pragma solidity ^0.4.11;

contract ERC20Interface {
    // Get the total token supply
    function totalSupply() constant returns (uint256);
 
    // Get the account balance of another account with address _owner
    function balanceOf(address _owner) constant returns (uint256 balance);
 
    // Send _value amount of tokens to address _to
    function transfer(address _to, uint256 _value) returns (bool success);
 
    // Send _value amount of tokens from address _from to address _to
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success);
 
    // Allow _spender to withdraw from your account, multiple times, up to the _value amount.
    // If this function is called again it overwrites the current allowance with _value.
    // this function is required for some DEX functionality
    function approve(address _spender, uint256 _value) returns (bool success);
 
    // Returns the amount which _spender is still allowed to withdraw from _owner
    function allowance(address _owner, address _spender) constant returns (uint256 remaining);
 
    // Triggered when tokens are transferred.
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
 
    // Triggered whenever approve(address _spender, uint256 _value) is called.
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}
 
contract DatCoin is ERC20Interface {
    uint8 public constant decimals = 5;
    string public constant symbol = "DTC";
    string public constant name = "DatCoin";

    uint public _totalSupply = 10 ** 14;
    uint public _originalBuyPrice = 10 ** 10;
    uint public _minimumBuyAmount = 10 ** 17;
    uint public _thresholdOne = 9 * (10 ** 13);
    uint public _thresholdTwo = 85 * (10 ** 12);
   
    // Owner of this contract
    address public owner;
 
    // Balances for each account
    mapping(address => uint256) balances;
 
    // Owner of account approves the transfer of an amount to another account
    mapping(address => mapping (address => uint256)) allowed;

    // Functions with this modifier can only be executed by the owner
    modifier onlyOwner() {
        if (msg.sender != owner) {
            revert();
        }
        _;
    }

    modifier thresholdTwo() {
        if (msg.value < _minimumBuyAmount || balances[owner] <= _thresholdTwo) {
            revert();
        }
        _;
    }
 
    // Constructor
    function DatCoin() {
        owner = msg.sender;
        balances[owner] = _totalSupply;
    }
 
    function totalSupply() constant returns (uint256) {
        return _totalSupply;
    }
 
    // What is the balance of a particular account?
    function balanceOf(address _owner) constant returns (uint256) {
        return balances[_owner];
    }
 
    // Transfer the balance from sender's account to another account
    function transfer(address _to, uint256 _amount) returns (bool) {
        if (balances[msg.sender] >= _amount
            && _amount > 0
            && balances[_to] + _amount > balances[_to]) {
            balances[msg.sender] -= _amount;
            balances[_to] += _amount;
            Transfer(msg.sender, _to, _amount);
            return true;
        } else {
            return false;
        }
    }
 
    // Send _value amount of tokens from address _from to address _to
    // The transferFrom method is used for a withdraw workflow, allowing contracts to send
    // tokens on your behalf, for example to "deposit" to a contract address and/or to charge
    // fees in sub-currencies; the command should fail unless the _from account has
    // deliberately authorized the sender of the message via some mechanism; we propose
    // these standardized APIs for approval:
    function transferFrom(
        address _from,
        address _to,
        uint256 _amount
    ) returns (bool) {
        if (balances[_from] >= _amount
            && allowed[_from][msg.sender] >= _amount
            && _amount > 0
            && balances[_to] + _amount > balances[_to]) {
            balances[_from] -= _amount;
            allowed[_from][msg.sender] -= _amount;
            balances[_to] += _amount;
            Transfer(_from, _to, _amount);
            return true;
        } else {
            return false;
        }
    }
 
    // Allow _spender to withdraw from your account, multiple times, up to the _value amount.
    // If this function is called again it overwrites the current allowance with _value.
    function approve(address _spender, uint256 _amount) returns (bool) {
        allowed[msg.sender][_spender] = _amount;
        Approval(msg.sender, _spender, _amount);
        return true;
    }
 
    function allowance(address _owner, address _spender) constant returns (uint256) {
        return allowed[_owner][_spender];
    }
    
    // Buy DatCoin by sending Ether
    function buy() payable thresholdTwo returns (uint256 amount) {
        uint value = msg.value;
        amount = value / _originalBuyPrice;
        
        if (balances[owner] <= _thresholdOne + amount) {
            uint temp = 0;
            if (balances[owner] > _thresholdOne)
                temp = balances[owner] - _thresholdOne;
            amount = temp + (amount - temp) * 10 / 13;
            if (balances[owner] < amount) {
                temp = (amount - balances[owner]) * (_originalBuyPrice * 13 / 10);
                msg.sender.transfer(temp);
                amount = balances[owner];
                value -= temp;
            }
        }

        owner.transfer(value);
        balances[msg.sender] += amount;
        balances[owner] -= amount;
        Transfer(owner, msg.sender, amount);
        return amount;
    }
    
    // Owner withdraws Ether in contract
    function withdraw() onlyOwner returns (bool) {
        return owner.send(this.balance);
    }
}