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🏢 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    • Any pending salary is automatically withdrawn when switching payment currencies.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

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.