// File: /Users/ebonassi/Desktop/Active_Development/yearn-truffle-verify/contracts/BaseStrategy.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0 <0.7.0;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";

struct StrategyParams {
    uint256 performanceFee;
    uint256 activation;
    uint256 debtLimit;
    uint256 rateLimit;
    uint256 lastReport;
    uint256 totalDebt;
    uint256 totalGain;
    uint256 totalLoss;
}

interface VaultAPI is IERC20 {
    function apiVersion() external view returns (string memory);

    function token() external view returns (address);

    function strategies(address _strategy) external view returns (StrategyParams memory);

    /**
     * View how much the Vault would increase this Strategy's borrow limit,
     * based on its present performance (since its last report). Can be used to
     * determine expectedReturn in your Strategy.
     */
    function creditAvailable() external view returns (uint256);

    /**
     * View how much the Vault would like to pull back from the Strategy,
     * based on its present performance (since its last report). Can be used to
     * determine expectedReturn in your Strategy.
     */
    function debtOutstanding() external view returns (uint256);

    /**
     * View how much the Vault expect this Strategy to return at the current
     * block, based on its present performance (since its last report). Can be
     * used to determine expectedReturn in your Strategy.
     */
    function expectedReturn() external view returns (uint256);

    /**
     * This is the main contact point where the Strategy interacts with the
     * Vault. It is critical that this call is handled as intended by the
     * Strategy. Therefore, this function will be called by BaseStrategy to
     * make sure the integration is correct.
     */
    function report(
        uint256 _gain,
        uint256 _loss,
        uint256 _debtPayment
    ) external returns (uint256);

    /**
     * This function is used in the scenario where there is a newer Strategy
     * that would hold the same positions as this one, and those positions are
     * easily transferrable to the newer Strategy. These positions must be able
     * to be transferred at the moment this call is made, if any prep is
     * required to execute a full transfer in one transaction, that must be
     * accounted for separately from this call.
     */
    function migrateStrategy(address _newStrategy) external;

    /**
     * This function should only be used in the scenario where the Strategy is
     * being retired but no migration of the positions are possible, or in the
     * extreme scenario that the Strategy needs to be put into "Emergency Exit"
     * mode in order for it to exit as quickly as possible. The latter scenario
     * could be for any reason that is considered "critical" that the Strategy
     * exits its position as fast as possible, such as a sudden change in
     * market conditions leading to losses, or an imminent failure in an
     * external dependency.
     */
    function revokeStrategy() external;

    /**
     * View the governance address of the Vault to assert privileged functions
     * can only be called by governance. The Strategy serves the Vault, so it
     * is subject to governance defined by the Vault.
     */
    function governance() external view returns (address);
}

/**
 * This interface is here for the keeper bot to use.
 */
interface StrategyAPI {
    function apiVersion() external pure returns (string memory);

    function name() external pure returns (string memory);

    function vault() external view returns (address);

    function keeper() external view returns (address);

    function tendTrigger(uint256 callCost) external view returns (bool);

    function tend() external;

    function harvestTrigger(uint256 callCost) external view returns (bool);

    function harvest() external;

    event Harvested(uint256 profit, uint256 loss, uint256 debtPayment, uint256 debtOutstanding);
}

/**
 * @title Yearn Base Strategy
 * @author yearn.finance
 * @notice
 *  BaseStrategy implements all of the required functionality to interoperate
 *  closely with the Vault contract. This contract should be inherited and the
 *  abstract methods implemented to adapt the Strategy to the particular needs
 *  it has to create a return.
 *
 *  Of special interest is the relationship between `harvest()` and
 *  `vault.report()'. `harvest()` may be called simply because enough time has
 *  elapsed since the last report, and not because any funds need to be moved
 *  or positions adjusted. This is critical so that the Vault may maintain an
 *  accurate picture of the Strategy's performance. See  `vault.report()`,
 *  `harvest()`, and `harvestTrigger()` for further details.
 */
abstract contract BaseStrategy {
    using SafeMath for uint256;

    /**
     * @notice
     *  Used to track which version of `StrategyAPI` this Strategy
     *  implements.
     * @dev The Strategy's version must match the Vault's `API_VERSION`.
     * @return A string which holds the current API version of this contract.
     */
    function apiVersion() public pure returns (string memory) {
        return "0.2.2";
    }

    /**
     * @notice This Strategy's name.
     * @dev
     *  You can use this field to manage the "version" of this Strategy, e.g.
     *  `StrategySomethingOrOtherV1`. However, "API Version" is managed by
     *  `apiVersion()` function above.
     * @return This Strategy's name.
     */
    function name() external virtual pure returns (string memory);

    VaultAPI public vault;
    address public strategist;
    address public rewards;
    address public keeper;

    IERC20 public want;

    // So indexers can keep track of this
    event Harvested(uint256 profit, uint256 loss, uint256 debtPayment, uint256 debtOutstanding);

    event UpdatedStrategist(address newStrategist);

    event UpdatedKeeper(address newKeeper);

    event UpdatedRewards(address rewards);

    event UpdatedReportDelay(uint256 delay);

    event UpdatedProfitFactor(uint256 profitFactor);

    event UpdatedDebtThreshold(uint256 debtThreshold);

    // The minimum number of seconds between harvest calls. See
    // `setMinReportDelay()` for more details.
    uint256 public minReportDelay = 86400; // ~ once a day

