🏗️ Advanced Counter Smart Contract - Starknet Basecamp 13 Final Project

A sophisticated counter smart contract showcasing advanced Starknet development concepts

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🎯 Project Overview

This project demonstrates advanced smart contract development on Starknet using Cairo 1.0, featuring a comprehensive counter contract with ERC20 token integration, ownership patterns, event emission, and comprehensive testing. Built as the final project for Starknet Basecamp 13, it showcases production-ready development practices and real-world blockchain interactions.

✨ Key Highlights

• 🔐 Ownership Control: OpenZeppelin's Ownable pattern for secure access management
• 💰 ERC20 Integration: STRK token payments for premium operations
• 📊 Event-Driven Architecture: Comprehensive event emission for frontend integration
• 🧪 100% Test Coverage: Extensive test suite covering all scenarios
• 🚀 Production Ready: Error handling, security checks, and gas optimization
• 🎨 Modern Frontend: Next.js with TypeScript and Tailwind CSS

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🏗️ Smart Contract Architecture

📋 Contract Interface

#[starknet::interface]
pub trait ICounter<T> {
    fn get_counter(self: @T) -> u32;
    fn increase_counter(ref self: T);
    fn decrease_counter(ref self: T);
    fn set_counter(ref self: T, new_value: u32);
    fn reset_counter(ref self: T);
}

🔧 Core Features

Function	Access Level	Description	Cost
get_counter()	Public	Read current counter value	Free
increase_counter()	Public	Increment counter by 1	Gas only
decrease_counter()	Public	Decrement counter by 1 (with bounds check)	Gas only
set_counter()	Owner Only	Set counter to any value	Gas only
reset_counter()	Public	Reset counter to 0	1 STRK

💎 Advanced Features

🔐 Ownership Pattern

• OpenZeppelin Integration: Secure ownership management
• Owner-Only Functions: set_counter() restricted to contract owner
• Flexible Ownership: Transferrable ownership capabilities

💰 ERC20 Token Integration

• STRK Token Payments: Reset operation requires 1 STRK payment
• Balance Validation: Checks user has sufficient STRK tokens
• Allowance Management: Requires token approval before reset
• Automatic Transfer: STRK sent to contract owner upon reset

📊 Event System

#[derive(Drop, starknet::Event)]
pub struct CounterChanged {
    #[key]
    pub caller: ContractAddress,
    pub old_value: u32,
    pub new_value: u32,
    pub reason: ChangeReason,
}

Event Types:

• Increase: Counter incremented
• Decrease: Counter decremented
• Set: Owner set new value
• Reset: Counter reset with payment

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🧪 Comprehensive Testing

📊 Test Coverage

Test Category	Tests	Coverage
Basic Operations	4	✅ 100%
Access Control	2	✅ 100%
Error Handling	2	✅ 100%
ERC20 Integration	3	✅ 100%
Event Emission	6	✅ 100%

🔍 Test Scenarios

✅ Happy Path Tests

#[test]
fn test_contract_initialization()
fn test_increase_counter()
fn test_decrease_counter_happy_path()
fn test_set_counter_owner()
fn test_reset_counter_success()

❌ Error Path Tests

#[test]
#[should_panic(expected: "Counter cannot be less than 0")]
fn test_decrease_counter_fail_path()

#[test]
#[should_panic]
fn test_set_counter_non_owner()

#[test]
#[should_panic(expected: "Caller does not have enough STARK tokens")]
fn test_reset_counter_insufficient_balance()

#[test]
#[should_panic(expected: "Contract is not allowed to spend the caller's STARK tokens")]
fn test_reset_counter_insufficient_allowance()

🎯 Advanced Testing Features

• Event Spy: Validates all events are emitted correctly
• Address Cheating: Tests different caller addresses
• Balance Manipulation: Tests ERC20 token scenarios
• Multi-Contract Interaction: STRK token approval and transfer testing

