calculate minExpectedTokens for bbd

src/components/AMMPrices/hooks/useERC20UniswapPrice.ts

@@ -2,6 +2,7 @@ import { Token } from '@uniswap/sdk-core'
 import IUniswapV3FactoryABI from '@uniswap/v3-core/artifacts/contracts/interfaces/IUniswapV3Factory.sol/IUniswapV3Factory.json'
 import IUniswapV3PoolABI from '@uniswap/v3-core/artifacts/contracts/interfaces/IUniswapV3Pool.sol/IUniswapV3Pool.json'
 import {
+  FeeAmount,
   Pool,
   FACTORY_ADDRESS as UNISWAP_V3_FACTORY_ADDRESS,
 } from '@uniswap/v3-sdk'
@@ -43,7 +44,12 @@ type Props = {
  * Pools are created at a specific fee tier.
  * https://docs.uniswap.org/protocol/concepts/V3-overview/fees#pool-fees-tiers
  */
-const UNISWAP_FEES_BPS = [10000, 3000, 500]
+const UNISWAP_FEES_BPS = [
+  FeeAmount.LOWEST,
+  FeeAmount.LOW,
+  FeeAmount.MEDIUM,
+  FeeAmount.HIGH,
+]
 const networkId = readNetwork.chainId
 
 /**

src/components/v2v3/V2V3Project/ProjectDashboard/components/PayProjectModal/components/ReceiveTokensItem.tsx

@@ -1,11 +1,16 @@
 import { Trans } from '@lingui/macro'
+import TooltipIcon from 'components/TooltipIcon'
 import { useProjectHasErc20Token } from 'components/v2v3/V2V3Project/ProjectDashboard/hooks/useProjectHasErc20Token'
 import { useProjectPaymentTokens } from 'components/v2v3/V2V3Project/ProjectDashboard/hooks/useProjectPaymentTokens'
+import { BUYBACK_DELEGATE_ENABLED_PROJECT_IDS } from 'constants/buybackDelegateEnabledProjectIds'
+import { ProjectMetadataContext } from 'contexts/shared/ProjectMetadataContext'
+import { useContext } from 'react'
 import { twMerge } from 'tailwind-merge'
 import { CartItemBadge } from '../../Cart/components/CartItem/CartItemBadge'
 import { ProjectHeaderLogo } from '../../ProjectHeader/components/ProjectHeaderLogo'
 
 export const ReceiveTokensItem = ({ className }: { className?: string }) => {
+  const { projectId } = useContext(ProjectMetadataContext)
   const { receivedTickets, receivedTokenSymbolText } = useProjectPaymentTokens()
   const projectHasErc20Token = useProjectHasErc20Token()
 
@@ -19,6 +24,9 @@ export const ReceiveTokensItem = ({ className }: { className?: string }) => {
     return null
   }
 
+  const buybackDelegateEnabled =
+    projectId && BUYBACK_DELEGATE_ENABLED_PROJECT_IDS.includes(projectId)
+
   return (
     <div className={twMerge('flex flex-col gap-4', className)}>
       <div className="flex items-center justify-between gap-3">
@@ -31,7 +39,18 @@ export const ReceiveTokensItem = ({ className }: { className?: string }) => {
             <Trans>{badgeTitle} Token</Trans>
           </CartItemBadge>
         </div>
-        <div>{receivedTickets}</div>
+        {buybackDelegateEnabled ? (
+          <div>
+            ≥ {receivedTickets}
+            <TooltipIcon
+              tip={
+                'This project may purchase tokens from a secondary market instead of minting new tokens, which may result in more tokens distributed depending on the swap price.'
+              }
+            />
+          </div>
+        ) : (
+          <div>{receivedTickets}</div>
+        )}
       </div>
     </div>
   )

src/components/v2v3/V2V3Project/ProjectDashboard/hooks/usePayProjectModal/usePayProjectTx.ts

@@ -97,7 +97,7 @@ export const usePayProjectTx = ({
       })
       const beneficiary = values.beneficiaryAddress ?? userAddress
 
