Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/test/helpers/eip712.js

@@ -0,0 +1,67 @@
+const ethSigUtil = require('eth-sig-util');
+const keccak256 = require('keccak256');
+
+const EIP712Domain = [
+  { name: 'name', type: 'string' },
+  { name: 'version', type: 'string' },
+  { name: 'chainId', type: 'uint256' },
+  { name: 'verifyingContract', type: 'address' },
+  { name: 'salt', type: 'bytes32' },
+];
+
+const Permit = [
+  { name: 'owner', type: 'address' },
+  { name: 'spender', type: 'address' },
+  { name: 'value', type: 'uint256' },
+  { name: 'nonce', type: 'uint256' },
+  { name: 'deadline', type: 'uint256' },
+];
+
+function bufferToHexString(buffer) {
+  return '0x' + buffer.toString('hex');
+}
+
+function hexStringToBuffer(hexstr) {
+  return Buffer.from(hexstr.replace(/^0x/, ''), 'hex');
+}
+
+async function getDomain(contract) {
+  const { fields, name, version, chainId, verifyingContract, salt, extensions } = await contract.eip712Domain();
+
+  if (extensions.length > 0) {
+    throw Error('Extensions not implemented');
+  }
+
+  const domain = { name, version, chainId, verifyingContract, salt };
+  for (const [i, { name }] of EIP712Domain.entries()) {
+    if (!(fields & (1 << i))) {
+      delete domain[name];
+    }
+  }
+
+  return domain;
+}
+
+function domainType(domain) {
+  return EIP712Domain.filter(({ name }) => domain[name] !== undefined);
+}
+
+function domainSeparator(domain) {
+  return bufferToHexString(
+    ethSigUtil.TypedDataUtils.hashStruct('EIP712Domain', domain, { EIP712Domain: domainType(domain) }),
+  );
+}
+
+function hashTypedData(domain, structHash) {
+  return bufferToHexString(
+    keccak256(Buffer.concat(['0x1901', domainSeparator(domain), structHash].map(str => hexStringToBuffer(str)))),
+  );
+}
+
+module.exports = {
+  Permit,
+  getDomain,
+  domainType,
+  domainSeparator,
+  hashTypedData,
+};