Bridge

General information about mechanism of work can be found here.

In order to interact with bridge on smart-contract level you need to interact with functions quote and bridgeTokens of the adapter smart-contract on a source chain.

In order to pay for execution on destination chain, LayerZero and DVN fees you need to attach sufficient value on source chain. Calling quote allows you to estimate this value:

function quote(
    string calldata symbol,
    uint256 amount,
    address receiver,
    uint32 targetChainId,
    bytes calldata _options
) public view returns (uint256 nativeFee)

Quote will return you an estimate in root token of the source chain.

Next step is to call bridgeTokens function:

function bridgeTokens(
    string calldata symbol, 
    uint256 amount, 
    address receiver,
    uint32 targetChainId,
    bytes calldata _options
)

To make call successful you need to make sure of two things:

1. Approved allowance by sender should be ≥ amount (sufficient amount allowed)

2. Attached value is equal to quote output

targetChainId can be found here (in column Endpoint Id). receiver address can be customised (it isn't mandatory that receiver is the same address as sender). _options can be constructed by @layerzerolabs/lz-v2-utilities library. Destination chain gas amount should be included in the call. We recommend to keep it 140000 gas. Example of options usage:

import { Options } from '@layerzerolabs/lz-v2-utilities';

const options = Options.newOptions().addExecutorLzReceiveOption(140000, 0);

const args = [
   'USDC',
   amount,
   receiver,
   targetChainId,
   options.toHex().toString(),
];

// Call quote/bridgeTokens with args

After successfull bridgeTokens call, event TokensBridged will be issued to simplify off-chain tracking of the transactions.

event TokensBridged(
   bytes32 indexed guid, 
   address indexed sender, 
   IERC20Metadata token, 
   uint256 amount, 
   address receiver, 
   uint256 fee, 
   uint32 targetChainId
);

Fields amount and fee in TokensBridged event are normalized to 18 decimals in order to support tokens with different amount of decimals on different chains. Keep in mind that to convert it to original token amount - you need to multiply it to 10^tokenDecimals and divide it by 10^18.

After message is processed, event TokensReleased event will be issued on destination chain by respective adapter smart-contract.

event TokensReleased(
   bytes32 indexed guid, 
   address indexed receiver, 
   IERC20Metadata token, 
   uint256 amount
);