Cryo Explorer Ethereum Mainnet

//
//  ███████╗██╗  ██╗ █████╗     ██████╗ ██████╗  ██████╗ ████████╗ ██████╗  ██████╗ ██████╗ ██╗
//  ██╔════╝╚██╗██╔╝██╔══██╗    ██╔══██╗██╔══██╗██╔═══██╗╚══██╔══╝██╔═══██╗██╔════╝██╔═══██╗██║
//  █████╗   ╚███╔╝ ███████║    ██████╔╝██████╔╝██║   ██║   ██║   ██║   ██║██║     ██║   ██║██║
//  ██╔══╝   ██╔██╗ ██╔══██║    ██╔═══╝ ██╔══██╗██║   ██║   ██║   ██║   ██║██║     ██║   ██║██║
//  ███████╗██╔╝ ██╗██║  ██║    ██║     ██║  ██║╚██████╔╝   ██║   ╚██████╔╝╚██████╗╚██████╔╝███████╗
//  ╚══════╝╚═╝  ╚═╝╚═╝  ╚═╝    ╚═╝     ╚═╝  ╚═╝ ╚═════╝    ╚═╝    ╚═════╝  ╚═════╝ ╚═════╝ ╚══════╝
//
// Project website: https://www.exaprotocol.com
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// Begin OpenZeppelin Contracts
// To make this a single-file contract, the necessary OpenZeppelin contracts have been inlined.
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 * This is a standard interface and is not expected to change.
 */
interface IERC20 {
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address to, uint256 amount) external returns (bool);
    function allowance(
        address owner,
        address spender
    ) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}

/**
 * @dev Provides information about the current execution context.
 * Useful for meta-transactions.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }
}

/**
 * @dev Contract module for basic access control.
 * The owner is set during construction and can transfer ownership.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    constructor(address initialOwner) {
        require(
            initialOwner != address(0),
            "Ownable: initial owner is the zero address"
        );
        _transferOwnership(initialOwner);
    }

    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    function owner() public view virtual returns (address) {
        return _owner;
    }

    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        _transferOwnership(newOwner);
    }

    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

/**
 * @dev Contract module that allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 */
abstract contract Pausable is Context {
    event Paused(address account);
    event Unpaused(address account);

    bool private _paused;

    constructor() {
        _paused = false;
    }

    modifier whenNotPaused() {
        _requireNotPaused();
        _;
    }

    modifier whenPaused() {
        _requirePaused();
        _;
    }

    function paused() public view virtual returns (bool) {
        return _paused;
    }

    function _requireNotPaused() internal view virtual {
        require(!paused(), "Pausable: paused");
    }

    function _requirePaused() internal view virtual {
        require(paused(), "Pausable: not paused");
    }

    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 */
abstract contract ReentrancyGuard {
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        _status = _NOT_ENTERED;
    }

    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == _ENTERED;
    }
}

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// End OpenZeppelin Contracts
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

/**
 * @title Airdrop
 * @dev This contract facilitates airdropping a specific ERC20 token to a list of addresses.
 * The contract owner can set individual airdrop amounts for each recipient and trigger the airdrop.
 * Tokens are transferred immediately from this contract's balance.
 * The owner should ensure this contract has a sufficient token balance before starting the airdrop.
 *
 * Security features:
 * - Reentrancy protection
 * - Emergency pause mechanism
 * - Gas limit protection via batch size limits
 * - Comprehensive input validation
 * - Proper checks-effects-interactions pattern
 * - Maximum amount validation per recipient
 * - Allows multiple airdrops to same address
 */
contract Airdrop is Ownable, Pausable, ReentrancyGuard {
    // The ERC20 token to be airdropped.
    IERC20 public immutable token;

    // Maximum number of recipients per batch to prevent gas limit issues
    uint256 public constant MAX_BATCH_SIZE = 200;

    // Maximum airdrop amount per recipient to prevent misconfiguration
    // Token has 8 decimal places, so 100 tokens = 100 * 10^8
    uint256 public constant MAX_AIRDROP_AMOUNT = 100 * 10 ** 8; // 100 tokens with 8 decimals

