HumanResources Smart Contract Documentation

Overview

The HumanResources smart contract is a decentralized payroll management system implemented on the Optimism network. It enables organizations to manage employee registrations and process salary payments in either USDC or ETH, leveraging Chainlink price feeds and Uniswap V3 for currency conversions.

Architecture

Core Components

• Contract: HumanResources.sol
• Network: Optimism
• Solidity Version: ^0.8.24

External Integrations

• Chainlink Price Feed: ETH/USD oracle for accurate price conversion
• Uniswap V3: Facilitates USDC-ETH swaps for salary payments
• WETH: Wrapped ETH for DEX interactions
• USDC: Stablecoin for salary denomination

Key Addresses (Optimism)

USDC: 0x0b2C639c533813f4Aa9D7837CAf62653d097Ff85
WETH: 0x4200000000000000000000000000000000000006
Chainlink ETH/USD: 0x13e3Ee699D1909E989722E753853AE30b17e08c5
Uniswap Router: 0xE592427A0AEce92De3Edee1F18E0157C05861564

Interface Implementation

Employee Management Functions

registerEmployee

function registerEmployee(address employee, uint256 weeklyUsdSalary) external

• Description: Registers a new employee with their weekly salary in USD
• Access: Only HR Manager
• Parameters:
  • employee: Employee's wallet address
  • weeklyUsdSalary: Weekly salary amount in USD (18 decimals)
• Events: Emits EmployeeRegistered
• Security: Prevents duplicate registrations of active employees
• State Changes: Increments active employee count

terminateEmployee

function terminateEmployee(address employee) external

• Description: Terminates an employee's contract
• Access: Only HR Manager
• Parameters:
  • employee: Address of employee to terminate
• Events: Emits EmployeeTerminated
• Effects:
  • Decrements active employee count
  • Sets termination timestamp
• Validation: Checks for registered and non-terminated employee

Salary Management Functions

withdrawSalary

function withdrawSalary() external

• Description: Processes salary payment in preferred currency (USDC/ETH)
• Access: Only registered employees
• Features:
  • Calculates pro-rated salary based on employment duration
  • Handles currency conversion if ETH is preferred
  • Implements slippage protection (2%)
• Security: Uses ReentrancyGuard
• Validation: Checks for available salary amount
• Events: Emits SalaryWithdrawn

switchCurrency

function switchCurrency() external

• Description: Toggles employee's preferred payment currency
• Access: Only registered employees
• Process:
  1. Checks employee is not terminated
  2. Withdraws available salary in current currency
  3. Updates currency preference
• Events:
  • Emits SalaryWithdrawn if salary was available
  • Emits CurrencySwitched
• Security: Uses ReentrancyGuard

Query Functions

salaryAvailable

function salaryAvailable(address employee) external view returns (uint256)

• Description: Calculates available salary for withdrawal
• Returns: Amount in USD (18 decimals)
• Calculation: Pro-rated based on time worked since last withdrawal

hrManager

function hrManager() external view returns (address)

• Description: Returns HR manager's address
• Usage: For verification and transparency

getActiveEmployeeCount

function getActiveEmployeeCount() external view returns (uint256)

• Description: Returns current number of active employees
• Updates: Automatically maintained during registration/termination

getEmployeeInfo

function getEmployeeInfo(address employee) external view returns (uint256, uint256, uint256)

• Description: Retrieves employee details
• Returns: Tuple of (weeklyUsdSalary, employedSince, terminatedAt)

AMM Integration

The contract integrates with Uniswap V3 for USDC-ETH conversions:

1. Price Determination:

   • Uses Chainlink ETH/USD price feed for accurate conversion rates
   • Implements 2% slippage protection

2. Swap Process:

   ISwapRouter.ExactInputSingleParams memory params = ISwapRouter.ExactInputSingleParams({
       tokenIn: address(USDC),
       tokenOut: address(WETH),
       fee: POOL_FEE_TIER,
       recipient: self,
       deadline: block.timestamp + SWAP_DEADLINE,
       amountIn: usdcAmount,
       amountOutMinimum: minOutputAmount,
       sqrtPriceLimitX96: 0
   });

Oracle Integration

Chainlink price feed integration for reliable ETH/USD conversion:

(,int256 latestPrice,,,) = CHAINLINK_ETH_USDC.latestRoundData();
uint256 estimatedWeiOutput = (usdcAmount * PRICE_PRECISION) / uint256(latestPrice);

Security Features

Access Control

modifier onlyHrManager() {
    if (msg.sender != hrManagerAddress) revert NotAuthorized();
    _;
}

modifier onlyRegisteredEmployee() {
    if (employees[msg.sender].employedSince == 0) revert EmployeeNotRegistered();
    _;
}

• HR Manager Functions: Protected by onlyHrManager
  • Employee registration
  • Employee termination
• Employee Functions: Protected by onlyRegisteredEmployee
  • Salary withdrawal
  • Currency preference switching
• Zero-address Validation
• Employee Status Checks

Reentrancy Protection

contract HumanResources is IHumanResources, ReentrancyGuard {
    function withdrawSalary() external nonReentrant {
        // Implementation
    }
}

• OpenZeppelin's ReentrancyGuard implementation
• State changes before external calls
• Secure withdrawal pattern
• Check-Effects-Interaction pattern

Slippage Protection

uint256 minOutputAmount = (estimatedWeiOutput * MIN_SLIPPAGE_PERCENT) / 100;

• 2% slippage tolerance
• Minimum output validation
• Price impact protection
• Short-term manipulation resistance

Time-based Protection

deadline: block.timestamp + SWAP_DEADLINE

• Short trade execution window (5 seconds)
• Accurate timestamp handling
• Employment period validation

Error Handling

Custom error types for precise error reporting:

error NotAuthorized()
error EmployeeAlreadyRegistered()
error EmployeeNotRegistered()
error NoSalaryAvailable()
error ExcessiveSlippage()
error EthTransferFailed()
error UsdcTransferFailed()
error UsdcApprovalFailed()

Events

event EmployeeRegistered(address indexed employee, uint256 weeklyUsdSalary)
event EmployeeTerminated(address indexed employee)
event SalaryWithdrawn(address indexed employee, bool isEth, uint256 amount)
event CurrencySwitched(address indexed employee, bool isEth)