// File: contracts/managers/DiscountManager.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

import {SafeMath} from "@openzeppelin/contracts/math/SafeMath.sol";
import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import {ReentrancyGuard} from "@openzeppelin/contracts/utils/ReentrancyGuard.sol";

import {DiscounterRole} from "../roles/DiscounterRole.sol";
import {IYLD} from "../interfaces/IYLD.sol";


interface IDiscountManager
{
  event Enroll(address indexed account, uint256 amount);
  event Exit(address indexed account);


  function isDiscounted(address account) external view returns (bool);

  function updateUnlockTime(address lender, address borrower, uint256 duration) external;
}


contract DiscountManager is IDiscountManager, DiscounterRole, ReentrancyGuard
{
  using SafeMath for uint256;


  address private immutable _YLD;

  uint256 private _requiredAmount = 50 * 1e18; // 50 YLD
  bool private _discountsActivated = true;

  mapping(address => uint256) private _balanceOf;
  mapping(address => uint256) private _unlockTimeOf;


  constructor()
  {
    _YLD = address(0xDcB01cc464238396E213a6fDd933E36796eAfF9f);
  }

  function requiredAmount () public view returns (uint256)
  {
    return _requiredAmount;
  }

  function discountsActivated () public view returns (bool)
  {
    return _discountsActivated;
  }

  function balanceOf (address account) public view returns (uint256)
  {
    return _balanceOf[account];
  }

  function unlockTimeOf (address account) public view returns (uint256)
  {
    return _unlockTimeOf[account];
  }

  function isDiscounted(address account) public view override returns (bool)
  {
    return _discountsActivated ? _balanceOf[account] >= _requiredAmount : false;
  }


  function enroll() external nonReentrant
  {
    require(_discountsActivated, "Discounts off");
    require(!isDiscounted(msg.sender), "In");

    require(IERC20(_YLD).transferFrom(msg.sender, address(this), _requiredAmount));

    _balanceOf[msg.sender] = _requiredAmount;
    _unlockTimeOf[msg.sender] = block.timestamp.add(4 weeks);

    emit Enroll(msg.sender, _requiredAmount);
  }

  function exit() external nonReentrant
  {
    require(_balanceOf[msg.sender] >= _requiredAmount, "!in");
    require(block.timestamp > _unlockTimeOf[msg.sender], "Discounting");

    require(IERC20(_YLD).transfer(msg.sender, _balanceOf[msg.sender]));

    _balanceOf[msg.sender] = 0;
    _unlockTimeOf[msg.sender] = 0;

    emit Exit(msg.sender);
  }


  function updateUnlockTime(address lender, address borrower, uint256 duration) external override onlyDiscounter
  {
    uint256 lenderUnlockTime = _unlockTimeOf[lender];
    uint256 borrowerUnlockTime = _unlockTimeOf[borrower];

    if (isDiscounted(lender))
    {
      _unlockTimeOf[lender] = (block.timestamp >= lenderUnlockTime || lenderUnlockTime.sub(block.timestamp) < duration) ? lenderUnlockTime.add(duration.add(4 weeks)) : lenderUnlockTime;
    }
    else if (isDiscounted(borrower))
    {
      _unlockTimeOf[borrower] = (block.timestamp >= borrowerUnlockTime || borrowerUnlockTime.sub(block.timestamp) < duration) ? borrowerUnlockTime.add(duration.add(4 weeks)) : borrowerUnlockTime;
    }
  }

  function activateDiscounts() external onlyDiscounter
  {
    require(!_discountsActivated, "Activated");

    _discountsActivated = true;
  }

  function deactivateDiscounts() external onlyDiscounter
  {
    require(_discountsActivated, "Deactivated");

    _discountsActivated = false;
  }

  function setRequiredAmount(uint256 newAmount) external onlyDiscounter
  {
    require(newAmount > (0.75 * 1e18) && newAmount < type(uint256).max, "Invalid val");

    _requiredAmount = newAmount;
  }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @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) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * 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);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * 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);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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 ^0.7.0;

/**
 * @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/utils/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: contracts/roles/DiscounterRole.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

import {Roles} from "./Roles.sol";


contract DiscounterRole
{
  using Roles for Roles.Role;

  Roles.Role private _discounters;

  event DiscounterAdded(address indexed account);
  event DiscounterRemoved(address indexed account);

  modifier onlyDiscounter()
  {
    require(isDiscounter(msg.sender), "!discounter");
    _;
  }

  constructor()
  {
    _discounters.add(msg.sender);

    emit DiscounterAdded(msg.sender);
  }

  function isDiscounter(address account) public view returns (bool)
  {
    return _discounters.has(account);
  }

  function addDiscounter(address account) public onlyDiscounter
  {
    _discounters.add(account);

    emit DiscounterAdded(account);
  }

  function renounceDiscounter() public
  {
    _discounters.remove(msg.sender);

    emit DiscounterRemoved(msg.sender);
  }
}

// File: contracts/interfaces/IYLD.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;


interface IYLD
{
  function renounceMinter() external;

  function mint(address account, uint256 amount) external returns (bool);
}

// File: contracts/roles/Roles.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles
{
  struct Role
  {
    mapping(address => bool) bearer;
  }

  /**
   * @dev Give an account access to this role.
   */
  function add(Role storage role, address account) internal
  {
    require(!has(role, account), "has role");
    role.bearer[account] = true;
  }

  /**
   * @dev Remove an account's access to this role.
   */
  function remove(Role storage role, address account) internal
  {
    require(has(role, account), "!has role");
    role.bearer[account] = false;
  }

  /**
   * @dev Check if an account has this role.
   * @return bool
   */
  function has(Role storage role, address account) internal view returns (bool)
  {
    require(account != address(0), "Roles: 0 addy");

    return role.bearer[account];
  }
}