    // The minimum multiple that `callCost` must be above the credit/profit to
    // be "justifiable". See `setProfitFactor()` for more details.
    uint256 public profitFactor = 100;

    // Use this to adjust the threshold at which running a debt causes a
    // harvest trigger. See `setDebtThreshold()` for more details.
    uint256 public debtThreshold = 0;

    // See note on `setEmergencyExit()`.
    bool public emergencyExit;

    // modifiers
    modifier onlyAuthorized() {
        require(msg.sender == strategist || msg.sender == governance(), "!authorized");
        _;
    }

    modifier onlyStrategist() {
        require(msg.sender == strategist, "!strategist");
        _;
    }

    modifier onlyGovernance() {
        require(msg.sender == governance(), "!authorized");
        _;
    }

    modifier onlyKeepers() {
        require(msg.sender == keeper || msg.sender == strategist || msg.sender == governance(), "!authorized");
        _;
    }

    /**
     * @notice
     *  Initializes the Strategy, this is called only once, when the
     *  contract is deployed.
     * @dev `_vault` should implement `VaultAPI`.
     * @param _vault The address of the Vault responsible for this Strategy.
     */
    constructor(address _vault) public {
        vault = VaultAPI(_vault);
        want = IERC20(vault.token());
        want.approve(_vault, uint256(-1)); // Give Vault unlimited access (might save gas)
        strategist = msg.sender;
        rewards = msg.sender;
        keeper = msg.sender;
    }

    /**
     * @notice
     *  Used to change `strategist`.
     *
     *  This may only be called by governance or the existing strategist.
     * @param _strategist The new address to assign as `strategist`.
     */
    function setStrategist(address _strategist) external onlyAuthorized {
        strategist = _strategist;
        emit UpdatedStrategist(_strategist);
    }

    /**
     * @notice
     *  Used to change `keeper`.
     *
     *  `keeper` is the only address that may call `tend()` or `harvest()`,
     *  other than `governance()` or `strategist`. However, unlike
     *  `governance()` or `strategist`, `keeper` may *only* call `tend()`
     *  and `harvest()`, and no other authorized functions, following the
     *  principle of least privilege.
     *
     *  This may only be called by governance or the strategist.
     * @param _keeper The new address to assign as `keeper`.
     */
    function setKeeper(address _keeper) external onlyAuthorized {
        keeper = _keeper;
        emit UpdatedKeeper(_keeper);
    }

    /**
     * @notice
     *  Used to change `rewards`. Any distributed rewards will cease flowing
     *  to the old address and begin flowing to this address once the change
     *  is in effect.
     *
     *  This will not change any Strategy reports in progress, only
     *  new reports made after this change goes into effect.
     *
     *  This may only be called by the strategist.
     * @param _rewards The address to use for collecting rewards.
     */
    function setRewards(address _rewards) external onlyStrategist {
        rewards = _rewards;
        emit UpdatedRewards(_rewards);
    }

    /**
     * @notice
     *  Used to change `minReportDelay`. `minReportDelay` is the minimum number
     *  of blocks that should pass before `harvest()` is called.
     *
     *  For external keepers (such as the Keep3r network), this is the minimum
     *  time between jobs, to prevent excessive costs. (see `harvestTrigger()`
     *  for more details.)
     *
     *  This may only be called by governance or the strategist.
     * @param _delay The minimum number of blocks to wait between harvests.
     */
    function setMinReportDelay(uint256 _delay) external onlyAuthorized {
        minReportDelay = _delay;
        emit UpdatedReportDelay(_delay);
    }

    /**
     * @notice
     *  Used to change `profitFactor`. `profitFactor` is used to determine
     *  if it's worthwhile to harvest, given gas costs. (See `harvestTrigger()`
     *  for more details.)
     *
     *  This may only be called by governance or the strategist.
     * @param _profitFactor A ratio to multiply anticipated
     * `harvest()` gas cost against.
     */
    function setProfitFactor(uint256 _profitFactor) external onlyAuthorized {
        profitFactor = _profitFactor;
        emit UpdatedProfitFactor(_profitFactor);
    }

    /**
     * @notice
     *  Sets how far the Strategy can go into loss without a harvest and report
     *  being required.
     *
     *  By default this is 0, meaning any losses would cause a harvest which
     *  will subsequently report the loss to the Vault for tracking. (See
     *  `harvestTrigger()` for more details.)
     *
     *  This may only be called by governance or the strategist.
     * @param _debtThreshold How big of a loss this Strategy may carry without
     * being required to report to the Vault.
     */
    function setDebtThreshold(uint256 _debtThreshold) external onlyAuthorized {
        debtThreshold = _debtThreshold;
        emit UpdatedDebtThreshold(_debtThreshold);
    }

    /**
     * Resolve governance address from Vault contract, used to make assertions
     * on protected functions in the Strategy.
     */
    function governance() internal view returns (address) {
        return vault.governance();
    }

