contract ERC20Interface {

	string public constant name = "Token Name";
	string public constant symbol = "SYM";
	uint8 public constant decimals = 18;  // 18 is the most common number of decimal places

	function totalSupply() public constant returns (uint);
	function balanceOf(address tokenOwner) public constant returns (uint balance);
	function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
	function transfer(address to, uint tokens) public returns (bool success);
	function approve(address spender, uint tokens) public returns (bool success);
	function transferFrom(address from, address to, uint tokens) public returns (bool success);

	event Transfer(address indexed from, address indexed to, uint tokens);
	event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}

pragma solidity ^0.4.16;


interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) public; }

//noinspection ALL contract TokenERC20 {
string public name;
string public symbol;
uint8 public decimals = 18;  // decimals 可以有的小数点个数，最小的代币单位。18 是建议的默认值
uint256 public totalSupply;

// 用mapping保存每个地址对应的余额
mapping (address => uint256) public balanceOf;
// 存储对账号的控制
mapping (address => mapping (address => uint256)) public allowance;

// 事件，用来通知客户端交易发生
event Transfer(address indexed from, address indexed to, uint256 value);

// 事件，用来通知客户端代币被消费
event Burn(address indexed from, uint256 value);

/**
 * 初始化构造
 */
function TokenERC20(uint256 initialSupply, string tokenName, string tokenSymbol) public {

	totalSupply = initialSupply * 10 ** uint256(decimals);  // 供应的份额，份额跟最小的代币单位有关，份额 = 币数 * 10 ** decimals。
	balanceOf[msg.sender] = totalSupply;                // 创建者拥有所有的代币
	name = tokenName;                                   // 代币名称
	symbol = tokenSymbol;                               // 代币符号
}

/**
 * 代币交易转移的内部实现
 */
function _transfer(address _from, address _to, uint _value) internal {
	// 确保目标地址不为0x0，因为0x0地址代表销毁
	require(_to != 0x0);
	// 检查发送者余额
	require(balanceOf[_from] >= _value);
	// 溢出检查
	require(balanceOf[_to] + _value > balanceOf[_to]);

	// 以下用来检查交易，
	uint previousBalances = balanceOf[_from] + balanceOf[_to];
	// Subtract from the sender
	balanceOf[_from] -= _value;
	// Add the same to the recipient
	balanceOf[_to] += _value;
	Transfer(_from, _to, _value);

	// 用assert来检查代码逻辑。
	assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
}

/**
 *  代币交易转移
 * 从自己（创建交易者）账号发送`_value`个代币到 `_to`账号
 *
 * @param _to 接收者地址
 * @param _value 转移数额
 */
function transfer(address _to, uint256 _value) public {
	_transfer(msg.sender, _to, _value);
}

/**
 * 账号之间代币交易转移
 * @param _from 发送者地址
 * @param _to 接收者地址
 * @param _value 转移数额
 */
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
	require(_value <= allowance[_from][msg.sender]);     // Check allowance
	allowance[_from][msg.sender] -= _value;
	_transfer(_from, _to, _value);
	return true;
}

/**
 * 设置某个地址（合约）可以创建交易者名义花费的代币数。
 *
 * 允许发送者`_spender` 花费不多于 `_value` 个代币
 *
 * @param _spender The address authorized to spend
 * @param _value the max amount they can spend
 */
function approve(address _spender, uint256 _value) public
returns (bool success) {
	allowance[msg.sender][_spender] = _value;
	return true;
}

/**
 * 设置允许一个地址（合约）以我（创建交易者）的名义可最多花费的代币数。
 *
 * @param _spender 被授权的地址（合约）
 * @param _value 最大可花费代币数
 * @param _extraData 发送给合约的附加数据
 */
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
	public
	returns (bool success) {
		tokenRecipient spender = tokenRecipient(_spender);
		if (approve(_spender, _value)) {
			// 通知合约
			spender.receiveApproval(msg.sender, _value, this, _extraData);
			return true;
		}
	}

/**
 * 销毁我（创建交易者）账户中指定个代币
 */
function burn(uint256 _value) public returns (bool success) {
	require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
	balanceOf[msg.sender] -= _value;            // Subtract from the sender
	totalSupply -= _value;                      // Updates totalSupply
	Burn(msg.sender, _value);
	return true;
}

/**
 * 销毁用户账户中指定个代币
 *
 * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
 *
 * @param _from the address of the sender
 * @param _value the amount of money to burn
 */
function burnFrom(address _from, uint256 _value) public returns (bool success) {
	require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
	require(_value <= allowance[_from][msg.sender]);    // Check allowance
	balanceOf[_from] -= _value;                         // Subtract from the targeted balance
	allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
	totalSupply -= _value;                              // Update totalSupply
	Burn(_from, _value);
	return true;
}
}

library SafeMath {

	/* 加法 */
	function add(uint a, uint b) internal pure returns (uint) {
		uint256 c = a + b;
		assert(c >= a);
		return c;
	}

