ForexSwap

WARNING: This code has not been audited. Treat it as experimental.

ForexSwap is a Uniswap v4 hook for FX stablecoin pools. It plugs custom accounting into the v4 swap and liquidity lifecycle so the pool can use a custom curve instead of the default v3 math.

The implementation in this repo follows the v4 architecture described in the official overview:

• PoolManager is the singleton that owns pool state and calls hooks.
• Hooks are permissioned contracts whose callback surface is encoded into the hook address.
• Dynamic fees are pool-level behavior in v4, but the fee policy itself is application-defined.
• Flash accounting is handled by v4; this repo focuses on custom accounting and curve logic.

Official reference:

• Uniswap v4 overview

Repo Layout

• src/ForexSwap.sol: main ForexSwap hook contract
• tests/ForexSwap.t.sol: Foundry tests
• script/Anvil.s.sol: local Anvil deployment and lifecycle script
• script/Deploy.s.sol: minimal non-local deploy stub

Contract Model

ForexSwap inherits BaseCustomCurve, so it opts into v4 custom accounting rather than implementing a standalone pool. The important contract responsibilities are:

• custom swap math via _getUnspecifiedAmount, _computeAmountOut, and _computeAmountIn
• owner-managed parameters for mean, width, and swapFee
• pause and unpause controls
• hook-local liquidity share accounting for deposits and withdrawals

The current implementation is intentionally conservative. It uses simplified reserve assumptions and approximations rather than a production-ready statistical engine.

Prerequisites

This repo expects git submodules to be present. A plain clone is not enough.

git clone https://github.com/robertleifke/forex-swap
cd forex-swap
git submodule update --init --recursive
bun install
forge build

If forge build fails with missing imports under lib/, the submodules were not initialized correctly.

Local Development

The quickest path is a local Anvil deployment:

anvil
forge script script/Anvil.s.sol:AnvilScript \
  --rpc-url http://localhost:8545 \
  --private-key 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80 \
  --broadcast -vv

Or use:

./deploy-local.sh

The Anvil script deploys:

• a local v4 PoolManager
• a minimal CREATE2 factory used to mine a valid hook address
• the ForexSwap hook at a mined address with the required hook permission bits

It does not currently deploy test routers, mock ERC20s, or seed a sample pool.

Using the Hook

Example setup:

IPoolManager poolManager = /* deployed v4 PoolManager */;
ForexSwap forexSwap = new ForexSwap(poolManager);

PoolKey memory poolKey = PoolKey({
    currency0: Currency.wrap(address(token0)),
    currency1: Currency.wrap(address(token1)),
    fee: LPFeeLibrary.DYNAMIC_FEE_FLAG,
    tickSpacing: 60,
    hooks: forexSwap
});

poolManager.initialize(poolKey, TickMath.getSqrtPriceAtTick(0));

forexSwap.updateLogNormalParams(
    1.1e18, // mean
    2.5e17, // width
    5e15    // 0.5% swap fee
);

Two important v4-specific notes:

• The hook address must be mined so its low bits advertise the enabled callbacks.
• PoolManager owns execution. The hook is not a standalone AMM contract.

Testing

forge test
forge test -vvv
forge test --gas-report
forge test --match-contract ForexSwapCorrectTest -vv

Current Caveats

• The non-local deploy script uses a placeholder PoolManager address and is not production-ready.
• The pricing logic is simplified. It should be treated as a prototype, not a validated FX curve.

License

MIT. See LICENSE.md.