Basic Paywall with ERC20

A gas-optimized smart contract implementation for payment systems that grant access to content or services, such as paywalls or premium subscriptions. The system supports multiple ERC20 tokens and different subscription durations.

Features

• Support for multiple ERC20 tokens
• Monthly and yearly subscription tiers
• Gas-optimized implementation
• Owner-controlled token and price management
• Secure withdrawal system
• Notice: This contract does not implement auto-renewable purchase logic.

Project Structure

├── src/
│   └── BasicPaywallWithERC20.sol    # Main contract
├── script/
│   ├── mocks                
│       └── ERC20DecimalsMock.sol    # ERC20 mock contract with configurable decimals
│   ├── Deploy.s.sol                 # Deployment script
│   └── HelperConfig.s.sol           # Network configurations
├── test/
│   └── integration/                  
│       └── DeployTest.t.sol         # Integration test files
│   └── unit/                        
│       └── BasicPaywallTest.t.sol   # Unit test files
├── docs/
│   └── BasicPaywallWithERC20.md     # Smart Contract documentation
└── Makefile                         # Build and deployment commands
└── foundry.toml                     # Foundry config

Requirements

• Git
  • You'll know you did it right if you can run git --version and see a response like git version x.x.x
• Foundry
  • You'll know you did it right if you can run forge --version and see a response like forge 0.2.0
• Make
  • You'll know you did it right if you can run make --version and see a response like GNU Make 3.81

Installing Foundry

curl -L https://foundry.paradigm.xyz | bash
foundryup

Quick Start

1. Clone the repository:

git clone https://github.com/FcoGomez92/basic-paywall-with-erc20.git
cd basic-paywall-with-erc20

2. Install dependencies:

make all

Development

Build

forge build

Test

forge test

Format

forge fmt

Gas Snapshots

forge snapshot

Local Blockchain

make anvil

Deployment

Configure Deployer Account

1. Import your deployer wallet:

cast wallet import deployer --interactive
# Enter private key when prompted
# Enter password when prompted

2. Create a .env file:

DEPLOYER_ADDRESS=<your-deployer-address>

SEPOLIA_RPC_URL=<your-sepolia-rpc-url>
ARBITRUM_RPC_URL=<your-arbitrum-rpc-url>

ETHERSCAN_API_KEY=<your-etherscan-api-key>
ARBISCAN_API_KEY=<your-arbiscan-api-key>

3. Configure the owner address in script/HelperConfig.s.sol:

address constant OWNER_ACCOUNT = <your-owner-address>; // Replace with actual owner address

Deploy Commands

Local deployment:

make deploy

Sepolia testnet deployment:

make deploySepolia

Arbitrum mainnet deployment:

make deployArbitrum

Contract Architecture

BasicPaywallWithERC20.sol

The main contract implements a subscription-based paywall system with the following key features:

Core Functions

• purchase(address _token, PurchaseDuration duration): Purchase a subscription
• withdrawToken(address _token, uint256 _amount): Withdraw specific amount of tokens
• withdrawAll(): Withdraw all supported tokens
• updatePrices(address token, uint256 _monthPrice, uint256 _yearPrice): Update subscription prices
• addSupportedToken(address token, uint256 monthPrice, uint256 yearPrice): Add new supported token
• removeSupportedToken(address token): Remove supported token

For detailed documentation of all functions, events, errors and more, see the Contract Documentation.

Network Configurations

The HelperConfig.s.sol contract provides configurations for:

• Local development (Anvil)
• Ethereum Sepolia Testnet
• Arbitrum Mainnet

Each network configuration includes:

• USDC and USDT addresses
• Monthly and yearly prices for each token
• Owner address

Adding Support for a New Chain

To add support for a new EVM-compatible chain, follow these steps:

1. Add the RPC URL to your .env file:

NEW_CHAIN_RPC_URL=<your-new-chain-rpc-url>

2. Add the chain configuration to foundry.toml:

[rpc_endpoints]
new_chain = "${NEW_CHAIN_RPC_URL}"

[etherscan]
new_chain = { key = "${NEW_CHAIN_EXPLORER_API_KEY}" }

3. Create a new configuration function in script/HelperConfig.s.sol:

function getNewChainConfig() public pure returns (NetworkConfig memory) {
    return NetworkConfig({
        usdcAddress: <usdc-address-on-new-chain>,
        usdtAddress: <usdt-address-on-new-chain>,
        usdcMonthPrice: USDC_MONTH_PRICE,
        usdtMonthPrice: USDT_MONTH_PRICE,
        usdcYearPrice: USDC_YEAR_PRICE,
        usdtYearPrice: USDT_YEAR_PRICE,
        owner: OWNER_ACCOUNT
    });
}

4. Add the chain ID and configuration to the constructor in script/HelperConfig.s.sol:

uint256 constant NEW_CHAIN_ID = <your-chain-id>;

constructor() {
    // ... existing configurations ...
    networkConfigs[NEW_CHAIN_ID] = getNewChainConfig();
}

5. Add a new deployment command to the Makefile:

deployNewChain : 
	@forge script script/Deploy.s.sol:Deploy --rpc-url new_chain --sender ${DEPLOYER_ADDRESS} --account deployer --broadcast --verify -vvvv

Now you can deploy to the new chain using:

make deployNewChain

License

This project is licensed under the MIT License.

Author

Francisco Gómez

• X: @FcoGomez92_
• GitHub: FcoGomez92