    // Mapping to track total amounts received by each address
    mapping(address => uint256) public totalReceivedByAddress;

    // Total number of successful airdrops executed
    uint256 public totalAirdropsExecuted;

    // Total amount of tokens distributed
    uint256 public totalTokensDistributed;

    // Removed Airdropped event to rely on ERC20 Transfer logs for per-recipient records
    event BatchProcessed(uint256 recipientCount, uint256 totalAmount);
    event EmergencyPaused(address indexed by, string reason);
    event EmergencyUnpaused(address indexed by, string reason);

    /**
     * @dev The contract's constructor.
     * It initializes the contract with the ERC20 token address and sets the owner.
     * @param _tokenAddress The address of the ERC20 token contract (e.g., XAP token).
     */
    constructor(address _tokenAddress) Ownable(msg.sender) {
        require(_tokenAddress != address(0), "Zero token");
        token = IERC20(_tokenAddress);
    }

    /**
     * @dev Airdrops tokens to a list of recipients with individual amounts.
     * The contract must be funded with enough tokens to cover the airdrop.
     * Recipients can receive multiple airdrops.
     * @param _recipients An array of addresses to receive the airdrop.
     * @param _amounts An array of amounts corresponding to each recipient.
     */
    function airdropToWallets(
        address[] calldata _recipients,
        uint256[] calldata _amounts
    ) public onlyOwner whenNotPaused nonReentrant {
        uint256 len = _recipients.length;
        require(len > 0, "Empty recipients");
        require(len == _amounts.length, "Len mismatch");
        require(len <= MAX_BATCH_SIZE, "Too many");

        IERC20 _token = token;

        // Single pass: validate and transfer per recipient
        uint256 successfulTransfers = 0;
        uint256 totalTransferred = 0;

        for (uint256 i = 0; i < len; ) {
            address recipient = _recipients[i];
            uint256 amount = _amounts[i];

            require(recipient != address(0), "Zero addr");
            require(amount > 0, "Zero amt");
            require(amount <= MAX_AIRDROP_AMOUNT, "Exceeds max");

            bool success = _token.transfer(recipient, amount);
            require(success, "Transfer failed");

            totalReceivedByAddress[recipient] += amount;
            successfulTransfers++;
            totalTransferred += amount;
            totalAirdropsExecuted++;
            totalTokensDistributed += amount;

            unchecked {
                ++i;
            }
        }

        emit BatchProcessed(successfulTransfers, totalTransferred);
    }

    /**
     * @dev Allows the owner to withdraw any remaining ERC20 tokens from this contract.
     * This is a safety measure to recover funds.
     */
    function withdrawRemainingTokens() public onlyOwner whenNotPaused {
        IERC20 _token = token;
        uint256 remainingBalance = _token.balanceOf(address(this));
        if (remainingBalance > 0) {
            bool success = _token.transfer(owner(), remainingBalance);
            require(success, "Withdraw failed");
        }
    }

    /**
     * @dev Emergency function to pause the contract.
     * Can only be called by the owner.
     * @param reason The reason for pausing the contract.
     */
    function pause(string calldata reason) public onlyOwner {
        _pause();
        emit EmergencyPaused(msg.sender, reason);
    }

    /**
     * @dev Function to unpause the contract.
     * Can only be called by the owner.
     * @param reason The reason for unpausing the contract.
     */
    function unpause(string calldata reason) public onlyOwner {
        _unpause();
        emit EmergencyUnpaused(msg.sender, reason);
    }

    /**
     * @dev Returns the current contract balance of the airdrop token.
     * @return The current token balance of this contract.
     */
    function getContractTokenBalance() public view returns (uint256) {
        return token.balanceOf(address(this));
    }

    /**
     * @dev Returns the total amount of tokens received by a specific address.
     * @param _recipient The address to check.
     * @return The total amount of tokens received by the address.
     */
    function getTotalReceivedByAddress(
        address _recipient
    ) public view returns (uint256) {
        require(_recipient != address(0), "Zero addr");
        return totalReceivedByAddress[_recipient];
    }

