// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/utils/ReentrancyGuardUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/utils/PausableUpgradeable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

/**
 * @title YTAssetVault
 * @notice 基于价格的资产金库，用户根据WUSD和YT代币价格进行兑换
 * @dev UUPS可升级合约，YT是份额代币
 */
contract YTAssetVault is 
    Initializable, 
    ERC20Upgradeable,
    UUPSUpgradeable,
    ReentrancyGuardUpgradeable,
    PausableUpgradeable 
{
    using SafeERC20 for IERC20;

    error Forbidden();
    error HardCapExceeded();
    error InvalidAmount();
    error InvalidHardCap();
    error InvalidPrice();
    error InsufficientWUSD();
    error InsufficientYTA();
    error StillInLockPeriod();
    
    /// @notice 工厂合约地址
    address public factory;
    
    /// @notice 管理员地址
    address public manager;
    
    /// @notice YT代币硬顶（最大可铸造的YT数量）
    uint256 public hardCap;
    
    /// @notice 已提取用于管理的WUSD数量
    uint256 public managedAssets;
    
    /// @notice WUSD代币地址
    address public wusdAddress;
    
    /// @notice WUSD价格（精度1e30）
    uint256 public wusdPrice;
    
    /// @notice YT价格（精度1e30）
    uint256 public ytPrice;
    
    /// @notice 价格精度
    uint256 public constant PRICE_PRECISION = 1e30;
    
    /// @notice 下一个赎回开放时间（所有用户统一）
    uint256 public nextRedemptionTime;
    
    event HardCapSet(uint256 newHardCap);
    event ManagerSet(address indexed newManager);
    event AssetsWithdrawn(address indexed to, uint256 amount);
    event AssetsDeposited(uint256 amount);
    event PriceUpdated(uint256 wusdPrice, uint256 ytPrice, uint256 timestamp);
    event Buy(address indexed user, uint256 wusdAmount, uint256 ytAmount);
    event Sell(address indexed user, uint256 ytAmount, uint256 wusdAmount);
    event NextRedemptionTimeSet(uint256 newRedemptionTime);
    
    modifier onlyFactory() {
        if (msg.sender != factory) revert Forbidden();
        _;
    }
    
    modifier onlyManager() {
        if (msg.sender != manager) revert Forbidden();
        _;
    }
    
    /**
     * @notice 初始化金库
     * @param _name YT代币名称
     * @param _symbol YT代币符号
     * @param _manager 管理员地址
     * @param _hardCap 硬顶限制
     * @param _wusd WUSD代币地址（可选，传0则使用默认地址）
     * @param _redemptionTime 赎回时间（Unix时间戳）
     * @param _initialWusdPrice 初始WUSD价格（精度1e30，传0则使用默认值1.0）
     * @param _initialYtPrice 初始YT价格（精度1e30，传0则使用默认值1.0）
     * 
     * @dev 价格精度为1e30
     */
    function initialize(
        string memory _name,
        string memory _symbol,
        address _manager,
        uint256 _hardCap,
        address _wusd,
        uint256 _redemptionTime,
        uint256 _initialWusdPrice,
        uint256 _initialYtPrice
    ) external initializer {
        wusdAddress = _wusd == address(0) 
            ? 0x7Cd017ca5ddb86861FA983a34b5F495C6F898c41 
            : _wusd;
        
        __ERC20_init(_name, _symbol);
        __UUPSUpgradeable_init();
        __ReentrancyGuard_init();
        __Pausable_init();
        
        factory = msg.sender;
        manager = _manager;
        hardCap = _hardCap;
        
        // 使用传入的初始价格，如果为0则使用默认值1.0
        wusdPrice = _initialWusdPrice == 0 ? PRICE_PRECISION : _initialWusdPrice;
        ytPrice = _initialYtPrice == 0 ? PRICE_PRECISION : _initialYtPrice;
        
        // 设置赎回时间
        nextRedemptionTime = _redemptionTime;
    }
    
    /**
     * @notice 授权升级（仅factory可调用）
     * @param newImplementation 新实现合约地址
     */
    function _authorizeUpgrade(address newImplementation) internal override onlyFactory {}
    
