Adding Base module for canonical TBTC

Most of the files were copied from the Optimism module and adjusted for
the Base chain, ie. ids and addresses. There is one change that had to
be added which is a custom network for hardhat etherscan plugin. Base is
not supported by this plugin by default and a custom network
configuration had to be added.

cross-chain/base/.eslintignore

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+artifacts/
+build/
+cache/
+deployments/
+export/
+hardhat-dependency-compiler/
+typechain/
+export.json

cross-chain/base/.eslintrc

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+{
+  "root": true,
+  "extends": ["@thesis-co"],
+  "parserOptions": {
+    "ecmaVersion": 2017,
+    "sourceType": "module"
+  },
+  "env": {
+    "es6": true,
+    "mocha": true
+  },
+  "rules": {
+    "new-cap": "off",
+    "import/no-extraneous-dependencies": "off",
+    "@typescript-eslint/no-use-before-define": "off",
+    "no-plusplus": ["error", { "allowForLoopAfterthoughts": true }]
+  }
+}

cross-chain/base/.gitignore

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+# Hardhat
+/artifacts/
+/build/
+/cache/
+/export/
+/external/npm
+/typechain/
+/export.json
+/deployments/*
+!/deployments/mainnet/
+!/deployments/base/
+!/deployments/baseGoerli/
+
+# OZ
+/.openzeppelin/unknown-*.json

cross-chain/base/.mocharc.json

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+{
+  "require": "ts-node/register/files"
+}

cross-chain/base/.prettierignore

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+.openzeppelin/
+artifacts/
+build/
+cache/
+deployments/
+export/
+hardhat-dependency-compiler/
+typechain/
+export.json

cross-chain/base/.prettierrc.js

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+module.exports = {
+  ...require("@thesis-co/prettier-config"),
+  overrides: [
+    {
+      files: "*.sol",
+      options: {
+        tabWidth: 4,
+      },
+    },
+  ],
+}

cross-chain/base/.solhint.json

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+{
+  "extends": "keep",
+  "plugins": [],
+  "rules": {
+    "func-visibility": ["error", { "ignoreConstructors": true }]
+  }
+}

cross-chain/base/.solhintignore

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+hardhat-dependency-compiler/
+node_modules/

cross-chain/base/.tsconfig-eslint.json

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+node_modules/@thesis-co/eslint-config/.tsconfig-eslint.json

cross-chain/base/README.adoc

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+:toc: macro
+
+= Threshold cross-chain - Base
+
+This package brings Bitcoin to Ethereum L2 Base. For more details please
+see link:https://github.com/keep-network/tbtc-v2/blob/main/docs/rfc/rfc-8.adoc[RFC 8: Cross-chain Tokenized Threshold BTC]
+
+== How it works?
+
+```
++----------------------------+         +-------------------------------------------------------------------+
+|          Ethereum          |         |                                Base                               |
+|                            |         |                                                                   |
+|  +----------------------+  |         |  +----------------------+  +---------------------+  +----------+  |
+|  | Wormhole TokenBridge |--|---------|--| Wormhole TokenBridge |--| BaseWormholeGateway |--| BaseTBTC |  |
+|  +----------------------+  |         |  +----------------------+  +---------------------+  +----------+  |
+|                            |         |                                                                   |
++----------------------------+         +-------------------------------------------------------------------+
+```
+
+- `BaseTBTC` canonical tBTC token on Base with a minting authority
+delegated to `BaseWormholeGateway`.
+- `BaseWormholeGateway` is a smart contract wrapping and unwrapping 
+Wormhole-specific tBTC representation into the canonical `BaseTBTC` token.
+
+=== Updating Wormhole Gateway mapping
+
+The deployment scripts are responsible for managing updates of the tBTC gateway
+addresses across various chains. These addresses are stored in the `external/`
+directory for a specific network, such as `arbitrumGoerli/ArbitrumWormholeGateway.json.` 
+It is important to note that these addresses should remain constant for the 
+mainnet network. However, there may be instances where a new version of a 
+cross-chain module is deployed to the testing network, which would require a 
+manual update of the corresponding address.
+
+=== Deploy contracts
+
+To deploy all contracts on the given network, please run:
+```
+yarn deploy --network <network>
+```
+
+Supported networks:
+- `hardhat` - for local development
+- `baseGoerli` - L2 testing network
+- `base` - L2 mainnet
+
+Currently, this module does not deploy any contracts on L1. All the existing 
+Wormhole contract addresses that are used in this module are stored under 
+`external/<network>` dir.
+
+If contracts haven't been built yet or changes occurred, `deploy` task will build
+the contracts before running the deployment script. This command produces
+an `export.json` file containing contract deployment info. Note that for the
+chains other than `hardhat` the following environment variables are needed:
+
+- `L2_CHAIN_API_URL` - URL to access blockchain services, e.g. `https://opt-goerli.g.alchemy.com/v2/<alchemy_api_key>`
+- `L2_ACCOUNTS_PRIVATE_KEYS` - Private keys for the deployer and council `<0xOwnerPrivKey,0xCouncilPrivKey>`
+- `BASESCAN_API_KEY` - Base Etherscan API key

