# CoW Protocol

### 1. Providing GPv2Settlement address in the RFQ

From the perspective of Liquorice, trade is performed with the CoW’s GPv2Settlement contract, not directly with the trader.

Therefore, a solver must first and foremost provide the [address of the CoW's GPv2Settlement smart contract](https://docs.cow.fi/cow-protocol/reference/contracts/core#deployments) in both trader and effectiveTrader fields of the RFQ message.

* [REST API RFQ](https://liquorice.gitbook.io/liquorice-docs/for-solvers/rest-api)
* [WS API RFQ](https://liquorice.gitbook.io/liquorice-docs/for-solvers/websocket-api)

### **2. Calling** [**GPv2Settlement.settle**](https://docs.cow.fi/cow-protocol/reference/contracts/core/settlement#settle) **function**

CoW settlement signature

```solidity
function settle(
        IERC20[] calldata tokens,
        uint256[] calldata clearingPrices,
        GPv2Trade.Data[] calldata trades,
        GPv2Interaction.Data[][3] calldata interactions
    ) external
```

During the settlement process, funds from the trader are transferred to the GPv2Settlement contract.

### **2.1 Trades argument**

To assemble trades\[] argument solver would need to use data from signed CoW’s trader order and configure flags argument according to the trader's  signed GPv2Order

However, when creating a GPv2Order to pass it for trader's signature, certain flags should comply with the following:

```solidity
bytes32 kind = GPv2Order.KIND_SELL;
bytes32 buyTokenBalance GPv2Order.BALANCE_ERC20;
```

If the selected kind is GPv2Order.KIND\_SELL

Otherwise, if kind is GPv2Order.KIND\_BUY, then

```solidity
bytes32 kind = GPv2Order.KIND_BUY;
bytes32 sellTokenBalance GPv2Order.BALANCE_ERC20;
```

### **2.2 Interactions**

CoW’s GPv2Settlement.settle function receives interactions in the following format:

```solidity
GPv2Interaction.Data[][3] calldata interactions
```

This format reflects that inside CoW’s settlement there are 3 groups of interactions

To interact with LiquoriceSettlement solver should use the second group (index \[]\[1] of array)

Here is what should be contained inside this array:

**Approval**

When performing the trade, Liquorice Balance Manager contract must have a baseToken approval given by the GPv2Settlement contract.

**Interaction with LiquoriceSettlement**

To make interaction with LiquoriceSettlement solver would need to use the following field from API:

* baseToken
* baseTokenAmount
* tx

**Solidity example**

```solidity
struct Transaction {
  address to;
  bytes data;
}

struct Allowance {
  address token;
  address spender;
  uint256 amount;
}

struct LiquoriceRFQQuoteLevel {
  address baseToken;
  uint256 baseTokenAmount;
  Transaction tx;
  Allowance[] allowances;
}

function getCoWInteractions(LiquoriceRFQQuoteLevel calldata quoteLevel) public pure returns (GPv2Interaction.Data[][3] memory) {
  GPv2Interaction.Data[] memory preInteractions = new GPv2Interaction.Data[](0);
  
  uint256 allowancesLength = quoteLevel.allowances.length;
  GPv2Interaction.Data[] memory interactions = new GPv2Interaction.Data[](allowancesLength + 1);
  
  for (uint256 i = 0; i < allowancesLength; i++) {
    interactions[i] = GPv2Interaction.Data(
      quoteLevel.allowances[i].token,
      0,
      abi.encodeWithSelector(IERC20.approve.selector, quoteLevel.allowances[i].spender, quoteLevel.allowances[i].amount)
    );
  }
  
  interactions[allowancesLength] = GPv2Interaction.Data(quoteLevel.tx.to, 0, quoteLevel.tx.data);
  
  GPv2Interaction.Data[] memory postInteractions = new GPv2Interaction.Data[](0);

  return [preInteractions, interactions, postInteractions];
}
```

### **2.3** Remaining **arguments**

Remaining arguments such as signature and order provided as is.


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