add ISimpleProvider, IInnerWithdraw, IBeforeTransfer

contracts/CalcUtils.sol

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+library CalcUtils {
+    function calcAmount(uint256 amount, uint256 rate) internal pure returns (uint256 tokenA) {
+        return (amount * rate) / 1e21;
+    }
+
+    function calcRate(uint256 tokenAValue, uint256 tokenBValue) internal pure returns (uint256 rate) {
+        return (tokenAValue * 1e21) / tokenBValue;
+    }
+}

contracts/interfaces/IBeforeTransfer.sol

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+interface IBeforeTransfer {
+    function beforeTransfer(address from, address to, uint256 poolId) external;
+}

contracts/interfaces/IInnerWithdraw.sol

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+interface IInnerWithdraw {
+    function getInnerIdsArray(uint256 poolId) external returns (uint256[] calldata ids);
+}

contracts/interfaces/ISimpleProvider.sol

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "./IProvider.sol";
+
+///@dev Interface for the simple providers
+interface ISimpleProvider is IProvider {
+    function withdraw(uint256 poolId, uint256 amount) external returns (uint256 withdrawnAmount, bool isFinal);
+}

contracts/mocks/CalcUtilsMock.sol

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "../CalcUtils.sol";
+
+contract CalcUtilsMock {
+    using CalcUtils for uint256;
+
+    function calcAmount(uint256 amount, uint256 rate) external pure returns (uint256 tokenA) {
+        return amount.calcAmount(rate);
+    }
+
+    function calcRate(uint256 tokenAValue, uint256 tokenBValue) external pure returns (uint256 rate) {
+        return tokenAValue.calcRate(tokenBValue);
+    }
+}

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@poolzfinance/poolz-helper-v2",
-  "version": "2.3.3",
+  "version": "2.3.5",
   "description": "A single source of truth of helper contracts used by Poolz.",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

test/10_CalcUtils.ts

@@ -0,0 +1,22 @@
+import { ethers } from 'hardhat';
+import { deployed } from '../scripts/deploy';
+import { CalcUtilsMock } from '../typechain-types';
+import { expect } from 'chai';
+
+describe('CalcUtils library tests', function () {
+  let calcUtils: CalcUtilsMock;
+  const amount = ethers.utils.parseUnits('100', 18);
+  const halfRate = ethers.utils.parseUnits('5', 20); // 50%
+
+  before(async () => {
+    calcUtils = await deployed('CalcUtilsMock');
+  });
+
+  it('should Calc Amount', async () => {
+    expect(await calcUtils.calcAmount(amount, halfRate)).to.equal(amount.div(2));
+  });
+
+  it('should Calc Rate', async () => {
+    expect(await calcUtils.calcRate(amount.div(2), amount)).to.equal(halfRate);
+  });
+});