/**
 * Developed by The Flowchain Foundation
 */
pragma solidity 0.5.16;

/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;
    address public newOwner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor() public {
        owner = msg.sender;
        newOwner = address(0);
    }

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    modifier onlyNewOwner() {
        require(msg.sender != address(0));
        require(msg.sender == newOwner);
        _;
    }
    
    function isOwner(address account) public view returns (bool) {
        if( account == owner ){
            return true;
        }
        else {
            return false;
        }
    }

    function transferOwnership(address _newOwner) public onlyOwner {
        require(_newOwner != address(0));
        newOwner = _newOwner;
    }

    function acceptOwnership() public onlyNewOwner {
        emit OwnershipTransferred(owner, newOwner);        
        owner = newOwner;
        newOwner = address(0);
    }
}

/**
 * @title Pausable
 * @dev The Pausable can pause and unpause the token transfers.
 */
contract Pausable is Ownable {
    event Paused(address account);
    event Unpaused(address account);

    bool private _paused;

    constructor () public {
        _paused = false;
    }    

    /**
     * @return true if the contract is paused, false otherwise.
     */
    function paused() public view returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     */
    modifier whenNotPaused() {
        require(!_paused);
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     */
    modifier whenPaused() {
        require(_paused);
        _;
    }

    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() public onlyOwner whenNotPaused {
        _paused = true;
        emit Paused(msg.sender);
    }

    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() public onlyOwner whenPaused {
        _paused = false;
        emit Unpaused(msg.sender);
    }
}

library SafeMath {
    function add(uint a, uint b) internal pure returns (uint) {
        uint c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }
    function sub(uint a, uint b) internal pure returns (uint) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }
    function sub(uint a, uint b, string memory errorMessage) internal pure returns (uint) {
        require(b <= a, errorMessage);
        uint c = a - b;

        return c;
    }
    function mul(uint a, uint b) internal pure returns (uint) {
        if (a == 0) {
            return 0;
        }

        uint c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }
    function div(uint a, uint b) internal pure returns (uint) {
        return div(a, b, "SafeMath: division by zero");
    }
    function div(uint a, uint b, string memory errorMessage) internal pure returns (uint) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint c = a / b;

        return c;
    }
}

/**
 * @title The ERC20 tokens
 */
interface IERC20 {
    function totalSupply() external view returns (uint);
    function balanceOf(address account) external view returns (uint);
    function transfer(address recipient, uint amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint);
    function approve(address spender, uint amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint value);
    event Approval(address indexed owner, address indexed spender, uint value);
}

contract Context {
    constructor () internal { }

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }
}

/**
 * @dev The ERC20 standard implementation.
 */
contract ERC20 is Context, IERC20 {
    using SafeMath for uint;

    mapping (address => uint) private _balances;
    mapping (address => mapping (address => uint)) private _allowances;

    uint private _totalSupply;

    function totalSupply() public view returns (uint) {
        return _totalSupply;
    }

    function balanceOf(address account) public view returns (uint) {
        return _balances[account];
    }

    function transfer(address recipient, uint amount) public returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    function allowance(address owner, address spender) public view returns (uint) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint amount) public returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    function increaseAllowance(address spender, uint addedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    function decreaseAllowance(address spender, uint subtractedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    function _transfer(address sender, address recipient, uint amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    function _mint(address account, uint amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    function _burn(address account, uint amount) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    function _approve(address owner, address spender, uint amount) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
}

contract ERC20Detailed is IERC20 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    constructor (string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }

    function name() public view returns (string memory) {
        return _name;
    }

    function symbol() public view returns (string memory) {
        return _symbol;
    }

    function decimals() public view returns (uint8) {
        return _decimals;
    }
}

/**
 * @title Address
 * @dev Check if the address is a contract using eip-1052
 */
library Address {
    function isContract(address account) internal view returns (bool) {
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != 0x0 && codehash != accountHash);
    }
}

library SafeERC20 {
    using SafeMath for uint;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint value) internal {
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

contract DexToken is ERC20, ERC20Detailed, Ownable, Pausable {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint;

    event Freeze(address indexed account);
    event Unfreeze(address indexed account);

    mapping (address => bool) public minters;
    mapping (address => bool) public frozenAccount;

    address public governance;    

    modifier notFrozen(address _account) {
        require(!frozenAccount[_account]);
        _;
    }

    constructor () public ERC20Detailed("Dextoken Governance", "DEXG", 18) {
        governance = msg.sender;
    }

    function transfer(address to, uint value) public notFrozen(msg.sender) whenNotPaused returns (bool) {
        return super.transfer(to, value);
    }   

    function transferFrom(address from, address to, uint value) public notFrozen(from) whenNotPaused returns (bool) {
        return super.transferFrom(from, to, value);
    }

    /**
     * @dev Freeze an user
     * @param account The address of the user who will be frozen
     * @return The result of freezing an user
     */
    function freezeAccount(address account) external onlyOwner returns (bool) {
        require(!frozenAccount[account], "ERC20: account frozen");
        frozenAccount[account] = true;
        emit Freeze(account);
        return true;
    }

    /**
     * @dev Unfreeze an user
     * @param account The address of the user who will be unfrozen
     * @return The result of unfreezing an user
     */
    function unfreezeAccount(address account) external onlyOwner returns (bool) {
        require(frozenAccount[account], "ERC20: account not frozen");
        frozenAccount[account] = false;
        emit Unfreeze(account);
        return true;
    }

    function setGovernance(address _governance) public {
        require(msg.sender == governance, "!governance");
        governance = _governance;
    }

    /**
     * @dev Setup the address that can mint tokens
     * @param minter The address of the minter
     * @return The result of the setup
     */
    function addMinter(address minter) external returns (bool success) {
        require(msg.sender == governance, "!governance");    
        minters[minter] = true;
        return true;
    }

    /**
     * @dev Remove the address from minters
     * @param minter The address of the minter
     * @return The result of the setup
     */
    function removeMinter(address minter) external returns (bool success) {
        require(msg.sender == governance, "!governance");
        minters[minter] = false;
        return true;
    }

    /**
     * @dev Mint an amount of tokens and transfer to the user
     * @param account The address of the user who will receive the tokens
     * @param amount The amount of tokens
     * @return The result of token minting
     */
    function mint(address account, uint amount) external returns (bool success) {
        require(minters[msg.sender], "!minter");    
        _mint(account, amount);
        return true;
    }

    /**
     * @dev Burn an amount of tokens
     * @param account The address of the wallet
     * @param amount The amount of tokens to burn
     * @return The result of token burning
     */
    function burn(address account, uint amount) external returns (bool success) {
        require(msg.sender == governance, "!governance");    
        _burn(account, amount);
        return true;
    }    
}

{
  "compilationTarget": {
    "DexToken.sol": "DexToken"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}