Tasks: Implement BPT exiter

packages/tasks/contracts/interfaces/liquidity/balancer/IBalancerBPTExiter.sol

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+// 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 >=0.8.0;
+
+import '../../ITask.sol';
+
+/**
+ * @dev BPT exiter task interface
+ */
+interface IBalancerBPTExiter is ITask {
+    /**
+     * @dev The token is zero
+     */
+    error TaskTokenZero();
+
+    /**
+     * @dev The amount is zero
+     */
+    error TaskAmountZero();
+
+    /**
+     * @dev The post balance is lower than the pre balance
+     */
+    error TaskPostBalanceUnexpected(uint256 postBalance, uint256 preBalance);
+
+    /**
+     * @dev The amount out is lower than the minimum amount out
+     */
+    error TaskBadAmountOut(uint256 amountOut, uint256 minAmountOut);
+
+    /**
+     * @dev Tells the address of the Balancer vault. It cannot be changed.
+     */
+    function balancerVault() external returns (address);
+
+    /**
+     * @dev Execute Balancer BPT exiter
+     */
+    function call(address token, uint256 amount) external;
+}

packages/tasks/contracts/interfaces/liquidity/balancer/IBalancerBoostedPool.sol

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+// 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 ^0.8.0;
+
+import './IBalancerPool.sol';
+
+interface IBalancerBoostedPool is IBalancerPool {
+    function getRate() external view returns (uint256);
+
+    function getBptIndex() external view returns (uint256);
+}

packages/tasks/contracts/interfaces/liquidity/balancer/IBalancerLinearPool.sol

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+// 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 ^0.8.0;
+
+import './IBalancerPool.sol';
+
+interface IBalancerLinearPool is IBalancerPool {
+    function getRate() external view returns (uint256);
+
+    function getMainToken() external view returns (address);
+}

packages/tasks/contracts/interfaces/liquidity/balancer/IBalancerPool.sol

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+// 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 ^0.8.0;
+
+import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
+
+interface IBalancerPool is IERC20 {
+    function getPoolId() external view returns (bytes32);
+}

packages/tasks/contracts/interfaces/liquidity/balancer/IBalancerVault.sol

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+// 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 ^0.8.0;
+
+import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
+
+interface IBalancerVault {
+    function getPool(bytes32 poolId) external view returns (address, uint256);
+
+    function getPoolTokens(bytes32 poolId)
+        external
+        view
+        returns (IERC20[] memory tokens, uint256[] memory balances, uint256 lastChangeBlock);
+
+    struct JoinPoolRequest {
+        IERC20[] assets;
+        uint256[] maxAmountsIn;
+        bytes userData;
+        bool fromInternalBalance;
+    }
+
+    function joinPool(bytes32 poolId, address sender, address recipient, JoinPoolRequest memory request)
+        external
+        payable;
+
+    struct ExitPoolRequest {
+        IERC20[] assets;
+        uint256[] minAmountsOut;
+        bytes userData;
+        bool toInternalBalance;
+    }
+
+    function exitPool(bytes32 poolId, address sender, address payable recipient, ExitPoolRequest memory request)
+        external;
+
+    enum SwapKind {
+        GIVEN_IN,
+        GIVEN_OUT
+    }
+
+    struct SingleSwap {
+        bytes32 poolId;
+        SwapKind kind;
+        address assetIn;
+        address assetOut;
+        uint256 amount;
+        bytes userData;
+    }
+
+    struct FundManagement {
+        address sender;
+        bool fromInternalBalance;
+        address payable recipient;
+        bool toInternalBalance;
+    }
+
+    function swap(SingleSwap memory singleSwap, FundManagement memory funds, uint256 limit, uint256 deadline)
+        external
+        payable
+        returns (uint256);
+
+    struct BatchSwapStep {
+        bytes32 poolId;
+        uint256 assetInIndex;
+        uint256 assetOutIndex;
+        uint256 amount;
+        bytes userData;
+    }
+
+    function batchSwap(
+        SwapKind kind,
+        BatchSwapStep[] memory swaps,
+        address[] memory assets,
+        FundManagement memory funds,
+        int256[] memory limits,
+        uint256 deadline
+    ) external payable returns (int256[] memory);
+}