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FundMe — Chainlink ETH/USD Funding Contract

This project implements a simple Ethereum smart contract called FundMe, which allows users to fund the contract in ETH — but only if their contribution exceeds a minimum USD value (determined via Chainlink price feeds). It includes scripts and a Makefile for deployment, testing, and interaction using Foundry and the cast CLI.

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Features

• Accepts ETH funding only if it exceeds $5 (using Chainlink ETH/USD oracle)
• Keeps track of who funded and how much
• Owner-only withdrawal mechanism
• Tested using Foundry's Forge framework
• Easily deployable to local or Sepolia testnet with one command
• Includes Makefile automation for build, test, deploy, fund, withdraw

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Project Structure

.
├── contracts/
│   └── FundMe.sol              # Main contract
│   └── PriceConverter.sol      # Library to convert ETH → USD
├── script/
│   └── DeployFundMe.s.sol      # Foundry deploy script
├── test/
│   └── FundMe.t.sol            # Foundry tests (optional)
├── Makefile                    # Project automation
├── foundry.toml                # Foundry config
└── .env                        # Secrets & RPC URLs (not committed)

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Setup

1. Install Foundry

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

2. Clone & Install Dependencies

git clone <your-repo-url>
cd <your-project>
make install

3. Create a .env file

SEPOLIA_RPC_URL=https://sepolia.infura.io/v3/YOUR_PROJECT_ID
ETHERSCAN_API_KEY=YOUR_ETHERSCAN_KEY
ACCOUNT=myDevKey

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Makefile Commands

Command	Description
make build	Compile contracts with Forge
make test	Run all tests
make deploy	Deploy to local anvil node
make deploy-sepolia ARGS="--network sepolia"	Deploy to Sepolia & verify
make fund	Call fund() with 0.002 ETH
make withdraw	Owner withdraws all funds
make anvil	Start local testnet with test mnemonic
make clean	Clean artifacts and cache
make update	Update dependencies
make format	Auto-format all Solidity files

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Deploying

Deploy to Local Anvil (default):

make anvil  # in a separate terminal
make deploy

Deploy to Sepolia:

make deploy-sepolia ARGS="--network sepolia"

Make sure .env has all required variables.

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Interacting with the Contract

After deployment, update the CONTRACT_ADDRESS variable in the Makefile.

Fund Contract

make fund

Withdraw Funds (owner only)

make withdraw

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Security Notes

• The contract enforces funding with a minimum USD value using a Chainlink oracle.
• Only the contract owner (set at deployment) can withdraw funds.
• call is used for withdrawals — reentrancy protection is recommended if extended.

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Example Contract Snippets

function fund() public payable {
    require(
        msg.value.getConversionRate(s_priceFeed) >= MINIMUM_USD,
        "You need to spend more ETH!"
    );
    s_addressToAmountFunded[msg.sender] += msg.value;
    s_funders.push(msg.sender);
}

function withdraw() public onlyOwner {
    for (uint256 i = 0; i < s_funders.length; i++) {
        address funder = s_funders[i];
        s_addressToAmountFunded[funder] = 0;
    }
    s_funders = new address ;
    (bool success, ) = payable(msg.sender).call{value: address(this).balance}("");
    require(success, "Call failed");
}

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📜 License

This project is licensed under the MIT License.

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