pragma solidity ^0.6.0;


/**
* @title interface IVariableDebtToken
* @author Aave
* @notice defines the basic interface for a variable debt token.
* @dev does not inherit from IERC20 to save in contract size
**/
interface IVariableDebtToken {

  /**
  * @dev mints new variable debt
  * @param _user the user receiving the debt
  * @param _amount the amount of debt being minted
  **/
  function mint(address _user, uint256 _amount) external virtual;

  /**
  * @dev burns user variable debt
  * @param _user the user which debt is burnt
  * @param _amount the amount of debt being burned
  **/
  function burn(address _user, uint256 _amount) external virtual;

  /**
  * @dev returns the last index of the user
  * @return the index of the user
  **/
  function getUserIndex(address _user) external virtual view returns(uint256);

}