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

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

/**
 * @title TestUSDT
 * @dev 用于测试环境的 USDT 代币合约
 *
 * 特性:
 * - 6 位小数 (与真实 USDT 一致)
 * - 部署者可以自由 mint
 * - 任何人都可以调用 faucet 获取测试代币
 *
 * 部署到:
 * - BSC Testnet (Chain ID: 97)
 * - KAVA Testnet (Chain ID: 2221)
 */
contract TestUSDT is ERC20, Ownable {
    uint256 public constant FAUCET_AMOUNT = 1000 * 10**6; // 1000 USDT
    uint256 public constant FAUCET_COOLDOWN = 1 hours;

    mapping(address => uint256) public lastFaucetTime;

    constructor() ERC20("Test USDT", "tUSDT") Ownable(msg.sender) {
        // 初始铸造 1,000,000 USDT 给部署者
        _mint(msg.sender, 1_000_000 * 10**6);
    }

    /**
     * @dev 返回 6 位小数 (与真实 USDT 一致)
     */
    function decimals() public pure override returns (uint8) {
        return 6;
    }

    /**
     * @dev Owner 可以铸造任意数量的代币
     */
    function mint(address to, uint256 amount) external onlyOwner {
        _mint(to, amount);
    }

    /**
     * @dev 水龙头: 任何人都可以每小时领取 1000 tUSDT
     */
    function faucet() external {
        require(
            block.timestamp >= lastFaucetTime[msg.sender] + FAUCET_COOLDOWN,
            "Faucet: Please wait 1 hour between requests"
        );

        lastFaucetTime[msg.sender] = block.timestamp;
        _mint(msg.sender, FAUCET_AMOUNT);
    }

    /**
     * @dev 批量空投 (Owner only)
     */
    function airdrop(address[] calldata recipients, uint256 amount) external onlyOwner {
        for (uint256 i = 0; i < recipients.length; i++) {
            _mint(recipients[i], amount);
        }
    }
}