cross-chain/base/contracts/test/BaseTBTCUpgraded.sol

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+// SPDX-License-Identifier: GPL-3.0-only
+
+pragma solidity ^0.8.17;
+
+import "@keep-network/tbtc-v2/contracts/l2/L2TBTC.sol";
+
+/// @notice Canonical tBTC Token on Base - upgraded version.
+/// @dev This contract is intended solely for testing purposes. As it currently
+///      stands in the implementation of L2TBTC.sol, there are no reserved
+///      storage gap slots available, thereby limiting the upgradability to a
+///      child contract only.
+contract BaseTBTCUpgraded is L2TBTC {
+    string public newVar;
+
+    function initializeV2(string memory _newVar) public {
+        newVar = _newVar;
+    }
+}

cross-chain/base/contracts/test/BaseWormholeGatewayUpgraded.sol

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+// SPDX-License-Identifier: GPL-3.0-only
+
+pragma solidity ^0.8.17;
+
+import "@keep-network/tbtc-v2/contracts/l2/L2WormholeGateway.sol";
+
+/// @notice Wormhole gateway for L2 Base - upgraded version.
+/// @dev This contract is intended solely for testing purposes. As it currently
+///      stands in the implementation of L2WormholeGateway.sol, there are no
+///      reserved storage gap slots available, thereby limiting the upgradability
+///      to a child contract only.
+contract BaseWormholeGatewayUpgraded is L2WormholeGateway {
+    string public newVar;
+
+    function initializeV2(string memory _newVar) public {
+        newVar = _newVar;
+    }
+}

cross-chain/base/deploy_l2/00_resolve_arbitrum_wormhole_gateway.ts

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+import type { HardhatRuntimeEnvironment } from "hardhat/types"
+import type { DeployFunction } from "hardhat-deploy/types"
+
+const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
+  const { helpers, deployments } = hre
+  const { log } = deployments
+
+  const ArbitrumWormholeGateway = await deployments.getOrNull(
+    "ArbitrumWormholeGateway"
+  )
+
+  if (
+    ArbitrumWormholeGateway &&
+    helpers.address.isValid(ArbitrumWormholeGateway.address)
+  ) {
+    log(
+      `using existing ArbitrumWormholeGateway at ${ArbitrumWormholeGateway.address}`
+    )
+  } else if (hre.network.name === "hardhat") {
+    log("using fake ArbitrumWormholeGateway for hardhat network")
+  } else {
+    throw new Error("deployed ArbitrumWormholeGateway contract not found")
+  }
+}
+
+export default func
+
+func.tags = ["ArbitrumWormholeGateway"]

cross-chain/base/deploy_l2/00_resolve_base_token_bridge.ts

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+import type { HardhatRuntimeEnvironment } from "hardhat/types"
+import type { DeployFunction } from "hardhat-deploy/types"
+
+const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
+  const { helpers, deployments } = hre
+  const { log } = deployments
+
+  const BaseTokenBridge = await deployments.getOrNull("BaseTokenBridge")
+
+  if (BaseTokenBridge && helpers.address.isValid(BaseTokenBridge.address)) {
+    log(`using existing Base TokenBridge at ${BaseTokenBridge.address}`)
+  } else if (hre.network.name === "hardhat") {
+    log("using fake Base TokenBridge for hardhat network")
+  } else {
+    throw new Error("deployed Base TokenBridge contract not found")
+  }
+}
+
+export default func
+
+func.tags = ["BaseTokenBridge"]

