// SPDX-License-Identifier: BUSL-1.1
pragma solidity 0.7.6;
pragma abicoder v2;

import "../../interfaces/IPendleAaveForge.sol";
import "../../libraries/MathLib.sol";
import "./../abstract/PendleMarketBase.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";

contract PendleAaveMarket is PendleMarketBase {
    using Math for uint256;
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    // the normalisedIncome of the last time paramL got updated
    uint256 private globalLastNormalizedIncome;
    mapping(address => uint256) private userLastNormalizedIncome;

    constructor(
        address _governanceManager,
        address _xyt,
        address _token
    ) PendleMarketBase(_governanceManager, _xyt, _token) {}

    function _getReserveNormalizedIncome() internal view returns (uint256) {
        return IPendleAaveForge(forge).getReserveNormalizedIncome(underlyingAsset);
    }

    function _afterBootstrap() internal override {
        globalLastNormalizedIncome = _getReserveNormalizedIncome();
    }

    /// @inheritdoc PendleMarketBase
    function _updateDueInterests(address user) internal override {
        // before calc the interest for users, updateParamL
        _updateParamL();

        uint256 lastIncome = userLastNormalizedIncome[user];
        // why use globalLastNormalizedIncome? Because of the caching of paramL, we pretend that there is no source
        // of income externally (from Xyt, compound interest...), that's why we have to use globalLastNormalizedIncome
        // , which is the normalisedIncome from the last time paramL got updated (aka the last time we get external income)
        uint256 normIncomeNow = globalLastNormalizedIncome;
        uint256 principal = balanceOf(user);
        uint256 _paramL = paramL; // save value in memory to save gas

        if (lastIncome == 0) {
            userLastNormalizedIncome[user] = normIncomeNow;
            lastParamL[user] = _paramL;
            return;
        }

        /*
        this part can be thought of as follows:
            * the last time the user redeems interest, the value of a LP is lastParamL[user]
                and he has redeemed all the available interest out
            * the market has 2 sources of income: compound interest of the yieldTokens in the market right now
            AND external income (XYT interest, people transferring wrongly...)
            * now the value of param L is paramL. So there has been an increase of paramL - lastParamL[user]
                in value of a single LP. But in Aave, even if there are no external income, the value of a paramL
                can grow on its own
            * so since the last time the user has fully redeemed all the available interest, he shouldn't receive
            the compound interest sof the asset in the pool at the moment he last withdrew
            * so the value of 1 LP for him will be paramL - compound(lastParamL[user])
                = paramL -  lastParamL[user] * globalLastNormalizedIncome /userLastNormalizedIncome[user]
        */
        uint256 interestValuePerLP = _paramL.subMax0(
            lastParamL[user].mul(normIncomeNow).div(lastIncome)
        );

        uint256 interestFromLp = principal.mul(interestValuePerLP).div(MULTIPLIER);

        dueInterests[user] = dueInterests[user].mul(normIncomeNow).div(lastIncome).add(
            interestFromLp
        );

        userLastNormalizedIncome[user] = normIncomeNow;
        lastParamL[user] = _paramL;
    }

    /// @inheritdoc PendleMarketBase
    function _getFirstTermAndParamR(uint256 currentNYield)
        internal
        override
        returns (uint256 firstTerm, uint256 paramR)
    {
        uint256 currentNormalizedIncome = _getReserveNormalizedIncome();
        // for Aave, the paramL can grow on its own (compound effect)
        firstTerm = paramL.mul(currentNormalizedIncome).div(globalLastNormalizedIncome);

        uint256 ix = lastNYield.mul(currentNormalizedIncome).div(globalLastNormalizedIncome);
        // paramR's meaning has been explained in the updateParamL function
        paramR = currentNYield.subMax0(ix);

        globalLastNormalizedIncome = currentNormalizedIncome;
    }

    /// @inheritdoc PendleMarketBase
    function _getIncomeIndexIncreaseRate() internal view override returns (uint256 increaseRate) {
        return _getReserveNormalizedIncome().rdiv(globalLastNormalizedIncome).sub(Math.RONE);
    }
}