feat(deploy): add task to credit LINK from deployer to VRF subscription

Author: zmalatrax

contracts/hardhat.config.ts

@@ -14,6 +14,7 @@ import "hardhat-docgen";
 import "hardhat-contract-sizer";
 import "hardhat-tracer";
 require("./scripts/simulations/tasks");
+require("./scripts/creditLink");
 
 dotenv.config();
 

contracts/scripts/creditLink.ts

@@ -0,0 +1,56 @@
+import { deployments, getNamedAccounts, getChainId, ethers } from "hardhat";
+import { LinkTokenInterface, VRFSubscriptionManagerV2 } from "../typechain-types";
+import { task, types } from "hardhat/config";
+import { BigNumber } from "ethers";
+
+enum HomeChains {
+  ARBITRUM_ONE = 42161,
+  ARBITRUM_GOERLI = 421613,
+}
+
+// https://docs.chain.link/resources/link-token-contracts?parent=vrf#arbitrum
+const linkByChain = new Map<HomeChains, string>([
+  [HomeChains.ARBITRUM_ONE, "0xf97f4df75117a78c1A5a0DBb814Af92458539FB4"],
+  [HomeChains.ARBITRUM_GOERLI, "0xd14838A68E8AFBAdE5efb411d5871ea0011AFd28"],
+]);
+
+const ONE_LINK_WEI = BigNumber.from(10).pow(18);
+
+task("credit-link", "Credit LINK tokens to the current Chainlink VRF Subscription")
+  .addParam("amount", "(in normal values, not wei!) The amount of LINK tokens to credit")
+  .setAction(async (taskArgs, hre) => {
+    const { deployments, getNamedAccounts, getChainId, ethers } = hre;
+    const { AddressZero } = ethers.constants;
+    const deployer = (await getNamedAccounts()).deployer ?? AddressZero;
+
+    const chainId = Number(await getChainId());
+    if (!HomeChains[chainId]) {
+      console.error(`Aborting: script is not compatible with ${chainId}`);
+      return;
+    } else {
+      console.log("Crediting %d LINK to %s with deployer %s", HomeChains[chainId], deployer);
+    }
+
+    const { amount } = taskArgs;
+    const amountInWei = BigNumber.from(amount).mul(ONE_LINK_WEI);
+
+    // Retrieve LINK token contract from artifact to interact with it
+    const linkTokenAddress = linkByChain.get(Number(await getChainId())) ?? AddressZero;
+    const linkTokenArtifact = await hre.artifacts.readArtifact("LinkTokenInterface");
+    const linkToken = (await ethers.getContractAtFromArtifact(
+      linkTokenArtifact,
+      linkTokenAddress
+    )) as LinkTokenInterface;
+
+    const vrfSubscriptionManagerDeployment = await deployments.get("VRFSubscriptionManagerV2");
+    const vrfSubscriptionManager = (await ethers.getContractAt(
+      "VRFSubscriptionManagerV2",
+      vrfSubscriptionManagerDeployment.address
+    )) as VRFSubscriptionManagerV2;
+
+    // Transfer LINK from deployer to the Subscription Manager
+    await linkToken.transfer(vrfSubscriptionManager.address, amountInWei);
+
+    // // Fund the subscription, sending `amount` LINK tokens
+    await vrfSubscriptionManager.topUpSubscription(amountInWei);
+  });