Add hintExamples script

packages/contracts/hardhat.config.js

@@ -1,6 +1,6 @@
 require("@nomiclabs/hardhat-truffle5");
 require("@nomiclabs/hardhat-ethers");
-require("@nomiclabs/hardhat-etherscan");
+// require("@nomiclabs/hardhat-etherscan");
 require("solidity-coverage");
 require("hardhat-gas-reporter");
 

packages/contracts/utils/hintExamples.js

@@ -0,0 +1,70 @@
+
+const { TestHelper: th } = require("../utils/testHelpers.js")
+const dh = require("./deploymentHelpers.js")
+const [alice, bob, carol] = await ethers.provider.listAccounts()
+
+async function main() {
+  const coreContracts = await dh.deployLiquityCoreHardhat()
+  const ARBITRARY_ADDRESS = "0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419" 
+  const LQTYContracts = await dh.deployLQTYContractsHardhat(
+      ARBITRARY_ADDRESS, 
+      ARBITRARY_ADDRESS,
+      ARBITRARY_ADDRESS
+    )
+
+ const { troveManager, borrowerOperations, hintHelpers, sortedTroves, priceFeedTestnet } = coreContracts
+
+  await dh.connectCoreContracts(coreContracts, LQTYContracts)
+  await dh.connectLQTYContracts(LQTYContracts)
+  await dh.connectLQTYContractsToCore(LQTYContracts, coreContracts)
+
+  // Examples of off-chain hint calculation for Open Trove
+
+  // Off-chain calculations
+  const toWei = web3.utils.toWei
+  const toBN = web3.utils.toBN
+
+  const price = toBN(toWei('2500'))
+  await priceFeedTestnet.setPrice(price)
+
+  const LUSDAmount = toBN(toWei('2500')) // borrower wants to withdraw 2500 LUSD
+  const ETHColl = toBN(toWei('5')) // borrower wants to lock 5 ETH collateral
+
+  // Call deployed TroveManager contract to read the liquidation reserve and latest borrowing fee
+  const liquidationReserve = await troveManager.LUSD_GAS_COMPENSATION()
+  const expectedFee = await troveManager.getBorrowingFeeWithDecay(LUSDAmount)
+
+  // Total debt of the new trove = LUSD amount drawn, plus fee, plus the liquidation reserve
+  const expectedDebt = LUSDAmount.add(expectedFee).add(liquidationReserve)
+
+  // Get the nominal NICR of the new trove
+  const _1e20 = toBN(toWei('100'))
+  const NICR = ETHColl.mul(_1e20).div(expectedDebt)
+
+  // Get an approximate address hint from the deployed HintHelper contract. Use (15 * number of troves) trials 
+  // to get an approx. hint that is close to the right position.
+  const numTroves = await sortedTroves.getSize()
+  const numTrials = numTroves.mul(toBN('15'))
+  const { 0: approxHint } = await hintHelpers.getApproxHint(NICR, numTrials, 42)  // random seed of 42
+
+  // Use the approximate hint to get the exact upper and lower hints from the deployed SortedTroves contract
+  const { 0: upperHint, 1: lowerHint } = await sortedTroves.findInsertPosition(NICR, approxHint, approxHint)
+
+  // Finally, call openTrove with the exact upperHint and lowerHint
+  const maxFee = '5'.concat('0'.repeat(16)) // Slippage protection: 5%
+  await borrowerOperations.openTrove(maxFee, LUSDAmount, upperHint, lowerHint, { value: ETHColl })
+
+  console.log(await troveManager.getCurrentICR(alice, price))
+
+
+
+  // --- adjust trove --- 
+}
+
+main()
+  .then(() => process.exit(0))
+  .catch(error => {
+    console.error(error);
+    process.exit(1);
+  });
+