fix: add unwind exit condition

src/filler.ts

@@ -15,6 +15,8 @@ import { stringify } from './utils/json.js';
 import { logger } from './utils/logger.js';
 import { SorobanHelper } from './utils/soroban_helper.js';
 
+const MAX_WITHDRAW = BigInt('9223372036854775807');
+
 /**
  * Check if the filler supports bidding on the auction.
  * @param filler - The filler to check
@@ -197,7 +199,7 @@ export function managePositions(
     let withdrawAmount: bigint;
     if (hasLeftoverLiabilities.length === 0) {
       // no liabilities, withdraw the full position
-      withdrawAmount = BigInt('9223372036854775807');
+      withdrawAmount = MAX_WITHDRAW;
     } else {
       if (filler.minHealthFactor * 1.005 > effectiveCollateral / effectiveLiabilities) {
         // stop withdrawing collateral if close to min health factor
@@ -208,20 +210,25 @@ export function managePositions(
         (reserve.getCollateralFactor() * price);
       const position = reserve.toAssetFromBTokenFloat(amount);
       withdrawAmount =
-        maxWithdraw > position ? BigInt('9223372036854775807') : FixedMath.toFixed(maxWithdraw, 7);
+        maxWithdraw > position ? MAX_WITHDRAW : FixedMath.toFixed(maxWithdraw, 7);
     }
 
     // if this is not a full withdrawal, and the colleratal is not also a liability, stop
     if (
       !hasLeftoverLiabilities.includes(reserve.config.index) &&
-      withdrawAmount !== BigInt('9223372036854775807')
+      withdrawAmount !== MAX_WITHDRAW
     ) {
       break;
     }
     // require the filler to keep at least the min collateral balance of their primary asset
     if (reserve.assetId === filler.primaryAsset) {
       const toMinPosition = reserve.toAssetFromBToken(amount) - filler.minPrimaryCollateral;
       withdrawAmount = withdrawAmount > toMinPosition ? toMinPosition : withdrawAmount;
+      // if withdrawAmount is less than 1% of the minPrimaryCollateral stop
+      // this prevents dust withdraws from looping unwind events due to interest accrual
+      if (withdrawAmount < filler.minPrimaryCollateral / 100n) {
+        break;
+      }
     }
 
     if (withdrawAmount > 0n) {

test/filler.test.ts

@@ -466,6 +466,52 @@ describe('filler', () => {
       expect(requests).toEqual(expectedRequests);
     });
 
+    it('does not withdraw primary collateral if it only slightly above min collateral', () => {
+      const positions = new Positions(
+        // dTokens
+        new Map<number, bigint>([]),
+        // bTokens - (1.007 is ~b_rate)
+        new Map<number, bigint>([
+          [1, FixedMath.toFixed(100.8 / 1.007, 7)],
+        ]),
+        new Map<number, bigint>([])
+      );
+      const balances = new Map<string, bigint>([
+        [assets[0], FixedMath.toFixed(575, 7)],
+        [assets[1], FixedMath.toFixed(3000, 7)],
+        [assets[2], FixedMath.toFixed(1000, 7)],
+        [assets[3], FixedMath.toFixed(0, 7)],
+      ]);
+
+      const requests = managePositions(filler, mockPool, mockOracle, positions, balances);
+
+      const expectedRequests: Request[] = [];
+      expect(requests).toEqual(expectedRequests);
+    });
+
+    it('does nothing when only primary collateral and other non-repayable liability remain', () => {
+      const positions = new Positions(
+        // dTokens
+        new Map<number, bigint>([[0, FixedMath.toFixed(200, 7)]]),
+        // bTokens
+        new Map<number, bigint>([
+          [1, FixedMath.toFixed(150, 7)],
+        ]),
+        new Map<number, bigint>([])
+      );
+      const balances = new Map<string, bigint>([
+        [assets[0], FixedMath.toFixed(0, 7)],
+        [assets[1], FixedMath.toFixed(3000, 7)],
+        [assets[2], FixedMath.toFixed(1000, 7)],
+        [assets[3], FixedMath.toFixed(0, 7)],
+      ]);
+
+      const requests = managePositions(filler, mockPool, mockOracle, positions, balances);
+
+      const expectedRequests: Request[] = [];
+      expect(requests).toEqual(expectedRequests);
+    });
+
     it('clears smallest collateral position first', () => {
       const positions = new Positions(
         // dTokens