    /**
     * @notice
     *  Provide an accurate estimate for the total amount of assets
     *  (principle + return) that this Strategy is currently managing,
     *  denominated in terms of `want` tokens.
     *
     *  This total should be "realizable" e.g. the total value that could
     *  *actually* be obtained from this Strategy if it were to divest its
     *  entire position based on current on-chain conditions.
     * @dev
     *  Care must be taken in using this function, since it relies on external
     *  systems, which could be manipulated by the attacker to give an inflated
     *  (or reduced) value produced by this function, based on current on-chain
     *  conditions (e.g. this function is possible to influence through
     *  flashloan attacks, oracle manipulations, or other DeFi attack
     *  mechanisms).
     *
     *  It is up to governance to use this function to correctly order this
     *  Strategy relative to its peers in the withdrawal queue to minimize
     *  losses for the Vault based on sudden withdrawals. This value should be
     *  higher than the total debt of the Strategy and higher than its expected
     *  value to be "safe".
     * @return The estimated total assets in this Strategy.
     */
    function estimatedTotalAssets() public virtual view returns (uint256);

    /**
     * Perform any Strategy unwinding or other calls necessary to capture the
     * "free return" this Strategy has generated since the last time its core
     * position(s) were adjusted. Examples include unwrapping extra rewards.
     * This call is only used during "normal operation" of a Strategy, and
     * should be optimized to minimize losses as much as possible.
     *
     * This method returns any realized profits and/or realized losses
     * incurred, and should return the total amounts of profits/losses/debt
     * payments (in `want` tokens) for the Vault's accounting (e.g.
     * `want.balanceOf(this) >= _debtPayment + _profit - _loss`).
     *
     * `_debtOutstanding` will be 0 if the Strategy is not past the configured
     * debt limit, otherwise its value will be how far past the debt limit
     * the Strategy is. The Strategy's debt limit is configured in the Vault.
     *
     * NOTE: `_debtPayment` should be less than or equal to `_debtOutstanding`.
     *       It is okay for it to be less than `_debtOutstanding`, as that
     *       should only used as a guide for how much is left to pay back.
     *       Payments should be made to minimize loss from slippage, debt,
     *       withdrawal fees, etc.
     *
     * See `vault.debtOutstanding()`.
     */
    function prepareReturn(uint256 _debtOutstanding)
        internal
        virtual
        returns (
            uint256 _profit,
            uint256 _loss,
            uint256 _debtPayment
        );

    /**
     * Perform any adjustments to the core position(s) of this Strategy given
     * what change the Vault made in the "investable capital" available to the
     * Strategy. Note that all "free capital" in the Strategy after the report
     * was made is available for reinvestment. Also note that this number
     * could be 0, and you should handle that scenario accordingly.
     *
     * See comments regarding `_debtOutstanding` on `prepareReturn()`.
     */
    function adjustPosition(uint256 _debtOutstanding) internal virtual;

    /**
     * Make as much capital as possible "free" for the Vault to take. Some
     * slippage is allowed, since when this method is called the strategist is
     * no longer receiving their performance fee. The goal is for the Strategy
     * to divest as quickly as possible while not suffering exorbitant losses.
     * This function is used during emergency exit instead of
     * `prepareReturn()`. This method returns any realized losses incurred,
     * and should also return the amount of `want` tokens available to repay
     * outstanding debt to the Vault.
     */
    function exitPosition(uint256 _debtOutstanding)
        internal
        virtual
        returns (
            uint256 _profit,
            uint256 _loss,
            uint256 _debtPayment
        );

    /**
     *  `Harvest()` calls this function after shares are created during
     *  `vault.report()`. You can customize this function to any share
     *  distribution mechanism you want.
     *
     *   See `vault.report()` for further details.
     */
    function distributeRewards() internal virtual {
        // Transfer 100% of newly-minted shares awarded to this contract to the rewards address.
        uint256 balance = vault.balanceOf(address(this));
        if (balance > 0) {
            vault.transfer(rewards, balance);
        }
    }

    /**
     * @notice
     *  Provide a signal to the keeper that `tend()` should be called. The
     *  keeper will provide the estimated gas cost that they would pay to call
     *  `tend()`, and this function should use that estimate to make a
     *  determination if calling it is "worth it" for the keeper. This is not
     *  the only consideration into issuing this trigger, for example if the
     *  position would be negatively affected if `tend()` is not called
     *  shortly, then this can return `true` even if the keeper might be
     *  "at a loss" (keepers are always reimbursed by Yearn).
     * @dev
     *  `callCost` must be priced in terms of `want`.
     *
     *  This call and `harvestTrigger()` should never return `true` at the same
     *  time.
     * @param callCost The keeper's estimated cast cost to call `tend()`.
     * @return `true` if `tend()` should be called, `false` otherwise.
     */
    function tendTrigger(uint256 callCost) public virtual view returns (bool) {
        // We usually don't need tend, but if there are positions that need
        // active maintainence, overriding this function is how you would
        // signal for that.
        return false;
    }

    /**
     * @notice
     *  Adjust the Strategy's position. The purpose of tending isn't to
     *  realize gains, but to maximize yield by reinvesting any returns.
     *
     *  See comments on `adjustPosition()`.
     *
     *  This may only be called by governance, the strategist, or the keeper.
     */
    function tend() external onlyKeepers {
        // Don't take profits with this call, but adjust for better gains
        adjustPosition(vault.debtOutstanding());
    }

