Meridian/contracts/core/MeridianToken.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "../interfaces/IReserveAggregator.sol";
import "../interfaces/ICompliance.sol";

/**
 * @title MeridianToken
 * @dev Core token contract implementing the Meridian Protocol Standard
 * @notice Regulated entities can issue tokens backed by reserves with built-in compliance
 */
contract MeridianToken is ERC20, ERC20Permit, AccessControl, Pausable, ReentrancyGuard {
    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
    bytes32 public constant BURNER_ROLE = keccak256("BURNER_ROLE");
    bytes32 public constant COMPLIANCE_ROLE = keccak256("COMPLIANCE_ROLE");
    bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");

    // Reserve and compliance contracts
    IReserveAggregator public reserveAggregator;
    ICompliance public compliance;
    
    // Token metadata
    string public currency; // e.g., "GBP", "USD", "EUR"
    string public issuerName; // e.g., "Meridian LLC", "HSBC"
    uint256 public minimumCollateralRatio; // e.g., 102% = 10200 (basis points * 100)
    
    // Minting controls
    uint256 public dailyMintLimit;
    uint256 public dailyBurnLimit;
    mapping(uint256 => uint256) public dailyMinted; // day => amount minted
    mapping(uint256 => uint256) public dailyBurned; // day => amount burned
    
    // Events
    event Minted(address indexed to, uint256 amount, bytes32 attestationHash);
    event Burned(address indexed from, uint256 amount, bytes32 attestationHash);
    event ReserveAggregatorUpdated(address indexed newAggregator);
    event ComplianceUpdated(address indexed newCompliance);
    event DailyLimitsUpdated(uint256 newMintLimit, uint256 newBurnLimit);
    event MinimumCollateralRatioUpdated(uint256 newRatio);

    /**
     * @dev Constructor sets up the token with initial parameters
     * @param name Token name (e.g., "Meridian GBP")
     * @param symbol Token symbol (e.g., "MGBP")
     * @param _currency Currency denomination (e.g., "GBP")
     * @param _issuerName Name of issuing entity
     * @param _reserveAggregator Address of reserve aggregator contract
     * @param _compliance Address of compliance contract
     * @param _admin Address to receive admin role
     */
    constructor(
        string memory name,
        string memory symbol,
        string memory _currency,
        string memory _issuerName,
        address _reserveAggregator,
        address _compliance,
        address _admin
    ) ERC20(name, symbol) ERC20Permit(name) {
        require(_reserveAggregator != address(0), "Invalid reserve aggregator");
        require(_compliance != address(0), "Invalid compliance contract");
        require(_admin != address(0), "Invalid admin address");
        
        currency = _currency;
        issuerName = _issuerName;
        reserveAggregator = IReserveAggregator(_reserveAggregator);
        compliance = ICompliance(_compliance);
        minimumCollateralRatio = 10200; // 102% default
        
        dailyMintLimit = 10000000 * 10**decimals(); // 10M default
        dailyBurnLimit = 10000000 * 10**decimals(); // 10M default
        
        _grantRole(DEFAULT_ADMIN_ROLE, _admin);
        _grantRole(MINTER_ROLE, _admin);
        _grantRole(BURNER_ROLE, _admin);
        _grantRole(COMPLIANCE_ROLE, _admin);
        _grantRole(PAUSER_ROLE, _admin);
    }

    /**
     * @dev Mint tokens with reserve attestation and compliance checks
     * @param to Address to mint tokens to
     * @param amount Amount to mint
     * @param attestationHash Hash of reserve attestation document
     */
    function mint(
        address to,
        uint256 amount,
        bytes32 attestationHash
    ) external onlyRole(MINTER_ROLE) nonReentrant whenNotPaused {
        require(to != address(0), "Cannot mint to zero address");
        require(amount > 0, "Amount must be positive");
        
        // Check daily mint limit
        uint256 today = block.timestamp / 86400; // days since epoch
        require(dailyMinted[today] + amount <= dailyMintLimit, "Daily mint limit exceeded");
        
        // Check compliance
        require(compliance.isWhitelisted(to), "Recipient not whitelisted");
        require(!compliance.isSanctioned(to), "Recipient is sanctioned");
        
        // Check reserve collateralization after mint
        uint256 newTotalSupply = totalSupply() + amount;
        (uint256 reserveValue, bool isValid) = reserveAggregator.getTotalReserveValue();
        require(isValid, "Reserve data is stale");
        
        uint256 requiredReserves = (newTotalSupply * minimumCollateralRatio) / 10000;
        require(reserveValue >= requiredReserves, "Insufficient reserves for mint");
        
