// File: openzeppelin-solidity/contracts/token/ERC20/IERC20.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */
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.
     *
     * > 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-solidity/contracts/math/SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20.sol

pragma solidity ^0.5.0;



/**
 * @dev Implementation of the `IERC20` interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using `_mint`.
 * For a generic mechanism see `ERC20Mintable`.
 *
 * *For a detailed writeup see our guide [How to implement supply
 * mechanisms](https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226).*
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an `Approval` event is emitted on calls to `transferFrom`.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard `decreaseAllowance` and `increaseAllowance`
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See `IERC20.approve`.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    /**
     * @dev See `IERC20.totalSupply`.
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See `IERC20.balanceOf`.
     */
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See `IERC20.transfer`.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    /**
     * @dev See `IERC20.allowance`.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See `IERC20.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev See `IERC20.transferFrom`.
     *
     * Emits an `Approval` event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of `ERC20`;
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `value`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to `transfer`, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a `Transfer` event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount);
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a `Transfer` event with `from` set to the zero address.
     *
     * Requirements
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

     /**
     * @dev Destoys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a `Transfer` event with `to` set to the zero address.
     *
     * Requirements
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an `Approval` event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 value) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    /**
     * @dev Destoys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See `_burn` and `_approve`.
     */
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, msg.sender, _allowances[account][msg.sender].sub(amount));
    }
}

// File: contracts/Festaking.sol

pragma solidity ^0.5.8;



contract Festaking {
    using SafeMath for uint256;

    mapping (address => uint256) private _stakes;

    string public name;
    address  public tokenAddress;
    uint public stakingStarts;
    uint public stakingEnds;
    uint public withdrawStarts;
    uint public withdrawEnds;
    uint256 public stakedTotal;
    uint256 public stakingCap;
    uint256 public totalReward;
    uint256 public earlyWithdrawReward;
    uint256 public rewardBalance;
    uint256 public stakedBalance;

    ERC20 public ERC20Interface;
    event Staked(address indexed token, address indexed staker_, uint256 requestedAmount_, uint256 stakedAmount_);
    event PaidOut(address indexed token, address indexed staker_, uint256 amount_, uint256 reward_);
    event Refunded(address indexed token, address indexed staker_, uint256 amount_);

    /**
     */
    constructor (string memory name_,
        address tokenAddress_,
        uint stakingStarts_,
        uint stakingEnds_,
        uint withdrawStarts_,
        uint withdrawEnds_,
        uint256 stakingCap_) public {
        name = name_;
        require(tokenAddress_ != address(0), "Festaking: 0 address");
        tokenAddress = tokenAddress_;

        require(stakingStarts_ > 0, "Festaking: zero staking start time");
        if (stakingStarts_ < now) {
            stakingStarts = now;
        } else {
            stakingStarts = stakingStarts_;
        }

        require(stakingEnds_ > stakingStarts, "Festaking: staking end must be after staking starts");
        stakingEnds = stakingEnds_;

        require(withdrawStarts_ >= stakingEnds, "Festaking: withdrawStarts must be after staking ends");
        withdrawStarts = withdrawStarts_;

        require(withdrawEnds_ > withdrawStarts, "Festaking: withdrawEnds must be after withdraw starts");
        withdrawEnds = withdrawEnds_;

        require(stakingCap_ > 0, "Festaking: stakingCap must be positive");
        stakingCap = stakingCap_;
    }

    function addReward(uint256 rewardAmount, uint256 withdrawableAmount)
    public
    _before(withdrawStarts)
    _hasAllowance(msg.sender, rewardAmount)
    returns (bool) {
        require(rewardAmount > 0, "Festaking: reward must be positive");
        require(withdrawableAmount >= 0, "Festaking: withdrawable amount cannot be negative");
        require(withdrawableAmount <= rewardAmount, "Festaking: withdrawable amount must be less than or equal to the reward amount");
        address from = msg.sender;
        if (!_payMe(from, rewardAmount)) {
            return false;
        }

        totalReward = totalReward.add(rewardAmount);
        rewardBalance = totalReward;
        earlyWithdrawReward = earlyWithdrawReward.add(withdrawableAmount);
        return true;
    }

    function stakeOf(address account) public view returns (uint256) {
        return _stakes[account];
    }

