pragma solidity ^0.4.21;

/**
 * @title SafeMath
 */
library SafeMath {
    /**
    * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    /**
    * @dev Adds two numbers, reverts on overflow.
    */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }
}

interface tokenRecipient {function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external;}

contract TokenERC20 {
    using SafeMath for uint256;
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;
    // the owner of this contract
    address public owner;

    // block list
    mapping(address => bool)   public  frozenAccount;
    // This creates an array with all balances
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This generates a public event on the blockchain that will notify clients
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

    // This notifies contract owner has changed
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    ///@notice check if the msgSender is owner
    modifier onlyOwner{
        require(msg.sender == owner);
        _;
    }
    /**
        reset owner
    **/
    function transferOwnership(address newOwner) public onlyOwner {
    require(newOwner != address(0));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
    }

    /**
     * Constructor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function TokenERC20(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol,
        address tokenOwner
    ) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);
        // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;
        // Give the creator all initial tokens
        name = tokenName;
        // Set the name for display purposes
        symbol = tokenSymbol;
        // Set the symbol for display purposes
        require(tokenOwner != address(0));
        owner = tokenOwner;
    }




    /**
        batch transfer , can only call by owner
    **/
    function batchTransfer(address[] destinations, uint256[] amounts) public returns (bool success){
        require(destinations.length == amounts.length);
        for (uint256 index = 0; index < destinations.length; index++) {
            _transfer(msg.sender, destinations[index], amounts[index]);
        }
        return true;
    }
    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        require(_to != address(0x0));
        require(!frozenAccount[_from]);
        require(!frozenAccount[_to]);
        balanceOf[_from] = balanceOf[_from].sub(_value);
        balanceOf[_to] = balanceOf[_to].add(_value);
        emit Transfer(_from, _to, _value);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public returns (bool success) {
        _transfer(msg.sender, _to, _value);
        return true;
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` on behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);
        // Check allowance
        allowance[_from][msg.sender].sub(_value);
        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens on your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public
    returns (bool success) {
        require(_value == 0 || allowance[msg.sender][_spender] == 0);
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
        freeze account
     **/
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
    }


    /**
     * Set allowance for other address and notify
     *
     * Allows `_spender` to spend no more than `_value` tokens on your behalf, and then ping the contract about it
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     * @param _extraData some extra information to send to the approved contract
     */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData) public returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, this, _extraData);
            return true;
        }
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);
        // Check if the sender has enough
        balanceOf[msg.sender] = balanceOf[msg.sender].sub(_value);
        // Subtract from the sender
        totalSupply = totalSupply.sub(_value);
        // Updates totalSupply
        emit Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balanceOf[_from] >= _value);
        // Check if the targeted balance is enough
        require(_value <= allowance[_from][msg.sender]);
        // Check allowance
        balanceOf[_from] = balanceOf[_from].sub(_value);
        // Subtract from the targeted balance
        allowance[_from][msg.sender] = allowance[_from][msg.sender].sub(_value);
        // Subtract from the sender's allowance
        totalSupply = totalSupply.sub(_value);
        // Update totalSupply
        emit Burn(_from, _value);
        return true;
    }
}