# Multi-bridge Message Receiver

### Features

* Receive messages from a predefined source chain, through an approved set of bridge receiver adapters.
* Enable scheduling a message for execution if a quorum of bridges relays the message
* Update the list of trusted bridge receiver adapters
* Update the quorum threshold for message validity

### Functions

#### receiveMessage

```solidity
function receiveMessage(MessageLibrary.Message calldata _message) external override onlyReceiverAdapter
```

Enables the contract to receive messages from a source chain, through a list of allowed bridge receiver adapters. A message can be delivered by a given bridge only once. 

`_message`: A `MessageLibrary.Message` an object containing the message details.

#### scheduleMessageExecution

```solidity
function scheduleMessageExecution(bytes32 _msgId, MessageLibrary.MessageExecutionParams calldata _execParams) external;
```

Sends a message, that has achieved a quorum and has not yet expired, to the governance timelock for eventual execution.

* `_msgId`: The unique identifier of the message
* `_execParams`: The parameters for message execution, including the target contract address and execution payload

#### updateReceiverAdapter

```solidity
function updateReceiverAdapters(address[] calldata _receiverAdapters, bool[] calldata _operations) external override onlyOwner
```

Updates the list of approved bridge receiver adapters. This function can only be called by the `owner`

* `_receiverAdapters`: An array of addresses of the receiver adapter contracts
* `_operations`: An array of operations for each receiver adapter. True implies add, and False implies remove. 

#### updateQuorum

```solidity
function updateQuorum(uint64 _newQuorum) external onlyOwner
```

Updates the quorum, which is the number of independent bridges that must deliver a message for it to be considered valid. This function can only be called by the `owner`

* `_newQuorum`: The new quorum threshold for message validation

#### updateQuorumAndReceiverAdapter

```solidity
    function updateReceiverAdaptersAndQuorum(
        address[] calldata _receiverAdapters,
        bool[] calldata _operations,
        uint64 _newQuorum,
    ) external override onlyOwner
```

Atomically updates the list of approved bridge receiver adapters and the quorum for message validation. This function can only be called by the `owner`

* `_receiverAdapters`: An array of addresses of the receiver adapter contracts
* `_operations`: An array of operations for each receiver adapter. True implies add, and False implies remove. 
* `_newQuorum`: The new quorum threshold for message validation

#### updateGovernanceTimelock

```solidity
function updateGovernanceTimelock(address _newGovernanceTimelock) external;
```

Updates the governance timelock address, which is the contract that ultimately executes valid messages.

* `_newGovernanceTimelock` is the new governance timelock contract address

### Events

* `BridgeMessageReceived`: Emitted when a message is received from a bridge receiver adapter
* `MessageExecutionScheduled`: Emitted when a message is scheduled for execution on the time lock contract on the destination chain
* `BridgeReceiverAdapterUpdated`: Emitted when a receiver adapter is updated
* `QuorumUpdated`: Emitted when the quorum threshold is updated

### Dependencies

* `IMultiBridgeMessageReceiver`: Interface for the MultiBridgeMessageReceiver contract
* `IMessageReceiverAdapter`: Common interface for AMB receiver adapters that builds on EIP-5164 MessageExecutor. Read more [here](https://github.com/pooltogether/ERC5164/blob/main/src/interfaces/IMessageExecutor.sol).
* `ExecutorAware`: EIP-5164 interface for trusted executor-aware contracts. Read more [here](https://github.com/pooltogether/ERC5164/blob/main/src/abstract/ExecutorAware.sol).
* `MessageLibrary`: Contains the message struct definition