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Runtime behavior

RialtoRouter settles a winning leg by calling swapExactIn through a generic RawCall action:
  1. Input delivery. For ERC20 input, the router approves your contract for exactly amountIn immediately before the call, so you pull it with transferFrom(router, you, amountIn). The router revokes the approval to 0 right after. For native-ETH input, the router calls swapExactIn{value: amountIn}, so the function is payable.
  2. Honor the amountIn parameter. It is the authoritative input amount for this fill. Pull and price against exactly the amountIn passed in; do not assume a fixed or pre-agreed size.
  3. Output delivery. Send the output token to to, which is the RialtoRouter address. The router measures its own balance delta of the output token and requires received >= amountOutMin, reverting the whole swap otherwise.
  4. deadline. Unix seconds. Enforcing it on your side is optional, since Rialto already bounds the swap’s validity window. Treat 0 as no deadline.
  5. Refunds. If you pull less than amountIn, the router refunds the unspent input, but the cleanest contract pulls and uses exactly amountIn.

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Parameters

ParamTypeMeaning
zeroForOneboolSame convention as the quote.
amountInuint256Exact input to pull, router-supplied and authoritative.
amountOutMinuint256Revert if you cannot deliver at least this.
toaddressRecipient of the output, always the RialtoRouter.
deadlineuint256Unix-seconds expiry.
returnsuint256Actual output delivered.

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Approval and transfer pattern (ERC20)

// Router, before the call:    IERC20(tokenIn).approve(you, amountIn);
// You, inside swapExactIn:     IERC20(tokenIn).transferFrom(msg.sender, address(this), amountIn);
//                              ... your pricing/inventory logic ...
//                              IERC20(tokenOut).transfer(to, amountOut);   // to == router
// Router, after the call:      IERC20(tokenIn).approve(you, 0);

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Native ETH

Native ETH is optional and advanced; most propAMM pairs are ERC20/ERC20, for example WETH/USDC. If you want a native-ETH side, accept msg.value on input and send ETH to to on output. Pick one convention across all your pairs, either ETH/token everywhere or WETH/token everywhere, and represent native ETH with the 0xEeee…EEeE sentinel. Confirm the wiring with Rialto.