refactor: use a single zcf.atomicReallocate for repaying

Agoric · Feb 26, 2025 · f01f6b4 · f01f6b4
1 parent f83e5a9
commit f01f6b4
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Showing 5 changed files with 46 additions and 117 deletions.
diff --git a/packages/fast-usdc/src/exos/liquidity-pool.js b/packages/fast-usdc/src/exos/liquidity-pool.js
@@ -1,12 +1,15 @@
 import { AmountMath, AmountShape, RatioShape } from '@agoric/ertp';
 import {
+  fromOnly,
+  toOnly,
   makeRecorderTopic,
   RecorderKitShape,
   TopicsRecordShape,
 } from '@agoric/zoe/src/contractSupport/index.js';
 import { SeatShape } from '@agoric/zoe/src/typeGuards.js';
 import { M } from '@endo/patterns';
 import { Fail, q } from '@endo/errors';
+import { TransferPartShape } from '@agoric/zoe/src/contractSupport/atomicTransfer.js';
 import {
   borrowCalc,
   checkPoolBalance,
@@ -83,7 +86,7 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
       }),
       repayer: M.interface('repayer', {
         repay: M.call(
-          SeatShape,
+          TransferPartShape,
           harden({
             Principal: makeNatAmountShape(USDC, 1n),
             PoolFee: makeNatAmountShape(USDC, 0n),
@@ -179,7 +182,6 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
          * @param {Amount<'nat'>} amount
          */
         returnToPool(borrowSeat, amount) {
-          const { zcfSeat: repaySeat } = zcf.makeEmptySeatKit();
           const returnAmounts = harden({
             Principal: amount,
             PoolFee: makeEmpty(USDC),
@@ -188,21 +190,18 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
           const borrowSeatAllocation = borrowSeat.getCurrentAllocation();
           isGTE(borrowSeatAllocation.USDC, amount) ||
             Fail`⚠️ borrowSeatAllocation ${q(borrowSeatAllocation)} less than amountKWR ${q(amount)}`;
-          // arrange payments in a format repay is expecting
-          zcf.atomicRearrange(
-            harden([[borrowSeat, repaySeat, { USDC: amount }, returnAmounts]]),
-          );
-          this.facets.repayer.repay(repaySeat, returnAmounts);
+
+          const transferSourcePart = fromOnly(borrowSeat, { USDC: amount });
+          this.facets.repayer.repay(transferSourcePart, returnAmounts);
           borrowSeat.exit();
-          repaySeat.exit();
         },
       },
       repayer: {
         /**
-         * @param {ZCFSeat} fromSeat
-         * @param {RepayAmountKWR} amounts
+         * @param {TransferPart} sourceTransfer
+         * @param {RepayAmountKWR} split
          */
-        repay(fromSeat, amounts) {
+        repay(sourceTransfer, split) {
           const {
             encumberedBalance,
             feeSeat,
@@ -215,32 +214,21 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
             shareWorth,
             encumberedBalance,
           );
-
-          const fromSeatAllocation = fromSeat.getCurrentAllocation();
-          // Validate allocation equals amounts and Principal <= encumberedBalance
+          // Validate Principal <= encumberedBalance and produce poolStats after
           const post = repayCalc(
             shareWorth,
-            fromSeatAllocation,
-            amounts,
+            split,
             encumberedBalance,
             poolStats,
           );
 
-          const { ContractFee, ...rest } = amounts;
-
           // COMMIT POINT
           // UNTIL #10684: ability to terminate an incarnation w/o terminating the contract
-          zcf.atomicRearrange(
-            harden([
-              [
-                fromSeat,
-                poolSeat,
-                rest,
-                { USDC: add(amounts.PoolFee, amounts.Principal) },
-              ],
-              [fromSeat, feeSeat, { ContractFee }, { USDC: ContractFee }],
-            ]),
-          );
+          zcf.atomicRearrange([
+            sourceTransfer,
+            toOnly(poolSeat, { USDC: add(split.PoolFee, split.Principal) }),
+            toOnly(feeSeat, { USDC: split.ContractFee }),
+          ]);
 
