feat: deployment config for fee oracle contract (#936)

* feat[contracts]: add GasPriceOracle w/o predeploy

Based on #912

* feat[contracts]: congestion price oracle

* chore: add changeset

* contracts: gas price oracle (#917)

* contracts: gas price oracle

* tests: update

* fees: fix tests

* contracts: simplify gas price oracle

* lint: fix

* test: execution price is at the 1st storage slot

* chore: rename predeploy to GasPriceOracle

* chore: rename gas price oracle test name
Co-authored-by: Mark Tyneway <mark.tyneway@gmail.com>
Co-authored-by: Georgios Konstantopoulos <me@gakonst.com>

* Add an L2 deploy script for gas oracle contract

* Add a kovan deployment artifact

* Add deployment to readme

* Add extra validation & initial execution price

* Update README.md

* Fix execution price logic

* Perform new deployment with final contract

* contracts: better require in ovm gas price oracle

* Deploy L2GasPriceOracle

* Update contract to use new fee logic & rename to gas

* Deploy updated contract

* Fix lint

* gas price oracle: do not restrict gas price

* gas price oracle: new deployment

* tests: delete dead test
Co-authored-by: smartcontracts <kelvinfichter@gmail.com>
Co-authored-by: Mark Tyneway <mark.tyneway@gmail.com>
Co-authored-by: Georgios Konstantopoulos <me@gakonst.com>

.changeset/seven-carpets-tell.md

+---
+'@eth-optimism/contracts': patch
+---
+
+Introduces the congestion price oracle contract

packages/contracts/contracts/optimistic-ethereum/OVM/predeploys/OVM_GasPriceOracle.sol

+// SPDX-License-Identifier: MIT
+pragma solidity >0.5.0 <0.8.0;
+
+/* External Imports */
+import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
+
+/**
+ * @title OVM_GasPriceOracle
+ * @dev This contract exposes the current l2 gas price, a measure of how congested the network
+ * currently is. This measure is used by the Sequencer to determine what fee to charge for
+ * transactions. When the system is more congested, the l2 gas price will increase and fees
+ * will also increase as a result.
+ *
+ * Compiler used: optimistic-solc
+ * Runtime target: OVM
+ */
+contract OVM_GasPriceOracle is Ownable {
+
+    /*************
+     * Variables *
+     *************/
+
+    // Current l2 gas price
+    uint256 public gasPrice;
+
+    /***************
+     * Constructor *
+     ***************/
+
+    /**
+     * @param _owner Address that will initially own this contract.
+     */
+    constructor(
+        address _owner,
+        uint256 _initialGasPrice
+    )
+        Ownable()
+    {
+        setGasPrice(_initialGasPrice);
+        transferOwnership(_owner);
+    }
+
+
+    /********************
+     * Public Functions *
+     ********************/
+
+    /**
+     * Allows the owner to modify the l2 gas price.
+     * @param _gasPrice New l2 gas price.
+     */
+    function setGasPrice(
+        uint256 _gasPrice
+    )
+        public
+        onlyOwner
+    {
+        gasPrice = _gasPrice;
+    }
+}

packages/contracts/deploy-l2/000-OVM_GasPriceOracle.deploy.ts

+/* Imports: External */
+import { DeployFunction } from 'hardhat-deploy/dist/types'
+
+/* Imports: Internal */
+import { getContractDefinition } from '../src'
+
+const deployFn: DeployFunction = async (hre: any) => {
+  const { deployments, getNamedAccounts } = hre
+  const { deploy } = deployments
+  const { deployer } = await getNamedAccounts()
+
+  const gasPriceOracle = getContractDefinition('OVM_GasPriceOracle', true)
+
+  const gasOracleOwner = (hre as any).deployConfig.ovmSequencerAddress
+  const initialGasPrice = (hre as any).deployConfig.initialGasPriceOracleGasPrice
+
+  if (!gasOracleOwner || !initialGasPrice) {
+    throw new Error('initialGasPrice & ovmSequencerAddress required to deploy gas price oracle')
+  }
+
+  await deploy('OVM_GasPriceOracle', {
+    contract: gasPriceOracle,
+    from: deployer,
+    args: [gasOracleOwner, initialGasPrice],
+    log: true,
+  });
+}
+
+deployFn.tags = ['OVM_GasPriceOracle']
+
+export default deployFn

