// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.7.6;

/**
* Ownable, Mintable, Burnable ERC20. 
* Max Supply of 500m (BNB.RUNE Supply)
* 10m RUNE minted on construction. Owner can mint more if needed to control supply. 
* ETH.RUNE is intended only to be a transitionary asset to be upgraded to native THOR.RUNE. 
* Users should not hold ETH.RUNE indefinitely. 
* Owner will be renounced when ETH.RUNE can be upgraded. 
*/

interface iERC20 {
  function totalSupply() external view returns (uint256);
  function decimals() external view returns (uint8);
  function symbol() external view returns (string memory);
  function name() external view returns (string memory);
  function getOwner() external view returns (address);
  function balanceOf(address account) external view returns (uint256);
  function transfer(address recipient, uint256 amount) external returns (bool);
  function allowance(address _owner, address spender) external view returns (uint256);
  function approve(address spender, uint256 amount) external returns (bool);
  function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

library SafeMath {
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, "SafeMath: addition overflow");
    return c;
  }
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    return sub(a, b, "SafeMath: subtraction overflow");
  }
  function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
    require(b <= a, errorMessage);
    uint256 c = a - b;
    return c;
  }
}

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

contract Ownable is Context {
  address private _owner;

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

  constructor () {
    address msgSender = _msgSender();
    _owner = msgSender;
    emit OwnershipTransferred(address(0), msgSender);
  }

  function owner() public view returns (address) {
    return _owner;
  }

  modifier onlyOwner() {
    require(_owner == _msgSender(), "Ownable: caller is not the owner");
    _;
  }

  function renounceOwnership() public onlyOwner {
    emit OwnershipTransferred(_owner, address(0));
    _owner = address(0);
  }

  function transferOwnership(address newOwner) public onlyOwner {
    _transferOwnership(newOwner);
  }

  function _transferOwnership(address newOwner) internal {
    require(newOwner != address(0), "Ownable: new owner is the zero address");
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
  }
}

contract ETH_RUNE is iERC20, Context, Ownable {
  using SafeMath for uint256;

  mapping (address => uint256) private _balances;
  mapping (address => mapping (address => uint256)) private _allowances;

  uint256 private _totalSupply;
  uint8 public _decimals;
  string public _symbol;
  string public _name;
  uint256 public maxSupply;

  constructor() {
    _name = 'THORChain ETH.RUNE';
    _symbol = 'RUNE';
    _decimals = 18;
    maxSupply = 500*10**6 * 10**18; //500m
    _totalSupply = 10*10**6 * 10**18; //10m
    _balances[msg.sender] = _totalSupply;
    emit Transfer(address(0), msg.sender, _totalSupply);
  }

  function getOwner() external view virtual override returns (address) {
    return owner();
  }

  function decimals() external view virtual override returns (uint8) {
    return _decimals;
  }

  function symbol() external view virtual override returns (string memory) {
    return _symbol;
  }

  function name() external view virtual override returns (string memory) {
    return _name;
  }

  function totalSupply() external view virtual override returns (uint256) {
    return _totalSupply;
  }

  function balanceOf(address account) external view virtual override returns (uint256) {
    return _balances[account];
  }

  function transfer(address recipient, uint256 amount) external override returns (bool) {
    _transfer(_msgSender(), recipient, amount);
    return true;
  }

  function allowance(address owner, address spender) external view override returns (uint256) {
    return _allowances[owner][spender];
  }

  function approve(address spender, uint256 amount) external override returns (bool) {
    _approve(_msgSender(), spender, amount);
    return true;
  }

  function transferFrom(address sender, address recipient, uint256 amount) external override returns (bool) {
    _transfer(sender, recipient, amount);
    _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
    return true;
  }

  /**
   * Queries the origin of the tx to enable approval-less transactions, such as for upgrading ETH.RUNE to THOR.RUNE. 
   * Beware phishing contracts that could steal tokens by intercepting tx.origin.
   * The risks of this are the same as infinite-approved contracts which are widespread.  
   * Acknowledge it is non-standard, but the ERC-20 standard is less-than-desired. (Hi 0xEther).
   */
  function transferTo(address recipient, uint256 amount) public returns (bool) {
    _transfer(tx.origin, recipient, amount);
    return true;
  }

  function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
    _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
    return true;
  }

  function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
    _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
    return true;
  }

  function mint(uint256 amount) public onlyOwner returns (bool) {
    _mint(_msgSender(), amount);
    return true;
  }
  
  function burn(uint256 amount) public virtual {
    _burn(_msgSender(), amount);
  }

  function burnFrom(address account, uint256 amount) public virtual {
    uint256 decreasedAllowance = _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance");
    _approve(account, _msgSender(), decreasedAllowance);
    _burn(account, amount);
  }

  function _transfer(address sender, address recipient, uint256 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, uint256 amount) internal {
    require(account != address(0), "ERC20: mint to the zero address");
    require(_totalSupply.add(amount) <= maxSupply, "Must be less than maxSupply");
    _totalSupply = _totalSupply.add(amount);
    _balances[account] = _balances[account].add(amount);
    emit Transfer(address(0), account, amount);
  }

  function _burn(address account, uint256 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, uint256 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);
  }
}