Add BAL Token Holder contract (#1149)

* Add BALTokenHolder and factory

Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>

pkg/standalone-utils/contracts/BALTokenHolder.sol

@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+pragma solidity ^0.7.0;
+
+import "@balancer-labs/v2-solidity-utils/contracts/helpers/Authentication.sol";
+import "@balancer-labs/v2-solidity-utils/contracts/openzeppelin/SafeERC20.sol";
+
+import "@balancer-labs/v2-vault/contracts/interfaces/IVault.sol";
+import "@balancer-labs/v2-liquidity-mining/contracts/interfaces/IBalancerToken.sol";
+
+import "./interfaces/IBALTokenHolder.sol";
+
+/**
+ * @dev This contract simply holds the BAL token and delegates to Balancer Governance the permission to withdraw it. It
+ * is intended to serve as the recipient of automated BAL minting via the liquidity mining gauges, allowing for the
+ * final recipient of the funds to be configurable without having to alter the gauges themselves.
+ *
+ * There is also a separate auxiliary function to sweep any non-BAL tokens sent here by mistake.
+ */
+contract BALTokenHolder is IBALTokenHolder, Authentication {
+    using SafeERC20 for IERC20;
+
+    IBalancerToken private immutable _balancerToken;
+    IVault private immutable _vault;
+
+    string private _name;
+
+    constructor(
+        IBalancerToken balancerToken,
+        IVault vault,
+        string memory name
+    ) Authentication(bytes32(uint256(address(this)))) {
+        // BALTokenHolder is often deployed from a factory for convenience, but it uses its own address instead of
+        // the factory's as a disambiguator to make sure the action IDs of all instances are unique, reducing likelihood
+        // of errors.
+
+        _balancerToken = balancerToken;
+        _vault = vault;
+        _name = name;
+    }
+
+    function getBalancerToken() external view returns (IBalancerToken) {
+        return _balancerToken;
+    }
+
+    function getVault() public view returns (IVault) {
+        return _vault;
+    }
+
+    function getName() external view returns (string memory) {
+        return _name;
+    }
+
+    function getAuthorizer() public view returns (IAuthorizer) {
+        return getVault().getAuthorizer();
+    }
+
+    function _canPerform(bytes32 actionId, address account) internal view override returns (bool) {
+        return getAuthorizer().canPerform(actionId, account, address(this));
+    }
+
+    function withdrawFunds(address recipient, uint256 amount) external override authenticate {
+        IERC20(_balancerToken).safeTransfer(recipient, amount);
+    }
+
+    function sweepTokens(
+        IERC20 token,
+        address recipient,
+        uint256 amount
+    ) external override authenticate {
+        require(token != _balancerToken, "Cannot sweep BAL");
+        IERC20(token).safeTransfer(recipient, amount);
+    }
+}

pkg/standalone-utils/contracts/BALTokenHolderFactory.sol

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+pragma solidity ^0.7.0;
+
+import "@balancer-labs/v2-solidity-utils/contracts/helpers/Authentication.sol";
+
+import "@balancer-labs/v2-vault/contracts/interfaces/IVault.sol";
+import "@balancer-labs/v2-liquidity-mining/contracts/interfaces/IBalancerToken.sol";
+
+import "./BALTokenHolder.sol";
+import "./interfaces/IBALTokenHolderFactory.sol";
+
+contract BALTokenHolderFactory is IBALTokenHolderFactory {
+    IBalancerToken private immutable _balancerToken;
+    IVault private immutable _vault;
+
+    mapping(address => bool) private _factoryCreatedHolders;
+
+    event BALTokenHolderCreated(BALTokenHolder balTokenHolder, string name);
+
+    constructor(IBalancerToken balancerToken, IVault vault) {
+        _balancerToken = balancerToken;
+        _vault = vault;
+    }
+
+    function getBalancerToken() public view override returns (IBalancerToken) {
+        return _balancerToken;
+    }
+
+    function getVault() public view override returns (IVault) {
+        return _vault;
+    }
+
+    function isHolderFromFactory(address holder) external view override returns (bool) {
+        return _factoryCreatedHolders[holder];
+    }
+
+    function create(string memory name) external override returns (IBALTokenHolder) {
+        BALTokenHolder holder = new BALTokenHolder(getBalancerToken(), getVault(), name);
+
+        _factoryCreatedHolders[address(holder)] = true;
+        emit BALTokenHolderCreated(holder, name);
+
+        return holder;
+    }
+}

pkg/standalone-utils/contracts/interfaces/IBALTokenHolder.sol

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+pragma solidity ^0.7.0;
+
+import "@balancer-labs/v2-solidity-utils/contracts/helpers/IAuthentication.sol";
+import "@balancer-labs/v2-solidity-utils/contracts/openzeppelin/IERC20.sol";
+
+interface IBALTokenHolder is IAuthentication {
+    function withdrawFunds(address recipient, uint256 amount) external;
+
+    function sweepTokens(
+        IERC20 token,
+        address recipient,
+        uint256 amount
+    ) external;
+}

pkg/standalone-utils/contracts/interfaces/IBALTokenHolderFactory.sol

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+pragma solidity ^0.7.0;
+
+import "@balancer-labs/v2-vault/contracts/interfaces/IVault.sol";
+import "@balancer-labs/v2-liquidity-mining/contracts/interfaces/IBalancerToken.sol";
+import "./IBALTokenHolder.sol";
+
+interface IBALTokenHolderFactory {
+    function getBalancerToken() external view returns (IBalancerToken);
+
+    function getVault() external view returns (IVault);
+
+    function isHolderFromFactory(address holder) external view returns (bool);
+
+    function create(string memory name) external returns (IBALTokenHolder);
+}