    /**
     * @notice
     *  Provide a signal to the keeper that `harvest()` should be called. The
     *  keeper will provide the estimated gas cost that they would pay to call
     *  `harvest()`, and this function should use that estimate to make a
     *  determination if calling it is "worth it" for the keeper. This is not
     *  the only consideration into issuing this trigger, for example if the
     *  position would be negatively affected if `harvest()` is not called
     *  shortly, then this can return `true` even if the keeper might be "at a
     *  loss" (keepers are always reimbursed by Yearn).
     * @dev
     *  `callCost` must be priced in terms of `want`.
     *
     *  This call and `tendTrigger` should never return `true` at the
     *  same time.
     *
     *  See `minReportDelay`, `profitFactor`, `debtThreshold` to adjust the
     *  strategist-controlled parameters that will influence whether this call
     *  returns `true` or not. These parameters will be used in conjunction
     *  with the parameters reported to the Vault (see `params`) to determine
     *  if calling `harvest()` is merited.
     *
     *  It is expected that an external system will check `harvestTrigger()`.
     *  This could be a script run off a desktop or cloud bot (e.g.
     *  https://github.com/iearn-finance/yearn-vaults/blob/master/scripts/keep.py),
     *  or via an integration with the Keep3r network (e.g.
     *  https://github.com/Macarse/GenericKeep3rV2/blob/master/contracts/keep3r/GenericKeep3rV2.sol).
     * @param callCost The keeper's estimated cast cost to call `harvest()`.
     * @return `true` if `harvest()` should be called, `false` otherwise.
     */
    function harvestTrigger(uint256 callCost) public virtual view returns (bool) {
        StrategyParams memory params = vault.strategies(address(this));

        // Should not trigger if Strategy is not activated
        if (params.activation == 0) return false;

        // Should trigger if hasn't been called in a while
        if (block.timestamp.sub(params.lastReport) >= minReportDelay) return true;

        // If some amount is owed, pay it back
        // NOTE: Since debt is adjusted in step-wise fashion, it is appropriate
        //       to always trigger here, because the resulting change should be
        //       large (might not always be the case).
        uint256 outstanding = vault.debtOutstanding();
        if (outstanding > 0) return true;

        // Check for profits and losses
        uint256 total = estimatedTotalAssets();
        // Trigger if we have a loss to report
        if (total.add(debtThreshold) < params.totalDebt) return true;

        uint256 profit = 0;
        if (total > params.totalDebt) profit = total.sub(params.totalDebt); // We've earned a profit!

        // Otherwise, only trigger if it "makes sense" economically (gas cost
        // is <N% of value moved)
        uint256 credit = vault.creditAvailable();
        return (profitFactor.mul(callCost) < credit.add(profit));
    }

    /**
     * @notice
     *  Harvests the Strategy, recognizing any profits or losses and adjusting
     *  the Strategy's position.
     *
     *  In the rare case the Strategy is in emergency shutdown, this will exit
     *  the Strategy's position.
     *
     *  This may only be called by governance, the strategist, or the keeper.
     * @dev
     *  When `harvest()` is called, the Strategy reports to the Vault (via
     *  `vault.report()`), so in some cases `harvest()` must be called in order
     *  to take in profits, to borrow newly available funds from the Vault, or
     *  otherwise adjust its position. In other cases `harvest()` must be
     *  called to report to the Vault on the Strategy's position, especially if
     *  any losses have occurred.
     */
    function harvest() external onlyKeepers {
        uint256 profit = 0;
        uint256 loss = 0;
        uint256 debtPayment = 0;
        if (emergencyExit) {
            // Free up as much capital as possible
            // NOTE: Don't take performance fee in this scenario
            (profit, loss, debtPayment) = exitPosition(vault.debtOutstanding());
        } else {
            // Free up returns for Vault to pull
            (profit, loss, debtPayment) = prepareReturn(vault.debtOutstanding());
        }

        // Allow Vault to take up to the "harvested" balance of this contract,
        // which is the amount it has earned since the last time it reported to
        // the Vault.
        uint256 debtOutstanding = vault.report(profit, loss, debtPayment);

        // Distribute any reward shares earned by the strategy on this report
        distributeRewards();

        // Check if free returns are left, and re-invest them
        adjustPosition(debtOutstanding);

        emit Harvested(profit, loss, debtPayment, debtOutstanding);
    }

    /**
     * Liquidate as many assets as possible to `want`, irregardless of
     * slippage, up to `_amountNeeded`. Any excess should be re-invested
     * here as well.
     */
    function liquidatePosition(uint256 _amountNeeded) internal virtual returns (uint256 _amountFreed);

    /**
     * @notice
     *  Withdraws `_amountNeeded` to `vault`.
     *
     *  This may only be called by the Vault.
     * @param _amountNeeded How much `want` to withdraw.
     */
    function withdraw(uint256 _amountNeeded) external {
        require(msg.sender == address(vault), "!vault");
        // Liquidate as much as possible to `want`, up to `_amount`
        uint256 amountFreed = liquidatePosition(_amountNeeded);
        // Send it directly back (NOTE: Using `msg.sender` saves some gas here)
        want.transfer(msg.sender, amountFreed);
    }

    /**
     * Do anything necessary to prepare this Strategy for migration, such as
     * transferring any reserve or LP tokens, CDPs, or other tokens or stores of
     * value.
     */
    function prepareMigration(address _newStrategy) internal virtual;

