Ethereum Contract SDK

A simple library for building Ethereum smart contract interactions. When offline, or away from a web3 wallet, smart
contract interaction is quite difficult. This is because it requires special transaction data that defines
a function call on a smart contract. This library intends to improve this experience by providing a simple interface
for common smart contract function calls. It also aims to be extensible to a wide variety of contracts.

Installing

``bash
npm i @bitgo/eth-contracts
`

Example Usage


The basic usage enables users to specify contracts by name and build transaction data from them.
`js
import { Contract } from '@bitgo/eth-contracts';
const cDAI = new Contract('Compound').instance('cDAI');
const { data, amount, address } = cDAI.methods().mint.call({ mintAmount: '1000000000' });
`

Users can specify an instance of the contract protocol by address instead of name
`js
import { Contract } from '@bitgo/eth-contracts';
const cDAI = new Contract('Compound').address('0x5d3a536e4d6dbd6114cc1ead35777bab948e3643');
const { data, amount, address } = cDAI.methods().mint.call({ mintAmount: '1000000000' });
`

The decoder can parse call data and output a human-readable explanation of a given contract call.
`js
import { Decoder } from '@bitgo/eth-contracts';
const decoder = new Decoder();
decoder.decode(Buffer.from('a9059cbb00000000000000000000000010d4f942617a231eb1430c88fe43c8c2050437d90000000000000000000000000000000000000000000000000000000000002710', 'hex'));
{ methodId: '0xa9059cbb',
name: 'transfer',
args:
[ { name: '_to',
type: 'address',
value: '0x10d4f942617a231eb1430c88fe43c8c2050437d9' },
{ name: '_value', type: 'uint256', value: 10000 } ],
contractName: 'StandardERC20' }
`




Integration with BitGo SDK

The output of this library is well formed as an argument to a BitGo SDK sendMany call. This makes it useful for
integration alongside the Bitgo SDK.

$3

`js
import { Contract } from '@bitgo/eth-contracts';

import { BitGo, Coin } from 'bitgo';

async function sendBitGoTx() {
const bitGo = new BitGo({ env: 'test' });
const baseCoin = bitGo.coin('eth');
const bitGoWallet = await baseCoin.wallets().get({ id: '5941ce2db42fcbc70717e5a898fd1595' });

const cDAI = new Contract('Compound').instance('cDAI');

const transaction = await bitGoWallet.sendMany({
recipients: cDAI.methods().mint.call({ mintAmount: '1000000000' }),
walletPassphrase: 'password'
})

}

sendBitGoTx();
`

Types

#### Contract
listContractTypes() -- get the available contract types.
`js
const types = Contract.listContractTypes();
// response: ['Compound', 'StandardERC20']
`

listMethods() -- get the available contract methods.
`js
const types = new Contract('StandardERC20').listMethods();
// response: [{ name: 'transfer', inputs: [...], outputs: [...] }, { name: 'approve', ... }]
`

methods() -- get contract method builder objects
`js
const types = new Contract('StandardERC20').methods();
// response: { transfer: { call: }, approve: { call: } }
`

getName() -- get contract name
`js
const types = new Contract('StandardERC20').getName();
// response: StandardERC20
`

address() -- set contract address
`js
const types = new Contract('StandardERC20').address('0x5d3a536e4d6dbd6114cc1ead35777bab948e3643');
// response: Contract with address set
`

instance() -- set contract instance
`js
const types = new Contract('StandardERC20').instance('DAI');
// response: Contract with DAI address set
`

Supported Protocols:

This library supports a limited number of smart contract protocols, as it maintains solidity ABIs locally.
- Compound -- Examples
- StandardERC20 -- Examples
- MakerDAO -- Examples

Adding a new ABI type


This library is quite extensible to new protocols -- if there are other contract types that you would like to use,
feel free to submit a PR adding them. To do so, make the following changes:
- Add the JSON ABI to abis directory, named [ProtocolName].json
- Add the ProtocolName and addresses for various instances of the protocol in config/instances.json
- For example, Compound protocol has cDAI, cUSDC, etc.
- Add the protocol to the README above
- Add some example usages in the examples` directory