1.額外實(shí)現(xiàn)功能包括代幣和eth的按比例自動(dòng)兌換、賬戶的凍結(jié)鎖定、代幣的增發(fā)、代幣的銷毀等。
2.如果不繼承StandardToken，自己實(shí)現(xiàn)ERC20接口可以在發(fā)布的時(shí)候節(jié)約大概100萬(wàn)gas，該示意繼承了StandardToken
3.必須使用SafeMath庫(kù)防止計(jì)算溢出帶來(lái)的BUG

pragma solidity ^0.4.24;
import 'zeppelin-solidity/contracts/token/ERC20/StandardToken.sol';

// ERC20 standard token
contract JB is StandardToken {
    address public admin; // 管理員
    string public name = "JB Token"; // 代幣名稱
    string public symbol = "JB"; // 代幣符號(hào)
    uint8 public decimals = 18; // 代幣精度
    uint256 public INITIAL_SUPPLY = 8000000000000000000000000000; // 總量80億 *10^18
    // 同一個(gè)賬戶滿足任意凍結(jié)條件均被凍結(jié)
    mapping (address => bool) public frozenAccount; //無(wú)限期凍結(jié)的賬戶
    mapping (address => uint256) public frozenTimestamp; // 有限期凍結(jié)的賬戶

    bool public exchangeFlag = true; // 代幣兌換開啟
    // 不滿足條件或募集完成多出的eth均返回給原賬戶
    uint256 public minWei = 1;  //最低打 1 wei  1eth = 1*10^18 wei
    uint256 public maxWei = 20000000000000000000000; // 最多一次打 20000 eth
    uint256 public maxRaiseAmount = 20000000000000000000000; // 募集上限 20000 eth
    uint256 public raisedAmount = 0; // 已募集 0 eth
    uint256 public raiseRatio = 200000; // 兌換比例 1eth = 20萬(wàn)token
    // event 通知
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Transfer(address indexed from, address indexed to, uint256 value);

    // 構(gòu)造函數(shù)
    constructor() public {
        totalSupply_ = INITIAL_SUPPLY;
        admin = msg.sender;
        balances[msg.sender] = INITIAL_SUPPLY;
    }

    // fallback 向合約地址轉(zhuǎn)賬 or 調(diào)用非合約函數(shù)觸發(fā)
    // 代幣自動(dòng)兌換eth
    function()
    public payable {
        require(msg.value > 0);
        if (exchangeFlag) {
            if (msg.value >= minWei && msg.value <= maxWei){
                if (raisedAmount < maxRaiseAmount) {
                    uint256 valueNeed = msg.value;
                    raisedAmount = raisedAmount.add(msg.value);
                    if (raisedAmount > maxRaiseAmount) {
                        uint256 valueLeft = raisedAmount.sub(maxRaiseAmount);
                        valueNeed = msg.value.sub(valueLeft);
                        msg.sender.transfer(valueLeft);
                        raisedAmount = maxRaiseAmount;
                    }
                    if (raisedAmount >= maxRaiseAmount) {
                        exchangeFlag = false;
                    }
                    // 已處理過精度 *10^18
                    uint256 _value = valueNeed.mul(raiseRatio);

                    require(_value <= balances[admin]);
                    balances[admin] = balances[admin].sub(_value);
                    balances[msg.sender] = balances[msg.sender].add(_value);

                    emit Transfer(admin, msg.sender, _value);

                }
            } else {
                msg.sender.transfer(msg.value);
            }
        } else {
            msg.sender.transfer(msg.value);
        }
    }

    /**
    * 修改管理員
    */
    function changeAdmin(
        address _newAdmin
    )
    public
    returns (bool)  {
        require(msg.sender == admin);
        require(_newAdmin != address(0));
        balances[_newAdmin] = balances[_newAdmin].add(balances[admin]);
        balances[admin] = 0;
        admin = _newAdmin;
        return true;
    }
    /**
    * 增發(fā)
    */
    function generateToken(
        address _target,
        uint256 _amount
    )
    public
    returns (bool)  {
        require(msg.sender == admin);
        require(_target != address(0));
        balances[_target] = balances[_target].add(_amount);
        totalSupply_ = totalSupply_.add(_amount);
        INITIAL_SUPPLY = totalSupply_;
        return true;
    }

    // 從合約提現(xiàn)
    // 只能提給管理員
    function withdraw (
        uint256 _amount
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        msg.sender.transfer(_amount);
        return true;
    }
    /**
    * 鎖定賬戶
    */
    function freeze(
        address _target,
        bool _freeze
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        require(_target != address(0));
        frozenAccount[_target] = _freeze;
        return true;
    }
    /**
    * 通過時(shí)間戳鎖定賬戶
    */
    function freezeWithTimestamp(
        address _target,
        uint256 _timestamp
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        require(_target != address(0));
        frozenTimestamp[_target] = _timestamp;
        return true;
    }