	/* 减法 */
	function sub(uint a, uint b) internal pure returns (uint) {
		assert(b <= a);
		return a - b;
	}

	/* 乘法 */
	function mul(uint a, uint b) internal pure returns (uint) {
		if (a == 0) {
			return 0;
		}
		uint c = a * b;
		assert(c / a == b);
		return c;
	}

	/* 除法 */
	function div(uint a, uint b) internal pure returns (uint) {
		uint c = a / b;
		return c;
	}

}

// 声明 token 合约接口
interface token {
	function transfer(address receiver, uint amount) external;
	function decimals() external returns(uint);
}

/**
 * crowd funds contract
 */
contract CrowdFunds {

    /* 导入安全运算库 */
    using SafeMath for uint;

    // 受益人地址
    address public beneficiary;
    // 众筹的目标金额，单位为 1 ehter
    uint public targetFunds;
    // 募资截止日期
    uint public deadline;
    // 代币价格，单位为 1 ether
    uint public price;
    // 预售代币合约地址
    token public tokenReward;
    // 是否完成众筹目标
    bool public reachedGoal = false;
    // 众筹是否结束
    bool public isCrowdClosed = false;
    // 已经募集的资金数量
    uint public fundsRaisedTotal = 0;
    // 记录每个投资者贡献了多少资金，单(wei)
    mapping(address => uint) public balanceOf;

    /**
    * 事件可以用来跟踪信息
    **/
    event GoalReached(address recipient, uint totalAmountRaised);
    event FundTransfer(address investor, uint amount, bool isContribution);
    event InvestorWithdraw(address investor, uint amount, bool success); // 投资人提现事件
    event BeneficiaryWithdraw(address beneficiary, uint amount, bool success); // 受益人提现事件



    modifier afterDeadline {
        require(now > deadline);
        _;
    }

    modifier beforeDeadline {
        require(now <= deadline);
        _;
    }

    constructor(
        address _beneficiary,
        uint _targetFunds,
        uint _duration,
        uint _price,
        address _tokenAddress
    ) public {

        beneficiary = _beneficiary;
        targetFunds = _targetFunds * 1 ether;
        deadline = now + _duration * 1 minutes;
        price = _price * 1 finney;
        tokenReward = token(_tokenAddress);
    }

    /**
     * 无函数名的Fallback函数，这里必须在众筹截止日期之前充值才有效
     * 在向合约转账时，这个函数会被调用
     */
    function () payable beforeDeadline public {
        require(!isCrowdClosed); // 判断众筹是否结束
        require(!reachedGoal); // 判断众筹是否达标

        // 计算购买的 token 数量
        uint amount = msg.value;
        // 这里需要注意要乘以 token 的 decimals, 否则会发现众筹得到的代币数量不对
        uint tokenDecimal = tokenReward.decimals();
        uint tokenNum = (amount / price) * 10 ** tokenDecimal;
        balanceOf[msg.sender] = balanceOf[msg.sender].add(amount);
        fundsRaisedTotal = fundsRaisedTotal.add(amount);

        // 众筹达标
        if (fundsRaisedTotal >= targetFunds) {
            reachedGoal = true;
            isCrowdClosed = true; //关闭众筹
            // 发送事件，记录日志
            emit GoalReached(beneficiary, fundsRaisedTotal);
        }
        // 发送代币
        tokenReward.transfer(msg.sender, tokenNum);
        emit FundTransfer(msg.sender, amount, true);
    }


    /**
     * 提现
     */
    function withdraw() afterDeadline public {

        //众筹没有成功，则把投资人款项退还
        if (!reachedGoal) {
            uint amout = balanceOf[msg.sender];

            if (amout > 0 && msg.sender.send(balanceOf[msg.sender])) {
                balanceOf[msg.sender] = 0;
                emit InvestorWithdraw(msg.sender, amout, true);
                // 发送事件, 记录日志
            } else {
                balanceOf[msg.sender] = amout;
                emit InvestorWithdraw(msg.sender, amout, false);
            }
        } else { //众筹成功 ，受益人把钱提走

            if (msg.sender == beneficiary && beneficiary.send(fundsRaisedTotal)) {
                emit BeneficiaryWithdraw(beneficiary, fundsRaisedTotal, true);
            } else {
                emit BeneficiaryWithdraw(msg.sender, fundsRaisedTotal, false);
            }

        }

    }

}

// 计算购买的 token 数量
uint amount = msg.value;
// 这里需要注意要乘以 token 的 decimals, 否则会发现众筹得到的代币数量不对
uint tokenDecimal = tokenReward.decimals();
uint tokenNum = (amount / price) * 10 ** tokenDecimal;
balanceOf[msg.sender] = balanceOf[msg.sender].add(amount);
fundsRaisedTotal = fundsRaisedTotal.add(amount);