    /**
     * @notice 设置硬顶
     * @param _hardCap 新的硬顶值
     */
    function setHardCap(uint256 _hardCap) external onlyFactory {
        if (_hardCap < totalSupply()) revert InvalidHardCap();
        hardCap = _hardCap;
        emit HardCapSet(_hardCap);
    }
    
    /**
     * @notice 设置管理员
     * @param _manager 新管理员地址
     */
    function setManager(address _manager) external onlyFactory {
        manager = _manager;
        emit ManagerSet(_manager);
    }
    
    /**
     * @notice 暂停合约（仅factory可调用）
     * @dev 暂停后，所有资金流动操作将被禁止
     */
    function pause() external onlyFactory {
        _pause();
    }
    
    /**
     * @notice 恢复合约（仅factory可调用）
     */
    function unpause() external onlyFactory {
        _unpause();
    }
    
    /**
     * @notice 设置下一个赎回开放时间（仅factory可调用）
     * @param _nextRedemptionTime 下一个赎回时间（Unix时间戳）
     * @dev 所有用户统一在此时间后才能赎回，类似基金的赎回日
     */
    function setNextRedemptionTime(uint256 _nextRedemptionTime) external onlyFactory {
        nextRedemptionTime = _nextRedemptionTime;
        emit NextRedemptionTimeSet(_nextRedemptionTime);
    }
    
    /**
     * @notice 更新价格（仅manager可调用）
     * @param _wusdPrice WUSD价格（精度1e30）
     * @param _ytPrice YT价格（精度1e30）
     */
    function updatePrices(uint256 _wusdPrice, uint256 _ytPrice) external onlyFactory {
        if (_wusdPrice == 0 || _ytPrice == 0) revert InvalidPrice();
        
        wusdPrice = _wusdPrice;
        ytPrice = _ytPrice;
        
        emit PriceUpdated(_wusdPrice, _ytPrice, block.timestamp);
    }
    
    /**
     * @notice 用WUSD购买YT
     * @param _wusdAmount 支付的WUSD数量
     * @return ytAmount 实际获得的YT数量
     * @dev 首次购买时，YT价格 = WUSD价格（1:1兑换）
     */
    function depositYT(uint256 _wusdAmount) 
        external 
        nonReentrant 
        whenNotPaused
        returns (uint256 ytAmount) 
    {
        if (_wusdAmount == 0) revert InvalidAmount();
        
        // 计算可以购买的YT数量
        ytAmount = (_wusdAmount * wusdPrice) / ytPrice;
        
        // 检查硬顶
        if (hardCap > 0 && totalSupply() + ytAmount > hardCap) {
            revert HardCapExceeded();
        }
        
        // 转入WUSD
        IERC20(wusdAddress).safeTransferFrom(msg.sender, address(this), _wusdAmount);
        
        // 铸造YT
        _mint(msg.sender, ytAmount);
        
        emit Buy(msg.sender, _wusdAmount, ytAmount);
    }
    
    /**
     * @notice 卖出YT换取WUSD（需要等到统一赎回时间）
     * @param _ytAmount 卖出的YT数量
     * @return wusdAmount 实际获得的WUSD数量
     */
    function withdrawYT(uint256 _ytAmount) 
        external 
        nonReentrant 
        whenNotPaused
        returns (uint256 wusdAmount) 
    {
        if (_ytAmount == 0) revert InvalidAmount();
        if (balanceOf(msg.sender) < _ytAmount) revert InsufficientYTA();
        
        // 检查是否到达统一赎回时间
        if (block.timestamp < nextRedemptionTime) {
            revert StillInLockPeriod();
        }
        
        // 计算可以换取的WUSD数量
        wusdAmount = (_ytAmount * ytPrice) / wusdPrice;
        
        // 检查合约是否有足够的WUSD
        uint256 availableWUSD = IERC20(wusdAddress).balanceOf(address(this));
        if (wusdAmount > availableWUSD) revert InsufficientWUSD();
        
        // 销毁YT
        _burn(msg.sender, _ytAmount);
        
