feat: add populateApprove

Author: fedorovdg

README.md

@@ -181,6 +181,15 @@ import curve from "@curvefi/api";
     //     '0xb0cada2a2983dc0ed85a26916d32b9caefe45fecde47640bd7d0e214ff22aed3',
     //     '0x00ea7d827b3ad50ce933e96c579810cd7e70d66a034a86ec4e1e10005634d041'
     // ]
+    
+    // Get populated approve transactions (without executing)
+    const approveTxs = await curve.populateApprove(["DAI", "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"], ['1000', '1000'], spender);
+    // Returns array of TransactionLike objects (may include reset to 0 if needed for some tokens)
+    console.log(approveTxs);
+    // [
+    //   { to: '0x6B17...', data: '0x095ea7b3...', from: '0x...', ... },
+    //   { to: '0xA0b8...', data: '0x095ea7b3...', from: '0x...', ... }
+    // ]
 })()
 ```
 
@@ -1191,6 +1200,14 @@ import curve from "@curvefi/api";
     // [
     //     '0xc111e471715ae6f5437e12d3b94868a5b6542cd7304efca18b5782d315760ae5'
     // ]
+    
+    // Get populated transactions for approve (without executing)
+    const approveTxs = await curve.router.populateApprove('DAI', 1000);
+    // OR const approveTxs = await curve.router.populateApprove('0x6B175474E89094C44Da98b954EedeAC495271d0F', 1000);
+    // OR with custom spender: await curve.router.populateApprove('DAI', 1000, '0x...customSpender');
+    console.log(approveTxs);
+    // [{ to: '0x6B17...', data: '0x...', ... }]
+    // Returns array of TransactionLike objects
     const swapTx = await curve.router.swap('DAI', 'CRV', '1000');
     // OR const swapTx = await curve.router.swap('0x6B175474E89094C44Da98b954EedeAC495271d0F', '0xD533a949740bb3306d119CC777fa900bA034cd52', '1000');
     console.log(swapTx.hash);

src/index.ts

@@ -16,6 +16,7 @@ import {
     swapIsApproved,
     swapApproveEstimateGas,
     swapApprove,
+    swapPopulateApprove,
     swapEstimateGas,
     swap,
     populateSwap,
@@ -63,6 +64,7 @@ import {
     hasAllowance,
     ensureAllowanceEstimateGas,
     ensureAllowance,
+    populateApprove,
     getUsdRate,
     getGasPriceFromL1,
     getGasPriceFromL2,
@@ -176,6 +178,7 @@ export const createCurve = () => {
         getAllowance: getAllowance.bind(_curve),
         hasAllowance: hasAllowance.bind(_curve),
         ensureAllowance: ensureAllowance.bind(_curve),
+        populateApprove: populateApprove.bind(_curve),
         getCoinsData: getCoinsData.bind(_curve),
         getVolume: getVolume.bind(_curve),
         hasDepositAndStake: hasDepositAndStake.bind(_curve),
@@ -353,6 +356,7 @@ export const createCurve = () => {
             priceImpact: swapPriceImpact.bind(_curve),
             isApproved: swapIsApproved.bind(_curve),
             approve: swapApprove.bind(_curve),
+            populateApprove: swapPopulateApprove.bind(_curve),
             swap: swap.bind(_curve),
             populateSwap: populateSwap.bind(_curve),
             getSwappedAmount: getSwappedAmount.bind(_curve),

src/router.ts

@@ -8,6 +8,7 @@ import {
     _get_small_x,
     _getCoinAddresses,
     _getCoinDecimals,
+    _getAllowance,
     _getUsdRate,
     BN,
     DIGas,
@@ -19,7 +20,9 @@ import {
     getTxCostsUsd,
     hasAllowance,
     isEth,
+    MAX_ALLOWANCE,
     parseUnits,
+    populateApprove,
     runWorker,
     smartNumber,
     toBN,
@@ -406,6 +409,11 @@ export async function swapApprove(this: Curve, inputCoin: string, amount: number
     return await ensureAllowance.call(this, [inputCoin], [amount], this.constants.ALIASES.router);
 }
 
+export async function swapPopulateApprove(this: Curve, inputCoin: string, amount: number | string, spender?: string, isMax = true): Promise<TransactionLike[]> {
+    const routerAddress = this.contracts[this.constants.ALIASES.router].contract.target as string;
+    return await populateApprove.call(this, [inputCoin], [amount], spender || routerAddress, isMax);
+}
+
 export async function swapEstimateGas(this: Curve, inputCoin: string, outputCoin: string, amount: number | string): Promise<number | number[]> {
     const [inputCoinAddress, outputCoinAddress] = _getCoinAddresses.call(this, inputCoin, outputCoin);
     const [inputCoinDecimals] = _getCoinDecimals.call(this, inputCoinAddress, outputCoinAddress);

src/utils.ts

@@ -1,4 +1,4 @@
-import {Contract, ethers} from 'ethers';
+import {Contract, ethers, TransactionLike} from 'ethers';
 import {Contract as MulticallContract} from "@curvefi/ethcall";
 import BigNumber from 'bignumber.js';
 import {
@@ -310,6 +310,32 @@ export async function ensureAllowance(this: Curve, coins: string[], amounts: (nu
     return await _ensureAllowance.call(this, coinAddresses, _amounts, spender, isMax)
 }
 
+export async function populateApprove(this: Curve, coins: string[], amounts: (number | string)[], spender: string, isMax = true): Promise<TransactionLike[]> {
+    const coinAddresses = _getCoinAddresses.call(this, coins);
+    const decimals = _getCoinDecimals.call(this, coinAddresses);
+    const _amounts = amounts.map((a, i) => parseUnits(a, decimals[i]));
+    
+    const address = this.signerAddress;
+    const allowance = await _getAllowance.call(this, coinAddresses, address, spender);
+    
+    const transactions: TransactionLike[] = [];
+    
+    for (let i = 0; i < allowance.length; i++) {
+        if (allowance[i] < _amounts[i]) {
+            const contract = this.contracts[coinAddresses[i]].contract;
+            const _approveAmount = isMax ? MAX_ALLOWANCE : _amounts[i];
+            
+            if (allowance[i] > parseUnits("0")) {
+                transactions.push(await contract.approve.populateTransaction(spender, parseUnits("0")));
+            }
+            
+            transactions.push(await contract.approve.populateTransaction(spender, _approveAmount));
+        }
+    }
+    
+    return transactions;
+}
+
 export function getPoolIdBySwapAddress(this: Curve, swapAddress: string): string {
     const poolsData = this.getPoolsData();
     const poolIds = Object.entries(poolsData).filter(([, poolData]) => poolData.swap_address.toLowerCase() === swapAddress.toLowerCase());