• 🧠 Executive Summary
• 💱 Oracle Integration Logic
• ⚡ Gas Optimization Engineering
• 🛡 Security & Access Control
• 🚀 Deployment & Testing

FundMe is a decentralized application (dApp) designed to solve the volatility problem in crypto crowdfunding.

Traditional crowdfunding accepts fixed ETH amounts (e.g., "Send 1 ETH"). However, if the price of ETH crashes, the project fails. This protocol enforces a Minimum USD Contribution (e.g., $50) by performing real-time cryptographic conversion using Chainlink Aggregators.

Core Value: "Fund in Crypto, Denominate in Fiat."

The core innovation is the Dynamic Price Conversion Library. We utilize modular arithmetic to handle precision loss between Ethereum (18 decimals) and Chainlink Oracles (8 decimals).

graph LR
    User((Funder))
    Contract[FundMe Contract]
    Oracle{Chainlink Oracle}
    Logic{Validation}

    User -- "1. Send ETH (wei)" --> Contract
    Contract -- "2. Request Price" --> Oracle
    Oracle -- "3. Return ETH/USD (8 dec)" --> Contract
    
    Contract -- "4. Normalize to 18 dec" --> Logic
    Logic -- "Check Value >= $50" --> Valid{Result}
    
    Valid -- "Pass" --> Accept[✅ State Update]
    Valid -- "Fail" --> Revert[❌ Revert Tx]

    style Oracle fill:#2d1b4e,stroke:#9d4edd,stroke-width:2px
    style Contract fill:#1a1a1a,stroke:#b298dc
    style Logic fill:#1a1a1a,stroke:#fff

To ensure accuracy, we perform the following conversion:

$$ \text{USD Value} = \frac{\text{ETH Amount (wei)} \times \text{ETH Price (8 decimals)} \times 10^{10}}{10^{18}} $$

• Adjustment: We multiply Chainlink's price by to match Ethereum's 18-decimal standard (wei).

This contract is engineered to minimize OpCode execution costs, saving users significantly on transaction fees.

Unlike simple wallets, FundMe implements strict State Management patterns to prevent re-entrancy or fund theft.

sequenceDiagram
    participant Attacker
    participant Owner
    participant Contract

    Attacker->>Contract: withdraw()
    Note right of Contract: ❌ Revert: NotOwner Error
    Contract-->>Attacker: Transaction Failed

    Owner->>Contract: withdraw()
    Note right of Contract: ✅ Check: i_owner == msg.sender
    
    Contract->>Owner: Transfer All ETH
    Contract->>Contract: Reset Funders Array (New)
    Contract->>Contract: Reset Mappings (0)
    Note left of Contract: State Cleaned Atomically

A clean, modular layout optimized for Foundry development. We support Forked Testing to simulate real Chainlink Oracles on a local blockchain.

FundMe-Contract/
├── src/
│   ├── FundMe.sol           // [CORE] Main crowdfunding logic
│   └── PriceConverter.sol   // [LIB]  Math library for 1e18 precision
├── script/
│   ├── DeployFundMe.s.sol   // [OPS]  Network-aware deployment
│   └── HelperConfig.s.sol   // [CONF] Mocks for local Anvil chains
└── test/
    ├── unit/                // [TEST] Isolated logic checks
    └── integration/         // [TEST] Full funding/withdrawal simulation