    /**
     * @dev Checks if an address has received any airdrops (backward compatibility).
     * @param _recipient The address to check.
     * @return Whether the address has received any airdrops.
     */
    function hasAddressReceivedAirdrop(
        address _recipient
    ) public view returns (bool) {
        require(_recipient != address(0), "Zero addr");
        return totalReceivedByAddress[_recipient] > 0;
    }

    /**
     * @dev Calculates the total tokens required for a batch of recipients with their amounts.
     * Only accessible by owner to prevent information disclosure.
     * @param _recipients The array of recipient addresses.
     * @param _amounts The array of amounts for each recipient.
     * @return totalRequired The total amount of tokens needed.
     * @return validCount The number of valid recipients.
     */
    function calculateBatchRequirement(
        address[] calldata _recipients,
        uint256[] calldata _amounts
    )
        public
        view
        onlyOwner
        returns (uint256 totalRequired, uint256 validCount)
    {
        uint256 len = _recipients.length;
        require(len > 0, "Empty");
        require(len == _amounts.length, "Len mismatch");
        require(len <= MAX_BATCH_SIZE, "Too many");

        for (uint256 i = 0; i < len; ) {
            address recipient = _recipients[i];
            uint256 amount = _amounts[i];

            if (
                recipient != address(0) &&
                amount > 0 &&
                amount <= MAX_AIRDROP_AMOUNT
            ) {
                totalRequired += amount;
                validCount++;
            }

            unchecked {
                ++i;
            }
        }
    }

    /**
     * @dev Returns the maximum allowed airdrop amount per recipient.
     * @return The maximum airdrop amount constant.
     */
    function getMaxAirdropAmount() public pure returns (uint256) {
        return MAX_AIRDROP_AMOUNT;
    }

    /**
     * @dev Returns the maximum batch size for airdrops.
     * @return The maximum batch size constant.
     */
    function getMaxBatchSize() public pure returns (uint256) {
        return MAX_BATCH_SIZE;
    }

    /**
     * @dev Checks if the contract has sufficient balance for a specific total amount.
     * @param _totalAmount The total amount needed.
     * @return Whether the contract has sufficient balance.
     */
    function hasSufficientBalance(
        uint256 _totalAmount
    ) public view returns (bool) {
        if (_totalAmount == 0) {
            return false;
        }

        return token.balanceOf(address(this)) >= _totalAmount;
    }

    /**
     * @dev Validates that all amounts in an array are within allowed limits.
     * @param _amounts Array of amounts to validate.
     * @return Whether all amounts are valid.
     */
    function validateAmounts(
        uint256[] calldata _amounts
    ) public pure returns (bool) {
        uint256 len = _amounts.length;
        for (uint256 i = 0; i < len; ) {
            if (_amounts[i] == 0 || _amounts[i] > MAX_AIRDROP_AMOUNT) {
                return false;
            }
            unchecked {
                ++i;
            }
        }
        return true;
    }

    /**
     * @dev Returns comprehensive statistics about the airdrop contract.
     * @return contractBalance Current token balance of the contract.
     * @return totalDistributed Total tokens distributed so far.
     * @return totalAirdrops Total number of airdrops executed.
     */
    function getAirdropStatistics()
        public
        view
        returns (
            uint256 contractBalance,
            uint256 totalDistributed,
            uint256 totalAirdrops
        )
    {
        contractBalance = token.balanceOf(address(this));
        totalDistributed = totalTokensDistributed;
        totalAirdrops = totalAirdropsExecuted;
    }

    /**
     * @dev Returns a list of total amounts received by multiple addresses.
     * @param _addresses Array of addresses to check.
     * @return amounts Array of total amounts received by each address.
     */
    function getBatchReceivedAmounts(
        address[] calldata _addresses
    ) public view returns (uint256[] memory amounts) {
        uint256 len = _addresses.length;
        amounts = new uint256[](len);
        for (uint256 i = 0; i < len; ) {
            amounts[i] = totalReceivedByAddress[_addresses[i]];
            unchecked {
                ++i;
            }
        }
    }
}