handle swap kind EXACT_OUT for CPP

balancer · Dec 22, 2024 · 7cb2282 · 7cb2282
1 parent 54505b5
commit 7cb2282
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Showing 5 changed files with 10,137 additions and 22 deletions.
diff --git a/packages/foundry/contracts/pools/ConstantProductPool.sol b/packages/foundry/contracts/pools/ConstantProductPool.sol
@@ -7,6 +7,7 @@ import { PoolSwapParams, Rounding } from "@balancer-labs/v3-interfaces/contracts
 import { IVault } from "@balancer-labs/v3-interfaces/contracts/vault/IVault.sol";
 import { FixedPoint } from "@balancer-labs/v3-solidity-utils/contracts/math/FixedPoint.sol";
 import { Math } from "@openzeppelin/contracts/utils/math/Math.sol";
+import { SwapKind } from "@balancer-labs/v3-interfaces/contracts/vault/VaultTypes.sol";
 
 /**
  * @title Constant Product Pool
@@ -25,15 +26,23 @@ contract ConstantProductPool is BalancerPoolToken, IBasePool {
 
     /**
      * @notice Execute a swap in the pool.
-     * @param params Swap parameters (see above for struct definition)
+     * @dev For AMM math walkthrough, see https://www.youtube.com/watch?v=QNPyFs8Wybk
+     * @param params Swap parameters
      * @return amountCalculatedScaled18 Calculated amount for the swap
      */
     function onSwap(PoolSwapParams calldata params) external pure returns (uint256 amountCalculatedScaled18) {
-        uint256 poolBalancetokenOut = params.balancesScaled18[params.indexOut];
-        uint256 poolBalancetokenIn = params.balancesScaled18[params.indexIn];
-        uint256 amountTokenIn = params.amountGivenScaled18;
+        uint256 poolBalancetokenIn = params.balancesScaled18[params.indexIn]; // X
+        uint256 poolBalancetokenOut = params.balancesScaled18[params.indexOut]; // Y
 
-        amountCalculatedScaled18 = (poolBalancetokenOut * amountTokenIn) / (poolBalancetokenIn + amountTokenIn);
+        if (params.kind == SwapKind.EXACT_IN) {
+            uint256 amountTokenIn = params.amountGivenScaled18; // dx
+            // dy = (Y * dx) / (X + dx)
+            amountCalculatedScaled18 = (poolBalancetokenOut * amountTokenIn) / (poolBalancetokenIn + amountTokenIn);
+        } else {
+            uint256 amountTokenOut = params.amountGivenScaled18; // dy
+            // dx = (X * dy) / (Y + dx)
+            amountCalculatedScaled18 = (poolBalancetokenIn * amountTokenOut) / (poolBalancetokenOut + amountTokenOut);
+        }
     }
 
     /**

diff --git a/packages/nextjs/components/Footer.tsx b/packages/nextjs/components/Footer.tsx
@@ -14,26 +14,32 @@ export const Footer = () => {
                 href="https://github.com/balancer/scaffold-balancer-v3"
                 target="_blank"
                 rel="noreferrer"
-                className="link"
+                className="link no-underline hover:underline"
               >
                 Github
               </a>
             </div>
+
             <span>·</span>
             <div className="text-center">
-              <a href="https://docs-v3.balancer.fi/" target="_blank" rel="noreferrer" className="link">
-                Docs
+              <a
+                href="https://github.com/balancer/balancer-v3-monorepo"
+                target="_blank"
+                rel="noreferrer"
+                className="link no-underline hover:underline"
+              >
+                Contracts
               </a>
             </div>
             <span>·</span>
             <div className="text-center">
               <a
-                href="https://github.com/balancer/balancer-v3-monorepo"
+                href="https://docs-v3.balancer.fi/"
                 target="_blank"
                 rel="noreferrer"
-                className="link"
+                className="link no-underline hover:underline"
               >
-                Contracts
+                Docs
               </a>
             </div>
           </div>