// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

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

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: contracts/Distirbutor.sol



// SPDX-License-Identifier: AGPL-3.0
pragma solidity 0.8.19;

import "@openzeppelin/contracts/access/Ownable.sol";
import "./interface/IQWN.sol";
import "./interface/ITreasury.sol";

/// @title   Distributor
/// @notice  QWN Staking Distributor
contract Distributor is Ownable {
    /// VARIABLES ///

    /// @notice QWN address
    IERC20 public immutable QWN;
    /// @notice Treasury address
    ITreasury public immutable treasury;
    /// @notice Staking address
    address public immutable staking;

    /// @notice In ten-thousandths ( 5000 = 0.5% )
    uint256 public rate;

    uint256 public constant rateDenominator = 1_000_000;

    /// CONSTRUCTOR ///

    /// @param _treasury  Address of treasury contract
    /// @param _QWN      Address of QWN
    /// @param _staking   Address of staking contract
    constructor(address _treasury, address _QWN, address _staking) {
        require(_treasury != address(0), "Zero address: Treasury");
        treasury = ITreasury(_treasury);
        require(_QWN != address(0), "Zero address: QWN");
        QWN = IQWN(_QWN);
        require(_staking != address(0), "Zero address: Staking");
        staking = _staking;
    }

    /// STAKING FUNCTION ///

    /// @notice Send epoch reward to staking contract
    function distribute() external {
        require(msg.sender == staking, "Only staking");
        treasury.mintQWN(staking, nextReward()); // mint and send tokens
    }

    /// VIEW FUNCTIONS ///

    /// @notice          Returns next reward at given rate
    /// @param _rate     Rate
    /// @return _reward  Next reward
    function nextRewardAt(uint256 _rate) public view returns (uint256 _reward) {
        return (QWN.totalSupply() * _rate) / rateDenominator;
    }

    /// @notice          Returns next reward of staking contract
    /// @return _reward  Next reward for staking contract
    function nextReward() public view returns (uint256 _reward) {
        uint256 excessReserves = treasury.excessReserves();
        _reward = nextRewardAt(rate);
        if (excessReserves < _reward) _reward = excessReserves;
    }

    /// POLICY FUNCTIONS ///

    /// @notice             Set reward rate for rebase
    /// @param _rewardRate  New rate
    function setRate(uint256 _rewardRate) external onlyOwner {
        require(
            _rewardRate <= rateDenominator,
            "Rate cannot exceed denominator"
        );
        rate = _rewardRate;
    }
}

// File: contracts/interface/IQWN.sol



import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";

pragma solidity 0.8.19;

interface IQWN is IERC20Metadata {
    function mint(address to_, uint256 amount_) external;

    function burnFrom(address account_, uint256 amount_) external;

    function burn(uint256 amount_) external;

    function uniswapV2Pair() external view returns (address);
}

// File: contracts/interface/ITreasury.sol



pragma solidity >=0.7.5;

interface ITreasury {
    function mintQWN(address to_, uint256 amount_) external;

    function QWN() external view returns (address);

    function excessReserves() external view returns (uint256);
}