contract NETLINK is IERC20, NETLINKStandard, Ownable {
    using SafeMath for uint256;

    string public name = "NETLINK SHARES";
    string public symbol = "NLS";
    uint public decimals = 18;

    uint public chainStartTime; //chain start time
    uint public chainStartBlockNumber; //chain start block number
    uint public stakeStartTime; //stake start time
    uint public stakeMinAge = 1 days; // minimum age for coin age: 1D
    uint public stakeMaxAge = 180 days; // stake age of full weight: 180D

    uint public totalSupply;
    uint public maxTotalSupply;
    uint public totalInitialSupply;

    uint constant MIN_STAKING = 1;  // minium amount of token to stake
    uint constant STAKE_START_TIME = 1576108800;  // 12.12.2019
    uint constant STEP1_ENDTIME = 1591833600;  //  11.06.2020
    uint constant STEP2_ENDTIME = 1607731200;  // 12.12.2020
    uint constant STEP3_ENDTIME = 1623369600;  // 11.06.2021
    uint constant STEP4_ENDTIME = 1639267200; // 12.12.2021
    uint constant STEP5_ENDTIME = 1923264000; // 12.12.2050

    struct Period {
        uint start;
        uint end;
        uint interest;
    }

    mapping (uint => Period) periods;

    mapping(address => bool) public noPOSRewards;

    struct transferInStruct {
        uint128 amount;
        uint64 time;
    }

    mapping(address => uint256) balances;
    mapping(address => mapping (address => uint256)) allowed;
    mapping(address => transferInStruct[]) transferIns;

    event Burn(address indexed burner, uint256 value);

    /**
     * @dev Fix for the ERC20 short address attack.
     */
    modifier onlyPayloadSize(uint size) {
        require(msg.data.length >= size + 4);
        _;
    }

    modifier canPoSMint() {
        require(totalSupply < maxTotalSupply);
        _;
    }

    constructor() public {
        // 50 mil is reserved for POS rewards
        maxTotalSupply = 1500 * 10**23; // 150 Mil.
        totalInitialSupply = 1000 * 10**23; // 100 Mil.

        chainStartTime = now;
        chainStartBlockNumber = block.number;

        balances[msg.sender] = totalInitialSupply;
        totalSupply = totalInitialSupply;

        // 4 periods for 2 years
        stakeStartTime = 1576108800;
        
        periods[0] = Period(STAKE_START_TIME, STEP1_ENDTIME, 65 * 10 ** 18);
        periods[1] = Period(STEP1_ENDTIME, STEP2_ENDTIME, 34 * 10 ** 18);
        periods[2] = Period(STEP2_ENDTIME, STEP3_ENDTIME, 20 * 10 ** 18);
        periods[3] = Period(STEP3_ENDTIME, STEP4_ENDTIME, 134 * 10 ** 16);
        periods[4] = Period(STEP4_ENDTIME, STEP5_ENDTIME, 134 * 10 ** 16);
    }

    function transfer(address _to, uint256 _value) onlyPayloadSize(2 * 32) public returns (bool) {
        if (msg.sender == _to)
            return mint();
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        if (transferIns[msg.sender].length > 0)
            delete transferIns[msg.sender];
        uint64 _now = uint64(now);
        transferIns[msg.sender].push(transferInStruct(uint128(balances[msg.sender]),_now));
        transferIns[_to].push(transferInStruct(uint128(_value),_now));
        return true;
    }

    function totalSupply() public view returns (uint256) {
        return totalSupply;
    }

    function balanceOf(address _owner) constant public returns (uint256 balance) {
        return balances[_owner];
    }

    function transferFrom(address _from, address _to, uint256 _value) onlyPayloadSize(3 * 32) public returns (bool) {
        require(_to != address(0));

        uint256 _allowance = allowed[_from][msg.sender];

        // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
        // require (_value <= _allowance);

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = _allowance.sub(_value);
        emit Transfer(_from, _to, _value);
        if (transferIns[_from].length > 0)
            delete transferIns[_from];
        uint64 _now = uint64(now);
        transferIns[_from].push(transferInStruct(uint128(balances[_from]),_now));
        transferIns[_to].push(transferInStruct(uint128(_value),_now));
        return true;
    }

    function approve(address _spender, uint256 _value) public returns (bool) {
        require((_value == 0) || (allowed[msg.sender][_spender] == 0));