           Object.assign(this.state, post);
           this.facets.external.publishPoolMetrics();

diff --git a/packages/fast-usdc/src/exos/settler.js b/packages/fast-usdc/src/exos/settler.js
@@ -6,6 +6,7 @@ import { E } from '@endo/far';
 import { M } from '@endo/patterns';
 
 import { decodeAddressHook } from '@agoric/cosmic-proto/address-hooks.js';
+import { fromOnly } from '@agoric/zoe/src/contractSupport/index.js';
 import { PendingTxStatus } from '../constants.js';
 import { makeFeeTools } from '../utils/fees.js';
 import {
@@ -323,10 +324,8 @@ export const prepareSettler = (
               harden({ In: received }),
             ),
           );
-          zcf.atomicRearrange(
-            harden([[settlingSeat, settlingSeat, { In: received }, split]]),
-          );
-          repayer.repay(settlingSeat, split);
+          const transferPart = fromOnly(settlingSeat, { In: received });
+          repayer.repay(transferPart, split);
           settlingSeat.exit();
 
           // update status manager, marking tx `DISBURSED`

diff --git a/packages/fast-usdc/src/pool-share-math.js b/packages/fast-usdc/src/pool-share-math.js
@@ -201,35 +201,23 @@ export const borrowCalc = (
 
 /**
  * @param {ShareWorth} shareWorth
- * @param {Allocation} fromSeatAllocation
- * @param {RepayAmountKWR} amounts
+ * @param {RepayAmountKWR} split
  * @param {Amount<'nat'>} encumberedBalance aka 'outstanding borrows'
  * @param {PoolStats} poolStats
- * @throws {Error} if allocations do not match amounts or Principal exceeds encumberedBalance
+ * @throws {Error} if Principal exceeds encumberedBalance
  */
-export const repayCalc = (
-  shareWorth,
-  fromSeatAllocation,
-  amounts,
-  encumberedBalance,
-  poolStats,
-) => {
-  (isEqual(fromSeatAllocation.Principal, amounts.Principal) &&
-    isEqual(fromSeatAllocation.PoolFee, amounts.PoolFee) &&
-    isEqual(fromSeatAllocation.ContractFee, amounts.ContractFee)) ||
-    Fail`Cannot repay. From seat allocation ${q(fromSeatAllocation)} does not equal amounts ${q(amounts)}.`;
-
-  isGTE(encumberedBalance, amounts.Principal) ||
-    Fail`Cannot repay. Principal ${q(amounts.Principal)} exceeds encumberedBalance ${q(encumberedBalance)}.`;
+export const repayCalc = (shareWorth, split, encumberedBalance, poolStats) => {
+  isGTE(encumberedBalance, split.Principal) ||
+    Fail`Cannot repay. Principal ${q(split.Principal)} exceeds encumberedBalance ${q(encumberedBalance)}.`;
 
   return harden({
-    shareWorth: withFees(shareWorth, amounts.PoolFee),
-    encumberedBalance: subtract(encumberedBalance, amounts.Principal),
+    shareWorth: withFees(shareWorth, split.PoolFee),
+    encumberedBalance: subtract(encumberedBalance, split.Principal),
     poolStats: {
       ...poolStats,
-      totalRepays: add(poolStats.totalRepays, amounts.Principal),
-      totalPoolFees: add(poolStats.totalPoolFees, amounts.PoolFee),
-      totalContractFees: add(poolStats.totalContractFees, amounts.ContractFee),
+      totalRepays: add(poolStats.totalRepays, split.Principal),
+      totalPoolFees: add(poolStats.totalPoolFees, split.PoolFee),
+      totalContractFees: add(poolStats.totalContractFees, split.ContractFee),
     },
   });
 };
diff --git a/packages/fast-usdc/test/exos/settler.test.ts b/packages/fast-usdc/test/exos/settler.test.ts
@@ -198,8 +198,8 @@ const makeTestContext = async t => {
   };
 
   const repayer = zone.exo('Repayer Mock', undefined, {
-    repay(fromSeat: ZCFSeat, amounts: AmountKeywordRecord) {
-      callLog.push(harden({ method: 'repay', fromSeat, amounts }));
+    repay(sourceTransfer: TransferPart, amounts: AmountKeywordRecord) {
+      callLog.push(harden({ method: 'repay', sourceTransfer, amounts }));
     },
   });
 