    /**
     * @notice
     *  Transfers all `want` from this Strategy to `_newStrategy`.
     *
     *  This may only be called by governance or the Vault.
     * @dev
     *  The new Strategy's Vault must be the same as this Strategy's Vault.
     * @param _newStrategy The Strategy to migrate to.
     */
    function migrate(address _newStrategy) external {
        require(msg.sender == address(vault) || msg.sender == governance());
        require(BaseStrategy(_newStrategy).vault() == vault);
        prepareMigration(_newStrategy);
        want.transfer(_newStrategy, want.balanceOf(address(this)));
    }

    /**
     * @notice
     *  Activates emergency exit. Once activated, the Strategy will exit its
     *  position upon the next harvest, depositing all funds into the Vault as
     *  quickly as is reasonable given on-chain conditions.
     *
     *  This may only be called by governance or the strategist.
     * @dev
     *  See `vault.setEmergencyShutdown()` and `harvest()` for further details.
     */
    function setEmergencyExit() external onlyAuthorized {
        emergencyExit = true;
        vault.revokeStrategy();
    }

    /**
     * Override this to add all tokens/tokenized positions this contract
     * manages on a *persistent* basis (e.g. not just for swapping back to
     * want ephemerally).
     *
     * NOTE: Do *not* include `want`, already included in `sweep` below.
     *
     * Example:
     *
     *    function protectedTokens() internal override view returns (address[] memory) {
     *      address[] memory protected = new address[](3);
     *      protected[0] = tokenA;
     *      protected[1] = tokenB;
     *      protected[2] = tokenC;
     *      return protected;
     *    }
     */
    function protectedTokens() internal virtual view returns (address[] memory);

    /**
     * @notice
     *  Removes tokens from this Strategy that are not the type of tokens
     *  managed by this Strategy. This may be used in case of accidentally
     *  sending the wrong kind of token to this Strategy.
     *
     *  Tokens will be sent to `governance()`.
     *
     *  This will fail if an attempt is made to sweep `want`, or any tokens
     *  that are protected by this Strategy.
     *
     *  This may only be called by governance.
     * @dev
     *  Implement `protectedTokens()` to specify any additional tokens that
     *  should be protected from sweeping in addition to `want`.
     * @param _token The token to transfer out of this vault.
     */
    function sweep(address _token) external onlyGovernance {
        require(_token != address(want), "!want");
        require(_token != address(vault), "!shares");

        address[] memory _protectedTokens = protectedTokens();
        for (uint256 i; i < _protectedTokens.length; i++) require(_token != _protectedTokens[i], "!protected");

        IERC20(_token).transfer(governance(), IERC20(_token).balanceOf(address(this)));
    }
}
// File: /Users/ebonassi/Desktop/Active_Development/yearn-truffle-verify/contracts/StrategyIdle.sol



// SPDX-License-Identifier: AGPL-3.0
// Feel free to change the license, but this is what we use

// Feel free to change this version of Solidity. We support >=0.6.0 <0.7.0;
pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

// These are the core Yearn libraries
import {
    BaseStrategy,
    StrategyParams
} from "./BaseStrategy.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";

import "../interfaces/Idle/IIdleTokenV3_1.sol";
import "../interfaces/Idle/IdleReservoir.sol";
import "../interfaces/Uniswap/IUniswapRouter.sol";

contract StrategyIdle is BaseStrategy {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;

    uint256 constant public FULL_ALLOC = 100000;

    address immutable public uniswapRouterV2;
    address immutable public weth;
    address immutable public idleReservoir;
    address immutable public idleYieldToken;
    address immutable public referral;

    bool public checkVirtualPrice;
    uint256 public lastVirtualPrice;

    bool public checkRedeemedAmount;

    bool public alreadyRedeemed;

    address[] public govTokens;

    modifier updateVirtualPrice() {
        uint256 currentTokenPrice = _getTokenPrice();
        if (checkVirtualPrice) {
            require(lastVirtualPrice <= currentTokenPrice, "Virtual price is decreasing from the last time, potential losses");
        }
        lastVirtualPrice = currentTokenPrice;
        _;
    }

    constructor(
        address _vault,
        address[] memory _govTokens,
        address _weth,
        address _idleReservoir,
        address _idleYieldToken,
        address _referral,
        address _uniswapRouterV2
    ) public BaseStrategy(_vault) {
        govTokens = _govTokens;
        weth = _weth;
        idleReservoir = _idleReservoir;
        idleYieldToken = _idleYieldToken;
        referral = _referral;

        uniswapRouterV2 = _uniswapRouterV2;

        checkVirtualPrice = true;
        lastVirtualPrice = IIdleTokenV3_1(_idleYieldToken).tokenPrice();

        alreadyRedeemed = false;

        checkRedeemedAmount = true;
    }

    function setCheckVirtualPrice(bool _checkVirtualPrice) external onlyGovernance {
        checkVirtualPrice = _checkVirtualPrice;
    }

    function setCheckRedeemedAmount(bool _checkRedeemedAmount) external onlyGovernance {
        checkRedeemedAmount = _checkRedeemedAmount;
    }

    function enableAllChecks() external onlyGovernance {
        checkVirtualPrice = true;
        checkRedeemedAmount = true;
    }

    function disableAllChecks() external onlyGovernance {
        checkVirtualPrice = false;
        checkRedeemedAmount = false;
    }

    function setGovTokens(address[] memory _govTokens) external onlyGovernance {
        _setGovTokens(_govTokens);
    }

