amount, outcome, contractId } = data
+
+  if (outcome !== 'YES' && outcome !== 'NO')
+    return { status: 'error', message: 'Invalid outcome' }
+
+  // run as transaction to prevent race conditions
+  return await firestore.runTransaction(async transaction => {
+    const userDoc = firestore.doc(`users/${userId}`)
+    const userSnap = await transaction.get(userDoc)
+    if (!userSnap.exists) return { status: 'error', message: 'User not found' }
+    const user = userSnap.data() as User
+
+    if (user.balanceUsd < amount)
+      return { status: 'error', message: 'Insufficient balance' }
+
+    const contractDoc = firestore.doc(`contracts/${contractId}`)
+    const contractSnap = await transaction.get(contractDoc)
+    if (!contractSnap.exists) return { status: 'error', message: 'Invalid contract' }
+    const contract = contractSnap.data() as Contract
+
+    const newBetDoc = firestore.collection(`contracts/${contractId}/bets`).doc()
+
+    const { newBet, newPot, newBalance } = getNewBetInfo(user, outcome, amount, contract, newBetDoc.id)
+
+    transaction.create(newBetDoc, newBet)
+    transaction.update(contractDoc, { pot: newPot })
+    transaction.update(userDoc, { balanceUsd: newBalance })
+
+    return { status: 'success' }
+  })
+})
+
+const firestore = admin.firestore()
+
+const getNewBetInfo = (user: User, outcome: 'YES' | 'NO', amount: number, contract: Contract, newBetId: string) => {
+  const { YES: yesPot, NO: noPot } = contract.pot
+
+  const dpmWeight = outcome === 'YES'
+    ? amount * Math.pow(noPot, 2) / (Math.pow(yesPot, 2) + amount * yesPot)
+    : amount * Math.pow(yesPot, 2) / (Math.pow(noPot, 2) + amount * noPot)
+
+  const newBet: Bet = {
+    id: newBetId,
+    userId: user.id,
+    contractId: contract.id,
+    amount,
+    dpmWeight,
+    outcome,
+    createdTime: Date.now()
+  }
+
+  const newPot = outcome === 'YES'
+    ? { YES: yesPot + amount, NO: noPot }
+    : { YES: yesPot, NO: noPot + amount }
+
+  const newBalance = user.balanceUsd - amount
+
+  return { newBet, newPot, newBalance }
+}

functions/src/types/bet.ts

@@ -0,0 +1,11 @@
+export type Bet = {
+  id: string
+  userId: string
+  contractId: string
+
+  amount: number // Amount of USD bid
+  outcome: 'YES' | 'NO' // Chosen outcome
+
+  createdTime: number
+  dpmWeight: number // Dynamic Parimutuel weight
+}

functions/src/types/contract.ts

@@ -0,0 +1,22 @@
+
+export type Contract = {
+  id: string // Chosen by creator; must be unique
+  creatorId: string
+  creatorName: string
+
+  question: string
+  description: string // More info about what the contract is about
+
+  outcomeType: 'BINARY' // | 'MULTI' | 'interval' | 'date'
+  // outcomes: ['YES', 'NO']
+  seedAmounts: { YES: number; NO: number } 
+  pot: { YES: number; NO: number } 
+
+  createdTime: number // Milliseconds since epoch
+  lastUpdatedTime: number // If the question or description was changed
+  closeTime?: number // When no more trading is allowed
+
+  // isResolved: boolean
+  resolutionTime?: 10293849 // When the contract creator resolved the market; 0 if unresolved
+  resolution?: 'YES' | 'NO' | 'CANCEL' // Chosen by creator; must be one of outcomes
+}

functions/src/types/user.ts

@@ -0,0 +1,10 @@
+export type User = {
+  id: string
+  email: string
+  name: string
+  username: string
+  avatarUrl: string
+  balanceUsd: number
+  createdTime: number
+  lastUpdatedTime: number
+}

functions/src/utils.ts

@@ -0,0 +1,23 @@
+import * as admin from 'firebase-admin'
+
+import { Contract } from './types/contract'
+import { User } from './types/user'
+
+export const getValue = async <T>(collection: string, doc: string) => {
+  const snap = await admin.firestore()
+    .collection(collection)
+    .doc(doc)
+    .get()
+
+  return snap.exists
+    ? snap.data() as T
+    : undefined
+}
+
+export const getContract = (contractId: string) => {
+  return getValue<Contract>('contracts', contractId)
+}
+
+export const getUser = (userId: string) => {
+  return getValue<User>('users', userId)
+}

web/components/bet-panel.tsx

@@ -1,7 +1,8 @@
+import { getFunctions, httpsCallable } from "firebase/functions"
 import clsx from 'clsx'
 import React, { useState } from 'react'
+
 import { useUser } from '../hooks/use-user'
-import { Bet, saveBet } from '../lib/firebase/bets'
 import { Contract } from '../lib/firebase/contracts'
 import { Col } from './layout/col'
 import { Row } from './layout/row'
@@ -27,23 +28,14 @@ export function BetPanel(props: { contract: Contract; className?: string }) {
   async function submitBet() {
     if (!user || !betAmount) return
 
-    const now = Date.now()
-
-    const bet: Bet = {
-      id: `${now}-${user.id}`,
-      userId: user.id,
-      contractId: contract.id,
-      createdTime: now,
-      outcome: betChoice,
-      amount: betAmount,
-
-      // Placeholder.
-      dpmWeight: betAmount,
-    }
-
     setIsSubmitting(true)
 
-    await saveBet(bet)
+    const result = await placeBet({
+      amount: betAmount,
+      outcome: betChoice,
+      contractId: contract.id
+    })
+    console.log('placed bet. Result:', result)
 
     setIsSubmitting(false)
     setWasSubmitted(true)
@@ -126,3 +118,7 @@ export function BetPanel(props: { contract: Contract; className?: string }) {
     </Col>
   )
 }
+
+
+const functions = getFunctions()
+export const placeBet = httpsCallable(functions, 'placeBet')

web/lib/firebase/contracts.ts

@@ -22,6 +22,7 @@ export type Contract = {
   outcomeType: 'BINARY' // | 'MULTI' | 'interval' | 'date'
   // outcomes: ['YES', 'NO']
   seedAmounts: { YES: number; NO: number } // seedBets: [number, number]
+  pot: { YES: number; NO: number } 
 
   createdTime: number // Milliseconds since epoch
   lastUpdatedTime: number // If the question or description was changed

web/pages/contract/index.tsx

@@ -80,6 +80,7 @@ export default function NewContract() {
     question: '',
     description: '',
     seedAmounts: { YES: 100, NO: 100 },
+    pot: { YES: 100, NO: 100 },
 
     // TODO: Set create time to Firestore timestamp
     createdTime: Date.now(),
@@ -178,6 +179,10 @@ export default function NewContract() {
                           ...contract.seedAmounts,
                           YES: parseInt(e.target.value),
                         },
+                        pot: {
+                          ...contract.pot,
+                          YES: parseInt(e.target.value),
+                        },
                       })
                     }}
                   />
@@ -201,6 +206,10 @@ export default function NewContract() {
                           ...contract.seedAmounts,
                           NO: parseInt(e.target.value),
                         },
+                        pot: {
+                          ...contract.pot,
+                          NO: parseInt(e.target.value),
+                        },
                       })
                     }}
                   />