packages/contracts/deployments/README.md

 # Optimism Regenesis Deployments
 ## LAYER 2
 
+## OPTIMISTIC-KOVAN
+
+Network : __optimistic-kovan (chain id: 69)__
+
+|Contract|Address|
+|--|--|
+|OVM_GasPriceOracle|[0x038a8825A3C3B0c08d52Cc76E5E361953Cf6Dc76](https://kovan-optimistic.etherscan.io/address/0x038a8825A3C3B0c08d52Cc76E5E361953Cf6Dc76)|
+---
+
 ### Chain IDs:
 - Mainnet: 10
 - Kovan: 69

packages/contracts/deployments/optimistic-kovan/.chainId

+69
\ No newline at end of file

packages/contracts/tasks/deploy.ts

@@ -99,6 +99,12 @@ task('deploy')
     undefined,
     types.string
   )
+  .addOptionalParam(
+    'initialGasPriceOracleGasPrice',
+    'The initial execution price for the gas price oracle.',
+    undefined,
+    types.int
+  )
   .setAction(async (args, hre: any, runSuper) => {
     // Necessary because hardhat doesn't let us attach non-optional parameters to existing tasks.
     const validateAddressArg = (argName: string) => {

packages/contracts/test/contracts/OVM/precompiles/OVM_GasPriceOracle.spec.ts

+import { expect } from '../../../setup'
+
+/* External Imports */
+import { ethers } from 'hardhat'
+import { ContractFactory, Contract, Signer } from 'ethers'
+
+describe('OVM_GasPriceOracle', () => {
+  const initialGasPrice = 0
+  let signer1: Signer
+  let signer2: Signer
+  before(async () => {
+    ;[signer1, signer2] = await ethers.getSigners()
+  })
+
+  let Factory__OVM_GasPriceOracle: ContractFactory
+  before(async () => {
+    Factory__OVM_GasPriceOracle = await ethers.getContractFactory(
+      'OVM_GasPriceOracle'
+    )
+  })
+
+  let OVM_GasPriceOracle: Contract
+  beforeEach(async () => {
+    OVM_GasPriceOracle = await Factory__OVM_GasPriceOracle.deploy(
+      await signer1.getAddress(),
+      initialGasPrice
+    )
+  })
+
+  describe('owner', () => {
+    it('should have an owner', async () => {
+      expect(await OVM_GasPriceOracle.owner()).to.equal(
+        await signer1.getAddress()
+      )
+    })
+  })
+
+  describe('setGasPrice', () => {
+    it('should revert if called by someone other than the owner', async () => {
+      await expect(OVM_GasPriceOracle.connect(signer2).setGasPrice(1234)).to.be
+        .reverted
+    })
+
+    it('should succeed if called by the owner and is equal to `0`', async () => {
+      await expect(OVM_GasPriceOracle.connect(signer1).setGasPrice(0)).to.not.be
+        .reverted
+    })
+  })
+
+  describe('get gasPrice', () => {
+    it('should return zero at first', async () => {
+      expect(await OVM_GasPriceOracle.gasPrice()).to.equal(initialGasPrice)
+    })
+
+    it('should change when setGasPrice is called', async () => {
+      const gasPrice = 1234
+
+      await OVM_GasPriceOracle.connect(signer1).setGasPrice(gasPrice)
+
+      expect(await OVM_GasPriceOracle.gasPrice()).to.equal(gasPrice)
+    })
+
+    it('is the 1st storage slot', async () => {
+      const gasPrice = 1234
+      const slot = 1
+
+      // set the price
+      await OVM_GasPriceOracle.connect(signer1).setGasPrice(gasPrice)
+
+      // get the storage slot value
+      const priceAtSlot = await signer1.provider.getStorageAt(
+        OVM_GasPriceOracle.address,
+        slot
+      )
+      expect(await OVM_GasPriceOracle.gasPrice()).to.equal(
+        ethers.BigNumber.from(priceAtSlot)
+      )
+    })
+  })
+})