pragma solidity ^0.4.21;
/**
* Math operations with safety checks
*/

library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a / b;
        //assert(a == b * c + a % b); // There is no case in which this doesn't hold
        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 && c>=b);
        return c;
    }
}


contract Ownable {
    address public owner;

    /**
      * @dev The Ownable constructor sets the original `owner` of the contract to the sender
      * account.
      */
    constructor() public {
        owner = msg.sender;
    }

    /**
      * @dev Throws if called by any account other than the owner.
      */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }
    
    /**
    * @dev Fix for the ERC20 short address attack.
    */    
    modifier onlyPayloadSize(uint size) {
        assert(msg.data.length >= size + 4);
        _;
    }
}


contract ARISTO is Ownable{
    using SafeMath for uint;
    string public name;     
    string public symbol;
    uint8 public decimals;  
    uint private _totalSupply;
    uint public basisPointsRate = 0;
    uint public minimumFee = 0;
    uint public maximumFee = 0;

    
    /* This creates an array with all balances */
    mapping (address => uint256) internal balances;
    mapping (address => mapping (address => uint256)) internal allowed;
    
    /* This generates a public event on the blockchain that will notify clients */
    /* notify about transfer to client*/
    event Transfer(
        address indexed from,
        address indexed to,
        uint256 value
    );
    
    /* notify about approval to client*/
    event Approval(
        address indexed _owner,
        address indexed _spender,
        uint256 _value
    );
    
    /* notify about basisPointsRate to client*/
    event Params(
        uint feeBasisPoints,
        uint maximumFee,
        uint minimumFee
    );
    
    // Called when new token are issued
    event Issue(
        uint amount
    );

    // Called when tokens are redeemed
    event Redeem(
        uint amount
    );
    
    /*
        The contract can be initialized with a number of tokens
        All the tokens are deposited to the owner address
        @param _balance Initial supply of the contract
        @param _name Token Name
        @param _symbol Token symbol
        @param _decimals Token decimals
    */
    constructor() public {
        name = 'ARISTO'; // Set the name for display purposes
        symbol = 'ARISTO'; // Set the symbol for display purposes
        decimals = 18; // Amount of decimals for display purposes
        _totalSupply = 20000000 * 10**uint(decimals); // Update total supply
        balances[msg.sender] = _totalSupply; // Give the creator all initial tokens
    }
    
    /*
        @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }
   
    /*
    @dev Gets the balance of the specified address.
    @param owner The address to query the balance of.
    @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view returns (uint256) {
        return balances[owner];
    }
    /*
        @dev transfer token for a specified address
        @param _to The address to transfer to.
        @param _value The amount to be transferred.
    */
    function transfer(address _to, uint256  _value) public onlyPayloadSize(2 * 32){
        //Calculate Fees from basis point rate 
        uint fee = (_value.mul(basisPointsRate)).div(1000);
        if (fee > maximumFee) {
            fee = maximumFee;
        }
        if (fee < minimumFee) {
            fee = minimumFee;
        }
        // Prevent transfer to 0x0 address.
        require (_to != 0x0);
        //check receiver is not owner
        require(_to != address(0));
        //Check transfer value is > 0;
        require (_value > 0); 
        // Check if the sender has enough
        require (balances[msg.sender] > _value);
        // Check for overflows
        require (balances[_to].add(_value) > balances[_to]);
        //sendAmount to receiver after deducted fee
        uint sendAmount = _value.sub(fee);
        // Subtract from the sender
        balances[msg.sender] = balances[msg.sender].sub(_value);
        // Add the same to the recipient
        balances[_to] = balances[_to].add(sendAmount); 
        //Add fee to owner Account
        if (fee > 0) {
            balances[owner] = balances[owner].add(fee);
            emit Transfer(msg.sender, owner, fee);
        }
        // Notify anyone listening that this transfer took place
        emit Transfer(msg.sender, _to, _value);
    }
    
