123 lines
3.3 KiB
TypeScript
123 lines
3.3 KiB
TypeScript
import * as functions from 'firebase-functions'
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import * as admin from 'firebase-admin'
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import { Contract } from './types/contract'
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import { User } from './types/user'
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import { Bet } from './types/bet'
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export const placeBet = functions
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.runWith({ minInstances: 1 })
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.https.onCall((data, context) => {
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placeBetLogic({ ...data, userId: context?.auth?.uid })
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})
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export const placeBetLogic = async (data: {
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amount: number
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outcome: string
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contractId: string
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userId: string
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}) => {
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console.log('placeBet called')
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// if (!userId) return { status: 'error', message: 'Not authorized' }
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const { amount, outcome, contractId, userId } = data
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if (outcome !== 'YES' && outcome !== 'NO')
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return { status: 'error', message: 'Invalid outcome' }
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// run as transaction to prevent race conditions
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return await firestore.runTransaction(async (transaction) => {
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const userDoc = firestore.doc(`users/${userId}`)
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const userSnap = await transaction.get(userDoc)
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if (!userSnap.exists) return { status: 'error', message: 'User not found' }
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const user = userSnap.data() as User
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if (user.balance < amount)
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return { status: 'error', message: 'Insufficient balance' }
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const contractDoc = firestore.doc(`contracts/${contractId}`)
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const contractSnap = await transaction.get(contractDoc)
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if (!contractSnap.exists)
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return { status: 'error', message: 'Invalid contract' }
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const contract = contractSnap.data() as Contract
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const newBetDoc = firestore.collection(`contracts/${contractId}/bets`).doc()
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const { newBet, newPool, newDpmWeights, newBalance } = getNewBetInfo(
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user,
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outcome,
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amount,
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contract,
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newBetDoc.id
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)
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transaction.create(newBetDoc, newBet)
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transaction.update(contractDoc, {
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pool: newPool,
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dpmWeights: newDpmWeights,
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})
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transaction.update(userDoc, { balance: newBalance })
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return { status: 'success' }
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})
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}
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const firestore = admin.firestore()
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const getNewBetInfo = (
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user: User,
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outcome: 'YES' | 'NO',
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amount: number,
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contract: Contract,
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newBetId: string
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) => {
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const { YES: yesPool, NO: noPool } = contract.pool
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const newPool =
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outcome === 'YES'
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? { YES: yesPool + amount, NO: noPool }
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: { YES: yesPool, NO: noPool + amount }
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const dpmWeight =
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outcome === 'YES'
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? (amount * noPool ** 2) / (yesPool ** 2 + amount * yesPool)
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: (amount * yesPool ** 2) / (noPool ** 2 + amount * noPool)
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const { YES: yesWeight, NO: noWeight } = contract.dpmWeights || {
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YES: 0,
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NO: 0,
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} // only nesc for old contracts
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const newDpmWeights =
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outcome === 'YES'
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? { YES: yesWeight + dpmWeight, NO: noWeight }
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: { YES: yesWeight, NO: noWeight + dpmWeight }
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const probBefore = yesPool ** 2 / (yesPool ** 2 + noPool ** 2)
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const probAverage =
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(amount +
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noPool * Math.atan(yesPool / noPool) -
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noPool * Math.atan((amount + yesPool) / noPool)) /
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amount
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const probAfter = newPool.YES ** 2 / (newPool.YES ** 2 + newPool.NO ** 2)
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const newBet: Bet = {
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id: newBetId,
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userId: user.id,
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contractId: contract.id,
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amount,
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dpmWeight,
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outcome,
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probBefore,
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probAverage,
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probAfter,
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createdTime: Date.now(),
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}
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const newBalance = user.balance - amount
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return { newBet, newPool, newDpmWeights, newBalance }
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}
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