// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * @title A standard interface for tokens.
 * @dev This interface uses the official ERC-20 specification from
 * https://eips.ethereum.org/EIPS/eip-20 with the additional requirement that
 * the functions specified as optional have become required.
 */
interface ERC20
{

  /**
   * @dev Returns the name of the token.
   * @return _name Token name.
   */
  function name()
    external
    view
    returns (string memory _name);

  /**
   * @dev Returns the symbol of the token.
   * @return _symbol Token symbol.
   */
  function symbol()
    external
    view
    returns (string memory _symbol);

  /**
   * @dev Returns the number of decimals the token uses.
   * @return _decimals Number of decimals.
   */
  function decimals()
    external
    view
    returns (uint8 _decimals);

  /**
   * @dev Returns the total token supply.
   * @return _totalSupply Total supply.
   */
  function totalSupply()
    external
    view
    returns (uint256 _totalSupply);

  /**
   * @dev Returns the account balance of another account with address _owner.
   * @param _owner The address from which the balance will be retrieved.
   * @return _balance Balance of _owner.
   */
  function balanceOf(
    address _owner
  )
    external
    view
    returns (uint256 _balance);

  /**
   * @dev Transfers _value amount of tokens to address _to, and MUST fire the Transfer event. The
   * function SHOULD throw if the message caller's account balance does not have enough tokens to
   * spend.
   * @param _to The address of the recipient.
   * @param _value The amount of token to be transferred.
   * @return _success Success of operation.
   */
  function transfer(
    address _to,
    uint256 _value
  )
    external
    returns (bool _success);

  /**
   * @dev Transfers _value amount of tokens from address _from to address _to, and MUST fire the
   * Transfer event.
   * @param _from The address of the sender.
   * @param _to The address of the recipient.
   * @param _value The amount of token to be transferred.
   * @return _success Success of operation.
   */
  function transferFrom(
    address _from,
    address _to,
    uint256 _value
  )
    external
    returns (bool _success);

  /**
   * @dev Allows _spender to withdraw from your account multiple times, up to
   * the _value amount. If this function is called again it overwrites the current
   * allowance with _value.
   * @param _spender The address of the account able to transfer the tokens.
   * @param _value The amount of tokens to be approved for transfer.
   * @return _success Success of operation.
   */
  function approve(
    address _spender,
    uint256 _value
  )
    external
    returns (bool _success);

  /**
   * @dev Returns the amount which _spender is still allowed to withdraw from _owner.
   * @param _owner The address of the account owning tokens.
   * @param _spender The address of the account able to transfer the tokens.
   * @return _remaining Remaining allowance.
   */
  function allowance(
    address _owner,
    address _spender
  )
    external
    view
    returns (uint256 _remaining);

  /**
   * @dev Triggers when tokens are transferred, including zero value transfers.
   */
  event Transfer(
    address indexed _from,
    address indexed _to,
    uint256 _value
  );

  /**
   * @dev Triggers on any successful call to approve(address _spender, uint256 _value).
   */
  event Approval(
    address indexed _owner,
    address indexed _spender,
    uint256 _value
  );

}