Provider contract - Biconomy Docs

Your inventory lives in a contract you own that implements IMMProvider. The executor calls it to settle each fill.

interface IMMProvider {
    function signer() external view returns (address);
    function previewSwap(address tokenIn, address tokenOut, uint256 amountIn, uint256 anchorPrice)
        external view returns (uint256 amountOut);
    function executeSwap(address tokenIn, address tokenOut, uint256 amountIn, uint256 anchorPrice, uint256 amountOut, address receiver)
        external returns (uint256 delivered);
}

Function	Called by	Must
`signer()`	executor, on every fill	return the address that signs your ladders (EOA or EIP-1271 contract)
`previewSwap(...)`	Biconomy, offchain, before routing to you	return what `executeSwap` would deliver for the same inputs, or `0` to decline
`executeSwap(...)`	executor only	pull `amountIn` of `tokenIn` from the executor, send `amountOut` of `tokenOut` to `receiver`, return the amount sent

executeSwap parameters

Parameter	Value
`tokenIn`	token the taker pays
`tokenOut`	token you deliver
`amountIn`	amount the executor has approved you to pull with `transferFrom`
`anchorPrice`	average price of this fill, `amountOut * 1e18 / amountIn`. Optional input for contracts that price from their own state
`amountOut`	amount your signed ladder pays for `amountIn`, computed by the executor from your stored ladder
`receiver`	address that receives `tokenOut`
returns `delivered`	amount of `tokenOut` sent to `receiver`

The executor computes amountOut only from a ladder your key signed, within its size, expiry and protections. Delivering less than amountOut makes the trade revert on the taker’s minAmountOut.

Deploy BasicMMProvider

BasicMMProvider.sol is the reference implementation. It accepts fills from the executor only and pays amountOut.

Constructor argument	Value
`signer`	address that signs your ladders
`executor`	the executor address, see Addresses
`owner`	admin address; use a multisig in production

Dependency	Path
`IMMProvider.sol`	`src/interfaces/IMMProvider.sol`
`BasicMMProvider.sol`	`src/periphery/examples/BasicMMProvider.sol`
solady	`forge install vectorized/solady`

Owner function	Effect
`setSigner(address)`	Changes the signing key. Ladders signed by the old key stop filling.
`setApprovedExecutor(address)`	Changes which contract may call `executeSwap`. Any other address stops all fills.
`withdraw(token, amount, to)`	Moves inventory out.

Implement IMMProvider on an existing contract

If your inventory already sits in a contract, add the three functions to it.

Requirement	Detail
Caller check	`executeSwap` reverts unless `msg.sender` is the executor
Pull input	`transferFrom(executor, address(this), amountIn)` on `tokenIn`
Pay output	transfer `amountOut` of `tokenOut` to `receiver` and return it
Preview	`previewSwap` matches `executeSwap` for the same inputs, or returns `0`
Optional ceiling	revert when `amountOut` exceeds a per-fill limit you set