pragma solidity >=0.6.12;

// Author:	Louis Holbrook <dev@holbrook.no> 0826EDA1702D1E87C6E2875121D2E7BB88C2A746
// SPDX-License-Identifier:	AGPL-3.0-or-later
// File-version: 1

// Methods to detect tokens that are subject to continuous change, and 

interface ITokenChangeRate {
	// Time unit resolution for rate of change.
	// A value of 0 indicates no rate of change,
	function changeTimeUnit() external view returns(uint256);

	// Rate of change per changeTimeUnit(), signed integer.
	// An effective value of 0 indicates no rate of change.
	function changeRate() external view returns (int256);

	// Number of decimals with which the changeRate is defined.
        // changeRate() should be divided by 10 ** changeRateDecimals() to obtain effective value
	function changeRateDecimals() external view returns(uint8);

	// Timestamp from when rate of change should be applied.
	// A value of 0 indicates no rate of change,
	function changeStartTime() external view returns(uint256);

	// Calculate value with change rate applied for given amount of time units.
	// Will calculate compounded change over the given amount of time units
	function applyChange(int256 _value, uint256 _changeTimeUnits) external view returns(int256);
}