🏢 HRManager

This repository contains the HRManager Solidity smart contract, designed to implement a Human Resources (HR) Payment System on the Optimism blockchain. It enables HR managers to efficiently manage employee registrations, terminations, and salary withdrawals, while ensuring secure and transparent payments.

---

🚀 Features

🔒 Role-Based Access Control

• HR Manager:
  • Register new employees and set their weekly salaries.
  • Terminate employees and stop their salary accrual.
• Employees:
  • Withdraw accrued salaries in their preferred currency.
  • Toggle salary payment preference between USDC and ETH.

---

👥 Employee Management

• Register Employee: Add an employee with their weekly USD salary. Re-registering starts salary accrual afresh.
• Terminate Employee: Stops salary accrual for an employee and emits a termination event.

---

💸 Salary Management

• Continuous Salary Accrual: Employees' salaries accrue linearly based on time (e.g., 2 days = 2/7th of weekly salary).
• Flexible Withdrawals:
  • Employees can withdraw salaries in USDC (default) or ETH.
  • Integration with Uniswap V3 AMM for real-time USDC-to-ETH conversion.
  • Chainlink Oracle ensures accurate ETH/USD price feeds for withdrawals.
• Automatic Withdrawal:
  • Any pending salary is automatically withdrawn when switching payment currencies.

---

🔄 Currency Switching

• Employees can toggle their payment currency between:
  • USDC (Default): Fast and stable currency.
  • ETH: Real-time exchange through Uniswap.
• Triggers the CurrencySwitched event for tracking.

---

🛠️ Technical Details

• Blockchain: Optimism Layer 2.
• Dependencies:
  • Chainlink Oracle for fetching ETH/USD price feeds.
  • Uniswap V3 Router for AMM-based USDC-to-ETH swaps.
• Precision:
  • USDC: 6 decimals.
  • ETH: 18 decimals.

---

📑 Installation & Usage

Prerequisites

• Foundry
• Node.js (for additional tools if needed)

Installation Steps

1. Clone the Repository:

   git clone https://github.com/TonyP4N/HRManager.git
   cd HRManager

2. Install Dependencies: Run the following commands to install the required dependencies for the project:

   bash install.sh

3. Build the Contracts:

   forge build

4. Test the Contracts:

   forge test
   

---

📚 Function Implementations

registerEmployee(address _employee, uint256 _weeklyUsdSalary)

• Access Control: Only HR manager.
• Purpose: Registers a new employee with a weekly USD salary.
• Validation: Salary must be greater than zero; reverts if employee is already registered.
• Updates:
  • Sets employee details in the Employee struct.
  • Increments activeEmployeeCount.
• Event: Emits EmployeeRegistered.

terminateEmployee(address _employee)

• Access Control: Only HR manager.
• Purpose: Terminates an employee.
• Validation: Reverts if employee is not registered.
• Updates:
  • Calculates unclaimed salary and updates totalUsdSalaries.
  • Sets isActive to false and updates terminatedAt.
  • Decrements activeEmployeeCount.
• Event: Emits EmployeeTerminated.

withdrawSalary()

• Access Control: Only callable by employees.
• Purpose: Allows employees to withdraw accumulated salary.
• Functionality:
  • Calculates unclaimed salary based on time worked.
  • Resets lastWithdrawalTime and totalUsdSalaries.
  • Distributes salary in USDC or swaps to ETH via Uniswap if prefersEth is true.
• Security: Uses nonReentrant to prevent reentrancy attacks.
• Event: Emits SalaryWithdrawn.

switchCurrency()

• Access Control: Only callable by employees.
• Purpose: Toggles salary payment between USDC and ETH.
• Functionality:
  • Calls withdrawSalary() before switching.
  • Toggles prefersEth.
• Event: Emits CurrencySwitched.

