# 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);
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.nucleusearn.io/nucleus-architecture/smart-contracts/contracts/base/roles/cross-chain/oappauth/oappauthreceiver.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.