// ----------------------------------------------------------------------------
// NED smart contract
// ----------------------------------------------------------------------------


// SPDX-License-Identifier: unlicensed
pragma solidity 0.8.4;
// ----------------------------------------------------------------------------
// Safe math
// ----------------------------------------------------------------------------
contract SafeMath {
    function safeAdd(uint a, uint b) public pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }
    function safeSub(uint a, uint b) public pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }
}
// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
// ----------------------------------------------------------------------------
abstract contract ERC20Interface {
    function totalSupply() virtual public view returns (uint);
    function balanceOf(address tokenOwner) virtual public view returns (uint balance);
    function allowance(address tokenOwner, address spender) virtual public view returns (uint remaining);
    function transfer(address to, uint tokens) virtual public returns (bool success);
    function approve(address spender, uint tokens) virtual public returns (bool success);
    function transferFrom(address from, address to, uint tokens) virtual public returns (bool success);
    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}
// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals
// assisted token transfers
// ----------------------------------------------------------------------------
contract Ned is ERC20Interface, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;
    address public fundsWallet = 0xf6eF12a7a3141695368C9a8204c47034557797af; // address where tokens will arrive to after the contract's deployment
    address public adminWallet = 0xf6eF12a7a3141695368C9a8204c47034557797af;
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;
    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    constructor() {
        symbol = "NED";
        name = "NED";
        decimals = 18;
        _totalSupply = 10000000000000000000000000000; // 10B
        balances[fundsWallet] = _totalSupply;
        emit Transfer(address(0), fundsWallet, _totalSupply); // when deployed, transfer all tokens to fundsWallet
    }

    // ------------------------------------------------------------------------
    // Check whether the deployer is admin
    // ------------------------------------------------------------------------
   modifier Admin(){
        require(msg.sender == fundsWallet || msg.sender == adminWallet);
        _;
    }

    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public override view returns (uint) {
        return _totalSupply - balances[address(0)];
    }
    // ------------------------------------------------------------------------
    // Get the token balance for account tokenOwner
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public override view returns (uint balance) {
        return balances[tokenOwner];
    }
    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to receiver account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transfer(address receiver, uint tokens) public override returns (bool success) {
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[receiver] = safeAdd(balances[receiver], tokens);
        emit Transfer(msg.sender, receiver, tokens);
        return true;
    }
    // ------------------------------------------------------------------------
    // Token owner can approve for spender to transferFrom(...) tokens
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public override returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }
    // ------------------------------------------------------------------------
    // Transfer tokens from sender account to receiver account
    //
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from sender account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transferFrom(address sender, address receiver, uint tokens) public override returns (bool success) {
        balances[sender] = safeSub(balances[sender], tokens);
        allowed[sender][msg.sender] = safeSub(allowed[sender][msg.sender], tokens);
        balances[receiver] = safeAdd(balances[receiver], tokens);
        emit Transfer(sender, receiver, tokens);
        return true;
    }
    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public override view returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }
    // ------------------------------------------------------------------------
    // Standart burn function
    // ------------------------------------------------------------------------
    function burn(uint256 amount) payable Admin external {
    _burn(msg.sender, amount);
    }

  function _burn(address account, uint256 amount) internal {
    require(amount != 0);
    require(amount <= balances[account]);
    _totalSupply = safeSub(_totalSupply ,amount);
    balances[account] = safeSub(balances[account], amount);
    emit Transfer(account, address(0), amount);
  }

  function burnFrom(address account, uint256 amount) payable Admin external {
    require(amount <= allowed[account][msg.sender]);
    allowed[account][msg.sender] = safeSub(allowed[account][msg.sender], amount);
    _burn(account, amount);
  }

}