@@ -261,8 +261,8 @@ test('happy path: disburse to LPs; StatusManager removes tx', async t => {
 
   t.log('Funds were disbursed to LP.');
   const calls = peekCalls();
-  t.is(calls.length, 3);
-  const [withdraw, rearrange, repay] = calls;
+  t.is(calls.length, 2);
+  const [withdraw, repay] = calls;
 
   t.deepEqual(
     withdraw,
@@ -284,16 +284,6 @@ test('happy path: disburse to LPs; StatusManager removes tx', async t => {
     Principal: usdc.make(146999999n),
   });
 
-  t.like(
-    rearrange,
-    { method: 'atomicRearrange' },
-    '2. settler called atomicRearrange ',
-  );
-  t.is(rearrange.parts.length, 1);
-  const [s1, s2, a1, a2] = rearrange.parts[0];
-  t.is(s1, s2, 'src and dest seat are the same');
-  t.deepEqual([a1, a2], [{ In }, expectedSplit]);
-
   t.like(
     repay,
     {
@@ -302,7 +292,9 @@ test('happy path: disburse to LPs; StatusManager removes tx', async t => {
     },
     '3. settler called repay() on liquidity pool repayer facet',
   );
-  t.is(repay.fromSeat, s1);
+  t.like(repay.sourceTransfer[2], {
+    In: usdc.units(150),
+  });
 
   t.deepEqual(
     statusManager.lookupPending(

diff --git a/packages/fast-usdc/test/pool-share-math.test.ts b/packages/fast-usdc/test/pool-share-math.test.ts
@@ -425,15 +425,8 @@ test('basic repay calculation', t => {
   };
   const encumberedBalance = make(USDC, 200n);
   const poolStats = makeInitialPoolStats();
-  const fromSeatAllocation = amounts;
 
-  const result = repayCalc(
-    shareWorth,
-    fromSeatAllocation,
-    amounts,
-    encumberedBalance,
-    poolStats,
-  );
+  const result = repayCalc(shareWorth, amounts, encumberedBalance, poolStats);
 
   t.deepEqual(
     result.encumberedBalance,
@@ -489,23 +482,13 @@ test('repay fails when principal exceeds encumbered balance', t => {
 
   const fromSeatAllocation = amounts;
 
-  t.throws(
-    () =>
-      repayCalc(
-        shareWorth,
-        fromSeatAllocation,
-        amounts,
-        encumberedBalance,
-        poolStats,
-      ),
-    {
-      message: /Cannot repay. Principal .* exceeds encumberedBalance/,
-    },
-  );
+  t.throws(() => repayCalc(shareWorth, amounts, encumberedBalance, poolStats), {
+    message: /Cannot repay. Principal .* exceeds encumberedBalance/,
+  });
 
   t.notThrows(
     () =>
-      repayCalc(shareWorth, fromSeatAllocation, amounts, make(USDC, 200n), {
+      repayCalc(shareWorth, amounts, make(USDC, 200n), {
         ...makeInitialPoolStats(),
         totalBorrows: make(USDC, 200n),
       }),
@@ -528,24 +511,9 @@ test('repay fails when seat allocation does not equal amounts', t => {
     totalBorrows: make(USDC, 100n),
   };
 
-  const fromSeatAllocation = {
-    ...amounts,
-    ContractFee: make(USDC, 1n),
-  };
-
-  t.throws(
-    () =>
-      repayCalc(
-        shareWorth,
-        fromSeatAllocation,
-        amounts,
-        encumberedBalance,
-        poolStats,
-      ),
-    {
-      message: /Cannot repay. From seat allocation .* does not equal amounts/,
-    },
-  );
+  t.throws(() => repayCalc(shareWorth, amounts, encumberedBalance, poolStats), {
+    message: /Cannot repay. Principal .* exceeds encumberedBalance/,
+  });
 });
 
 test('repay succeeds with no Pool or Contract Fee', t => {
@@ -563,13 +531,7 @@ test('repay succeeds with no Pool or Contract Fee', t => {
     totalBorrows: make(USDC, 100n),
   };
   const fromSeatAllocation = amounts;
-  const actual = repayCalc(
-    shareWorth,
-    fromSeatAllocation,
-    amounts,
-    encumberedBalance,
-    poolStats,
-  );
+  const actual = repayCalc(shareWorth, amounts, encumberedBalance, poolStats);
   t.like(actual, {
     shareWorth,
     encumberedBalance: {