/*
# @version 0.3.0
# @dev Implementation of ERC-20 token standard, vyper/examples/tokens/ERC20.vy at tag v0.3.0
# @author Takayuki Jimba (@yudetamago)
# https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md

# compiled using `vyper -f bytecode_runtime`: 1579 bytes

from vyper.interfaces import ERC20

implements: ERC20
*/

// compiled using `solc --optimize --optimize-runs=1 --bin-runtime`: 1970 bytes

pragma solidity ^0.8.9;

contract ERC20 {
  /*
     event Transfer:
sender: indexed(address)
receiver: indexed(address)
value: uint256
   */

  event Transfer(address indexed sender, address indexed received, uint256 value);

  /*
     event Approval:
owner: indexed(address)
spender: indexed(address)
value: uint256
   */
  event Approval(address indexed owner, address indexed spender, uint256 value);

  //name: public(String[64])
  string public name;
  //symbol: public(String[32])
  string public symbol;
  //decimals: public(uint256)
  uint256 public decimals;

  /*
# NOTE: By declaring `balanceOf` as public, vyper automatically generates a 'balanceOf()' getter
#       method to allow access to account balances.
#       The _KeyType will become a required parameter for the getter and it will return _ValueType.
#       See: https://vyper.readthedocs.io/en/v0.1.0-beta.8/types.html?highlight=getter#mappings
balanceOf: public(HashMap[address, uint256])
   */
  mapping(address => uint256) public balanceOf;
  /*
# By declaring `allowance` as public, vyper automatically generates the `allowance()` getter
allowance: public(HashMap[address, HashMap[address, uint256]])
   */
  mapping(address => mapping(address => uint256)) public allowance;
  /*
# By declaring `totalSupply` as public, we automatically create the `totalSupply()` getter
totalSupply: public(uint256)
   */
  uint256 public totalSupply;
  //minter: address
  address minter;

/*
@external
def __init__(_name: String[64], _symbol: String[32], _decimals: uint256, _supply: uint256):
    init_supply: uint256 = _supply * 10 ** _decimals
    self.name = _name
    self.symbol = _symbol
    self.decimals = _decimals
    self.balanceOf[msg.sender] = init_supply
    self.totalSupply = init_supply
    self.minter = msg.sender
    log Transfer(ZERO_ADDRESS, msg.sender, init_supply)
*/
  constructor(string memory _name, string memory _symbol, uint256 _decimals, uint256 _supply) {
    uint256 init_supply = _supply * 10 ** _decimals;
    require(bytes(_name).length <= 64);
    name = _name;
    require(bytes(_symbol).length <= 32);
    symbol = _symbol;
    decimals = _decimals;
    balanceOf[msg.sender] = init_supply;
    totalSupply = init_supply;
    minter = msg.sender;
    emit Transfer(address(0), msg.sender, init_supply);
  }


    /*
    @external
def transfer(_to : address, _value : uint256) -> bool:

    """
  @dev Transfer token for a specified address
  @param _to The address to transfer to.
    @param _value The amount to be transferred.
      """
    # NOTE: vyper does not allow underflows
    #       so the following subtraction would revert on insufficient balance
    self.balanceOf[msg.sender] -= _value
    self.balanceOf[_to] += _value
    log Transfer(msg.sender, _to, _value)
    return True
   */
  function transfer(address _to, uint256 _value) external returns(bool) {
    balanceOf[msg.sender] -= _value;
    balanceOf[_to] += _value;
    emit Transfer(msg.sender, _to, _value);
    return true;
  }

/*
    @external
    def transferFrom(_from : address, _to : address, _value : uint256) -> bool:
      """
    @dev Transfer tokens from one address to another.
    @param _from address The address which you want to send tokens from
    @param _to address The address which you want to transfer to
    @param _value uint256 the amount of tokens to be transferred
    """
    # NOTE: vyper does not allow underflows
    #       so the following subtraction would revert on insufficient balance
    self.balanceOf[_from] -= _value
    self.balanceOf[_to] += _value
    # NOTE: vyper does not allow underflows
    #      so the following subtraction would revert on insufficient allowance
    self.allowance[_from][msg.sender] -= _value
    log Transfer(_from, _to, _value)
    return True
*/
  function transferFrom(address _from, address _to, uint256 _value) external returns(bool) {
    balanceOf[_from] -= _value;
    balanceOf[_to] += _value;
    allowance[_from][msg.sender] -= _value;
    emit Transfer(_from, _to, _value);
    return true;
  }

/*
    @external
    def approve(_spender : address, _value : uint256) -> bool:
      """
    @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    Beware that changing an allowance with this method brings the risk that someone may use both the old
    and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
    race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
    https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    @param _spender The address which will spend the funds.
      @param _value The amount of tokens to be spent.
      """
    self.allowance[msg.sender][_spender] = _value
    log Approval(msg.sender, _spender, _value)
    return True
*/
  function approve(address _spender, uint256 _value) external returns (bool) {
    allowance[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }
/*
    @external
    def mint(_to: address, _value: uint256):
      """
    @dev Mint an amount of the token and assigns it to an account.
    This encapsulates the modification of balances such that the
    proper events are emitted.
      @param _to The account that will receive the created tokens.
      @param _value The amount that will be created.
      """
    assert msg.sender == self.minter
    assert _to != ZERO_ADDRESS
    self.totalSupply += _value
    self.balanceOf[_to] += _value
    log Transfer(ZERO_ADDRESS, _to, _value)
*/
  function mint(address _to, uint256 _value) external {
    require(msg.sender == minter);
    require(_to != address(0));
    totalSupply += _value;
    balanceOf[_to] += _value;
    emit Transfer(address(0), _to, _value);
  }
/*
    @internal
    def _burn(_to: address, _value: uint256):
      """
    @dev Internal function that burns an amount of the token of a given
    account.
      @param _to The account whose tokens will be burned.
      @param _value The amount that will be burned.
      """
    assert _to != ZERO_ADDRESS
    self.totalSupply -= _value
    self.balanceOf[_to] -= _value
    log Transfer(_to, ZERO_ADDRESS, _value)
*/
  function _burn(address _to, uint256 _value) internal {
    require(_to != address(0));
    totalSupply -= _value;
    balanceOf[_to] -= _value;
    emit Transfer(_to, address(0), _value);
  }

  /*
    @external
    def burn(_value: uint256):
      """
    @dev Burn an amount of the token of msg.sender.
    @param _value The amount that will be burned.
      """
    self._burn(msg.sender, _value)
*/
  function burn(uint256 _value) external {
    _burn(msg.sender, _value);
  }
/*
    @external
    def burnFrom(_to: address, _value: uint256):
      """
    @dev Burn an amount of the token from a given account.
    @param _to The account whose tokens will be burned.
      @param _value The amount that will be burned.
      """
    self.allowance[_to][msg.sender] -= _value
    self._burn(_to, _value)
   */
  function burnFrom(address _to, uint256 _value) external {
    allowance[_to][msg.sender] -= _value;
    _burn(_to, _value);
  }
}