change fee structure (paid only on winnings); calculateMoneyRatio

common/calculate.ts

@@ -68,14 +68,18 @@ export function calculateRawShareValue(
   return currentValue - postSaleValue
 }
 
-export function calculateMoneyRatio(contract: Contract) {
+export function calculateMoneyRatio(contract: Contract, bet: Bet) {
   const { totalShares, pool } = contract
+  const { amount } = bet
+
   const p = getProbability(totalShares)
 
-  const actual = pool.YES + pool.NO
+  const actual = pool.YES + pool.NO - amount
-  const expected = p * contract.totalBets.YES + (1 - p) * contract.totalBets.NO
 
-  return expected === 0 ? 0 : actual / expected
+  const expected =
+    p * contract.totalBets.YES + (1 - p) * contract.totalBets.NO - amount
+
+  return expected <= 0 ? 0 : actual / expected
 }
 
 export function calculateShareValue(contract: Contract, bet: Bet) {
@@ -84,7 +88,7 @@ export function calculateShareValue(contract: Contract, bet: Bet) {
     bet.shares,
     bet.outcome
   )
-  const f = calculateMoneyRatio(contract)
+  const f = calculateMoneyRatio(contract, bet)
 
   const myPool = contract.pool[bet.outcome]
   const adjShareValue = Math.min(Math.min(1, f) * shareValue, myPool)
@@ -92,7 +96,7 @@ export function calculateShareValue(contract: Contract, bet: Bet) {
 }
 
 export function calculateSaleAmount(contract: Contract, bet: Bet) {
-  return (1 - FEES) * calculateShareValue(contract, bet)
+  return (1 - 2 * FEES) * calculateShareValue(contract, bet)
 }
 
 export function calculatePayout(
@@ -133,7 +137,7 @@ export function calculateStandardPayout(
     totalShares[outcome] - phantomShares[outcome] - totalBets[outcome]
   const winningsPool = truePool - totalBets[outcome]
 
-  return (1 - FEES) * (amount + ((shares - amount) / total) * winningsPool)
+  return amount + (1 - 2 * FEES) * ((shares - amount) / total) * winningsPool
 }
 
 export function calculatePayoutAfterCorrectBet(contract: Contract, bet: Bet) {
@@ -188,9 +192,10 @@ function calculateMktPayout(contract: Contract, bet: Bet) {
         contract.totalBets.NO)
 
   return (
-    (1 - FEES) *
+    betP * bet.amount +
-    (betP * bet.amount +
+    (1 - 2 * FEES) *
-      ((betP * (bet.shares - bet.amount)) / weightedShareTotal) * winningsPool)
+      ((betP * (bet.shares - bet.amount)) / weightedShareTotal) *
+      winningsPool
   )
 }
 

common/payouts.ts

@@ -27,7 +27,21 @@ export const getStandardPayouts = (
 
   if (betSum >= truePool) return getCancelPayouts(truePool, winningBets)
 
-  const creatorPayout = CREATOR_FEE * truePool
+  const shareDifferenceSum = sumBy(winningBets, (b) => b.shares - b.amount)
+
+  const winningsPool = truePool - betSum
+
+  const winnerPayouts = winningBets.map((bet) => ({
+    userId: bet.userId,
+    payout:
+      bet.amount +
+      (1 - 2 * FEES) *
+        ((bet.shares - bet.amount) / shareDifferenceSum) *
+        winningsPool,
+  }))
+
+  const creatorPayout = 2 * CREATOR_FEE * winningsPool
+
   console.log(
     'resolved',
     outcome,
@@ -37,18 +51,6 @@ export const getStandardPayouts = (
     creatorPayout
   )
 
-  const shareDifferenceSum = sumBy(winningBets, (b) => b.shares - b.amount)
-
-  const winningsPool = truePool - betSum
-
-  const winnerPayouts = winningBets.map((bet) => ({
-    userId: bet.userId,
-    payout:
-      (1 - FEES) *
-      (bet.amount +
-        ((bet.shares - bet.amount) / shareDifferenceSum) * winningsPool),
-  }))
-
   return winnerPayouts.concat([
     { userId: contract.creatorId, payout: creatorPayout },
   ]) // add creator fee
@@ -87,21 +89,22 @@ export const getMktPayouts = (
   const yesPayouts = yesBets.map((bet) => ({
     userId: bet.userId,
     payout:
-      (1 - FEES) *
+      p * bet.amount +
-      (p * bet.amount +
+      (1 - 2 * FEES) *
-        ((p * (bet.shares - bet.amount)) / weightedShareTotal) * winningsPool),
+        ((p * (bet.shares - bet.amount)) / weightedShareTotal) *
+        winningsPool,
   }))
 
   const noPayouts = noBets.map((bet) => ({
     userId: bet.userId,
     payout:
-      (1 - FEES) *
+      (1 - p) * bet.amount +
-      ((1 - p) * bet.amount +
+      (1 - 2 * FEES) *
         (((1 - p) * (bet.shares - bet.amount)) / weightedShareTotal) *
-          winningsPool),
+        winningsPool,
   }))
 
-  const creatorPayout = CREATOR_FEE * truePool
+  const creatorPayout = 2 * CREATOR_FEE * winningsPool
 
   return [
     ...yesPayouts,

common/sell-bet.ts

@@ -36,8 +36,8 @@ export const getSellBetInfo = (
   const probBefore = getProbability(contract.totalShares)
   const probAfter = getProbability(newTotalShares)
 
-  const creatorFee = CREATOR_FEE * adjShareValue
+  const creatorFee = 2 * CREATOR_FEE * adjShareValue
-  const saleAmount = (1 - FEES) * adjShareValue
+  const saleAmount = (1 - 2 * FEES) * adjShareValue
 
   console.log(
     'SELL M$',