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STREAM-1597: account for transfer fees when creating Airdrops #177

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merged 3 commits into from
May 24, 2024

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Yolley
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@Yolley Yolley commented May 24, 2024

When creating an Airdrop for mint with Transfer Fee extension we need to account for such fees, so that the Escrow has enough funds to distribute.

Logic loosely based on what we have in Rust Solana library https://github.com/solana-labs/solana-program-library/blob/master/token/program-2022/src/extension/transfer_fee/mod.rs#L90

Example transaction https://explorer.solana.com/tx/51qRMSAy8bXW93mGekBZZjQPv7zjja6Eibfab2j2RVKBSVFnn6Fo8qCap1CNPVWybKwQMfj12KpDyayqqwRRP2sU?cluster=devnet

@Yolley Yolley requested review from RolginRoman, LukaStreamflow and Johnny3223 and removed request for Johnny3223 May 24, 2024 21:19
import { SignerWalletAdapter } from "@solana/wallet-adapter-base";
import { Connection, Keypair, PublicKey, Transaction, VersionedTransaction } from "@solana/web3.js";
import { ContractError } from "@streamflow/common";
import { ConfirmationParams, signAndExecuteTransaction, ThrottleParams } from "@streamflow/common/solana";

import { fromTxError } from "./generated/errors";
import { ONE_IN_BASIS_POINTS } from "./constants";

export const divCeilN = (n: bigint, d: bigint): bigint => n / d + (n % d ? BigInt(1) : BigInt(0));
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Since it's Friday, BigInt isn't as big as BN.
Also, BN has all of these operations.

I'll merge this and migrate it with staging so Milan can test it during the weekend, but let's fix this with BN asap :)

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BigInt is used in solana js-sdk, that's why we use it here.

const rawPreFeeAmount = divCeilN(numerator, denominator);
const fee = rawPreFeeAmount - transferAmount;
transferAmount = rawPreFeeAmount;
feeCharged = fee > transferFee.maximumFee ? transferFee.maximumFee : fee;
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Math.max()

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That's the max configured in Transfer Fee Config.

let feeCharged = BigInt(0);

if (transferFeeBasisPoints !== BigInt(0)) {
const numerator = transferAmount * ONE_IN_BASIS_POINTS;
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Comment around this math would be helpful :)

@LukaStreamflow LukaStreamflow merged commit 9e892b3 into master May 24, 2024
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2 participants