    /**
        * 批量鎖定賬戶
        */
    function multiFreeze(
        address[] _targets,
        bool[] _freezes
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        require(_targets.length == _freezes.length);
        uint256 len = _targets.length;
        require(len > 0);
        for (uint256 i = 0; i < len; i = i.add(1)) {
            address _target = _targets[i];
            require(_target != address(0));
            bool _freeze = _freezes[i];
            frozenAccount[_target] = _freeze;
        }
        return true;
    }
    /**
            * 批量通過時(shí)間戳鎖定賬戶
            */
    function multiFreezeWithTimestamp(
        address[] _targets,
        uint256[] _timestamps
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        require(_targets.length == _timestamps.length);
        uint256 len = _targets.length;
        require(len > 0);
        for (uint256 i = 0; i < len; i = i.add(1)) {
            address _target = _targets[i];
            require(_target != address(0));
            uint256 _timestamp = _timestamps[i];
            frozenTimestamp[_target] = _timestamp;
        }
        return true;
    }
    /**
    * 批量轉(zhuǎn)賬
    */
    function multiTransfer(
        address[] _tos,
        uint256[] _values
    )
    public
    returns (bool) {
        require(!frozenAccount[msg.sender]);
        require(now > frozenTimestamp[msg.sender]);
        require(_tos.length == _values.length);
        uint256 len = _tos.length;
        require(len > 0);
        uint256 amount = 0;
        for (uint256 i = 0; i < len; i = i.add(1)) {
            amount = amount.add(_values[i]);
        }
        require(amount <= balances[msg.sender]);
        for (uint256 j = 0; j < len; j = j.add(1)) {
            address _to = _tos[j];
            require(_to != address(0));
            balances[_to] = balances[_to].add(_values[j]);
            balances[msg.sender] = balances[msg.sender].sub(_values[j]);
            emit Transfer(msg.sender, _to, _values[j]);
        }
        return true;
    }
    /**
    * 從調(diào)用者轉(zhuǎn)賬至_to
    */
    function transfer(
        address _to,
        uint256 _value
    )
    public
    returns (bool) {
        require(!frozenAccount[msg.sender]);
        require(now > frozenTimestamp[msg.sender]);
        require(_to != address(0));
        require(_value <= balances[msg.sender]);

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);

        emit Transfer(msg.sender, _to, _value);
        return true;
    }
    /*
    * 從調(diào)用者作為from代理將from賬戶中的token轉(zhuǎn)賬至to
    * 調(diào)用者在from的許可額度中必須>=value
    */
    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    returns (bool)
    {
        require(!frozenAccount[_from]);
        require(now > frozenTimestamp[msg.sender]);
        require(_to != address(0));
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);

        emit Transfer(_from, _to, _value);
        return true;
    }
    /**
    * 調(diào)整轉(zhuǎn)賬代理方spender的代理的許可額度
    */
    function approve(
        address _spender,
        uint256 _value
    ) public
    returns (bool) {
        // 轉(zhuǎn)賬的時(shí)候會(huì)校驗(yàn)balances，該處require無(wú)意義
        // require(_value <= balances[msg.sender]);

        allowed[msg.sender][_spender] = _value;

        emit Approval(msg.sender, _spender, _value);
        return true;
    }
    /**
    * 增加轉(zhuǎn)賬代理方spender的代理的許可額度
    * 意義不大的function
    */
    function increaseApproval(
        address _spender,
        uint256 _addedValue
    )
    public
    returns (bool)
    {
        // uint256 value_ = allowed[msg.sender][_spender].add(_addedValue);
        // require(value_ <= balances[msg.sender]);
        // allowed[msg.sender][_spender] = value_;

        // emit Approval(msg.sender, _spender, value_);
        return true;
    }
    /**
    * 減少轉(zhuǎn)賬代理方spender的代理的許可額度
    * 意義不大的function
    */
    function decreaseApproval(
        address _spender,
        uint256 _subtractedValue
    )
    public
    returns (bool)
    {
        // uint256 oldValue = allowed[msg.sender][_spender];
        // if (_subtractedValue > oldValue) {
        //    allowed[msg.sender][_spender] = 0;
        // } else {
        //    uint256 newValue = oldValue.sub(_subtractedValue);
        //    require(newValue <= balances[msg.sender]);
        //   allowed[msg.sender][_spender] = newValue;
        //}

        // emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    //********************************************************************************
    //查詢賬戶是否存在鎖定時(shí)間戳
    function getFrozenTimestamp(
        address _target
    )
    public view
    returns (uint256) {
        require(_target != address(0));
        return frozenTimestamp[_target];
    }
    //查詢賬戶是否被鎖定
    function getFrozenAccount(
        address _target
    )
    public view
    returns (bool) {
        require(_target != address(0));
        return frozenAccount[_target];
    }
    //查詢合約的余額
    function getBalance()
    public view
    returns (uint256) {
        return address(this).balance;
    }
    // 修改name
    function setName (
        string _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        name = _value;
        return true;
    }
    // 修改symbol
    function setSymbol (
        string _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        symbol = _value;
        return true;
    }

    // 修改募集flag
    function setExchangeFlag (
        bool _flag
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        exchangeFlag = _flag;
        return true;

    }
    // 修改單筆募集下限
    function setMinWei (
        uint256 _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        minWei = _value;
        return true;

    }
    // 修改單筆募集上限
    function setMaxWei (
        uint256 _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        maxWei = _value;
        return true;
    }
    // 修改總募集上限
    function setMaxRaiseAmount (
        uint256 _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        maxRaiseAmount = _value;
        return true;
    }

    // 修改已募集數(shù)
    function setRaisedAmount (
        uint256 _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        raisedAmount = _value;
        return true;
    }

    // 修改募集比例
    function setRaiseRatio (
        uint256 _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        raiseRatio = _value;
        return true;
    }

    // 銷毀合約
    function kill()
    public {
        require(msg.sender == admin);
        selfdestruct(admin);
    }

}