CrowdFunding

 pragma solidity ^0.6.2;

contract Ico {
    
    mapping(address => uint256) amountMap; // 每个用户众筹数量
    uint256 public totalErc20Amount;    // 总分发的ERC20数量
    uint256 public totalEthAmount;   // 众筹的总ETH数量
    uint256 public minValue = 1 ether;    // 最小金额限制
    address payable owner;      // 众筹发起人
    bool status;    // 众筹状态
    ERC20 erc20;
    
    constructor() public{
        owner = msg.sender;
        status = true;
    }
    // 众筹ETH
    function crowdFunding() public payable{
        require(status,"crowd funding is close");       // 确保还在众筹阶段
        require(msg.value >= minValue,"crowd funding value must be > 1 ether");
        amountMap[msg.sender] += msg.value;     // 用户众筹金额增加记录账本
        uint256 beforeTotalEthAmount = totalEthAmount;  // 用来防止溢出攻击
        totalEthAmount += msg.value;    // 总众筹资产增加
        assert(beforeTotalEthAmount <= totalEthAmount); // 防止溢出攻击
    }
    // 项目方获取众筹资产
    function turnOutEth(uint256 _value,address _ercContractAddress) public onlyOwner{
        owner.transfer(address(this).balance);   // 所有众筹ETH转入项目方钱包地址
        erc20 = ERC20(_ercContractAddress);     // 初始化ERC20代币合约
        bool success = erc20.transferFrom(owner,address(this),_value);  // 项目方转入ERC20代币
        require(success,"transferFrom is fail");    // 确保转账成功
        totalErc20Amount = _value;  // 更新用户总分配ERC20数量
        status = false;         // 众筹结束
    }
    //  领取代币
    function turnOutErc() public{
        require(!status,"crowd funding is not close");  // 确保众筹结束
        uint256 turnOutAmount = amountMap[msg.sender] * totalErc20Amount / totalEthAmount; // 计算单个用户能得到的ERC20数量
        bool success = erc20.transfer(msg.sender,turnOutAmount);      // 转出ERC20给用户
        require(success,"transfer is fail");        // 确保转账成功
        amountMap[msg.sender] = 0;  // 预防重复领取
    }
    //  仅限管理员操作
    modifier onlyOwner(){
        require(msg.sender == owner, "No authority");
        _;
    }
}
interface ERC20{
    function transfer(address,uint256) external returns(bool);
    function transferFrom(address,address,uint256) external returns(bool);
}