Balancer CoW AMM

Balancer CoW AMM is an automated portfolio manager, liquidity provider, and price sensor, that allows swaps to be executed via the CoW Protocol.

Balancer is based on an N-dimensional invariant surface which is a generalization of the constant product formula described by Vitalik Buterin and proven viable by the popular Uniswap dapp.

Development

Most users will want to consume the ABI definitions for BPool, BCoWPool, BFactory and BCoWFactory.

This project follows the standard Foundry project structure.

yarn build   # build artifacts to `out/`
yarn test    # run the tests

Changes on BPool from Balancer V1

• Migrated to Foundry project structure
• Implementation of interfaces with Natspec documentation
• Replaced require(cond, 'STRING') for if(!cond) revert CustomError()
• Bumped Solidity version from 0.5.12 to 0.8.25 (required for transient storage)
  • Added explicit unchecked blocks to BNum operations (to avoid Solidity overflow checks)
• Deprecated Record.balance storage (in favour of ERC20.balanceOf(address(this)))
• Deprecated gulp method (not needed since reading ERC20 balances)
• Deprecated manageable pools:
  • Deprecated isPublicSwap mechanism (for pools to be swapped before being finalized)
  • Deprecated rebind method (in favour of bind + unbind + bind)
  • Deprecated exit fee on unbind (since the pool is not supposed to have collected any fees)
• Deprecated BBaseToken (in favour of OpenZeppelin ERC20 implementation)
• Deprecated BColor and BBronze (unused contracts)
• Deprecated Migrations contract (not needed)
• Added an _afterFinalize hook (to be called at the end of the finalize routine)
• Implemented reentrancy locks using transient storage.
• Deprecated joinswap and exitswap methods (avoid single-token math precision issues)

Features on BCoWPool (added via inheritance to BPool)

• Immutably stores CoW Protocol's SolutionSettler and VaultRelayer addresses at deployment
• Immutably stores Cow Protocol's a Domain Separator at deployment (to avoid replay attacks)
• Immutably stores Cow Protocol's GPv2Order.appData to be allowed to swap
• Gives infinite ERC20 approval to the CoW Protocol's VaultRelayer contract at finalization time.
• Implements IERC1271 isValidSignature method to allow for validating intentions of swaps
• Implements a commit method to avoid multiple swaps from conflicting with each other.
  • This is stored in the same transient storage slot as reentrancy locks in order to prevent calls to swap/join functions within a settlement execution or vice versa.
  • It's an error to override a commitment since that could be used to clear reentrancy locks. Commitments can only be cleared by ending a transaction.
• Validates the GPv2Order requirements before allowing the swap

Features on BCoWFactory

• Added a logBCoWPool to log the finalization of BCoWPool contracts, to be called by a child pool.

Creating a Pool

• Create a new pool by calling the corresponding pool factory:
  • IBFactory.newBPool(name, symbol) for regular Balancer BPools
  • IBCoWFactory.newBPool(name, symbol) for Balancer BCoWPools, compatible with CoW Protocol

    Being name and symbol strings with the desired name and symbol of the pool's ERC20 LP token

• Give ERC20 allowance to the pool by calling IERC20.approve(pool, amount)
• Bind tokens one by one by calling IBPool.bind(token, amount, weight)
  • The amount represents the initial balance of the token in the pool (pulled from the caller's balance)
  • The weight represents the intended distribution of value between the tokens in the pool
• Modify the pool's swap fee by calling IBPool.setSwapFee(fee)
• Finalize the pool by calling IBPool.finalize()

Deployments

Ethereum Mainnet:

• BCoWFactory: 0xf76c421bAb7df8548604E60deCCcE50477C10462
• BCoWHelper: 0x3FF0041A614A9E6Bf392cbB961C97DA214E9CB31

Ethereum Sepolia:

• BCoWFactory: 0x1E3D76AC2BB67a2D7e8395d3A624b30AA9056DF9
• BCoWHelper: 0xf5CEd4769ce2c90dfE0084320a0abfB9d99FB91D
• BCoWPool: 0xE4aBfDa4E8c02fcAfC34981daFAeb426AA4186e6

Gnosis Mainnet:

• BCoWFactory: 0x703Bd8115E6F21a37BB5Df97f78614ca72Ad7624
• BCoWHelper: 0x198B6F66dE03540a164ADCA4eC5db2789Fbd4751