/**
* Token approval utilities
*
* Manages ERC20 token approvals for DeFi protocols.
*/
import {
type PublicClient,
type WalletClient,
encodeFunctionData,
parseUnits,
maxUint256,
} from "viem";
/**
* ERC20 ABI for approval operations
*/
const ERC20_ABI = [
{
inputs: [
{ name: "owner", type: "address" },
{ name: "spender", type: "address" },
],
name: "allowance",
outputs: [{ name: "", type: "uint256" }],
stateMutability: "view",
type: "function",
},
{
inputs: [
{ name: "spender", type: "address" },
{ name: "amount", type: "uint256" },
],
name: "approve",
outputs: [{ name: "", type: "bool" }],
stateMutability: "nonpayable",
type: "function",
},
{
inputs: [],
name: "decimals",
outputs: [{ name: "", type: "uint8" }],
stateMutability: "view",
type: "function",
},
] as const;
/**
* Check current token allowance
*/
export async function checkAllowance(
publicClient: PublicClient,
tokenAddress: `0x${string}`,
owner: `0x${string}`,
spender: `0x${string}`
): Promise<bigint> {
const allowance = await publicClient.readContract({
address: tokenAddress,
abi: ERC20_ABI,
functionName: "allowance",
args: [owner, spender],
});
return allowance as bigint;
}
/**
* Check if approval is needed for an amount
*/
export async function needsApproval(
publicClient: PublicClient,
tokenAddress: `0x${string}`,
owner: `0x${string}`,
spender: `0x${string}`,
amount: bigint
): Promise<boolean> {
const currentAllowance = await checkAllowance(
publicClient,
tokenAddress,
owner,
spender
);
return currentAllowance < amount;
}
/**
* Approve exact amount
*/
export async function approveToken(
publicClient: PublicClient,
walletClient: WalletClient,
tokenAddress: `0x${string}`,
spender: `0x${string}`,
amount: bigint
): Promise<`0x${string}`> {
const account = walletClient.account;
if (!account) {
throw new Error("Wallet client has no account");
}
const { request } = await publicClient.simulateContract({
address: tokenAddress,
abi: ERC20_ABI,
functionName: "approve",
args: [spender, amount],
account: account.address,
});
const hash = await walletClient.writeContract(request);
return hash;
}
/**
* Approve unlimited amount (max uint256)
*/
export async function approveUnlimited(
publicClient: PublicClient,
walletClient: WalletClient,
tokenAddress: `0x${string}`,
spender: `0x${string}`
): Promise<`0x${string}`> {
return approveToken(publicClient, walletClient, tokenAddress, spender, maxUint256);
}
/**
* Ensure sufficient approval, approve if needed
*/
export async function ensureApproval(
publicClient: PublicClient,
walletClient: WalletClient,
tokenAddress: `0x${string}`,
spender: `0x${string}`,
amount: bigint,
useUnlimited: boolean = false
): Promise<{ approved: boolean; txHash?: `0x${string}` }> {
const account = walletClient.account;
if (!account) {
throw new Error("Wallet client has no account");
}
const isApprovalNeeded = await needsApproval(
publicClient,
tokenAddress,
account.address,
spender,
amount
);
if (!isApprovalNeeded) {
return { approved: true };
}
const approvalAmount = useUnlimited ? maxUint256 : amount;
const txHash = await approveToken(
publicClient,
walletClient,
tokenAddress,
spender,
approvalAmount
);
// Wait for transaction confirmation
await publicClient.waitForTransactionReceipt({ hash: txHash });
return { approved: true, txHash };
}
/**
* Revoke approval (set to 0)
*/
export async function revokeApproval(
publicClient: PublicClient,
walletClient: WalletClient,
tokenAddress: `0x${string}`,
spender: `0x${string}`
): Promise<`0x${string}`> {
return approveToken(publicClient, walletClient, tokenAddress, spender, 0n);
}
/**
* Get token decimals
*/
export async function getTokenDecimals(
publicClient: PublicClient,
tokenAddress: `0x${string}`
): Promise<number> {
const decimals = await publicClient.readContract({
address: tokenAddress,
abi: ERC20_ABI,
functionName: "decimals",
});
return decimals as number;
}
/**
* Batch check multiple token allowances
*/
export async function batchCheckAllowances(
publicClient: PublicClient,
tokens: `0x${string}`[],
owner: `0x${string}`,
spender: `0x${string}`
): Promise<Map<`0x${string}`, bigint>> {
const allowances = await Promise.all(
tokens.map((token) => checkAllowance(publicClient, token, owner, spender))
);
const result = new Map<`0x${string}`, bigint>();
tokens.forEach((token, index) => {
result.set(token, allowances[index]);
});
return result;
}
