# GemJoin

[Git Source](https://github.com/Ion-Protocol/ion-protocol/blob/88cc595825f1dc2eb738fb93e172a3e8ab7a5c43/src/join/GemJoin.sol)

**Inherits:** Ownable2Step, Pausable

Collateral deposits are held independently from the `IonPool` core contract, but credited to users through `gem` balances.

*Separating collateral deposits from the core contract allows for handling tokens with non-standard behavior, if needed. This contract implements access control through `Ownable2Step`. This contract implements pausing through OpenZeppelin's `Pausable`.*

### [State Variables](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#state-variables" id="state-variables"></a>

#### [GEM](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#gem" id="gem"></a>

```
IERC20 public immutable GEM;
```

#### [POOL](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#pool" id="pool"></a>

```
IonPool public immutable POOL;
```

#### [ILK\_INDEX](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#ilk_index" id="ilk_index"></a>

```
uint8 public immutable ILK_INDEX;
```

#### [totalGem](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#totalgem" id="totalgem"></a>

```
uint256 public totalGem;
```

### [Functions](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#functions" id="functions"></a>

#### [constructor](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#constructor" id="constructor"></a>

Creates a new `GemJoin` instance.

```
constructor(IonPool _pool, IERC20 _gem, uint8 _ilkIndex, address owner) Ownable(owner);
```

**Parameters**

| Name        | Type      | Description                                                     |
| ----------- | --------- | --------------------------------------------------------------- |
| `_pool`     | `IonPool` | Address of the `IonPool` contract.                              |
| `_gem`      | `IERC20`  | ERC20 collateral to be associated with this `GemJoin` instance. |
| `_ilkIndex` | `uint8`   | of the associated collateral.                                   |
| `owner`     | `address` | Admin of the contract.                                          |

#### [pause](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#pause" id="pause"></a>

Pauses the contract.

*Pauses the contract.*

```
function pause() external onlyOwner;
```

#### [unpause](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#unpause" id="unpause"></a>

Unpauses the contract.

*Unpauses the contract.*

```
function unpause() external onlyOwner;
```

#### [join](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#join" id="join"></a>

Converts ERC20 token into gem (credit inside of the `IonPool`'s internal accounting).

*Gem will be sourced from `msg.sender` and credited to `user`.*

```
function join(address user, uint256 amount) external whenNotPaused;
```

**Parameters**

| Name     | Type      | Description           |
| -------- | --------- | --------------------- |
| `user`   | `address` | to credit the gem to. |
| `amount` | `uint256` | of gem to add. \[WAD] |

#### [exit](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#exit" id="exit"></a>

Debits gem from the `IonPool`'s internal accounting and withdraws it into ERC20 token.

*Gem will be debited from `msg.sender` and sent to `user`.*

```
function exit(address user, uint256 amount) external whenNotPaused;
```

**Parameters**

| Name     | Type      | Description                            |
| -------- | --------- | -------------------------------------- |
| `user`   | `address` | to send the withdrawn ERC20 tokens to. |
| `amount` | `uint256` | of gem to remove. \[WAD]               |

### [Errors](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#errors" id="errors"></a>

#### [Int256Overflow](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#int256overflow" id="int256overflow"></a>

```
error Int256Overflow();
```

#### [WrongIlkAddress](https://docs.ionprotocol.io/devs/smart-contract-architecture/join/broken-reference) <a href="#wrongilkaddress" id="wrongilkaddress"></a>

```
error WrongIlkAddress(uint8 ilkIndex, IERC20 gem);
```


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