filters.js

/**
 * Pluggable filter system. A filter is a function that takes a transaction
 * object and returns true to keep it, false to drop it.
 *
 * Compose filters with `allOf` / `anyOf`. Add your own filters here.
 */
import { getAddress } from "viem";

const KNOWN_METHODS = {
  "0xa9059cbb": "transfer(address,uint256)",
  "0x23b872dd": "transferFrom(address,address,uint256)",
  "0x095ea7b3": "approve(address,uint256)",
  "0x38ed1739": "swapExactTokensForTokens(uint256,uint256,address[],address,uint256)",
  "0x7ff36ab5": "swapExactETHForTokens(uint256,address[],address,uint256)",
  "0x18cbafe5": "swapExactTokensForETH(uint256,uint256,address[],address,uint256)",
  "0x791ac947": "swapExactTokensForETHSupportingFeeOnTransferTokens(...)",
  "0xb6f9de95": "swapExactETHForTokensSupportingFeeOnTransferTokens(...)",
  "0xfb3bdb41": "swapETHForExactTokens(uint256,address[],address,uint256)",
  "0x5ae401dc": "multicall(uint256,bytes[])",
  "0x3593564c": "execute(bytes,bytes[],uint256)",
  "0xc04b8d59": "exactInput((bytes,address,uint256,uint256,uint256))",
};

export function methodSignature(tx) {
  if (!tx.input || tx.input === "0x" || tx.input.length < 10) return null;
  const sig = tx.input.slice(0, 10).toLowerCase();
  return { selector: sig, name: KNOWN_METHODS[sig] ?? null };
}

// --- Composable filters ---

export const allOf = (...filters) => (tx) => filters.every((f) => f(tx));
export const anyOf = (...filters) => (tx) => filters.some((f) => f(tx));
export const not   = (filter)     => (tx) => !filter(tx);

// --- Common filter primitives ---

export const minValueWei = (min) => (tx) => BigInt(tx.value ?? "0x0") >= BigInt(min);

export const toAddress = (addr) => {
  const target = getAddress(addr);
  return (tx) => tx.to && getAddress(tx.to) === target;
};

export const fromAddress = (addr) => {
  const target = getAddress(addr);
  return (tx) => tx.from && getAddress(tx.from) === target;
};

export const methodSelector = (selector) => {
  const target = selector.toLowerCase();
  return (tx) => methodSignature(tx)?.selector === target;
};

export const isContractCall = () => (tx) => tx.input && tx.input.length >= 10;

export const isEthTransfer = () => (tx) => !tx.input || tx.input === "0x";