Lending Smart Contract

A professional and secure lending smart contract built with Rust using the ink! framework for Substrate-based blockchains.

Features

• Loan Creation: Users can create loan requests with specified amounts, interest rates, and collateral
• Loan Funding: Lenders can fund pending loans and earn interest
• Loan Repayment: Borrowers can repay loans with interest
• Early Repayment with Discount: Save 1-5% on interest by repaying early
• Partial Repayment: Pay off loans in multiple smaller installments
• Loan Extension: Extend loan duration with configurable fees
• Late Payment Penalties: Automatic late fees for overdue loans
• Loan Refinancing: Refinance loans with better terms and lower rates
• Variable Interest Rates: Dynamic rates with risk-based pricing
• Collateral Management: Secure collateral system with configurable ratios
• User Profiles: Track user borrowing/lending history and credit scores
• Event System: Comprehensive event logging for all operations
• Security Features: Input validation, access control, and error handling

🚀 Feature Roadmap

For a comprehensive overview of planned features and development phases, see FEATURE_ROADMAP.md.

Current Phase: Core contract implementation ✅
Next Phase: Enhanced lending features (early repayment, partial payments, loan extensions)

The roadmap includes 8 development phases covering:

• Core lending enhancements
• Advanced financial features
• Liquidity pool management
• Risk management & security
• DeFi integrations
• Performance optimizations

Project Structure

lending-smart-contract/
├── src/
│   ├── lib.rs              # Main library entry point
│   ├── lending_contract.rs # Core lending contract implementation
│   ├── types.rs            # Data structures and types
│   └── errors.rs           # Custom error definitions
├── tests/
│   └── lending_contract_tests.rs # Test suite (requires updates for ink! 5.x)
├── examples/
│   ├── basic_usage.rs      # Basic usage examples
│   └── advanced_features.rs # Advanced features demonstration
├── scripts/
│   └── build.sh            # Build automation script
├── Cargo.toml              # Project dependencies and configuration
├── README.md               # This file
└── FEATURE_ROADMAP.md      # Comprehensive feature development roadmap

Prerequisites

• Rust 1.70.0 or later
• Cargo package manager
• ink! 5.x toolchain

Installation

1. Clone the repository:

git clone https://github.com/tkmy401/lending-smart-contract.git
cd lending-smart-contract

2. Build the contract:

cargo build

Current Status

✅ Core Contract: Successfully compiles and builds
⚠️ Tests & Examples: Require updates for ink! 5.x compatibility
🔧 Dependencies: Updated to use ink! 5.1.1 with compatible crates

Dependencies

The project uses the following key dependencies:

• ink = "5.1.1" - Core ink! framework
• parity-scale-codec = "3.6.0" - SCALE encoding/decoding
• scale-info = "2.11.6" - Type information for ink! contracts

Usage

Contract Deployment

After building, you can deploy the contract to a Substrate-based blockchain:

# Build the contract
cargo build --release

# The compiled contract will be available in target/ink/

Core Functions

Create Loan

create_loan(
    amount: Balance,        // Loan amount
    interest_rate: u16,     // Interest rate in basis points (500 = 5%)
    duration: u64,          // Loan duration in blocks
    collateral: Balance     // Collateral amount
) -> Result<u64, LendingError>

Fund Loan

fund_loan(loan_id: u64) -> Result<(), LendingError>

Repay Loan

repay_loan(loan_id: u64) -> Result<(), LendingError>

Early Repay Loan (with Discount)

early_repay_loan(loan_id: u64) -> Result<(), LendingError>

Partial Repay Loan

partial_repay_loan(loan_id: u64) -> Result<(), LendingError>

Extend Loan

extend_loan(loan_id: u64, extension_duration: u64) -> Result<(), LendingError>

Apply Late Fees

apply_late_fees(loan_id: u64) -> Result<(), LendingError>

Refinance Loan

refinance_loan(loan_id: u64, new_interest_rate: u16, new_duration: u64) -> Result<(), LendingError>

Variable Interest Rate Management

adjust_interest_rate(loan_id: u64, new_base_rate: u16, reason: RateAdjustmentReason) -> Result<(), LendingError>
update_risk_multiplier(loan_id: u64, new_risk_multiplier: u16) -> Result<(), LendingError>
convert_to_variable_rate(loan_id: u64, new_base_rate: u16) -> Result<(), LendingError>

Query Functions

get_loan(loan_id: u64) -> Option<Loan>
get_user_profile(user: AccountId) -> Option<UserProfile>
get_total_loans() -> u64
get_total_liquidity() -> Balance
get_early_repayment_discount(loan_id: u64) -> Result<u16, LendingError>
get_loan_payment_info(loan_id: u64) -> Result<(Balance, Balance, Vec<PartialPayment>), LendingError>
get_partial_payment_count(loan_id: u64) -> Result<u32, LendingError>
get_loan_extension_info(loan_id: u64) -> Result<(u32, u32, u16), LendingError>
can_extend_loan(loan_id: u64) -> Result<bool, LendingError>
calculate_extension_fee(loan_id: u64) -> Result<Balance, LendingError>
get_late_fee_info(loan_id: u64) -> Result<(Balance, u16, u16, Option<u64>), LendingError>
calculate_current_late_fees(loan_id: u64) -> Result<Balance, LendingError>
is_loan_overdue(loan_id: u64) -> Result<bool, LendingError>
get_loan_refinance_info(loan_id: u64) -> Result<(u32, u32, u16), LendingError>
can_refinance_loan(loan_id: u64) -> Result<bool, LendingError>
calculate_refinance_fee(loan_id: u64) -> Result<Balance, LendingError>
get_refinance_history(loan_id: u64) -> Result<Vec<RefinanceRecord>, LendingError>

Testing

Currently, the test suite requires updates for ink! 5.x compatibility. The main contract compiles successfully:

# Build the contract (works)
cargo build

# Run tests (requires updates)
cargo test

Security Features

• Input Validation: All inputs are validated before processing
• Access Control: Only authorized users can perform specific actions
• Collateral Requirements: Minimum collateral ratios enforced
• Error Handling: Comprehensive error handling with custom error types
• Event Logging: All operations are logged for transparency

Configuration

The contract includes several configurable parameters:

• protocol_fee: Protocol fee in basis points (default: 50 = 0.5%)
• min_collateral_ratio: Minimum collateral ratio (default: 150 = 150%)
• max_interest_rate: Maximum allowed interest rate (default: 10000 = 100%)

Recent Fixes Applied

The following issues have been resolved:

• ✅ Fixed compilation errors with ink! 5.x compatibility
• ✅ Updated dependencies to use compatible versions
• ✅ Added missing TypeInfo derive macros
• ✅ Fixed type mismatches and import issues
• ✅ Corrected module structure and exports

Next Steps

To complete the project setup:

1. Update test suite for ink! 5.x compatibility
2. Update examples for ink! 5.x compatibility
3. Add comprehensive integration tests
4. Implement additional security features

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests for new functionality
5. Submit a pull request

License

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

Disclaimer

This smart contract is for educational and development purposes. Please conduct thorough testing and security audits before using in production environments.