Hardhat task to ensure accounts ether balances

We add a hardhat task that can be used to ensure addresses are funded
with a minimum value of ether. This will be used in test environments
setup to ensure when a client starts the operator has enough funds to
run.

Sample command:
```
npx hardhat ensure-eth-balance "0.5 ether" 0x6299496199d99941193Fdd2d717ef585F431eA05 0x93df7c54c41A9D7FB17C1E8039d387a2A924708c
```

Author: nkuba

solidity/random-beacon/tasks/ensure-eth-balance.ts

@@ -0,0 +1,58 @@
+import { task, types } from "hardhat/config"
+
+import { parseValue, TASK_SEND_ETH } from "./send-eth"
+
+export const TASK_ENSURE_ETH_BALANCE = "ensure-eth-balance"
+
+task(
+  TASK_ENSURE_ETH_BALANCE,
+  "Ensure addresses hold a minimum ether balance, top-up if needed"
+)
+  .addOptionalParam(
+    "from",
+    "Address to send value from",
+    undefined,
+    types.string
+  )
+  .addPositionalParam(
+    "balance",
+    'Minimum ether balance the addresses are expected to hold, e.g. "0.5 ether", "100 gwei"',
+    undefined,
+    types.string
+  )
+  .addVariadicPositionalParam(
+    "addresses",
+    "Addresses for which balance should be validated",
+    undefined,
+    types.string
+  )
+  .setAction(async (args, hre) => {
+    const { ethers } = hre
+
+    // FIXME: `validate` will fail for badly checksummed addresses
+    // see: https://github.com/ethers-io/ethers.js/discussions/3261
+    const addresses: Set<string> = new Set(
+      Array.from(args.addresses).map(hre.helpers.address.validate)
+    )
+
+    for (let address of addresses) {
+      const expectedBalance = parseValue(args.balance, hre)
+      const currentBalance = await ethers.provider.getBalance(address)
+
+      console.log(
+        `current balance of ${address} is ${ethers.utils.formatEther(
+          currentBalance
+        )} ether`
+      )
+
+      if (currentBalance.lt(expectedBalance)) {
+        const topUpAmount = expectedBalance.sub(currentBalance)
+
+        await hre.run(TASK_SEND_ETH, {
+          from: args.from,
+          value: topUpAmount.toString(),
+          to: address,
+        })
+      }
+    }
+  })

solidity/random-beacon/tasks/index.ts

@@ -2,3 +2,5 @@
 require("./unlock-eth-accounts")
 require("./initialize")
 require("./genesis")
+require("./send-eth")
+require("./ensure-eth-balance")

solidity/random-beacon/tasks/send-eth.ts

@@ -0,0 +1,59 @@
+import { BigNumber, Signer } from "ethers"
+import { task, types } from "hardhat/config"
+import { HardhatRuntimeEnvironment } from "hardhat/types"
+
+import type { TransactionResponse } from "@ethersproject/abstract-provider"
+
+export const TASK_SEND_ETH = "send-eth"
+
+task(TASK_SEND_ETH, "Send ether to an address")
+  .addOptionalParam(
+    "from",
+    "Address to send value from",
+    undefined,
+    types.string
+  )
+  .addParam(
+    "value",
+    'Value to transfer with unit, e.g. "0.5 ether", "100 gwei"',
+    undefined,
+    types.string
+  )
+  .addParam("to", "Transfer receiver address", undefined, types.string)
+  .setAction(async (args, hre) => {
+    const from: Signer = args.from
+      ? await hre.ethers.getSigner(args.from)
+      : (await hre.ethers.getSigners())[0]
+
+    const value: BigNumber = parseValue(args.value, hre)
+
+    // FIXME: `validate` will fail for badly checksummed addresses
+    // see: https://github.com/ethers-io/ethers.js/discussions/3261
+    const to = hre.helpers.address.validate(args.to)
+
+    const tx: TransactionResponse = await from.sendTransaction({
+      to: to,
+      value: value,
+    })
+
+    console.log(
+      `sending ${value} wei from ${await from.getAddress()} to ${to} in tx ${
+        tx.hash
+      }...`
+    )
+
+    await tx.wait()
+  })
+
+export function parseValue(
+  value: string,
+  hre: HardhatRuntimeEnvironment
+): BigNumber {
+  const parsed = String(value).trim().split(" ")
+
+  if (parsed.length == 0 || parsed.length > 2) {
+    throw new Error(`invalid value: ${value}`)
+  }
+
+  return hre.ethers.utils.parseUnits(parsed[0], parsed[1] || "wei")
+}

solidity/random-beacon/tsconfig.json

@@ -10,6 +10,7 @@
   ],
   "compilerOptions": {
     "esModuleInterop": true,
-    "noImplicitAny": true
+    "noImplicitAny": true,
+    "downlevelIteration": true
   }
 }