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

    function allowance(address _owner, address _spender) constant public returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

    function mint() canPoSMint public returns (bool) {
        // minimum stake of 1 NLS is required to earn staking.
        if (balances[msg.sender] < MIN_STAKING.mul(1 ether))
            return false;
        if (transferIns[msg.sender].length <= 0)
            return false;

        uint reward = getProofOfStakeReward(msg.sender);
        if (reward <= 0)
            return false;
       
        totalSupply = totalSupply.add(reward);
        balances[msg.sender] = balances[msg.sender].add(reward);
        delete transferIns[msg.sender];
        transferIns[msg.sender].push(transferInStruct(uint128(balances[msg.sender]),uint64(now)));

        emit Transfer(address(0), msg.sender, reward);
        emit Mint(msg.sender, reward);
        return true;
    }

    function getBlockNumber() view public returns (uint blockNumber) {
        blockNumber = block.number.sub(chainStartBlockNumber);
    }

    function coinAge() constant public returns (uint myCoinAge) {
        myCoinAge = getCoinAge(msg.sender,now);
    }

    function annualInterest() constant public returns (uint interest) {        
        uint _now = now;
        interest = periods[getPeriodNumber(_now)].interest;
    }

    function getProofOfStakeReward(address _address) public view returns (uint totalReward) {
        require((now >= stakeStartTime) && (stakeStartTime > 0));
        require(!noPOSRewards[_address]);

        uint _now = now;

        totalReward = 0;
        for (uint i=0; i < getPeriodNumber(_now) + 1; i ++) {
            totalReward += (getCoinAgeofPeriod(_address, i, _now)).mul(periods[i].interest).div(100).div(365);
        }
    }

    function getPeriodNumber(uint _now) public view returns (uint periodNumber) {
        for (uint i = 4; i >= 0; i --) {
            if( _now >= periods[i].start){
                return i;
            }
        }
    }

    function getCoinAgeofPeriod(address _address, uint _pid, uint _now) public view returns (uint _coinAge) {        
        if (transferIns[_address].length <= 0)
            return 0;

        if (_pid < 0 || _pid > 4)
            return 0;

        _coinAge = 0;
        uint nCoinSeconds;
        uint i;

        if (periods[_pid].start < _now && 
            periods[_pid].end >= _now) {
            // calculate the current period
            for (i = 0; i < transferIns[_address].length; i ++) {
                if (uint(periods[_pid].start) > uint(transferIns[_address][i].time) || 
                    uint(periods[_pid].end) <= uint(transferIns[_address][i].time))
                    continue;
                
                nCoinSeconds = _now.sub(uint(transferIns[_address][i].time));
                
                if (nCoinSeconds < stakeMinAge)
                    continue;

                if ( nCoinSeconds > stakeMaxAge )
                    nCoinSeconds = stakeMaxAge;    
                
                nCoinSeconds = nCoinSeconds.sub(stakeMinAge);
                _coinAge = _coinAge.add(uint(transferIns[_address][i].amount) * nCoinSeconds.div(1 days));
            }

        }else{
            // calculate for the ended preriods which user did not claimed
            for (i = 0; i < transferIns[_address].length; i++) {
                if (uint(periods[_pid].start) > uint(transferIns[_address][i].time) || 
                    uint(periods[_pid].end) <= uint(transferIns[_address][i].time))
                    continue;

                nCoinSeconds = (uint(periods[_pid].end)).sub(uint(transferIns[_address][i].time));
                
                if (nCoinSeconds < stakeMinAge)
                    continue;

                if ( nCoinSeconds > stakeMaxAge )
                    nCoinSeconds = stakeMaxAge;

                nCoinSeconds = nCoinSeconds.sub(stakeMinAge);
                _coinAge = _coinAge.add(uint(transferIns[_address][i].amount) * nCoinSeconds.div(1 days));
            }
        }