    // ******** OVERRIDE THESE METHODS FROM BASE CONTRACT ************

    function name() external override virtual pure returns (string memory) {
        return "StrategyIdle";
    }

    function estimatedTotalAssets() public override view returns (uint256) {
        // TODO: Build a more accurate estimate using the value of all positions in terms of `want`
        return want.balanceOf(address(this))
                   .add(balanceOnIdle()) //TODO: estimate gov tokens value
        ;
    }

    /*
     * Perform any strategy unwinding or other calls necessary to capture the "free return"
     * this strategy has generated since the last time it's core position(s) were adjusted.
     * Examples include unwrapping extra rewards. This call is only used during "normal operation"
     * of a Strategy, and should be optimized to minimize losses as much as possible. This method
     * returns any realized profits and/or realized losses incurred, and should return the total
     * amounts of profits/losses/debt payments (in `want` tokens) for the Vault's accounting
     * (e.g. `want.balanceOf(this) >= _debtPayment + _profit - _loss`).
     *
     * NOTE: `_debtPayment` should be less than or equal to `_debtOutstanding`. It is okay for it
     *       to be less than `_debtOutstanding`, as that should only used as a guide for how much
     *       is left to pay back. Payments should be made to minimize loss from slippage, debt,
     *       withdrawal fees, etc.
     */
    function prepareReturn(uint256 _debtOutstanding)
        internal
        override
        returns (
            uint256 _profit,
            uint256 _loss,
            uint256 _debtPayment
        )
    {
        // Reset, it could have been set during a withdrawal
        if(alreadyRedeemed) {
            alreadyRedeemed = false;
        }

        // Assure IdleController has IDLE tokens
        IdleReservoir(idleReservoir).drip();

        // Try to pay debt asap
        if (_debtOutstanding > 0) {
            uint256 _amountFreed = liquidatePosition(_debtOutstanding);
            // Using Math.min() since we might free more than needed
            _debtPayment = Math.min(_amountFreed, _debtOutstanding);
        }

        // Claim only if not done in the previous liquidate step during redeem
        if (!alreadyRedeemed) {
            IIdleTokenV3_1(idleYieldToken).redeemIdleToken(0);
        } else {
            alreadyRedeemed = false;
        }

        // If we have govTokens, let's convert them!
        // This is done in a separate step since there might have been
        // a migration or an exitPosition
        
        // This might be > 0 because of a strategy migration
        uint256 balanceOfWantBeforeSwap = balanceOfWant();
        _liquidateGovTokens();
        _profit = balanceOfWant().sub(balanceOfWantBeforeSwap);
    }

    /*
     * Perform any adjustments to the core position(s) of this strategy given
     * what change the Vault made in the "investable capital" available to the
     * strategy. Note that all "free capital" in the strategy after the report
     * was made is available for reinvestment. Also note that this number could
     * be 0, and you should handle that scenario accordingly.
     */
    function adjustPosition(uint256 _debtOutstanding) internal override updateVirtualPrice {
        // TODO: Do something to invest excess `want` tokens (from the Vault) into your positions
        // NOTE: Try to adjust positions so that `_debtOutstanding` can be freed up on *next* harvest (not immediately)

        //emergency exit is dealt with in prepareReturn
        if (emergencyExit) {
            return;
        }

        uint256 balanceOfWant = balanceOfWant();
        if (balanceOfWant > _debtOutstanding) {
            uint256 _wantAvailable = balanceOfWant.sub(_debtOutstanding);

            want.safeApprove(idleYieldToken, 0);
            want.safeApprove(idleYieldToken, _wantAvailable);
            IIdleTokenV3_1(idleYieldToken).mintIdleToken(_wantAvailable, true, referral);
        }
    }

    /*
     * Make as much capital as possible "free" for the Vault to take. Some
     * slippage is allowed. The goal is for the strategy to divest as quickly as possible
     * while not suffering exorbitant losses. This function is used during emergency exit
     * instead of `prepareReturn()`. This method returns any realized losses incurred, and
     * should also return the amount of `want` tokens available to repay outstanding debt
     * to the Vault.
     */
    function exitPosition(uint256 _debtOutstanding)
        internal
        override
        returns (uint256 _profit, uint256 _loss, uint256 _debtPayment)
    {
        if(checkVirtualPrice) {
            // Temporarily suspend virtual price check
            checkVirtualPrice = false;
            (_profit, _loss, _debtPayment) = prepareReturn(_debtOutstanding);
            checkVirtualPrice = true;
        } else {
            return prepareReturn(_debtOutstanding);
        }
    }

    /*
     * Liquidate as many assets as possible to `want`, irregardless of slippage,
     * up to `_amountNeeded`. Any excess should be re-invested here as well.
     */
    function liquidatePosition(uint256 _amountNeeded)
        internal
        override
        updateVirtualPrice
        returns (uint256 _amountFreed)
    {
        // TODO: Do stuff here to free up to `_amountNeeded` from all positions back into `want`
        // NOTE: Return `_amountFreed`, which should be `<= _amountNeeded`

        if (balanceOfWant() < _amountNeeded) {
            // Note: potential drift by 1 wei, reduce to max balance in the case approx is rounded up
            uint256 valueToRedeemApprox = (_amountNeeded.sub(balanceOfWant())).mul(1e18).div(lastVirtualPrice) + 1;
            uint256 valueToRedeem = Math.min(
                valueToRedeemApprox,
                IERC20(idleYieldToken).balanceOf(address(this))
            );

            alreadyRedeemed = true;
            if (checkRedeemedAmount) {
                uint256 preBalanceOfWant = balanceOfWant();
                IIdleTokenV3_1(idleYieldToken).redeemIdleToken(valueToRedeem);
                uint256 postBalanceOfWant = balanceOfWant();

