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Bridge Funds and anyCall

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You're able to utilize Multichain's vast liquidity to bridge funds and execute the destination contract in one tx. This is only live on testnets at the time of writing

Introduction

This feature would be implemented in Router V7. (At the time of writing, Router V6 is live) This would combine our token router and anyCall which allows dapps to bridge funds and execute destination contracts with flexibility.
This allows the transfer of monetary values and data information cross-chain in one transaction.
The method is called anySwapOutAndCall .

Applications include:

  • Cross-chain atomic swaps
  • Cross-chain staking
  • Cross-chain lending

Testnet Information

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Quick Start

Please fork the above hardhat repo and follow the readme. This repo will do the following:
  1. 1.
    Acquire some test token A for bridging on chain A.
  2. 2.
    Bridge funds and swap to other tokens on chain B.
Commands:
  1. 1.
    Git clone https://github.com/bscethbot/BridgeFundsAndAnyCallExample.git​
  2. 2.
    yarn
  3. 3.
    Enter prvkey for your TESTNET account in env.example file and rename it to .env
  4. 4.
    Get some testnet matic at https://faucet.polygon.technology/​
  5. 5.
    yarn hardhat run ./scripts/0swapMaticToA1token.js --network polygonmumbai
  6. 6.
    yarn hardhat run ./scripts/bridgefundsRouterV7.js --network polygonmumbai
Congrats, you've swapped assets cross-chain.

anySwapOutAndCall workflow

Make sure you're familiar with the basics of anyCall before reading on as this method combines anyCall and bridge functions.
The anySwapOutAndCall function exists on our router contracts. This function would bridge tokens and call your receiver contract on the destination chain.
DAPPS need to deploy a receiver Exec/Anycallproxy Contract which would handle the bridged funds. On the receiver contract, a function named exec needs to be present and it will be called.
A sender contract is optional. You can deploy a sender contract that calls
anySwapOutAndCall if you want to implement additional features like extra fees, swap on source chain.
The general flow is specified below:
DAPPS -> anySwapOutAndCall(Chain A) -> SMPC Network -> anySwapInAndExec(Chain B) ->AnycallExecutor-> exec by DAPP receiver contract(Chain B)
DAPPS call anySwapOutAndCall on Chain A. Then the SMPC network will relay this event and invoke anySwapInAndExec on Chain B which will send the tokens to the DAPP receiver contract.
Then use AnycallExecutortor as a sandbox to call the exec function on the DAPP receiver contract. Hence a function named exec needs to be present in the DAPP receiver contract.
If the exec function execution failed on Chain B, your Exec Contract would handle the fail case.

Interfaces

anySwapOutAndCall (Called by Dapps)

function anySwapOutAndCall( address token, string calldata to, uint256 amount, uint256 toChainID, string calldata anycallProxy, bytes calldata data )

Parameters

Param
Type
Description
token
address
The token you want to bridge.
to
string
to is the fallback receive address if exec failed on the destination chain
amount
uint256
Amount of tokens bridged
toChainID
uint256
The target chain id to interact with
anycallProxy
string
Your destination contract to process the bridge tokens.
data
bytes
The bytes calldata to pass into your destination contract anycallProxy.

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Requirements to be compatible with anyCall interfaces:

  1. 1.
    Receiver Contract: A method named execneeds to exist on your anycallProxy contract address. This is needed because the destination router will call execon your receiver contract.
The exec function below is an example of an implementation to allow cross-chain swap.
function exec(
address token,
address receiver,
uint256 amount,
bytes calldata data
) external onlyAuth returns (bool success, bytes memory result) {
AnycallInfo memory anycallInfo = decode_anycall_info(data);
require(
anycallInfo.deadline >= block.timestamp,
"SushiSwapAnycallProxy: EXPIRED"
);
​
address[] memory path = anycallInfo.path;
require(path.length >= 2, "SushiSwapAnycallProxy: invalid path length");
require(
path[0] == token,
"SushiSwapAnycallProxy: source token mismatch"
);
​
require(
anycallInfo.amountInMax <= amount,
"SushiSwapAnycallProxy:EXCESSIVE_INPUT_AMOUNT"
);
​
uint256[] memory amounts;
if (anycallInfo.amountOut == 0) {
amounts = swapExactTokensForTokens(anycallInfo);
} else {
amounts = swapTokensForExactTokens(anycallInfo);
}
​
IERC20(path[0]).safeTransfer(
SushiswapV2Library.pairFor(sushiFactory, path[0], path[1]),
amounts[0]
);
​
address recvToken;
uint256 recvAmount;
​
if (anycallInfo.toNative) {
require(
path[path.length - 1] == wNATIVE,
"SushiSwapAnycallProxy:INVALID_PATH"
);
(recvToken, recvAmount) = _swap(
amounts,
path,
address(this)
);
IwNATIVE(wNATIVE).withdraw(recvAmount);
Address.sendValue(payable(receiver), recvAmount);
recvToken = address(0);
} else {
(recvToken, recvAmount) = _swap(
amounts,
path,
receiver
);
}
emit TokenSwap(recvToken, receiver, recvAmount);
​
if (amount.sub(amounts[0]) > 0) {
IERC20(path[0]).safeTransfer(
receiver,
amount.sub(amounts[0])
);
emit TokenBack(token, receiver, amount.sub(amounts[0]));
}
​
return (
true,
abi.encode(recvToken, recvAmount)
);
}
2. Whitelist: Your anycallProxy contract needs to be whitelisted by our team. Please contact us on telegram. A proxy contract can be whitelisted on testnet to ease development.
3. If your anycallProxy contract needs role control, use the AnycallExecutor listed in the above table. It will be the sandbox executing the contract. Refer to the role control below.
modifier onlyAuth() {
require(supportedCaller[msg.sender], "SushiSwapAnycallProxy: only auth");
_;
}
​

Examples

Please read through our example contracts to see how to design an anycallproxy contract. This contract swaps the users' funds via Sushiswap to other tokens after receiving the bridged tokens on the destination chain.
Polygon mumbai
BNB Testnet
AnycallProxy Example
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Please follow our QuickStart Guide now to try this out. Quick Start​
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Examples - Previous
Permissionless Token Bridges
Next - previous versions
V6
Last modified 5mo ago