        _coinAge = _coinAge.div(1 ether);
    }


    function getCoinAge(address _address, uint _now) internal view returns (uint _coinAge) {
        if (transferIns[_address].length <= 0)
            return 0;

        for (uint i = 0; i < transferIns[_address].length; i++) {
            if (_now < uint(transferIns[_address][i].time).add(stakeMinAge))
                continue;

            uint nCoinSeconds = _now.sub(uint(transferIns[_address][i].time));
            if ( nCoinSeconds > stakeMaxAge )
                nCoinSeconds = stakeMaxAge;
            
            nCoinSeconds = nCoinSeconds.sub(stakeMinAge);
            _coinAge = _coinAge.add(uint(transferIns[_address][i].amount) * nCoinSeconds.div(1 days));
        }
        _coinAge = _coinAge.div(1 ether);
        // return _coinAge;
    }

    // function ownerSetStakeStartTime(uint timestamp) onlyOwner public {
    //     require((stakeStartTime <= 0) && (timestamp >= chainStartTime));
    //     //stakeStartTime = timestamp;
    //     stakeStartTime = 1537228800
    // }

    function burn(uint256 _value) public {
        require(_value <= balances[msg.sender]);
        // no need to require value <= totalSupply, since that would imply the
        // sender's balance is greater than the totalSupply, which *should* be an assertion failure

        address burner = msg.sender;
        balances[burner] = balances[burner].sub(_value);
        delete transferIns[msg.sender];
        transferIns[msg.sender].push(transferInStruct(uint128(balances[msg.sender]),uint64(now)));
        totalSupply = totalSupply.sub(_value);
        emit Burn(burner, _value);
    }

    /**
    * @dev Burns a specific amount of tokens.
    * @param _value The amount of token to be burned.
    */
    function ownerBurnToken(uint _value) public onlyOwner {
        require(_value > 0);

        balances[msg.sender] = balances[msg.sender].sub(_value);
        delete transferIns[msg.sender];
        transferIns[msg.sender].push(transferInStruct(uint128(balances[msg.sender]),uint64(now)));

        totalSupply = totalSupply.sub(_value);
        totalInitialSupply = totalInitialSupply.sub(_value);
        maxTotalSupply = maxTotalSupply.sub(_value*10);

        emit Burn(msg.sender, _value);
    }

    /* Batch token transfer. Used by contract creator to distribute initial tokens to holders */
    function batchTransfer(address[] _recipients, uint[] _values) onlyOwner public returns (bool) {
        require(_recipients.length > 0 && _recipients.length == _values.length);

        uint total = 0;
        for (uint i = 0; i < _values.length; i++) {
            total = total.add(_values[i]);
        }
        require(total <= balances[msg.sender]);

        uint64 _now = uint64(now);
        for (uint j = 0; j < _recipients.length; j++) {
            balances[_recipients[j]] = balances[_recipients[j]].add(_values[j]);
            transferIns[_recipients[j]].push(transferInStruct(uint128(_values[j]),_now));
            emit Transfer(msg.sender, _recipients[j], _values[j]);
        }

        balances[msg.sender] = balances[msg.sender].sub(total);
        if (transferIns[msg.sender].length > 0)
            delete transferIns[msg.sender];
        if (balances[msg.sender] > 0)
            transferIns[msg.sender].push(transferInStruct(uint128(balances[msg.sender]),_now));

        return true;
    }

    function disablePOSReward(address _account, bool _enabled) onlyOwner public {
        noPOSRewards[_account] = _enabled;
    }
}
function burn(uint256 _value) public {
    require(_value <= balances[msg.sender]);
    // no need to require value <= totalSupply, since that would imply the
    // sender's balance is greater than the totalSupply, which *should* be an assertion failure

    address burner = msg.sender;
    balances[burner] = balances[burner].sub(_value);
    delete transferIns[msg.sender];
    transferIns[msg.sender].push(transferInStruct(uint128(balances[msg.sender]),uint64(now)));
    totalSupply = totalSupply.sub(_value);
    emit Burn(burner, _value);
}

// function ownerSetStakeStartTime(uint timestamp) onlyOwner public {
//     require((stakeStartTime <= 0) && (timestamp >= chainStartTime));
//     //stakeStartTime = timestamp;
//     stakeStartTime = 1537228800
// }