# Surplus Collateral

In addition to paying and receiving surplus collateral in the input/output of swap, mint and burn calls user can directly deposit, withdraw or transfer their surplus collateral balance. 

All of these surplus collateral use callpath 0 with specific 

### Deposits

To deposit surplus collateral, the user should call the following user command:

```
userCmd(1, abi.encode(
    73,     // Fixed sub-command code
    recv,   // address
    value,  // uint128
    token   // address
))
```

* recv - The address the surplus collateral will be credited
* value - The total amount deposited
* token - The address of the ERC20 token deposited or `address(0)` for native Ethereum)

Note that deposit will use `transferFrom()` in to deposit the surplus collateral, so the user must approve or permit at least `value` amount of the token. In the case of native Ethereum, the deposit is collected from `msg.value` so the user must attach at least the amount matching the value parameter to the Ethereum transaction.

For EIP-2612 compliant tokens, users can deposit using an off-chain permit signature avoiding the need to approve the DEX contract:

```
userCmd(0, abi.encode(
    83,     // Fixed sub-command code
    recv,       // address
    value,      // uint128
    token,      // address
    deadline,   // uint256
    v,          // uint8
    r,          // bytes32
    s           // bytes32
))
```

* deadline - The deadline for the permit call
* v, r, s - The EIP-712 signature to be passed directly to the token contract

### Withdraw

To withdraw surplus collateral, the user should call the following user command:

```
userCmd(0, abi.encode(
    74,     // Fixed sub-command code
    recv,   // address
    value,  // uint128
    token   // address
))
```

* recv - The address the surplus collateral will be sent to
* value - The total amount to withdraw from surplus collateral. 0 is treated as a magic value that will withdraw the entire balance.
* token - The address of the ERC20 token or `address(0)` for native Ethereum)

### Transfer

Users can also bilaterally transfer surplus liquidity between owner addresses:

```
userCmd(0, abi.encode(
    75,     // Fixed sub-command code
    recv,   // address
    value,  // uint128
    token   // address
))
```

* recv - The address the surplus collateral will be transferred to
* value - The total amount to transfer from surplus collateral. 0 is treated as a magic value that will withdraw the entire balance.
* token - The address of the ERC20 token or `address(0)` for native Ethereum


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