Complete Example Contract

This page combines everything from the EVM integration guides into a production-ready example: a simple stablecoin-priced vault that accepts deposits, tracks value in USD using IFÁ Labs prices, and includes staleness checks, gas optimizations, and best practices.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.29;

import "ifapricefeed-interface/IIfaPriceFeed.sol";

contract StablecoinVault {
    IIfaPriceFeed public constant ORACLE = IIfaPriceFeed(0xA9F17344689C2c2328F94464998db1d3e35B80dC); // Base Mainnet

    // Common asset IDs (keccak256("SYMBOL/USD"))
    bytes32 public constant USDT_ASSET_ID = 0x6ca0cef6107263f3b09a51448617b659278cff744f0e702c24a2f88c91e65a0d;
    bytes32 public constant USDC_ASSET_ID = 0xf989296bde68043d307a2bc0e59de3445defc5f292eb390b80d78162c8a6b13d;
    bytes32 public constant CNGN_ASSET_ID = 0x83a18c73cf75a028a24b79cbedb3b8d8ba363b748a3210ddbcaa95eec3b87b3a;

    uint256 public constant MAX_STALENESS = 3600; // 1 hour
    uint256 public constant MAX_DEVIATION_BP = 500; // 5% in basis points

    mapping(address => uint256) public balances; // user => USD value (scaled to 18 decimals)

    event Deposit(address indexed user, bytes32 indexed assetId, uint256 amount, uint256 usdValue);
    event Withdraw(address indexed user, uint256 usdValue);

    /**
     * @dev Deposit an amount of a supported stablecoin and credit USD value
     * @param assetId The IFÁ Labs asset ID
     * @param amount Raw token amount (must approve vault first)
     */
    function deposit(bytes32 assetId, uint256 amount, IERC20 token) external {
        int256 usdValue = _getVerifiedPrice(assetId) * int256(amount);

        require(usdValue > 0, "Invalid price");

        uint256 scaledUsd = uint256(usdValue) / 1e18; // Adjust to 18 decimals if needed

        balances[msg.sender] += scaledUsd;

        token.transferFrom(msg.sender, address(this), amount);

        emit Deposit(msg.sender, assetId, amount, scaledUsd);
    }

    /**
     * @dev Internal: Fetch and verify price with staleness + deviation checks
     */
    function _getVerifiedPrice(bytes32 assetId) internal view returns (int256 price) {
        (IIfaPriceFeed.PriceFeed memory info, bool exists) = ORACLE.getAssetInfo(assetId);

        require(exists, "Asset not supported");
        require(block.timestamp - info.lastUpdateTime <= MAX_STALENESS, "Price stale");

        // Deviation check from $1 peg (common for stablecoins)
        int256 deviation = info.price - 1e18;
        if (deviation < 0) deviation = -deviation;
        require(uint256(deviation) <= 1e18 * MAX_DEVIATION_BP / 10000, "Excessive peg deviation");

        return info.price;
    }

    // Additional functions: withdraw, getUserValueUSD, etc.
    // Implement with similar verification
}

Key Features in This Example

• Constants for oracle address and asset IDs → gas savings.

• Verification → existence, staleness, and peg deviation checks.

• Safe math → careful handling of signed prices and scaling.

• Extensible → easy to add batch reads or caching.

This pattern is suitable for lending protocols, vaults, stablecoin swaps, or any price-sensitive application.

This concludes the EVM Smart Contracts integration guides.

Next: Dive into Core Concepts to understand the oracle mechanics under the hood.