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🚀 Quick Start

Prerequisites

• Node.js (v22+)
• Yarn
• Starknet Devnet
• Scarb (v2.11.4)
• Starknet Foundry (v0.46.0)

Installation

# Clone the repository
git clone <your-repo-url>
cd snapp

# Install dependencies
yarn install

# Start local Starknet network
yarn chain

# Deploy contracts (in new terminal)
yarn deploy

# Start frontend (in new terminal)
yarn start

Testing

# Run all tests
yarn test

# Run with coverage
yarn test --coverage

# Run specific test file
yarn test test_counter.cairo

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🏛️ Project Structure

packages/
├── nextjs/                    # Frontend application
│   ├── app/                   # Next.js 13+ app directory
│   ├── components/            # React components
│   ├── hooks/                 # Custom React hooks
│   ├── utils/                 # Utility functions
│   └── contracts/             # Contract ABIs and addresses
└── snfoundry/                 # Smart contract development
    ├── contracts/
    │   ├── src/
    │   │   ├── counter.cairo  # Main counter contract
    │   │   ├── utils.cairo    # Helper functions
    │   │   └── lib.cairo      # Library file
    │   └── tests/
    │       └── test_counter.cairo  # Comprehensive test suite
    └── scripts-ts/            # Deployment scripts

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🔧 Technical Implementation

🏗️ Contract Components

Counter Contract

• Storage: Simple counter state with OpenZeppelin ownership
• Constructor: Initializes counter value and sets owner
• Functions: Five main functions with different access levels

Utility Functions

pub fn strk_address() -> ContractAddress
pub fn strk_to_fri(amount: u256) -> u256

🎨 Frontend Integration

• Scaffold-Stark Hooks: useScaffoldReadContract, useScaffoldWriteContract
• Multi-Write Support: useScaffoldMultiWriteContract for token approval + reset
• Event Monitoring: Real-time event listening and display
• Balance Integration: STRK balance checking and display

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🛡️ Security Features

🔒 Access Control

• Ownership Pattern: Critical functions restricted to owner
• Public Functions: Safe operations available to all users
• Payment Verification: STRK balance and allowance checks

💰 Token Security

• Balance Validation: Prevents insufficient balance operations
• Allowance Checks: Requires explicit token approval
• Atomic Operations: Multi-write transactions ensure consistency

🚨 Error Handling

• Bounds Checking: Prevents counter underflow
• Assert Statements: Clear error messages for failed operations
• Graceful Failures: Proper panic messages for debugging

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📈 Performance & Gas Optimization

• Minimal Storage: Only essential state variables
• Efficient Events: Key-indexed events for easy filtering
• Gas-Efficient Operations: Optimized for Starknet's gas model
• Batch Operations: Multi-write support for complex transactions

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🌐 Network Support

• Starknet Devnet: Local development and testing
• Starknet Sepolia: Testnet deployment
• Starknet Mainnet: Production deployment ready

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🤝 Contributing

This project was developed as part of Starknet Basecamp 13. While it's a final project, contributions and improvements are welcome!

Development Guidelines

1. Testing: All new features must include comprehensive tests
2. Documentation: Update README for any new functionality
3. Code Style: Follow Cairo and TypeScript best practices
4. Security: Review all access controls and token interactions

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📚 Learning Resources

Starknet Development

• Starknet Documentation
• Cairo Book
• Scaffold-Stark

Smart Contract Security

• OpenZeppelin Cairo
• Starknet Security Best Practices

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🏆 Basecamp 13 Achievements

This project demonstrates mastery of:

• ✅ Cairo 1.0 smart contract development
• ✅ OpenZeppelin component integration
• ✅ ERC20 token interaction patterns
• ✅ Event-driven architecture
• ✅ Comprehensive testing with Starknet Foundry
• ✅ Frontend integration with React/Next.js
• ✅ Production deployment practices
• ✅ Security patterns and access control

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📄 License

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

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Built with ❤️ for Starknet Basecamp 13

Starknet • Cairo • Scaffold-Stark