109 lines
2.6 KiB
TypeScript
109 lines
2.6 KiB
TypeScript
import { Bet } from './bet'
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import { Contract } from './contract'
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import { CREATOR_FEE, PLATFORM_FEE } from './fees'
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import { User } from './user'
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export const getSellBetInfo = (
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user: User,
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bet: Bet,
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contract: Contract,
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newBetId: string
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) => {
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const { id: betId, amount, shares, outcome } = bet
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const { YES: yesPool, NO: noPool } = contract.pool
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const { YES: yesStart, NO: noStart } = contract.startPool
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const { YES: yesShares, NO: noShares } = contract.totalShares
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const { YES: yesBets, NO: noBets } = contract.totalBets
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const [y, n, s] = [yesPool, noPool, shares]
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const shareValue =
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outcome === 'YES'
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? // https://www.wolframalpha.com/input/?i=b+%2B+%28b+n%5E2%29%2F%28y+%28-b+%2B+y%29%29+%3D+c+solve+b
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(n ** 2 +
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s * y +
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y ** 2 -
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Math.sqrt(
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n ** 4 + (s - y) ** 2 * y ** 2 + 2 * n ** 2 * y * (s + y)
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)) /
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(2 * y)
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: (y ** 2 +
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s * n +
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n ** 2 -
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Math.sqrt(
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y ** 4 + (s - n) ** 2 * n ** 2 + 2 * y ** 2 * n * (s + n)
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)) /
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(2 * n)
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const startPool = yesStart + noStart
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const pool = yesPool + noPool - startPool
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const probBefore = yesPool ** 2 / (yesPool ** 2 + noPool ** 2)
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const f = pool / (probBefore * yesShares + (1 - probBefore) * noShares)
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const myPool = outcome === 'YES' ? yesPool - yesStart : noPool - noStart
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const adjShareValue = Math.min(Math.min(1, f) * shareValue, myPool)
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const newPool =
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outcome === 'YES'
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? { YES: yesPool - adjShareValue, NO: noPool }
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: { YES: yesPool, NO: noPool - adjShareValue }
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const newTotalShares =
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outcome === 'YES'
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? { YES: yesShares - shares, NO: noShares }
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: { YES: yesShares, NO: noShares - shares }
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const newTotalBets =
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outcome === 'YES'
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? { YES: yesBets - amount, NO: noBets }
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: { YES: yesBets, NO: noBets - amount }
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const probAfter = newPool.YES ** 2 / (newPool.YES ** 2 + newPool.NO ** 2)
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const creatorFee = CREATOR_FEE * adjShareValue
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const saleAmount = (1 - CREATOR_FEE - PLATFORM_FEE) * adjShareValue
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console.log(
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'SELL M$',
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amount,
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outcome,
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'for M$',
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saleAmount,
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'M$/share:',
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f,
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'creator fee: M$',
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creatorFee
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)
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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: -adjShareValue,
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shares: -shares,
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outcome,
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probBefore,
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probAfter,
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createdTime: Date.now(),
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sale: {
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amount: saleAmount,
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betId,
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},
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}
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const newBalance = user.balance + saleAmount
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return {
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newBet,
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newPool,
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newTotalShares,
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newTotalBets,
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newBalance,
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creatorFee,
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}
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}
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