ILiquidityAccumulator.sol

//SPDX-License-Identifier: MIT
pragma solidity >=0.5.0 <0.9.0;

pragma experimental ABIEncoderV2;

import "./IAccumulator.sol";

import "../libraries/AccumulationLibrary.sol";
import "../libraries/ObservationLibrary.sol";

/**
 * @title ILiquidityAccumulator
 * @notice An interface that defines a "liquidity accumulator" - that is, cumulative liquidity levels - with a
 *   single quote token and many exchange tokens.
 * @dev Liquidity accumulators are used to calculate time-weighted average liquidity levels.
 */
abstract contract ILiquidityAccumulator is IAccumulator {
    /// @notice Emitted when the accumulator is updated.
    /// @dev The accumulator's observation and cumulative values are updated when this is emitted.
    /// @param token The address of the token that the update is for.
    /// @param tokenLiquidity The amount of the token that is liquid in the underlying pool, in wei.
    /// @param quoteTokenLiquidity The amount of the quote token that is liquid in the underlying pool, in wei.
    /// @param timestamp The epoch timestamp of the update (in seconds).
    event Updated(address indexed token, uint256 tokenLiquidity, uint256 quoteTokenLiquidity, uint256 timestamp);

    /**
     * @notice Calculates a liquidity levels from two different cumulative liquidity levels.
     * @param firstAccumulation The first cumulative liquidity levels.
     * @param secondAccumulation The last cumulative liquidity levels.
     * @dev Reverts if the timestamp of the first accumulation is 0, or if it's not strictly less than the timestamp of
     *  the second.
     * @return tokenLiquidity A time-weighted average liquidity level for a token, in wei, derived from two cumulative
     *  liquidity levels.
     * @return quoteTokenLiquidity A time-weighted average liquidity level for the quote token, in wei, derived from two
     *  cumulative liquidity levels.
     */
    function calculateLiquidity(
        AccumulationLibrary.LiquidityAccumulator calldata firstAccumulation,
        AccumulationLibrary.LiquidityAccumulator calldata secondAccumulation
    ) external view virtual returns (uint112 tokenLiquidity, uint112 quoteTokenLiquidity);

    /// @notice Gets the last cumulative liquidity levels for the token and quote token that was stored.
    /// @param token The address of the token to get the cumulative liquidity levels for (with the quote token).
    /// @return The last cumulative liquidity levels (in wei) along with the timestamp of those levels.
    function getLastAccumulation(
        address token
    ) public view virtual returns (AccumulationLibrary.LiquidityAccumulator memory);

    /// @notice Gets the current cumulative liquidity levels for the token and quote token.
    /// @param token The address of the token to get the cumulative liquidity levels for (with the quote token).
    /// @return The current cumulative liquidity levels (in wei) along with the timestamp of those levels.
    function getCurrentAccumulation(
        address token
    ) public view virtual returns (AccumulationLibrary.LiquidityAccumulator memory);

    function liquidityDecimals() public view virtual returns (uint8);
}