Detailed explanation of HealthSaveDeFi

1. Account Creation:
• Users create a HealthSaveDeFi account, which is essentially a smart contract wallet.
• The account is linked to their Ethereum address and can receive tax-advantaged contributions (in a real-world scenario, this would require integration with tax systems).

2. Contributions:
• Users can deposit funds (e.g., stablecoins) into their HSA account.
• Employers can also contribute directly to an employee's account.

3. Investment:
• Deposited funds can be invested in various DeFi protocols to earn interest.
• Users can choose from a range of investment options with different risk-return profiles.
• Smart contracts automatically manage these investments based on user preferences.

4. Qualified Medical Expenses:
• The platform maintains a list of qualified medical expenses, which is updatable through governance.
• Users can submit expense claims, providing necessary documentation (hashed for privacy).

5. Withdrawals:
• For qualified medical expenses, withdrawals are tax-free.
• Non-qualified withdrawals may incur penalties (simulated in the smart contract).

6. Healthcare Provider Integration:
• The platform can integrate with healthcare providers to allow direct payments using HSA funds.

7. Peer-to-Peer Lending:
• Users can lend part of their HSA balance to other users for medical expenses.
• Smart contracts manage the lending process, including interest calculations and repayments.

8. Reporting:
• The platform generates reports for users to track their contributions, investments, and withdrawals for tax purposes.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract HealthSaveDeFi is AccessControl, ReentrancyGuard {
    bytes32 public constant ADMIN_ROLE = keccak256("ADMIN_ROLE");
    bytes32 public constant PROVIDER_ROLE = keccak256("PROVIDER_ROLE");

    struct Account {
        uint256 balance;
        uint256 investedAmount;
        mapping(address => uint256) investments; // protocol address => amount
    }

    struct Loan {
        address borrower;
        address lender;
        uint256 amount;
        uint256 interest;
        uint256 dueDate;
        bool isPaid;
    }

    mapping(address => Account) public accounts;
    mapping(bytes32 => bool) public qualifiedExpenses;
    mapping(uint256 => Loan) public loans;
    uint256 public loanCounter;

    IERC20 public stablecoin;

    uint256 public constant PENALTY_RATE = 10; // 10% penalty for non-qualified withdrawals
    uint256 public constant MAX_INVESTMENT_PERCENTAGE = 80; // Max 80% of balance can be invested

    event Deposit(address indexed user, uint256 amount);
    event Withdraw(address indexed user, uint256 amount, bool isQualified);
    event InvestmentMade(address indexed user, address indexed protocol, uint256 amount);
    event LoanCreated(uint256 indexed loanId, address indexed borrower, address indexed lender, uint256 amount);
    event LoanRepaid(uint256 indexed loanId);

    constructor(address _stablecoin) {
        _setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
        _setupRole(ADMIN_ROLE, msg.sender);
        stablecoin = IERC20(_stablecoin);
    }

    function deposit(uint256 _amount) external nonReentrant {
        require(stablecoin.transferFrom(msg.sender, address(this), _amount), "Transfer failed");
        accounts[msg.sender].balance += _amount;
        emit Deposit(msg.sender, _amount);
    }

    function withdraw(uint256 _amount, bytes32 _expenseHash, bool _isQualified) external nonReentrant {
        require(accounts[msg.sender].balance >= _amount, "Insufficient balance");

        uint256 amountToTransfer = _amount;
        if (!_isQualified) {
            uint256 penalty = (_amount * PENALTY_RATE) / 100;
            amountToTransfer -= penalty;
            // In a real implementation, the penalty would be handled according to regulations
        }

        accounts[msg.sender].balance -= _amount;
        require(stablecoin.transfer(msg.sender, amountToTransfer), "Transfer failed");

        emit Withdraw(msg.sender, _amount, _isQualified);
    }

    function invest(address _protocol, uint256 _amount) external nonReentrant {
        require(accounts[msg.sender].balance >= _amount, "Insufficient balance");
        require(accounts[msg.sender].investedAmount + _amount <= (accounts[msg.sender].balance * MAX_INVESTMENT_PERCENTAGE) / 100, "Investment limit exceeded");

        // In a real implementation, this would interact with the DeFi protocol
        accounts[msg.sender].balance -= _amount;
        accounts[msg.sender].investedAmount += _amount;
        accounts[msg.sender].investments[_protocol] += _amount;

        emit InvestmentMade(msg.sender, _protocol, _amount);
    }

    function createLoan(address _borrower, uint256 _amount, uint256 _interest, uint256 _duration) external nonReentrant {
        require(accounts[msg.sender].balance >= _amount, "Insufficient balance");

        accounts[msg.sender].balance -= _amount;
        accounts[_borrower].balance += _amount;

        loanCounter++;
        loans[loanCounter] = Loan({
            borrower: _borrower,
            lender: msg.sender,
            amount: _amount,
            interest: _interest,
            dueDate: block.timestamp + _duration,
            isPaid: false
        });

        emit LoanCreated(loanCounter, _borrower, msg.sender, _amount);
    }

    function repayLoan(uint256 _loanId) external nonReentrant {
        Loan storage loan = loans[_loanId];
        require(msg.sender == loan.borrower, "Only borrower can repay");
        require(!loan.isPaid, "Loan already repaid");

        uint256 totalRepayment = loan.amount + loan.interest;
        require(accounts[msg.sender].balance >= totalRepayment, "Insufficient balance for repayment");

        accounts[msg.sender].balance -= totalRepayment;
        accounts[loan.lender].balance += totalRepayment;

        loan.isPaid = true;

        emit LoanRepaid(_loanId);
    }

    function addQualifiedExpense(bytes32 _expenseHash) external onlyRole(ADMIN_ROLE) {
        qualifiedExpenses[_expenseHash] = true;
    }

    function removeQualifiedExpense(bytes32 _expenseHash) external onlyRole(ADMIN_ROLE) {
        qualifiedExpenses[_expenseHash] = false;
    }

    function providerPayment(address _user, uint256 _amount, bytes32 _expenseHash) external onlyRole(PROVIDER_ROLE) nonReentrant {
        require(qualifiedExpenses[_expenseHash], "Not a qualified expense");
        require(accounts[_user].balance >= _amount, "Insufficient user balance");

        accounts[_user].balance -= _amount;
        require(stablecoin.transfer(msg.sender, _amount), "Transfer to provider failed");

        emit Withdraw(_user, _amount, true);
    }

    // Additional functions would be needed for:
    // - Handling investment returns
    // - Generating account statements and tax reports
    // - Updating investment strategies
    // - Governance for platform upgrades and parameter changes
}

1. Users can deposit funds into their HSA using the deposit function.

2. Withdrawals can be made using the withdraw function, with different handling for qualified and non-qualified expenses.

3. Users can invest their HSA funds using the invest function (simplified in this example).

4. The platform supports peer-to-peer lending with createLoan and repayLoan functions.

5. Healthcare providers can directly charge HSA accounts using the providerPayment function.

6. Admins can manage the list of qualified expenses.

• Integration with actual DeFi protocols for investments.

• More sophisticated lending mechanisms, including credit checks and collateralization.

• Advanced privacy features to protect sensitive health information.

• Integration with tax systems for proper handling of tax-advantaged contributions and withdrawals.

• More robust expense verification processes.

• Enhanced security measures, including multi-sig capabilities for large transactions.

• Detailed reporting and analytics features for users and administrators.

• Governance mechanisms for platform upgrades and parameter adjustments.