add eulerswaphook audit note

Author: saucepoint

docs/audits/EulerSwapHook_Audit_Scope.md

@@ -0,0 +1,46 @@
+# EulerSwapHook Audit
+
+Through a new partnership between Euler Labs and Uniswap Foundation, the teams intend to expose EulerSwap's core logic and mechanisms via a Uniswap v4 Hook interface.
+
+This is primarily done by inheriting `EulerSwap.sol:EulerSwap`, i.e. `EulerSwapHook is EulerSwap, BaseHook`, and implementing a "custom curve" via `beforeSwap`. The implementation will allow integrators, interfaces, and aggregators, to trade on EulerSwap as-if it is any other Uniswap v4 Pool
+
+```solidity
+// assuming the EulerSwapHook was instantiated via EulerSwapFactory
+PoolKey memory poolKey = PoolKey({
+    currency0: currency0,
+    currency1: currency1,
+    fee: fee,
+    tickSpacing: 60,
+    hooks: IHooks(address(eulerSwapHook))
+});
+
+minimalRouter.swap(poolKey, zeroForOne, amountIn, 0);
+```
+
+
+## Audit Scope
+
+The scope of audit involves the code-diff introduced by [PR #48](https://github.com/euler-xyz/euler-swap/pull/48/files). **As of Apr 1st, 2025, the diff is subject to change but will be code-complete by the audit start time.**
+
+Major Changes will include:
+
+* Replacing `binarySearch` quoting algorithm with a closed-form formula
+* Implementing a protocol fee, as a percentage of LP fees, enacted by governance
+
+As for the files in scope, only files from `src/` should be considered:
+
+```
+├── src
+│   ├── EulerSwapFactory.sol
+│   ├── EulerSwapHook.sol
+│   └── utils
+│       └── HookMiner.sol
+```
+
+## Known Caveats
+
+### Prepaid Inputs
+
+Due to technical requirements, EulerSwapHook must take the input token from PoolManager and deposit it into Euler Vaults. It will appear that EulerSwapHook can only support input sizes of `IERC20.balanceOf(PoolManager)`. However swap routers can pre-emptively send input tokens (from user wallet to PoolManager) prior to calling `poolManager.swap` to get around this limitation.
+
+An example `test/utils/MinimalRouter.sol` is provided as an example.