salaryAvailable(address _employee) → uint256

• Purpose: Returns the amount of salary available for withdrawal.
• Functionality:
  • Calculates accumulated salary.
    • Salary Calculation:
      • Calculates the time since the last withdrawal.
      • Determines unclaimedSalary based on timeDiff and weeklyUsdSalary.
      • Calculates totalAmount as the sum of unclaimedSalary and any totalUsdSalaries.
  • Converts amount to ETH if prefersEth is true.

hrManager() → address

• Purpose: Returns the HR manager's address.

getActiveEmployeeCount() → uint256

• Purpose: Returns the count of active employees.

getEmployeeInfo(address _employee) → (uint256, uint256, uint256)

• Purpose: Retrieves employee's salary, employment start, and termination time.
• Functionality:
  • If the employee is not active, returns zeros for all values.
  • Otherwise, returns:
    • weeklyUsdSalary
    • employedSince
    • terminatedAt

---

🔌 AMM and Oracle Integration

Uniswap V3 Integration

• Function: swapUSDCToETH(uint256 usdcAmount)
• Purpose: Swaps USDC to ETH when employees prefer to receive their salary in ETH.
• Implementation:
  • Approvals:
    • Uses safeIncreaseAllowance to allow the Uniswap router to spend USDC.
  • Slippage Consideration:
    • Calculates expectedEthAmount based on the current ETH price.
    • Sets amountOutMinimum to 98% of expectedEthAmount to allow up to 2% slippage.
  • Swap Execution:
    • Constructs ExactInputSingleParams for the Uniswap router.
    • Calls exactInputSingle on the Uniswap router to execute the swap.
  • ETH Handling:
    • Unwraps WETH to ETH using IWETH9.withdraw(wethReceived).
    • Returns the amount of ETH received.

Chainlink ETH/USD Price Feed

• Function: getLatestETHPrice()
• Purpose: Retrieves the latest ETH price in USD.
• Implementation:
  • Calls latestRoundData() on the price feed.
  • Ensures the retrieved price is valid (greater than zero).
  • Adjusts price to 18 decimals for consistency.

---

⚠️ Error Handling

• NotAuthorized
  • Thrown when an unauthorized user attempts to call a restricted function.
• EmployeeAlreadyRegistered
  • Thrown when trying to register an employee who is already registered.
• EmployeeNotRegistered
  • Thrown when attempting to terminate or interact with an employee who is not registered.
• Invalid Price From Oracle
  • Thrown when the price retrieved from the oracle is invalid.
• Slippage Protection
  • Swap reverts if slippage exceeds 2% during USDC to ETH conversion.

---

✨ Key Events

The contract emits several events to enable tracking of important actions:

• EmployeeRegistered(address indexed employee, uint256 weeklyUsdSalary)
  • Emitted when a new employee is registered.
• EmployeeTerminated(address indexed employee)
  • Emitted when an employee is terminated.
• SalaryWithdrawn(address indexed employee, bool isEth, uint256 amount)
  • Emitted when an employee withdraws their salary.
• CurrencySwitched(address indexed employee, bool isEth)
  • Emitted when an employee switches their salary currency preference.

---

🔒 Security and Additional Details

• Security:
  • Access control enforced via modifiers.
  • Reentrancy protection on critical functions.
  • Uses SafeERC20 for secure token operations.
• Employee Struct Fields:
  • weeklyUsdSalary: The weekly salary in USD (scaled to 18 decimals).
  • employedSince: Timestamp of when the employee was registered.
  • terminatedAt: Timestamp of when the employee was terminated (0 if active).
  • lastWithdrawalTime: Timestamp of the last salary withdrawal.
  • totalUsdSalaries: Accumulated unclaimed salary in USD.
  • prefersEth: Indicates if the employee prefers salary in ETH (true) or USDC (false).
  • isActive: Indicates if the employee is currently active.
• Salary Accumulation:
  • Salary accrues continuously over time, regardless of non-working hours.

---

📜 License

This project is licensed under the MIT License. See the LICENSE file for details.