atomic-swap/docs/developing.md

Developing

Deploying or using deployed SwapFactory.sol

The swap program uses a "factory" contract for the Ethereum side to reduce gas costs from deploying a new contract for each swap. The contract can be found in here. For each new swap, the eth-holding party will call NewSwap on the factory contract, initiating a swap instance inside the contract.

If you're developing on a local network, running a swapd instance with the --dev-alice flag will automatically deploy an instance of SwapFactory.sol for you. You should see the following log shortly after starting ./swapd --dev-alice:

# 2022-01-26T18:39:04.600-0500	INFO	cmd	daemon/contract.go:35	deployed SwapFactory.sol: address=0x3F2aF34E4250de94242Ac2B8A38550fd4503696d tx hash=0x638caf280178b3cfe06854b8a76a4ce355d38c5d81187836f0733cad1287b657

If you wish to use an instance of SwapFactory.sol that's already deployed on-chain, you can use the --contract-address flag to specify the address. For example:

$ ./swapd --dev-alice --contract-address 0x3F2aF34E4250de94242Ac2B8A38550fd4503696d
# 2022-01-26T18:56:31.627-0500	INFO	cmd	daemon/contract.go:42	loaded SwapFactory.sol from address 0x3F2aF34E4250de94242Ac2B8A38550fd4503696d

If you want to deploy the contract without running swapd, you can use hardhat. You will need node.js installed.

cd ethereum
npm install --save-dev hardhat

Then, you can run the deployment script against your desired network to deploy the contract.

$ npx hardhat run --network localhost scripts/deploy.js 
# Compiling 2 files with 0.8.5
# Compilation finished successfully
# SwapFactory deployed to: 0xB0f6EC177Ab867E372479C0bfdBB0068bb5E1554

Compiling DLEq binaries

The program utilizes a Rust DLEq library implemented by Farcaster.

To compile the farcaster-dleq binaries used, you can run:

make build-dleq

This will install Rust (if it isn't already installed) and build the binaries. The resulting binaries will be in ./farcaster-dleq/target/release/.

Compiling contract bindings

If you update the Swap.sol contract for some reason, you will need to re-generate the Go bindings for the contract. Note: you do not need to do this to try out the swap; only if you want to edit the contract for development purposes.

Download solc v0.8.9: https://github.com/ethereum/solidity/releases/tag/v0.8.9

Set SOLC_BIN to the downloaded binary

export SOLC_BIN=solc

Install abigen

git clone https://github.com/ethereum/go-ethereum.git && cd go-ethereum/cmd/abigen
go install

Generate the bindings

./scripts/generate-bindings.sh

Note: you may need to add $GOPATH and $GOPATH/bin to your path.

Testing

To setup the test environment and run all unit tests, execute:

make test

This include tests for main protocol functionality, such as:

1. Success case, where both parties obey the protocol
2. Case where Bob never locks monero on his side. Alice can Refund
3. Case where Bob locks monero, but never claims his ether from the contract