From 3eb0bb1711e72ee012e85b576e5fb8c0247015f7 Mon Sep 17 00:00:00 2001
From: James Grugett <jahooma@gmail.com>
Date: Tue, 29 Mar 2022 21:30:04 -0500
Subject: [PATCH] Throw error if sell conditions don't hold

---
 common/calculate-cpmm.ts        | 28 +++++++++++++++++++++++-----
 common/calculate.ts             |  5 +++--
 common/sell-bet.ts              |  7 ++++---
 web/components/amount-input.tsx |  9 +++++----
 web/components/bet-panel.tsx    |  9 +++++----
 5 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/common/calculate-cpmm.ts b/common/calculate-cpmm.ts
index 44e195a2..7ecd87d7 100644
--- a/common/calculate-cpmm.ts
+++ b/common/calculate-cpmm.ts
@@ -159,13 +159,16 @@ function calculateCpmmShareValue(
 
 export function calculateCpmmSale(
   contract: FullContract<CPMM, Binary>,
-  bet: { shares: number; outcome: string }
+  shares: number,
+  outcome: string
 ) {
-  const { shares, outcome } = bet
+  if (shares < 0) {
+    throw new Error('Cannot sell non-positive shares')
+  }
 
   const rawSaleValue = calculateCpmmShareValue(
     contract,
-    Math.abs(shares),
+    shares,
     outcome as 'YES' | 'NO'
   )
 
@@ -185,6 +188,20 @@ export function calculateCpmmSale(
       ? [y + shares - saleValue + fee, n - saleValue + fee]
       : [y - saleValue + fee, n + shares - saleValue + fee]
 
+  if (newY < 0 || newN < 0) {
+    console.log('calculateCpmmSale', {
+      newY,
+      newN,
+      y,
+      n,
+      shares,
+      saleValue,
+      fee,
+      outcome,
+    })
+    throw new Error('Cannot sell more than in pool')
+  }
+
   const postBetPool = { YES: newY, NO: newN }
 
   const { newPool, newP } = addCpmmLiquidity(postBetPool, contract.p, fee)
@@ -194,9 +211,10 @@ export function calculateCpmmSale(
 
 export function getCpmmProbabilityAfterSale(
   contract: FullContract<CPMM, Binary>,
-  bet: Bet
+  shares: number,
+  outcome: 'YES' | 'NO'
 ) {
-  const { newPool } = calculateCpmmSale(contract, bet)
+  const { newPool } = calculateCpmmSale(contract, shares, outcome)
   return getCpmmProbability(newPool, contract.p)
 }
 
diff --git a/common/calculate.ts b/common/calculate.ts
index 3bf57c2b..f3adf46f 100644
--- a/common/calculate.ts
+++ b/common/calculate.ts
@@ -72,7 +72,7 @@ export function calculateShares(
 
 export function calculateSaleAmount(contract: Contract, bet: Bet) {
   return contract.mechanism === 'cpmm-1' && contract.outcomeType === 'BINARY'
-    ? calculateCpmmSale(contract, bet).saleValue
+    ? calculateCpmmSale(contract, Math.abs(bet.shares), bet.outcome).saleValue
     : calculateDpmSaleAmount(contract, bet)
 }
 
@@ -90,7 +90,8 @@ export function getProbabilityAfterSale(
   return contract.mechanism === 'cpmm-1'
     ? getCpmmProbabilityAfterSale(
         contract as FullContract<CPMM, Binary>,
-        { shares, outcome } as Bet
+        shares,
+        outcome as 'YES' | 'NO'
       )
     : getDpmProbabilityAfterSale(contract.totalShares, outcome, shares)
 }
diff --git a/common/sell-bet.ts b/common/sell-bet.ts
index 750cfb39..1bdc1fd6 100644
--- a/common/sell-bet.ts
+++ b/common/sell-bet.ts
@@ -92,10 +92,11 @@ export const getCpmmSellBetInfo = (
 ) => {
   const { pool, p } = contract
 
-  const { saleValue, newPool, newP, fees } = calculateCpmmSale(contract, {
+  const { saleValue, newPool, newP, fees } = calculateCpmmSale(
+    contract,
     shares,
-    outcome,
-  })
+    outcome
+  )
 
   const probBefore = getCpmmProbability(pool, p)
   const probAfter = getCpmmProbability(newPool, p)
diff --git a/web/components/amount-input.tsx b/web/components/amount-input.tsx
index e77802bc..f0a64a6b 100644
--- a/web/components/amount-input.tsx
+++ b/web/components/amount-input.tsx
@@ -212,10 +212,11 @@ export function SellAmountInput(props: {
   const prevLoanAmount = _.sumBy(openUserBets, (bet) => bet.loanAmount ?? 0)
 
   const sharesSold = Math.min(amount ?? 0, yesShares || noShares)
-  const { saleValue } = calculateCpmmSale(contract, {
-    shares: sharesSold,
-    outcome: sellOutcome as 'YES' | 'NO',
-  })
+  const { saleValue } = calculateCpmmSale(
+    contract,
+    sharesSold,
+    sellOutcome as 'YES' | 'NO'
+  )
 
   const loanRepaid = Math.min(prevLoanAmount, saleValue)
 
diff --git a/web/components/bet-panel.tsx b/web/components/bet-panel.tsx
index 8175a3ed..fc96fb53 100644
--- a/web/components/bet-panel.tsx
+++ b/web/components/bet-panel.tsx
@@ -441,10 +441,11 @@ function SellPanel(props: {
   }
 
   const initialProb = getProbability(contract)
-  const { newPool } = calculateCpmmSale(contract, {
-    shares: Math.min(amount ?? 0, shares),
-    outcome: sharesOutcome,
-  })
+  const { newPool } = calculateCpmmSale(
+    contract,
+    Math.min(amount ?? 0, shares),
+    sharesOutcome
+  )
   const resultProb = getCpmmProbability(newPool, contract.p)
 
   return (