    /**
    * Requirements:
    * - `amount` Amount to be staked
    */
    function stake(uint256 amount)
    public
    _positive(amount)
    _realAddress(msg.sender)
    returns (bool) {
        address from = msg.sender;
        return _stake(from, amount);
    }

    function withdraw(uint256 amount)
    public
    _after(withdrawStarts)
    _positive(amount)
    _realAddress(msg.sender)
    returns (bool) {
        address from = msg.sender;
        require(amount <= _stakes[from], "Festaking: not enough balance");
        if (now < withdrawEnds) {
            return _withdrawEarly(from, amount);
        } else {
            return _withdrawAfterClose(from, amount);
        }
    }

    function _withdrawEarly(address from, uint256 amount)
    private
    _realAddress(from)
    returns (bool) {
        // This is the formula to calculate reward:
        // r = (earlyWithdrawReward / stakedTotal) * (now - stakingEnds) / (withdrawEnds - stakingEnds)
        // w = (1+r) * a
        uint256 denom = (withdrawEnds.sub(stakingEnds)).mul(stakedTotal);
        uint256 reward = (
        ( (now.sub(stakingEnds)).mul(earlyWithdrawReward) ).mul(amount)
        ).div(denom);
        uint256 payOut = amount.add(reward);
        rewardBalance = rewardBalance.sub(reward);
        stakedBalance = stakedBalance.sub(amount);
        _stakes[from] = _stakes[from].sub(amount);
        if (_payDirect(from, payOut)) {
            emit PaidOut(tokenAddress, from, amount, reward);
            return true;
        }
        return false;
    }

    function _withdrawAfterClose(address from, uint256 amount)
    private
    _realAddress(from)
    returns (bool) {
        uint256 reward = (rewardBalance.mul(amount)).div(stakedBalance);
        uint256 payOut = amount.add(reward);
        _stakes[from] = _stakes[from].sub(amount);
        if (_payDirect(from, payOut)) {
            emit PaidOut(tokenAddress, from, amount, reward);
            return true;
        }
        return false;
    }

    function _stake(address staker, uint256 amount)
    private
    _after(stakingStarts)
    _before(stakingEnds)
    _positive(amount)
    _hasAllowance(staker, amount)
    returns (bool) {
        // check the remaining amount to be staked
        uint256 remaining = amount;
        if (remaining > (stakingCap.sub(stakedBalance))) {
            remaining = stakingCap.sub(stakedBalance);
        }
        // These requires are not necessary, because it will never happen, but won't hurt to double check
        // this is because stakedTotal and stakedBalance are only modified in this method during the staking period
        require(remaining > 0, "Festaking: Staking cap is filled");
        require((remaining + stakedTotal) <= stakingCap, "Festaking: this will increase staking amount pass the cap");
        if (!_payMe(staker, remaining)) {
            return false;
        }
        emit Staked(tokenAddress, staker, amount, remaining);

        if (remaining < amount) {
            // Return the unstaked amount to sender (from allowance)
            uint256 refund = amount.sub(remaining);
            if (_payTo(staker, staker, refund)) {
                emit Refunded(tokenAddress, staker, refund);
            }
        }

        // Transfer is completed
        stakedBalance = stakedBalance.add(remaining);
        stakedTotal = stakedTotal.add(remaining);
        _stakes[staker] = _stakes[staker].add(remaining);
        return true;
    }

    function _payMe(address payer, uint256 amount)
    private
    returns (bool) {
        return _payTo(payer, address(this), amount);
    }

    function _payTo(address allower, address receiver, uint256 amount)
    _hasAllowance(allower, amount)
    private
    returns (bool) {
        // Request to transfer amount from the contract to receiver.
        // contract does not own the funds, so the allower must have added allowance to the contract
        // Allower is the original owner.
        ERC20Interface = ERC20(tokenAddress);
        return ERC20Interface.transferFrom(allower, receiver, amount);
    }

    function _payDirect(address to, uint256 amount)
    private
    _positive(amount)
    returns (bool) {
        ERC20Interface = ERC20(tokenAddress);
        return ERC20Interface.transfer(to, amount);
    }

    modifier _realAddress(address addr) {
        require(addr != address(0), "Festaking: zero address");
        _;
    }

    modifier _positive(uint256 amount) {
        require(amount >= 0, "Festaking: negative amount");
        _;
    }

    modifier _after(uint eventTime) {
        require(now >= eventTime, "Festaking: bad timing for the request");
        _;
    }

    modifier _before(uint eventTime) {
        require(now < eventTime, "Festaking: bad timing for the request");
        _;
    }

    modifier _hasAllowance(address allower, uint256 amount) {
        // Make sure the allower has provided the right allowance.
        ERC20Interface = ERC20(tokenAddress);
        uint256 ourAllowance = ERC20Interface.allowance(allower, address(this));
        require(amount <= ourAllowance, "Festaking: Make sure to add enough allowance");
        _;
    }
}