    /*
        @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
        @param _spender The address which will spend the funds.
        @param _value The amount of tokens to be spent.
    */
    function approve(address _spender, uint256 _value) public onlyPayloadSize(2 * 32) returns (bool success) {
        //Check approve value is > 0;
        require (_value > 0);
        //Check balance of owner is greater than
        require (balances[owner] > _value);
        //check _spender is not itself
        require (_spender != msg.sender);
        //Allowed token to _spender
        allowed[msg.sender][_spender] = _value;
        //Notify anyone listening that this Approval took place
        emit Approval(msg.sender,_spender, _value);
        return true;
    }
    
    /*
        @dev Transfer tokens from one address to another
        @param _from address The address which you want to send tokens from
        @param _to address The address which you want to transfer to
        @param _value uint the amount of tokens to be transferred
    */
    function transferFrom(address _from, address _to, uint256 _value) public onlyPayloadSize(2 * 32) returns (bool success) {
        //Calculate Fees from basis point rate 
        uint fee = (_value.mul(basisPointsRate)).div(1000);
        if (fee > maximumFee) {
                fee = maximumFee;
        }
        if (fee < minimumFee) {
            fee = minimumFee;
        }
        // Prevent transfer to 0x0 address. Use burn() instead
        require (_to != 0x0);
        //check receiver is not owner
        require(_to != address(0));
        //Check transfer value is > 0;
        require (_value > 0); 
        // Check if the sender has enough
        require(_value < balances[_from]);
        // Check for overflows
        require (balances[_to].add(_value) > balances[_to]);
        // Check allowance
        require (_value <= allowed[_from][msg.sender]);
        uint sendAmount = _value.sub(fee);
        balances[_from] = balances[_from].sub(_value);// Subtract from the sender
        balances[_to] = balances[_to].add(sendAmount); // Add the same to the recipient
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        if (fee > 0) {
            balances[owner] = balances[owner].add(fee);
            emit Transfer(_from, owner, fee);
        }
        emit Transfer(_from, _to, sendAmount);
        return true;
    }
    
    /*
        @dev Function to check the amount of tokens than an owner allowed to a spender.
        @param _owner address The address which owns the funds.
        @param _spender address The address which will spend the funds.
        @return A uint specifying the amount of tokens still available for the spender.
    */
    function allowance(address _from, address _spender) public view returns (uint remaining) {
        return allowed[_from][_spender];
    }
    
    /*
        @dev Function to set the basis point rate .
        @param newBasisPoints uint which is <= 9.
    */
    function setParams(uint newBasisPoints,uint newMaxFee,uint newMinFee) public onlyOwner {
        // Ensure transparency by hardcoding limit beyond which fees can never be added
        require(newBasisPoints <= 9);
        require(newMaxFee <= 100);
        require(newMinFee <= 5);
        basisPointsRate = newBasisPoints;
        maximumFee = newMaxFee.mul(10**uint(decimals));
        minimumFee = newMinFee.mul(10**uint(decimals));
        emit Params(basisPointsRate, maximumFee, minimumFee);
    }
    /*
    Issue a new amount of tokens
    these tokens are deposited into the owner address
    @param _amount Number of tokens to be issued
    */
    function increaseSupply(uint amount) public onlyOwner {
        require(amount <= 10000000);
        amount = amount.mul(10**uint(decimals));
        require(_totalSupply.add(amount) > _totalSupply);
        require(balances[owner].add(amount) > balances[owner]);
        balances[owner] = balances[owner].add(amount);
        _totalSupply = _totalSupply.add(amount);
        emit Issue(amount);
    }
    /*
    Redeem tokens.
    These tokens are withdrawn from the owner address
    if the balance must be enough to cover the redeem
    or the call will fail.
    @param _amount Number of tokens to be issued
    */
    function decreaseSupply(uint amount) public onlyOwner {
        require(amount <= 10000000);
        amount = amount.mul(10**uint(decimals));
        require(_totalSupply >= amount);
        require(balances[owner] >= amount);
        _totalSupply = _totalSupply.sub(amount);
        balances[owner] = balances[owner].sub(amount);
        emit Redeem(amount);
    }
}