        // Update daily tracking
        dailyMinted[today] += amount;
        
        // Mint tokens
        _mint(to, amount);
        
        emit Minted(to, amount, attestationHash);
    }

    /**
     * @dev Burn tokens with attestation
     * @param from Address to burn tokens from
     * @param amount Amount to burn
     * @param attestationHash Hash of burn attestation document
     */
    function burn(
        address from,
        uint256 amount,
        bytes32 attestationHash
    ) external onlyRole(BURNER_ROLE) nonReentrant whenNotPaused {
        require(from != address(0), "Cannot burn from zero address");
        require(amount > 0, "Amount must be positive");
        require(balanceOf(from) >= amount, "Insufficient balance");
        
        // Check daily burn limit
        uint256 today = block.timestamp / 86400;
        require(dailyBurned[today] + amount <= dailyBurnLimit, "Daily burn limit exceeded");
        
        // Update daily tracking
        dailyBurned[today] += amount;
        
        // Burn tokens
        _burn(from, amount);
        
        emit Burned(from, amount, attestationHash);
    }

    /**
     * @dev Override transfer to include compliance checks
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual override {
        super._beforeTokenTransfer(from, to, amount);
        
        // Skip compliance for minting/burning (handled in mint/burn functions)
        if (from == address(0) || to == address(0)) {
            return;
        }
        
        // Check compliance for regular transfers
        require(!paused(), "Token transfers paused");
        require(compliance.isWhitelisted(to), "Recipient not whitelisted");
        require(!compliance.isSanctioned(from), "Sender is sanctioned");
        require(!compliance.isSanctioned(to), "Recipient is sanctioned");
        
        // Check velocity limits
        require(compliance.checkVelocityLimits(from, amount), "Velocity limit exceeded");
    }

    /**
     * @dev Get current collateralization ratio
     * @return ratio Current ratio in basis points * 100 (e.g., 10200 = 102%)
     * @return isValid Whether the reserve data is current and valid
     */
    function getCurrentCollateralizationRatio() external view returns (uint256 ratio, bool isValid) {
        (uint256 reserveValue, bool _isValid) = reserveAggregator.getTotalReserveValue();
        if (!_isValid || totalSupply() == 0) {
            return (0, false);
        }
        ratio = (reserveValue * 10000) / totalSupply();
        return (ratio, true);
    }

    /**
     * @dev Update reserve aggregator contract
     */
    function updateReserveAggregator(address newAggregator) external onlyRole(DEFAULT_ADMIN_ROLE) {
        require(newAggregator != address(0), "Invalid aggregator address");
        reserveAggregator = IReserveAggregator(newAggregator);
        emit ReserveAggregatorUpdated(newAggregator);
    }

    /**
     * @dev Update compliance contract
     */
    function updateCompliance(address newCompliance) external onlyRole(DEFAULT_ADMIN_ROLE) {
        require(newCompliance != address(0), "Invalid compliance address");
        compliance = ICompliance(newCompliance);
        emit ComplianceUpdated(newCompliance);
    }

    /**
     * @dev Update daily mint/burn limits
     */
    function updateDailyLimits(
        uint256 newMintLimit,
        uint256 newBurnLimit
    ) external onlyRole(DEFAULT_ADMIN_ROLE) {
        dailyMintLimit = newMintLimit;
        dailyBurnLimit = newBurnLimit;
        emit DailyLimitsUpdated(newMintLimit, newBurnLimit);
    }

    /**
     * @dev Update minimum collateral ratio
     */
    function updateMinimumCollateralRatio(uint256 newRatio) external onlyRole(DEFAULT_ADMIN_ROLE) {
        require(newRatio >= 10000, "Ratio must be at least 100%");
        minimumCollateralRatio = newRatio;
        emit MinimumCollateralRatioUpdated(newRatio);
    }

    /**
     * @dev Pause token operations
     */
    function pause() external onlyRole(PAUSER_ROLE) {
        _pause();
    }

    /**
     * @dev Unpause token operations  
     */
    function unpause() external onlyRole(PAUSER_ROLE) {
        _unpause();
    }

    /**
     * @dev Get remaining mint capacity for today
     */
    function getRemainingMintCapacity() external view returns (uint256) {
        uint256 today = block.timestamp / 86400;
        return dailyMintLimit - dailyMinted[today];
    }

    /**
     * @dev Get remaining burn capacity for today
     */
    function getRemainingBurnCapacity() external view returns (uint256) {
        uint256 today = block.timestamp / 86400;
        return dailyBurnLimit - dailyBurned[today];
    }
}