/**
 * Source Code first verified at https://etherscan.io on Sunday, March 17, 2019
 (UTC) */

pragma solidity 0.5.6; /*

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// ----------------------------------------------------------------------------
// 'DlikeToken' contract with following features
//      => ERC20 Compliance
//      => Higher degree of control by owner - safeguard functionality
//      => SafeMath implementation 
//      => Burnable and minting 
//      => in-built buy/sell functions (owner can control buying/selling process)
//
// Name        : DlikeToken
// Symbol      : DLIKE
// Total supply: 800,000,000 (800 Million)
// Decimals    : 18
//
// Copyright 2019 onwards - Dlike ( https://dlike.io )
// Contract designed and audited by EtherAuthority ( https://EtherAuthority.io )
// Special thanks to openzeppelin for inspiration:  ( https://github.com/OpenZeppelin )
// ----------------------------------------------------------------------------
*/ 

//*******************************************************************//
//------------------------ 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;
    assert(c / a == b);
    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) {
    assert(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}


//*******************************************************************//
//------------------ Contract to Manage Ownership -------------------//
//*******************************************************************//
    
contract owned {
    address payable internal owner;
    
     constructor () public {
        owner = msg.sender;
    }

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

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

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

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

    // Public variables of the token
    using SafeMath for uint256;
    string constant public name = "DlikeToken";
    string constant public symbol = "DLIKE";
    uint256 constant public decimals = 18;
    uint256 public totalSupply = 800000000 * (10**decimals);   //800 million tokens
    uint256 public maximumMinting;
    bool public safeguard = false;  //putting safeguard on will halt all non-owner functions
    
    // This creates a mapping with all data storage
    mapping (address => uint256) internal _balanceOf;
    mapping (address => mapping (address => uint256)) internal _allowance;
    mapping (address => bool) internal _frozenAccount;


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

    // This generates a public event of token transfer
    event Transfer(address indexed from, address indexed to, uint256 value);
    
    // This will log approval of token Transfer
    event Approval(address indexed from, address indexed spender, 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 FrozenFunds(address indexed target, bool indexed frozen);



    /*======================================
    =       STANDARD ERC20 FUNCTIONS       =
    ======================================*/
    
    /**
     * Check token balance of any user
     */
    function balanceOf(address owner) public view returns (uint256) {
        return _balanceOf[owner];
    }
    
    /**
     * Check allowance of any spender versus owner
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowance[owner][spender];
    }
    
    /**
     * Check if particular user address is frozen or not
     */
    function frozenAccount(address owner) public view returns (bool) {
        return _frozenAccount[owner];
    }

    /**
     * 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);
        _allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
    
    /**
     * @dev Increase the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To increment
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to increase the _allowance by.
     */
    function increase_allowance(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));

        _allowance[msg.sender][spender] = _allowance[msg.sender][spender].add(value);
        emit Approval(msg.sender, spender, _allowance[msg.sender][spender]);
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To decrement
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to decrease the _allowance by.
     */
    function decrease_allowance(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));

        _allowance[msg.sender][spender] = _allowance[msg.sender][spender].sub(value);
        emit Approval(msg.sender, spender, _allowance[msg.sender][spender]);
        return true;
    }


    /*=====================================
    =       CUSTOM PUBLIC FUNCTIONS       =
    ======================================*/
    
    constructor() public{
        //sending all the tokens to Owner
        _balanceOf[owner] = totalSupply;
        
        //maximum minting set to totalSupply
        maximumMinting = totalSupply;
        
        //firing event which logs this transaction
        emit Transfer(address(0), owner, totalSupply);
    }
    
    /* No need for empty fallback function as contract without it will automatically rejects incoming ether */
    //function () external payable { revert; }

    /**
        * 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);
        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);
        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  FrozenFunds(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 {
        totalSupply = totalSupply.add(mintedAmount);
        //owner can not mint more than max supply of tokens, to prevent 'Evil Mint' issue!!
        require(totalSupply <= maximumMinting, 'Minting reached its maximum minting limit' );
        _balanceOf[target] = _balanceOf[target].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;    
        }
    }

}