                // Note: could be equal, prefer >= in case of rounding
                // We just need that is at least the _amountNeeded, not below
                require(
                    (postBalanceOfWant.sub(preBalanceOfWant)) >= _amountNeeded,
                    'Redeemed amount must be >= _amountNeeded');
            } else {
                IIdleTokenV3_1(idleYieldToken).redeemIdleToken(valueToRedeem);
            }
        }

        // Min, otw vault accounting breaks
        _amountFreed = Math.min(balanceOfWant(), _amountNeeded);
    }

    // NOTE: Can override `tendTrigger` and `harvestTrigger` if necessary

    function harvestTrigger(uint256 callCost) public view override returns (bool) {
        return super.harvestTrigger(ethToWant(callCost));
    }

    function prepareMigration(address _newStrategy) internal override {
        // TODO: Transfer any non-`want` tokens to the new strategy
        // NOTE: `migrate` will automatically forward all `want` in this strategy to the new one

        // this automatically claims the gov tokens in addition to want
        IIdleTokenV3_1(idleYieldToken).redeemIdleToken(IERC20(idleYieldToken).balanceOf(address(this)));

        // Transfer gov tokens to new strategy
        for (uint256 i = 0; i < govTokens.length; i++) {
            IERC20 govToken = IERC20(govTokens[i]);
            govToken.transfer(_newStrategy, govToken.balanceOf(address(this)));
        }
    }

    function protectedTokens()
        internal
        override
        view
        returns (address[] memory)
    {
        address[] memory protected = new address[](1+govTokens.length);

        for (uint256 i = 0; i < govTokens.length; i++) {
            protected[i] = govTokens[i];
        }
        protected[govTokens.length] = idleYieldToken;

        return protected;
    }

    function balanceOnIdle() public view returns (uint256) {
        return IERC20(idleYieldToken).balanceOf(address(this)).mul(_getTokenPrice()).div(1e18);
    }

    function balanceOfWant() public view returns (uint256) {
        return IERC20(want).balanceOf(address(this));
    }

    function ethToWant(uint256 _amount) public view returns (uint256) {
        if (_amount == 0) {
            return 0;
        }

        address[] memory path = new address[](2);
        path[0] = address(weth);
        path[1] = address(want);
        uint256[] memory amounts = IUniswapRouter(uniswapRouterV2).getAmountsOut(_amount, path);

        return amounts[amounts.length - 1];
    }

    function getTokenPrice() view public returns (uint256) {
        return _getTokenPrice();
    }

    function _liquidateGovTokens() internal {
        for (uint256 i = 0; i < govTokens.length; i++) {
            IERC20 govToken = IERC20(govTokens[i]);
            uint256 balance = govToken.balanceOf(address(this));
            if (balance > 0) {
                govToken.safeApprove(uniswapRouterV2, 0);
                govToken.safeApprove(uniswapRouterV2, balance);

                address[] memory path = new address[](3);
                path[0] = address(govToken);
                path[1] = weth;
                path[2] = address(want);

                IUniswapRouter(uniswapRouterV2).swapExactTokensForTokens(
                    balance, 1, path, address(this), now.add(1800)
                );
            }
        }
    }

    function _setGovTokens(address[] memory _govTokens) internal {
        govTokens = _govTokens;
    }

    function _getTokenPrice() view internal returns (uint256) {
        /*
         *  As per https://github.com/Idle-Labs/idle-contracts/blob/ad0f18fef670ea6a4030fe600f64ece3d3ac2202/contracts/IdleTokenGovernance.sol#L878-L900
         *
         *  Price on minting is currentPrice
         *  Price on redeem must consider the fee
         *
         *  Below the implementation of the following redeemPrice formula
         *
         *  redeemPrice := underlyingAmount/idleTokenAmount
         *
         *  redeemPrice = currentPrice * (1 - scaledFee * ΔP%)
         *
         *  where:
         *  - scaledFee   := fee/FULL_ALLOC
         *  - ΔP% := 0 when currentPrice < userAvgPrice (no gain) and (currentPrice-userAvgPrice)/currentPrice
         *
         *  n.b: gain := idleTokenAmount * ΔP% * currentPrice
         */

        IIdleTokenV3_1 iyt = IIdleTokenV3_1(idleYieldToken);

        uint256 userAvgPrice = iyt.userAvgPrices(address(this));
        uint256 currentPrice = iyt.tokenPrice();

        uint256 tokenPrice;

        // When no deposits userAvgPrice is 0 equiv currentPrice
        // and in the case of issues
        if (userAvgPrice == 0 || currentPrice < userAvgPrice) {
            tokenPrice = currentPrice;
        } else {
            uint256 fee = iyt.fee();

            tokenPrice = ((currentPrice.mul(FULL_ALLOC))
                .sub(
                    fee.mul(
                         currentPrice.sub(userAvgPrice)
                    )
                )).div(FULL_ALLOC);
        }

        return tokenPrice;
    }
}

// File: /Users/ebonassi/Desktop/Active_Development/yearn-truffle-verify/contracts/StrategyIdleUSDC_BY.sol



pragma experimental ABIEncoderV2;
// SPDX-License-Identifier: AGPL-3.0

pragma solidity 0.6.12;

import "./StrategyIdle.sol";