cross-chain/base/deploy_l2/00_resolve_base_wormhole_tbtc.ts

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+import type { HardhatRuntimeEnvironment } from "hardhat/types"
+import type { DeployFunction } from "hardhat-deploy/types"
+
+const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
+  const { helpers, deployments } = hre
+  const { log } = deployments
+
+  const BaseWormholeTBTC = await deployments.getOrNull("BaseWormholeTBTC")
+
+  if (BaseWormholeTBTC && helpers.address.isValid(BaseWormholeTBTC.address)) {
+    log(`using existing Base WormholeTBTC at ${BaseWormholeTBTC.address}`)
+  } else if (hre.network.name === "hardhat") {
+    log("using fake Base WormholeTBTC for hardhat network")
+  } else {
+    throw new Error("deployed Base WormholeTBTC contract not found")
+  }
+}
+
+export default func
+
+func.tags = ["BaseWormholeTBTC"]

cross-chain/base/deploy_l2/00_resolve_optimism_wormhole_gateway.ts

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+import type { HardhatRuntimeEnvironment } from "hardhat/types"
+import type { DeployFunction } from "hardhat-deploy/types"
+
+const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
+  const { helpers, deployments } = hre
+  const { log } = deployments
+
+  const OptimismWormholeGateway = await deployments.getOrNull(
+    "OptimismWormholeGateway"
+  )
+
+  if (
+    OptimismWormholeGateway &&
+    helpers.address.isValid(OptimismWormholeGateway.address)
+  ) {
+    log(
+      `using existing OptimismWormholeGateway at ${OptimismWormholeGateway.address}`
+    )
+  } else if (hre.network.name === "hardhat") {
+    log("using fake OptimismWormholeGateway for hardhat network")
+  } else {
+    throw new Error("deployed OptimismWormholeGateway contract not found")
+  }
+}
+
+export default func
+
+func.tags = ["OptimismWormholeGateway"]

cross-chain/base/deploy_l2/00_resolve_polygon_wormhole_gateway.ts

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+import type { HardhatRuntimeEnvironment } from "hardhat/types"
+import type { DeployFunction } from "hardhat-deploy/types"
+
+const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
+  const { helpers, deployments } = hre
+  const { log } = deployments
+
+  const PolygonWormholeGateway = await deployments.getOrNull(
+    "PolygonWormholeGateway"
+  )
+
+  if (
+    PolygonWormholeGateway &&
+    helpers.address.isValid(PolygonWormholeGateway.address)
+  ) {
+    log(
+      `using existing PolygonWormholeGateway at ${PolygonWormholeGateway.address}`
+    )
+  } else if (hre.network.name === "hardhat") {
+    log("using fake PolygonWormholeGateway for hardhat network")
+  } else {
+    throw new Error("deployed PolygonWormholeGateway contract not found")
+  }
+}
+
+export default func
+
+func.tags = ["PolygonWormholeGateway"]

cross-chain/base/deploy_l2/01_deploy_base_tbtc_token.ts

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+import type { HardhatRuntimeEnvironment } from "hardhat/types"
+import type { DeployFunction } from "hardhat-deploy/types"
+
+const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
+  const { ethers, getNamedAccounts, helpers } = hre
+  const { deployer } = await getNamedAccounts()
+
+  const [, proxyDeployment] = await helpers.upgrades.deployProxy("BaseTBTC", {
+    contractName: "@keep-network/tbtc-v2/contracts/l2/L2TBTC.sol:L2TBTC",
+    initializerArgs: ["Base tBTC v2", "tBTC"],
+    factoryOpts: { signer: await ethers.getSigner(deployer) },
+    proxyOpts: {
+      kind: "transparent",
+    },
+  })
+
+  // TODO: Investigate the possibility of adding Tenderly verification for
+  // L2 and upgradable proxy.
+
+  // Contracts can be verified on L2 Base Etherscan in a similar way as we
+  // do it on L1 Etherscan
+  if (hre.network.tags.basescan) {
+    // We use `verify` instead of `verify:verify` as the `verify` task is defined
+    // in "@openzeppelin/hardhat-upgrades" to verify the proxy’s implementation
+    // contract, the proxy itself and any proxy-related contracts, as well as
+    // link the proxy to the implementation contract’s ABI on (Ether)scan.
+    await hre.run("verify", {
+      address: proxyDeployment.address,
+      constructorArgsParams: proxyDeployment.args,
+    })
+  }
+}
+
+export default func
+
+func.tags = ["BaseTBTC"]