VRFSubscriptionManagerV2

Author: Simon Malatrait simon.malatrait@grenoble-inp.org

This contracts implements a subscription manager for using VRF v2 with the Subscription Method.

It allows to create subscriptions, manage them and consumers.

LINK Token Arbitrum: https://docs.chain.link/resources/link-token-contracts?parent=vrf#arbitrum

VRFCoordinatorV2 address: https://docs.chain.link/vrf/v2/subscription/supported-networks#arbitrum-mainnet

For SECURITY CONSIDERATIONS, you might also have a look to: https://github.com/smartcontractkit/chainlink/blob/develop/contracts/src/v0.8/vrf/VRFCoordinatorV2.sol

State Variables

vrfCoordinator

VRFCoordinatorV2Interface public vrfCoordinator;

linkToken

LinkTokenInterface public linkToken;

subscriptionId

uint64 public subscriptionId;

governor

address public governor;

Functions

onlyByGovernor

modifier onlyByGovernor();

constructor

Constructs the Chainlink VRF v2 Subscription Manager.

constructor(address _governor, address _vrfCoordinator, address _linkToken);

Parameters

Name	Type	Description
`_governor`	`address`	The Governor of the contract
`_vrfCoordinator`	`address`	The address of the VRFCoordinator contract.
`_linkToken`	`address`	The address of the LINK token.

changeVrfCoordinator

Changes the vrfCoordinator storage variable.

function changeVrfCoordinator(address _vrfCoordinator) external onlyByGovernor;

Parameters

Name	Type	Description
`_vrfCoordinator`	`address`	The new value for the `vrfCoordinator` storage variable.

requestSubscriptionOwnerTransfer

Request the ownership transfer of the current subscription to newOwner

The current owner of the subscription is the Subscription Manager contract

function requestSubscriptionOwnerTransfer(address newOwner) external onlyByGovernor;

Parameters

Name	Type	Description
`newOwner`	`address`	Address of the proposed new owner of the current subscription Note: Transferring the ownership should be used when migrating a subscription from one Subscription Manager to another without removing the consumers nor cancelling the subscription

acceptSubscriptionOwnerTransfer

Accept the subscription transfer of ownership.

function acceptSubscriptionOwnerTransfer(uint64 _subscriptionId) external onlyByGovernor;

Parameters

Name	Type	Description
`_subscriptionId`	`uint64`	ID of the subscription to be accepted. It will override the current subscription if any.

createNewSubscription

Creates a new subscription, overriding the previous one to be manageable by the contract.

function createNewSubscription() public onlyByGovernor;

topUpSubscription

Funds the current subscription by amount LINK tokens.

function topUpSubscription(uint256 amount) external;

Parameters

Name	Type	Description
`amount`	`uint256`	Amount of LINK token in wei.

addConsumer

Add a Consumer to the subscription.

function addConsumer(address consumer) external onlyByGovernor;

Parameters

Name	Type	Description
`consumer`	`address`	Address of the Consumer contract added to the subscription.

removeConsumer

Removes a Consumer to the subscription

function removeConsumer(address consumer) external onlyByGovernor;

Parameters

Name	Type	Description
`consumer`	`address`	Address of the Consumer contract removed from the subscription.

cancelSubscriptionToGovernor

Cancel the current subscription and send the remaining LINK of the subscription to the governor.

function cancelSubscriptionToGovernor() external onlyByGovernor;

withdrawLinkToGovernor

Transfers amount LINK tokens of the Subscription Manager (this contract) to the governor.

function withdrawLinkToGovernor(uint256 amount) external onlyByGovernor;

Parameters

Name	Type	Description
`amount`	`uint256`	Amount of LINK token in wei.

getSubscription

Returns information on the current subscription

function getSubscription()
    external
    view
    returns (uint96 balance, uint64 reqCount, address owner, address[] memory consumers);

Returns

Name	Type	Description
`balance`	`uint96`	LINK token balance of the current subscription.
`reqCount`	`uint64`	Number of requests made to the subscription.
`owner`	`address`	Address of the current owner of the subscription.
`consumers`	`address[]`	List of consumers subscribed to the current subscription.

Events

SubscriptionFunded

Emitted when LINK tokens are sent from this contract to the current subscription.

event SubscriptionFunded(uint64 subscriptionId, uint256 amount);

LinkWithdrawn

Emitted when the governor withdraws amount LINK from the subscription manager.

event LinkWithdrawn(address indexed receiver, uint256 indexed amount);