Tok1t4N1k0 / solidity-examples

example contracts

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LayerZero Omnichain Contract Examples

• This code is currently not audited *
• The code in this repo will be undergoing a formal audit in Q2 2022 -- until then use at your own risk! *

Install & Run tests

yarn install
npx hardhat test 

• The code in the /contracts folder demonstrates LayerZero behaviours.
• NonblockingLzApp is a great contract to extend. Take a look at how OmniCounter overrides _nonblockingLzReceive and _LzReceive to easily handle messaging. There are also example for OFT and ONFT which illustrate erc20 and erc721 cross chain functionality.
• Always audit your own code and test extensively on testnet before going to mainnet 🙏

The examples below use two chains, however you could substitute any LayerZero supported chain!

OmnichainFungibleToken (OFT)

The OmnichainFungibleToken has two varieties of deployments:

1. BasedOFT.sol - The token supply is minted (on deployment) on the base chain. Other chains deploy with 0 supply initially.
2. OFT.sol - At deploy time, any quantity of tokens can be minted, regardless of chain.

For the BasedOFT, the initial supply will be minted entirely on the Base Chain on deployment. All tokens transferred out of the base chain will be locked in the contract (and minted on destination), and tokens transferred out of other chains will be burned on that chain. Tokens returning to the base chain will be unlocked and transferred to the destination address. This results in the Base chain being like the home base, hence the name.

In the example deployment below we use BasedOFT and the base chain is rinkeby. This setting is configured in constants/oftBaseChain.json. The OmnichainFungibleToken deployed on other chains will use this configuration to set their base chain. Using the Ethereum network (testnet: rinkeby) as a base (really its like the source of truth) is a security decision. In the event a chain goes rogue, Ethereum will be the final source of truth for OFT tokens.

Deploy Setup

1. Add a .env file (to the root project directory) with your MNEMONIC="" and fund your wallet in order to deploy!
2. Follow any of the tutorials below

BasedOFT.sol - an omnichain ERC20

WARNING: You must perform the setTrustedRemote() (step 2).

1. Deploy two contracts: rinkeby is the base chain. Fuji is the oft for the other chain.

npx hardhat --network rinkeby deploy --tags ExampleBasedOFT
npx hardhat --network fuji deploy --tags ExampleOFT

2. Set the "trusted remotes" (ie: your contracts) so each of them can receive messages from one another, and only one another.

npx hardhat --network rinkeby setTrustedRemote --target-network fuji
npx hardhat --network fuji setTrustedRemote --target-network rinkeby

3. Send tokens from rinkeby to fuji

npx hardhat --network rinkeby oftSend --target-network fuji --qty 42

Pro-tip: Check the ERC20 transactions tab of the destination chain block explorer and await your tokens!

OmnichainNonFungibleToken721 (ONFT721)

This ONFT contract allows minting of nftIds on separate chains. To ensure two chains can not mint the same nfId each contract on each chain is only allowed to mintnftIds in certain ranges. Check constants/onftArgs.json for the specific test configuration used in this demo.

UniversalONFT.sol

WARNING: You must perform the setTrustedRemote() (step 2).

1. Deploy two contracts:

 npx hardhat --network bsc-testnet deploy --tags ExampleUniversalONFT721
 npx hardhat --network fuji deploy --tags ExampleUniversalONFT721

2. Set the "trusted remotes", so each contract can send & receive messages from one another, and only one another.

 npx hardhat --network bsc-testnet onftSetTrustedRemote --target-network fuji
 npx hardhat --network fuji onftSetTrustedRemote --target-network bsc-testnet

3. Mint an NFT on each chain!

 npx hardhat --network bsc-testnet onftMint
 npx hardhat --network fuji onftMint

4. [Optional] Show the token owner(s)

 npx hardhat --network bsc-testnet onftOwnerOf --token-id 1
 npx hardhat --network fuji onftOwnerOf --token-id 11

5. Send ONFT across chains

npx hardhat --network bsc-testnet onftSend --target-network fuji --token-id 1

6. Verify your token no longer exists on the source chain & wait for it to reach the destination side.

 npx hardhat --network bsc-testnet onftOwnerOf --token-id 1
 npx hardhat --network fuji onftOwnerOf --token-id 1

OmniCounter.sol

OmniCounter is a simple contract with a counter. You can only remotely increment the counter!

1. Deploy both OmniCounters:

npx hardhat --network bsc-testnet deploy --tags OmniCounter
npx hardhat --network fuji deploy --tags OmniCounter

2. Set the remote addresses, so each contract can receive messages

npx hardhat --network bsc-testnet ocSetTrustedRemote --target-network fuji
npx hardhat --network fuji ocSetTrustedRemote --target-network bsc-testnet

3. Send a cross chain message from bsc-testnet to fuji !

npx hardhat --network bsc-testnet ocIncrementCounter --target-network fuji

Optionally use this command in a separate terminal to watch the counter increment in real-time.

npx hardhat --network fuji ocPoll    

Check your setTrustedRemote's are wired up correctly

Just use our checkWireUpAll task by running the following command with the correct Contract parameter

npx hardhat checkWireUpAll --e testnet --contract OmniCounter

See some examples in /contracts 🙌

Many of the example contracts make use of LayerZeroEndpointMock.sol which is a nice way to test LayerZero locally!

For further reading, and a list of endpoint ids and deployed LayerZero contract addresses please take a look at the Gitbook here: https://layerzero.gitbook.io/

Most recently tested with node version 16.13.1