-      let weiAmount
+      let weiAmount: BigNumber
       if (!totalAmount) {
         weiAmount = parseWad(0)
       } else if (totalAmount.currency === V2V3_CURRENCY_ETH) {
@@ -111,18 +111,33 @@ export const usePayProjectTx = ({
         .flat()
 
       // Total tokens that should be minted by pay() tx, including reserved tokens
-      const totalMintedTokens = fundingCycleMetadata
-        ? BigNumber.from(receivedTickets)
+      const requiredTokens = fundingCycleMetadata
+        ? parseWad(receivedTickets)
             .mul(MAX_RESERVED_RATE)
             .div(fundingCycleMetadata.reservedRate)
         : undefined
 
+      const expectedTokensFromSwap = weiAmount.div(
+        BigNumber.from(priceQuery?.projectTokenPrice.numerator.toString()).div(
+          BigNumber.from(priceQuery?.projectTokenPrice.denominator.toString()),
+        ),
+      )
+
       const shouldUseBuybackDelegate =
         projectId &&
         priceQuery &&
-        totalMintedTokens &&
+        requiredTokens &&
         BUYBACK_DELEGATE_ENABLED_PROJECT_IDS.includes(projectId) &&
-        BigNumber.from(totalMintedTokens).mul(2).lt(priceQuery.liquidity) // total token amount must be less than half of available liquidity (arbitrary)
+        expectedTokensFromSwap.gte(requiredTokens) &&
+        BigNumber.from(requiredTokens).mul(2).lt(priceQuery.liquidity) // total token amount must be less than half of available liquidity (arbitrary) to avoid slippage
+
+      // Expect whichever is greater: 95% of expected tokens from swap, or minimum amount of tokens required to be minted
+      // We don't really care if less tokens are returned from the swap than what we've estimated (as long as we're getting at least the minimum amount that would otherwise be minted). The main concern is sending as high a minimum as possible to limit arbitrage possibility
+      const minExpectedTokens =
+        requiredTokens &&
+        expectedTokensFromSwap.mul(95).div(100).gt(requiredTokens)
+          ? expectedTokensFromSwap.mul(95).div(100)
+          : requiredTokens
 
       // Encode metadata for jb721Delegate AND/OR jbBuybackDelegate
       const delegateMetadata = encodeDelegateMetadata({
@@ -134,12 +149,13 @@ export const usePayProjectTx = ({
           },
           version: JB721DelegateVersion,
         },
-        jbBuybackDelegate: shouldUseBuybackDelegate
-          ? {
-              amountToSwap: 0, // use all ETH
-              minExpectedTokens: totalMintedTokens, // must receive minimum of expected tokens
-            }
-          : undefined,
+        jbBuybackDelegate:
+          shouldUseBuybackDelegate && minExpectedTokens !== undefined
+            ? {
+                amountToSwap: 0, // use all ETH
+                minExpectedTokens,
+              }
+            : undefined,
       })
 
       let onError = undefined

src/utils/delegateMetadata/encodeDelegateMetadata.ts

@@ -55,11 +55,11 @@ export function encodeDelegateMetadata({
     )
   }
 
-  const ids: string[] = []
+  const delegateIds: string[] = []
   const metadatas: string[] = []
 
   if (jbBuybackDelegate) {
-    ids.push(IJBBuybackDelegate_INTERFACE_ID)
+    delegateIds.push(IJBBuybackDelegate_INTERFACE_ID)
     metadatas.push(
       utils.defaultAbiCoder.encode(
         ['uint256', 'uint256'],
@@ -78,12 +78,14 @@ export function encodeDelegateMetadata({
     )
 
     if (encoded) {
-      ids.push(IJBTiered721Delegate_V3_4_PAY_ID)
+      delegateIds.push(IJBTiered721Delegate_V3_4_PAY_ID)
       metadatas.push(encoded)
     }
   }
 
-  return createMetadata(ids, metadatas)
+  if (!delegateIds.length || !metadatas.length) return
+
+  return createMetadata(delegateIds, metadatas)
 }
 
 /**