/**
* Adds the mainnet addresses to the StrategyIdle
* BY = Best-Yield
*/
contract StrategyIdleUSDC_BY is StrategyIdle {

  address constant public __comp = address(0xc00e94Cb662C3520282E6f5717214004A7f26888);
  address constant public __idle = address(0x875773784Af8135eA0ef43b5a374AaD105c5D39e);
  address constant public __weth = address(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
  address constant public __usdc = address(0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48);

  address constant public __idleReservoir = address(0x031f71B5369c251a6544c41CE059e6b3d61e42C6);
  
  address constant public __idleYieldToken= address(0x5274891bEC421B39D23760c04A6755eCB444797C);
  address constant public __referral = address(0x652c1c23780d1A015938dD58b4a65a5F9eFBA653);
  address constant public __uniswapRouterV2 = address(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);

  constructor(
    address _vault
  )
  StrategyIdle(
        _vault,
        new address[](0),
        __weth,
        __idleReservoir,
        __idleYieldToken,
        __referral,
        __uniswapRouterV2
  )
  public {
    require(address(want) == __usdc, "Vault want is not USDC");

    address[] memory _govTokens = new address[](2);
    _govTokens[0] = __comp;
    _govTokens[1] = __idle;

    _setGovTokens(_govTokens);
  }

  function name() external override pure returns (string memory) {
      return "StrategyIdleUSDC_BY";
  }
}
// File: /Users/ebonassi/Desktop/Active_Development/yearn-truffle-verify/interfaces/Idle/IIdleTokenV3_1.sol



// SPDX-License-Identifier: AGPL-3.0
pragma solidity 0.6.12;

interface IIdleTokenV3_1 {
    // view
    /**
     * IdleToken price calculation not considering fees, in underlying
     *
     * @return price : price in underlying token
     */
    function tokenPrice() external view returns (uint256 price);

    // view
    /**
     * Map which saves avg idleToken minting price per user
     * Used in calculating redeem price
     *
     * @return price : price in underlying token
     */
    function userAvgPrices(address user) external view returns (uint256 price);


    // view
    /**
     * Current fee on interest gained
     *
     * @return fee : fee on interest gained
     */
    function fee() external view returns (uint256 fee);

    /**
     * @return underlying : underlying token address
     */
    function token() external view returns (address underlying);

    /**
     * Get APR of every ILendingProtocol
     *
     * @return addresses : array of token addresses
     * @return aprs : array of aprs (ordered in respect to the `addresses` array)
     */
    function getAPRs() external view returns (address[] memory addresses, uint256[] memory aprs);

    // external
    // We should save the amount one has deposited to calc interests

    /**
     * Used to mint IdleTokens, given an underlying amount (eg. DAI).
     * This method triggers a rebalance of the pools if needed
     * NOTE: User should 'approve' _amount of tokens before calling mintIdleToken
     * NOTE 2: this method can be paused
     *
     * @param _amount : amount of underlying token to be lended
     * @param _skipRebalance : flag for skipping rebalance for lower gas price
     * @param _referral : referral address
     * @return mintedTokens : amount of IdleTokens minted
     */
    function mintIdleToken(uint256 _amount, bool _skipRebalance, address _referral) external returns (uint256 mintedTokens);

    /**
     * Here we calc the pool share one can withdraw given the amount of IdleToken they want to burn
     * This method triggers a rebalance of the pools if needed
     * NOTE: If the contract is paused or iToken price has decreased one can still redeem but no rebalance happens.
     * NOTE 2: If iToken price has decresed one should not redeem (but can do it) otherwise he would capitalize the loss.
     *         Ideally one should wait until the black swan event is terminated
     *
     * @param _amount : amount of IdleTokens to be burned
     * @return redeemedTokens : amount of underlying tokens redeemed
     */
    function redeemIdleToken(uint256 _amount) external returns (uint256 redeemedTokens);
    /**
     * Here we calc the pool share one can withdraw given the amount of IdleToken they want to burn
     * and send interest-bearing tokens (eg. cDAI/iDAI) directly to the user.
     * Underlying (eg. DAI) is not redeemed here.
     *
     * @param _amount : amount of IdleTokens to be burned
     */
    function redeemInterestBearingTokens(uint256 _amount) external;

    /**
     * @return : whether has rebalanced or not
     */
    function rebalance() external returns (bool);
}
// File: /Users/ebonassi/Desktop/Active_Development/yearn-truffle-verify/interfaces/Idle/IdleReservoir.sol



// SPDX-License-Identifier: AGPL-3.0
pragma solidity 0.6.12;

interface IdleReservoir {
  function drip() external returns (uint256);
}
// File: /Users/ebonassi/Desktop/Active_Development/yearn-truffle-verify/interfaces/Uniswap/IUniswapRouter.sol




// SPDX-License-Identifier: AGPL-3.0

pragma solidity ^0.6.12;

interface IUniswapRouter {
    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);

    function getAmountsOut(uint256 amountIn, address[] memory path) external view returns (uint256[] memory amounts);
}
// File: @openzeppelin/contracts/math/Math.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.2;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}