feat: add f token supply and updated retained amount (#172)

.changeset/twelve-teachers-greet.md

@@ -0,0 +1,5 @@
+---
+"@folks-finance/xchain-sdk": patch
+---
+
+add f token supply and updated retained amount

src/chains/evm/hub/modules/folks-hub-pool.ts

@@ -1,6 +1,11 @@
 import { multicall } from "viem/actions";
 
-import { calcBorrowInterestIndex, calcDepositInterestIndex } from "../../../../common/utils/formulae.js";
+import {
+  calcBorrowInterestIndex,
+  calcDepositInterestIndex,
+  calcOverallBorrowInterestRate,
+  calcRetention,
+} from "../../../../common/utils/formulae.js";
 import { compoundEveryHour, compoundEverySecond } from "../../../../common/utils/math-lib.js";
 import { getHubTokenData } from "../utils/chain.js";
 import { getHubPoolContract } from "../utils/contract.js";
@@ -32,6 +37,7 @@ export async function getPoolInfo(
     stableBorrowData,
     capsData,
     configData,
+    fTokenCirculatingSupply,
   ] = await multicall(provider, {
     contracts: [
       {
@@ -74,12 +80,23 @@ export async function getPoolInfo(
         abi: hubPool.abi,
         functionName: "getConfigData",
       },
+      {
+        address: hubPool.address,
+        abi: hubPool.abi,
+        functionName: "totalSupply",
+      },
     ],
     allowFailure: false,
   });
 
-  const { flashLoanFee, retentionRate, fTokenFeeRecipient, tokenFeeClaimer, totalRetainedAmount, tokenFeeRecipient } =
-    feeData;
+  const {
+    flashLoanFee,
+    retentionRate,
+    fTokenFeeRecipient,
+    tokenFeeClaimer,
+    totalRetainedAmount: actualRetained,
+    tokenFeeRecipient,
+  } = feeData;
   const {
     optimalUtilisationRatio,
     totalAmount: depositTotalAmount,
@@ -118,7 +135,18 @@ export async function getPoolInfo(
     feeData: {
       flashLoanFee: [BigInt(flashLoanFee), 6],
       retentionRate: [BigInt(retentionRate), 6],
-      totalRetainedAmount,
+      totalRetainedAmount: calcRetention(
+        actualRetained,
+        variableBorrowTotalAmount + stableBorrowTotalAmount,
+        calcOverallBorrowInterestRate(
+          variableBorrowTotalAmount,
+          stableBorrowTotalAmount,
+          [variableBorrowInterestRate, 18],
+          [stableBorrowAverageInterestRate, 18],
+        ),
+        [BigInt(retentionRate), 6],
+        lastUpdateTimestamp,
+      ),
       fTokenFeeRecipient: fTokenFeeRecipient as EvmAddress,
       tokenFeeClaimer: tokenFeeClaimer as EvmAddress,
       tokenFeeRecipient: tokenFeeRecipient as GenericAddress,
@@ -173,5 +201,6 @@ export async function getPoolInfo(
       canMintFToken,
       flashLoanSupported,
     },
+    fTokenCirculatingSupply,
   };
 }

src/chains/evm/hub/types/pool.ts

@@ -68,4 +68,5 @@ export type PoolInfo = {
   stableBorrowData: StableBorrowData;
   capsData: CapsData;
   configData: ConfigData;
+  fTokenCirculatingSupply: bigint;
 };

src/common/utils/formulae.ts

@@ -12,6 +12,25 @@ export function calcNextPeriodReset(periodNumber: bigint, offset: bigint, length
   return (periodNumber + BigInt(1)) * length - offset;
 }
 
+export function calcOverallBorrowInterestRate(
+  totalVarDebt: bigint,
+  totalStableDebt: bigint,
+  variableBorInterestRate: Dnum,
+  avgStableBorInterestRate: Dnum,
+): Dnum {
+  const totalDebt = totalVarDebt + totalStableDebt;
+  if (totalDebt === 0n) return dn.from(0, 18);
+
+  return dn.div(
+    dn.add(
+      dn.mul(totalVarDebt, variableBorInterestRate, { rounding: "ROUND_DOWN", decimals: 0 }),
+      dn.mul(totalStableDebt, avgStableBorInterestRate, { rounding: "ROUND_DOWN", decimals: 0 }),
+    ),
+    totalDebt,
+    { rounding: "ROUND_DOWN", decimals: 18 },
+  );
+}
+
 export function calcDepositInterestIndex(dirt1: Dnum, diit1: Dnum, latestUpdate: bigint): Dnum {
   const dt = BigInt(unixTime()) - latestUpdate;
   return dn.mul(
@@ -35,6 +54,32 @@ export function calcBorrowInterestIndex(birt1: Dnum, biit1: Dnum, latestUpdate:
   );
 }
 
+export function calcRetention(
+  actualRetained: bigint,
+  totalDebt: bigint,
+  overallBorrowInterestRate: Dnum,
+  retentionRate: Dnum,
+  latestUpdate: bigint,
+): bigint {
+  const dt = BigInt(unixTime()) - latestUpdate;
+
+  const [retainedDelta] = dn.div(
+    dn.mul(
+      dn.mul(dn.mul(totalDebt, overallBorrowInterestRate, { rounding: "ROUND_DOWN", decimals: 0 }), retentionRate, {
+        rounding: "ROUND_DOWN",
+        decimals: 0,
+      }),
+      dt,
+      { rounding: "ROUND_DOWN" },
+    ),
+    SECONDS_IN_YEAR,
+    {
+      rounding: "ROUND_DOWN",
+    },
+  );
+  return actualRetained + retainedDelta;
+}
+
 export function calcRewardIndex(used: bigint, ma: bigint, rit1: Dnum, rs: Dnum, latestUpdate: bigint): Dnum {
   if (used <= ma) return rit1;
   const dt = BigInt(unixTime()) - latestUpdate;