pragma solidity ^0.4.18;

library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a * b;
        assert(a == 0 || c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a / b;
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}

contract Ownable {
    address public owner;

    function Ownable() public {
        owner = msg.sender;
    }

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        owner = newOwner;
    }
}

contract ERC20Basic {
    uint256 public totalSupply;
    function balanceOf(address who) public constant returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
}

contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) public constant returns (uint256);
    function transferFrom(address from, address to, uint256 value) public returns (bool);
    function approve(address spender, uint256 value) public returns (bool);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract PoSTokenStandard {
    uint256 public stakeStartTime;
    uint256 public stakeMinAge;
    uint256 public stakeMaxAge;
    function mint() public returns (bool);
    function coinAge() public view returns (uint256);
    function annualInterest() public constant returns (uint256);
    event Mint(address indexed _address, uint _reward);
}

contract Crescent is ERC20,PoSTokenStandard,Ownable {
    using SafeMath for uint256;

    string public name = "Crescent";
    string public symbol = "CSN";
    uint public decimals = 8;

    uint public chainStartTime;
    uint public chainStartBlockNumber;
    uint public stakeStartTime;
    uint public stakeMinAge = 3 days;
    uint public stakeMaxAge = 90 days;
    uint public maxMintProofOfStake = 10**7;

    uint public totalSupply;
    uint public maxTotalSupply;
    uint public totalInitialSupply;

    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);

    modifier onlyPayloadSize(uint size) {
        require(msg.data.length >= size + 4);
        _;
    }

    modifier canPoSMint() {
        require(totalSupply < maxTotalSupply);
        _;
    }

    function Crescent() public {
        maxTotalSupply = 1100000000000000;
        totalInitialSupply = 135000000000000;

        chainStartTime = now;
        chainStartBlockNumber = block.number;

        balances[msg.sender] = totalInitialSupply;
        totalSupply = totalInitialSupply;
    }

    function transfer(address _to, uint256 _value) public  onlyPayloadSize(2 * 32) returns (bool) {
        if(msg.sender == _to) return mint();
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        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 balanceOf(address _owner) public constant returns (uint256 balance) {
        return balances[_owner];
    }

    function transferFrom(address _from, address _to, uint256 _value) public  onlyPayloadSize(3 * 32) returns (bool) {
        require(_to != address(0));

        var _allowance = allowed[_from][msg.sender];

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = _allowance.sub(_value);
        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;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public  constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

    function mint() public canPoSMint returns (bool) {
        if(balances[msg.sender] <= 0) 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)));

        Mint(msg.sender, reward);
        return true;
    }

    function getBlockNumber() public view returns (uint blockNumber) {
        blockNumber = block.number.sub(chainStartBlockNumber);
    }

    function coinAge() public view returns (uint myCoinAge) {
        myCoinAge = getCoinAge(msg.sender,now);
    }

    function annualInterest() public constant returns(uint interest) {
        uint _now = now;
        interest = maxMintProofOfStake;
        if((_now.sub(stakeStartTime)).div(1 years) == 0) {
            interest = (1650 * maxMintProofOfStake).div(100);
        } else if((_now.sub(stakeStartTime)).div(1 years) == 1) {
            interest = (770 * maxMintProofOfStake).div(100);
        } else if((_now.sub(stakeStartTime)).div(1 years) == 2){
            interest = (435 * maxMintProofOfStake).div(100);
        }
    }

    function getProofOfStakeReward(address _address) public view returns (uint) {
        require( (now >= stakeStartTime) && (stakeStartTime > 0) );

        uint _now = now;
        uint _coinAge = getCoinAge(_address, _now);
        if(_coinAge <= 0) return 0;

        uint interest = maxMintProofOfStake;
        if((_now.sub(stakeStartTime)).div(1 years) == 0) {
            interest = (1650 * maxMintProofOfStake).div(100);
        } else if((_now.sub(stakeStartTime)).div(1 years) == 1) {
            interest = (770 * maxMintProofOfStake).div(100);
        } else if((_now.sub(stakeStartTime)).div(1 years) == 2){
            interest = (435 * maxMintProofOfStake).div(100);
        }

        return (_coinAge * interest).div(365 * (10**decimals));
    }

    function getCoinAge(address _address, uint _now) public 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;

            _coinAge = _coinAge.add(uint(transferIns[_address][i].amount) * nCoinSeconds.div(1 days));
        }
    }

   function ownerSetStakeStartTime(uint timestamp) public onlyOwner {
        require((stakeStartTime <= 0) && (timestamp >= chainStartTime));
        stakeStartTime = timestamp;
    }

}