pragma solidity 0.5.11; /*

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=== 'Bitpayer' Token contract with following features ===
    => ERC20 Compliance
    => Higher degree of control by owner - safeguard functionality
    => SafeMath implementation 
    => Burnable and minting 


======================= Quick Stats ===================
    => Name        : Bitpayer Token
    => Symbol      : BPT
    => Total supply: 8,000,000,000 (8 Billion)
    => Decimals    : 9


============= Independant Audit of the code ============
    => Multiple Freelancers Auditors
    => Community Audit by Bug Bounty program


-------------------------------------------------------------------
 Copyright (c) 2019 onwards Bitpayer IO ( https://bitpayer.io )
 Contract designed with ❤ by EtherAuthority ( https://EtherAuthority.io )
-------------------------------------------------------------------
*/ 




//*******************************************************************//
//------------------------ SafeMath Library -------------------------//
//*******************************************************************//
/**
    * @title SafeMath
    * @dev Math operations with safety checks that throw on error
    */
library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0) {
        return 0;
    }
    uint256 c = a * b;
    require(c / a == b, 'SafeMath mul failed');
    return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    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) {
    require(b <= a, 'SafeMath sub failed');
    return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, 'SafeMath add failed');
    return c;
    }
}


//*******************************************************************//
//------------------ Contract to Manage Ownership -------------------//
//*******************************************************************//
    
contract owned {
    address payable public owner;
    address payable internal newOwner;

    event OwnershipTransferred(address indexed _from, address indexed _to);

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

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

    function transferOwnership(address payable _newOwner) public onlyOwner {
        newOwner = _newOwner;
    }

    //this flow is to prevent transferring ownership to wrong wallet by mistake
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}
 

    
//****************************************************************************//
//---------------------        MAIN CODE STARTS HERE     ---------------------//
//****************************************************************************//
    
contract BitpayerToken is owned {
    

    /*===============================
    =         DATA STORAGE          =
    ===============================*/

    // Public variables of the token
    using SafeMath for uint256;
    string constant public name = "Bitpayer Token";
    string constant public symbol = "BPT";
    uint256 constant public decimals = 9;
    uint256 public totalSupply = 8000000000 * (10**decimals);   //8 billion tokens
    uint256 constant public maxSupply = 8000000000 * (10**decimals);   //8 billion tokens
    bool public safeguard = false;  //putting safeguard on will halt all non-owner functions

    // This creates a mapping with all data storage
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    mapping (address => bool) public frozenAccount;


    /*===============================
    =         PUBLIC EVENTS         =
    ===============================*/

    // This generates a public event of token transfer
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);
        
    // This generates a public event for frozen (blacklisting) accounts
    event FrozenAccounts(address target, bool frozen);
    
    // This will log approval of token Transfer
    event Approval(address indexed from, address indexed spender, uint256 value);



    /*======================================
    =       STANDARD ERC20 FUNCTIONS       =
    ======================================*/

    /* Internal transfer, only can be called by this contract */
    function _transfer(address _from, address _to, uint _value) internal {
        
        //checking conditions
        require(!safeguard);
        require (_to != address(0));                      // Prevent transfer to 0x0 address. Use burn() instead
        require(!frozenAccount[_from]);                     // Check if sender is frozen
        require(!frozenAccount[_to]);                       // Check if recipient is frozen
        
        // overflow and undeflow checked by SafeMath Library
        balanceOf[_from] = balanceOf[_from].sub(_value);    // Subtract from the sender
        balanceOf[_to] = balanceOf[_to].add(_value);        // Add the same to the recipient
        
        // emit Transfer event
        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) {
        //no need to check for input validations, as that is ruled by SafeMath
        _transfer(msg.sender, _to, _value);
        
        return true;
    }

    /**
        * Transfer tokens from other address
        *
        * Send `_value` tokens to `_to` in 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] = 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 in 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(!safeguard);
        require(balanceOf[msg.sender] >= _value, "Balance does not have enough tokens");
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }


    /*=====================================
    =       CUSTOM PUBLIC FUNCTIONS       =
    ======================================*/
    
    constructor() public{
        //sending all the tokens to Owner
        balanceOf[owner] = totalSupply;
        
        //firing event which logs this transaction
        emit Transfer(address(0), owner, totalSupply);
    }
    
    function () external payable {
        
    }

    /**
        * 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(!safeguard);
        //checking of enough token balance is done by SafeMath
        balanceOf[msg.sender] = balanceOf[msg.sender].sub(_value);  // Subtract from the sender
        totalSupply = totalSupply.sub(_value);                      // Updates totalSupply
        emit Burn(msg.sender, _value);
        emit Transfer(msg.sender, address(0), _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(!safeguard);
        //checking of allowance and token value is done by SafeMath
        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);
        emit Transfer(_from, address(0), _value);
        return true;
    }
        
    
    /** 
        * @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
        * @param target Address to be frozen
        * @param freeze either to freeze it or not
        */
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        emit  FrozenAccounts(target, freeze);
    }
    
    /** 
        * @notice Create `mintedAmount` tokens and send it to `target`
        * @param target Address to receive the tokens
        * @param mintedAmount the amount of tokens it will receive
        */
    function mintToken(address target, uint256 mintedAmount) onlyOwner public {
		    require(totalSupply + mintedAmount <= maxSupply, "Total supply can not exceed maximum supply of 8,000,000,000");
        balanceOf[target] = balanceOf[target].add(mintedAmount);
        totalSupply = totalSupply.add(mintedAmount);
        emit Transfer(address(0), target, mintedAmount);
    }

        

    /**
        * Owner can transfer tokens from contract to owner address
        *
        * When safeguard is true, then all the non-owner functions will stop working.
        * When safeguard is false, then all the functions will resume working back again!
        */
    
    function manualWithdrawTokens(uint256 tokenAmount) public onlyOwner{
        // no need for overflow checking as that will be done in transfer function
        _transfer(address(this), owner, tokenAmount);
    }
    
    //Just in rare case, owner wants to transfer Ether from contract to owner address
    function manualWithdrawEther()onlyOwner public{
        address(owner).transfer(address(this).balance);
    }
    
    /**
        * Change safeguard status on or off
        *
        * When safeguard is true, then all the non-owner functions will stop working.
        * When safeguard is false, then all the functions will resume working back again!
        */
    function changeSafeguardStatus() onlyOwner public{
        if (safeguard == false){
            safeguard = true;
        }
        else{
            safeguard = false;    
        }
    }
    
    

}