        // 转出WUSD
        IERC20(wusdAddress).safeTransfer(msg.sender, wusdAmount);
        
        emit Sell(msg.sender, _ytAmount, wusdAmount);
    }
    
    /**
     * @notice 查询距离下次赎回开放还需等待多久
     * @return remainingTime 剩余时间（秒），0表示可以赎回
     */
    function getTimeUntilNextRedemption() external view returns (uint256 remainingTime) {
        if (block.timestamp >= nextRedemptionTime) {
            return 0;
        }
        return nextRedemptionTime - block.timestamp;
    }
    
    /**
     * @notice 检查当前是否可以赎回
     * @return 是否可以赎回
     */
    function canRedeemNow() external view returns (bool) {
        return block.timestamp >= nextRedemptionTime;
    }
    
    /**
     * @notice 提取WUSD用于外部投资
     * @param _to 接收地址
     * @param _amount 提取数量
     */
    function withdrawForManagement(address _to, uint256 _amount) external onlyManager nonReentrant whenNotPaused {
        if (_amount == 0) revert InvalidAmount();
        
        uint256 availableAssets = IERC20(wusdAddress).balanceOf(address(this));
        if (_amount > availableAssets) revert InvalidAmount();
        
        managedAssets += _amount;
        IERC20(wusdAddress).safeTransfer(_to, _amount);
        
        emit AssetsWithdrawn(_to, _amount);
    }
    
    /**
     * @notice 将管理的资产归还到金库（可以归还更多，产生收益）
     * @param _amount 归还数量
     */
    function depositManagedAssets(uint256 _amount) external onlyManager nonReentrant whenNotPaused {
        if (_amount == 0) revert InvalidAmount();
        
        // 先更新状态（遵循CEI模式）
        if (_amount >= managedAssets) {
            // 归还金额 >= 已管理资产，managedAssets归零，多余部分是收益
            managedAssets = 0;
        } else {
            // 归还金额 < 已管理资产，部分归还
            managedAssets -= _amount;
        }
        
        // 从manager转入WUSD到合约
        IERC20(wusdAddress).safeTransferFrom(msg.sender, address(this), _amount);
        
        emit AssetsDeposited(_amount);
    }
    
    /**
     * @notice 获取总资产（包含被管理的资产）
     * @return 总资产 = 合约余额 + 被管理的资产
     */
    function totalAssets() public view returns (uint256) {
        return IERC20(wusdAddress).balanceOf(address(this)) + managedAssets;
    }
    
    /**
     * @notice 获取空闲资产（可用于提取的资产）
     * @return 合约中实际持有的WUSD数量
     */
    function idleAssets() public view returns (uint256) {
        return IERC20(wusdAddress).balanceOf(address(this));
    }
    
    /**
     * @notice 预览购买：计算支付指定WUSD可获得的YT数量
     * @param _wusdAmount 支付的WUSD数量
     * @return ytAmount 可获得的YT数量
     */
    function previewBuy(uint256 _wusdAmount) external view returns (uint256 ytAmount) {
        ytAmount = (_wusdAmount * wusdPrice) / ytPrice;
    }
    
    /**
     * @notice 预览卖出：计算卖出指定YT可获得的WUSD数量
     * @param _ytAmount 卖出的YT数量
     * @return wusdAmount 可获得的WUSD数量
     */
    function previewSell(uint256 _ytAmount) external view returns (uint256 wusdAmount) {
        wusdAmount = (_ytAmount * ytPrice) / wusdPrice;
    }
    
    /**
     * @notice 获取金库信息
     */
    function getVaultInfo() external view returns (
        uint256 _totalAssets,
        uint256 _idleAssets,
        uint256 _managedAssets,
        uint256 _totalSupply,
        uint256 _hardCap,
        uint256 _wusdPrice,
        uint256 _ytPrice,
        uint256 _nextRedemptionTime
    ) {
        _totalAssets = totalAssets();
        _idleAssets = idleAssets();
        _managedAssets = managedAssets;
        _totalSupply = totalSupply();
        _hardCap = hardCap;
        _wusdPrice = wusdPrice;
        _ytPrice = ytPrice;
        _nextRedemptionTime = nextRedemptionTime;
    }
    
    /**
     * @dev 预留存储空间，用于未来升级时添加新的状态变量
     * 50个slot = 50 * 32 bytes = 1600 bytes
     */
    uint256[50] private __gap;
}