# OAppAuthReceiver

[Git Source](https://github.com/Ion-Protocol/nucleus-boring-vault/blob/cc0b494b83e17b9b169a73b96050d2810b690477/src/base/Roles/CrossChain/OAppAuth/OAppAuthReceiver.sol)

**Inherits:** IOAppReceiver, OAppAuthCore

*Abstract contract implementing the ILayerZeroReceiver interface and extending OAppCore for OApp receivers.*

*This Auth version of OAppCore uses solmate's Auth instead of OZ's Ownable for compatibility purposes*

## State Variables

### RECEIVER\_VERSION

```solidity
uint64 internal constant RECEIVER_VERSION = 2;
```

## Functions

### oAppVersion

Retrieves the OApp version information.

*Providing 0 as the default for OAppSender version. Indicates that the OAppSender is not implemented. ie. this is a RECEIVE only OApp.*

*If the OApp uses both OAppSender and OAppReceiver, then this needs to be override returning the correct versions.*

```solidity
function oAppVersion() public view virtual returns (uint64 senderVersion, uint64 receiverVersion);
```

**Returns**

| Name              | Type     | Description                                   |
| ----------------- | -------- | --------------------------------------------- |
| `senderVersion`   | `uint64` | The version of the OAppSender.sol contract.   |
| `receiverVersion` | `uint64` | The version of the OAppReceiver.sol contract. |

### isComposeMsgSender

Indicates whether an address is an approved composeMsg sender to the Endpoint.

\*\_origin The origin information containing the source endpoint and sender address.

* srcEid: The source chain endpoint ID.
* sender: The sender address on the src chain.
* nonce: The nonce of the message.\*

*\_message The lzReceive payload.*

*Applications can optionally choose to implement separate composeMsg senders that are NOT the bridging layer.*

*The default sender IS the OAppReceiver implementer.*

```solidity
function isComposeMsgSender(Origin calldata, bytes calldata, address _sender) public view virtual returns (bool);
```

**Parameters**

| Name      | Type      | Description         |
| --------- | --------- | ------------------- |
| `<none>`  | `Origin`  |                     |
| `<none>`  | `bytes`   |                     |
| `_sender` | `address` | The sender address. |

**Returns**

| Name     | Type   | Description                 |
| -------- | ------ | --------------------------- |
| `<none>` | `bool` | isSender Is a valid sender. |

### allowInitializePath

Checks if the path initialization is allowed based on the provided origin.

*This indicates to the endpoint that the OApp has enabled msgs for this particular path to be received.*

*This defaults to assuming if a peer has been set, its initialized. Can be overridden by the OApp if there is other logic to determine this.*

```solidity
function allowInitializePath(Origin calldata origin) public view virtual returns (bool);
```

**Parameters**

| Name     | Type     | Description                                                               |
| -------- | -------- | ------------------------------------------------------------------------- |
| `origin` | `Origin` | The origin information containing the source endpoint and sender address. |

**Returns**

| Name     | Type   | Description                            |
| -------- | ------ | -------------------------------------- |
| `<none>` | `bool` | Whether the path has been initialized. |

### nextNonce

Retrieves the next nonce for a given source endpoint and sender address.

*\_srcEid The source endpoint ID.*

*\_sender The sender address.*

*The path nonce starts from 1. If 0 is returned it means that there is NO nonce ordered enforcement.*

*Is required by the off-chain executor to determine the OApp expects msg execution is ordered.*

*This is also enforced by the OApp.*

*By default this is NOT enabled. ie. nextNonce is hardcoded to return 0.*

```solidity
function nextNonce(uint32, bytes32) public view virtual returns (uint64 nonce);
```

**Returns**

| Name    | Type     | Description     |
| ------- | -------- | --------------- |
| `nonce` | `uint64` | The next nonce. |

### lzReceive

*Entry point for receiving messages or packets from the endpoint.*

*Entry point for receiving msg/packet from the LayerZero endpoint.*

```solidity
function lzReceive(
    Origin calldata _origin,
    bytes32 _guid,
    bytes calldata _message,
    address _executor,
    bytes calldata _extraData
)
    public
    payable
    virtual;
```

**Parameters**

| Name         | Type      | Description                                                                                                                                                                                         |
| ------------ | --------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `_origin`    | `Origin`  | The origin information containing the source endpoint and sender address. - srcEid: The source chain endpoint ID. - sender: The sender address on the src chain. - nonce: The nonce of the message. |
| `_guid`      | `bytes32` | The unique identifier for the received LayerZero message.                                                                                                                                           |
| `_message`   | `bytes`   | The payload of the received message.                                                                                                                                                                |
| `_executor`  | `address` | The address of the executor for the received message.                                                                                                                                               |
| `_extraData` | `bytes`   | Additional arbitrary data provided by the corresponding executor.                                                                                                                                   |

### \_lzReceive

*Internal function to implement lzReceive logic without needing to copy the basic parameter validation.*

```solidity
function _lzReceive(
    Origin calldata _origin,
    bytes32 _guid,
    bytes calldata _message,
    address _executor,
    bytes calldata _extraData
)
    internal
    virtual;
```

## Errors

### OnlyEndpoint

```solidity
error OnlyEndpoint(address addr);
```