wip: buy with stable/cusd

[sirpy]

Description

about: #290

[sourcery-ai]

Hey - I've found 3 issues, and left some high level feedback:

• In BuyGDCloneV2.swap, the Bought event emitted in the cUSD/stable branch still uses celo as the token address, which will mislead consumers of the event and should be updated to emit the correct token (likely CUSD or stable).
• In swapCusd, gasCosts are carved out from the contract’s CUSD balance but the refund is paid in stable, which will fail or behave unexpectedly when stable != CUSD; consider refunding from the same token the gas was reserved in or explicitly ensuring sufficient stable balance for the refund.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `BuyGDCloneV2.swap`, the `Bought` event emitted in the cUSD/stable branch still uses `celo` as the token address, which will mislead consumers of the event and should be updated to emit the correct token (likely `CUSD` or `stable`).
- In `swapCusd`, `gasCosts` are carved out from the contract’s `CUSD` balance but the refund is paid in `stable`, which will fail or behave unexpectedly when `stable != CUSD`; consider refunding from the same token the gas was reserved in or explicitly ensuring sufficient `stable` balance for the refund.

## Individual Comments

### Comment 1
<location> `contracts/utils/BuyGDClone.sol:93-101` </location>
<code_context>
 		uint256 gasCosts;
+		uint24[] memory fees = new uint24[](1);
+		fees[0] = 100;
 		if (refundGas != owner) {
-			(gasCosts, ) = oracle.quoteAllAvailablePoolsWithTimePeriod(
+			(gasCosts, ) = oracle.quoteSpecificFeeTiersWithTimePeriod(
</code_context>

<issue_to_address>
**issue (bug_risk):** Gas refund is taken from CUSD balance but paid out in `stable`, which can mis-account funds when `stable != CUSD`.

`swapCusd` subtracts `gasCosts` from the CUSD balance (`amountIn = ERC20(CUSD).balanceOf(address(this)) - gasCosts;`) but sends the refund in `stable` (`ERC20(stable).transfer(refundGas, gasCosts)`). When `stable != CUSD`, this reduces CUSD while spending an unreserved amount of `stable`, which can desync balances and underfund future swaps. Consider either refunding in CUSD or charging gas costs from `stable` consistently.
</issue_to_address>

### Comment 2
<location> `contracts/utils/BuyGDClone.sol:72` </location>
<code_context>
 			return bought;
 		}
-		balance = ERC20(cusd).balanceOf(address(this));
+		balance = ERC20(CUSD).balanceOf(address(this));
 		if (balance > 0) {
 			bought = swapCusd(_minAmount, refundGas);
</code_context>

<issue_to_address>
**issue (bug_risk):** `swap` only checks CUSD balance, even though the contract now supports a generic `stable` token.

The second branch still checks `ERC20(CUSD).balanceOf(address(this))` and calls `swapCusd`, so if `stable` is set to a different token and only that token is funded, this path never runs and those funds are never swapped. Either restrict the docstring to CUSD only, or update this branch to work off `stable` (and a corresponding `swapStable`) when `stable != CUSD`.
</issue_to_address>

### Comment 3
<location> `contracts/utils/BuyGDClone.sol:34` </location>
<code_context>

 	constructor(
 		ISwapRouter _router,
-		address _cusd,
+		address _stable,
 		address _gd,
</code_context>

<issue_to_address>
**nitpick:** Constructor parameter name `_cusd` in `DonateGDClone` is now misleading since it represents a generic stable token.

The parameter is still named `_cusd` in `DonateGDClone` while it now represents a generic stable token and is passed through to `BuyGDCloneV2`. Please rename it to `_stable` to align with `BuyGDCloneV2` and avoid confusion when deploying with non-cUSD stablecoins.
</issue_to_address>

---

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[openzeppelin-code]

wip: buy with stable/cusd

Generated at commit: 72eaec3a8a44341439c6652be434092511adf418

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	3 5 0 16 44 68
Dependencies	Critical High Medium Low Note Total	0 0 1 0 131 132

---

For more details view the full report in OpenZeppelin Code Inspector

[blueogin]

@sirpy
I’ve completed step 1 for BuyGDClone - the swap from cUSD to G$ works successfully via the cUSD -> GLO -> G$ path on Uniswap.

[sirpy]

the swappath should be an input to the buy methods.
so it is the UI responsibility to set the correct path.
remove the changes you did, instead do:

1. buygdclone instance should have hardcoded path defaults.
2. add buyXWithPath methods for celo/cusd the regular buy methods should use the default path

[blueogin]

I will do it

[blueogin]

@sirpy
Could you please review it

[sirpy]

too many changes
this should be a simple change of adding a variable to swapCusd and swapCelo and renaming them to swapCusdWithPath and swapCelowithPath
and the new swapCusd and swapCelo should call the swapwithpath version with default path

[sirpy]

why is this required?
swapCusd should be converted to swapCusdWithPath adding a variable
new swapCusd should call swapCusdWithPath with default path

[blueogin]

_swapCusdChooseRoute is an internal function that handles the core logic for swapping cUSD.
Currently, swapCusd calls swapCusdWithPath using a default path, and swapCusdWithPath then calls _swapCusdChooseRoute to execute the core swap logic.
The 'ChooseRoute' in name means it selects the route between Mento and Uniswap.

[sirpy]

keep functions in order add new functions at the end so easier to review changes

[blueogin]

Okay

[blueogin]

@sirpy
The feature could have been “add a path argument, rename to WithPath, and add thin swapCusd/swapCelo that call WithPath with the default path.”
Instead, the PR introduced internal functions for core logic and added getters. So the diff is large because of the new abstraction and refactor of existing internals and factory, not just the small public interface change