> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# Interaction

> TypeScript interaction module API for executing arbitrary smart contract calls during settlements

# Interaction

The interaction module enables CoW Protocol settlements to invoke arbitrary smart contracts, supporting capabilities such as EIP-2612 permit calls for gasless approvals and AMM trades (Uniswap, Balancer, Curve, etc.).

## Types

### Interaction

Represents a complete smart contract call with three components:

```typescript theme={null}
interface Interaction {
  target: string;   // Contract address to invoke
  value: BigNumberish; // Native Ether amount in wei (defaults to 0)
  callData: string;    // Encoded function data (defaults to "0x")
}
```

### InteractionLike

A flexible partial type requiring only the target address:

```typescript theme={null}
interface InteractionLike {
  target: string;
  value?: BigNumberish;
  callData?: string;
}
```

## Functions

### normalizeInteraction

Processes a single interaction, applying default values for optional fields.

```typescript theme={null}
function normalizeInteraction(interaction: InteractionLike): Interaction;
```

### normalizeInteractions

Handles arrays of interactions.

```typescript theme={null}
function normalizeInteractions(interactions: InteractionLike[]): Interaction[];
```

Both functions ensure complete, ABI-compatible interaction objects with defaults of `0` for value and `"0x"` for callData.

## Execution Stages

```typescript theme={null}
enum InteractionStage {
  PRE = 0,   // Setup operations before token transfers
  INTRA = 1, // Swaps after sell tokens arrive (default)
  POST = 2,  // Cleanup after all trading concludes
}
```

## Common Use Cases

```typescript theme={null}
import { ethers } from "ethers";

// EIP-2612 permit (PRE stage)
const permitInteraction = {
  target: tokenAddress,
  value: 0,
  callData: tokenContract.interface.encodeFunctionData("permit", [
    owner, spender, value, deadline, v, r, s
  ]),
};

// Uniswap swap (INTRA stage)
const swapInteraction = {
  target: uniswapRouterAddress,
  value: 0,
  callData: router.interface.encodeFunctionData("exactInputSingle", [params]),
};

// WETH unwrap (POST stage)
const unwrapInteraction = {
  target: wethAddress,
  value: 0,
  callData: weth.interface.encodeFunctionData("withdraw", [amount]),
};
```

## Best Practices

* Validate target addresses before constructing interactions
* Use Ethers.js for safe calldata encoding
* Exercise caution with Ether transfers (non-zero `value`)
* Test extensively on testnets prior to mainnet use
* Select appropriate stages based on token balance availability