feat(uniswapx-sdk): Helper for minimum output of a curve (Uniswap#188)

alex-stone · Oct 31, 2024 · 8b2649b · 8b2649b
1 parent 7448890
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Showing 2 changed files with 49 additions and 1 deletion.
diff --git a/sdks/uniswapx-sdk/src/builder/V3DutchOrderBuilder.test.ts b/sdks/uniswapx-sdk/src/builder/V3DutchOrderBuilder.test.ts
@@ -865,6 +865,34 @@ describe("V3DutchOrderBuilder", () => {
             const maxout = V3DutchOrderBuilder.getMaxAmountOut(startAmount, relativeAmounts);
             expect(maxout).toEqual(startAmount);
         });
+
+        it("Test minAmountOut", () => {
+            const startAmount = OUTPUT_START_AMOUNT;
+            const relativeAmounts = [BigInt(0), BigInt(3), BigInt(-2), BigInt(-4), BigInt(-3)];
+            const minout = V3DutchOrderBuilder.getMinAmountOut(startAmount, relativeAmounts);
+            expect(minout).toEqual(startAmount.sub(3));
+        });
+
+        it("Test minAmountOut with empty curve", () => {
+            const startAmount = OUTPUT_START_AMOUNT;
+            const relativeAmounts : bigint[] = [];
+            const minout = V3DutchOrderBuilder.getMinAmountOut(startAmount, relativeAmounts);
+            expect(minout).toEqual(startAmount);
+        });
+
+        it("Test minAmountOut with negative relativeAmounts", () => {
+            const startAmount = OUTPUT_START_AMOUNT;
+            const relativeAmounts = [BigInt(-1), BigInt(-2), BigInt(-3)];
+            const minout = V3DutchOrderBuilder.getMinAmountOut(startAmount, relativeAmounts);
+            expect(minout).toEqual(startAmount);
+        });
+
+        it("Test minAmountOut with entirely positive relativeAmounts", () => {
+            const startAmount = OUTPUT_START_AMOUNT;
+            const relativeAmounts = [BigInt(1), BigInt(2), BigInt(3)];
+            const minout = V3DutchOrderBuilder.getMinAmountOut(startAmount, relativeAmounts);
+            expect(minout).toEqual(startAmount.sub(3));
+        });
     });
 
     describe("fromOrder", () => {

diff --git a/sdks/uniswapx-sdk/src/builder/V3DutchOrderBuilder.ts b/sdks/uniswapx-sdk/src/builder/V3DutchOrderBuilder.ts
@@ -319,7 +319,7 @@ export class V3DutchOrderBuilder extends OrderBuilder {
     );
   }
 
-  // A helper function for users of the class to easily the value to pass to maxAmount in an input
+  // A helper function for users of the class to easily find the value to pass to maxAmount in an input
   static getMaxAmountOut(
     startAmount: BigNumber,
     relativeAmounts: bigint[]
@@ -338,4 +338,24 @@ export class V3DutchOrderBuilder extends OrderBuilder {
     const maxOut = startAmount.sub(minRelativeAmount.toString());
     return maxOut;
   }
+
+  // A helper function for users of the class find the lowest possible output amount
+  static getMinAmountOut(
+    startAmount: BigNumber,
+    relativeAmounts: bigint[]
+  ): BigNumber {
+    if (relativeAmounts.length == 0) {
+      return startAmount;
+    }
+
+    // Find the maximum of the relative amounts
+    const maxRelativeAmount = relativeAmounts.reduce(
+      (max, amount) => (amount > max ? amount : max),
+      BigInt(0)
+    );
+
+    // Minimum is the start - the max of the relative amounts
+    const minOut = startAmount.sub(maxRelativeAmount.toString());
+    return minOut;
+  }
 }