pkg/standalone-utils/package.json

@@ -28,6 +28,7 @@
     "test:watch": "nodemon --ext js,ts --watch test --watch lib --exec 'clear && yarn test --no-compile'"
   },
   "dependencies": {
+    "@balancer-labs/v2-liquidity-mining": "workspace:*",
     "@balancer-labs/v2-pool-utils": "workspace:*",
     "@balancer-labs/v2-solidity-utils": "workspace:*",
     "@balancer-labs/v2-vault": "workspace:*"

pkg/standalone-utils/test/BALTokenHolder.test.ts

@@ -0,0 +1,115 @@
+import { ethers } from 'hardhat';
+import { SignerWithAddress } from '@nomiclabs/hardhat-ethers/dist/src/signer-with-address';
+
+import { deploy, deployedAt } from '@balancer-labs/v2-helpers/src/contract';
+import { actionId } from '@balancer-labs/v2-helpers/src/models/misc/actions';
+
+import Vault from '@balancer-labs/v2-helpers/src/models/vault/Vault';
+import TokenList from '@balancer-labs/v2-helpers/src/models/tokens/TokenList';
+import { expectBalanceChange } from '@balancer-labs/v2-helpers/src/test/tokenBalance';
+import { Contract } from 'ethers';
+import { expect } from 'chai';
+import Token from '@balancer-labs/v2-helpers/src/models/tokens/Token';
+
+describe('BALTokenHolder', function () {
+  let tokens: TokenList;
+  let BAL: Token, DAI: Token;
+  let vault: Vault;
+  let holder: Contract;
+  let admin: SignerWithAddress, authorized: SignerWithAddress, other: SignerWithAddress;
+
+  const holderName = 'DAO Treasury';
+
+  before('get signers', async () => {
+    [, admin, authorized, other] = await ethers.getSigners();
+  });
+
+  sharedBeforeEach(async () => {
+    // Deploy Balancer Vault
+    vault = await Vault.create({ admin });
+
+    // Deploy BAL token
+    tokens = await TokenList.create([{ symbol: 'BAL' }, { symbol: 'DAI' }]);
+    BAL = await tokens.findBySymbol('BAL');
+    DAI = await tokens.findBySymbol('DAI');
+
+    holder = await deploy('BALTokenHolder', { args: [BAL.address, vault.address, holderName] });
+
+    // Deposit all tokens in the holder
+    await tokens.mint({ to: holder });
+  });
+
+  it('returns the BAL address', async () => {
+    expect(await holder.getBalancerToken()).to.equal(BAL.address);
+  });
+
+  it('returns the address of the vault', async () => {
+    expect(await holder.getVault()).to.equal(vault.address);
+  });
+
+  it('returns its name', async () => {
+    expect(await holder.getName()).to.equal(holderName);
+  });
+
+  describe('withdrawFunds', () => {
+    context('when the caller is authorized', () => {
+      sharedBeforeEach(async () => {
+        const authorizer = await deployedAt('v2-vault/Authorizer', await vault.instance.getAuthorizer());
+        const withdrawActionId = await actionId(holder, 'withdrawFunds');
+        await authorizer.connect(admin).grantPermissions([withdrawActionId], authorized.address, [holder.address]);
+      });
+
+      it('sends funds to the recipient', async () => {
+        await expectBalanceChange(() => holder.connect(authorized).withdrawFunds(other.address, 100), tokens, {
+          account: other.address,
+          changes: { BAL: 100 },
+        });
+      });
+    });
+
+    context('when the caller is not authorized', () => {
+      it('reverts', async () => {
+        await expect(holder.connect(other).withdrawFunds(other.address, 100)).to.be.revertedWith('SENDER_NOT_ALLOWED');
+      });
+    });
+  });
+
+  describe('sweepTokens', () => {
+    context('when the caller is authorized', () => {
+      sharedBeforeEach(async () => {
+        const authorizer = await deployedAt('v2-vault/Authorizer', await vault.instance.getAuthorizer());
+        const sweepActionId = await actionId(holder, 'sweepTokens');
+        await authorizer.connect(admin).grantPermissions([sweepActionId], authorized.address, [holder.address]);
+      });
+
+      context('when the token is not BAL', () => {
+        it('sends funds to the recipient', async () => {
+          await expectBalanceChange(
+            () => holder.connect(authorized).sweepTokens(DAI.address, other.address, 100),
+            tokens,
+            {
+              account: other.address,
+              changes: { DAI: 100 },
+            }
+          );
+        });
+      });
+
+      context('when the token is BAL', () => {
+        it('reverts', async () => {
+          await expect(holder.connect(authorized).sweepTokens(BAL.address, other.address, 100)).to.be.revertedWith(
+            'Cannot sweep BAL'
+          );
+        });
+      });
+    });
+
+    context('when the caller is not authorized', () => {
+      it('reverts', async () => {
+        await expect(holder.connect(other).sweepTokens(DAI.address, other.address, 100)).to.be.revertedWith(
+          'SENDER_NOT_ALLOWED'
+        );
+      });
+    });
+  });
+});