/*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: RewardsDistribution.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/RewardsDistribution.sol
* Docs: https://docs.synthetix.io/contracts/RewardsDistribution
*
* Contract Dependencies: 
*	- IRewardsDistribution
*	- Owned
* Libraries: 
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2023 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/



pragma solidity ^0.5.16;

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        _onlyOwner();
        _;
    }

    function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// https://docs.synthetix.io/contracts/source/interfaces/irewardsdistribution
interface IRewardsDistribution {
    // Structs
    struct DistributionData {
        address destination;
        uint amount;
    }

    // Views
    function authority() external view returns (address);

    function distributions(uint index) external view returns (address destination, uint amount); // DistributionData

    function distributionsLength() external view returns (uint);

    // Mutative Functions
    function distributeRewards(uint amount) external returns (bool);
}


/**
 * @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;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/source/libraries/safedecimalmath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    // Computes `a - b`, setting the value to 0 if b > a.
    function floorsub(uint a, uint b) internal pure returns (uint) {
        return b >= a ? 0 : a - b;
    }

    /* ---------- Utilities ---------- */
    /*
     * Absolute value of the input, returned as a signed number.
     */
    function signedAbs(int x) internal pure returns (int) {
        return x < 0 ? -x : x;
    }

    /*
     * Absolute value of the input, returned as an unsigned number.
     */
    function abs(int x) internal pure returns (uint) {
        return uint(signedAbs(x));
    }
}


// https://docs.synthetix.io/contracts/source/interfaces/ierc20
interface IERC20 {
    // ERC20 Optional Views
    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Events
    event Transfer(address indexed from, address indexed to, uint value);

    event Approval(address indexed owner, address indexed spender, uint value);
}


// https://docs.synthetix.io/contracts/source/interfaces/ifeepool
interface IFeePool {
    // Views

    // solhint-disable-next-line func-name-mixedcase
    function FEE_ADDRESS() external view returns (address);

    function feesAvailable(address account) external view returns (uint, uint);

    function feesBurned(address account) external view returns (uint);

    function feesToBurn(address account) external view returns (uint);

    function feePeriodDuration() external view returns (uint);

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

    function targetThreshold() external view returns (uint);

    function totalFeesAvailable() external view returns (uint);

    function totalFeesBurned() external view returns (uint);

    function totalRewardsAvailable() external view returns (uint);

    // Mutative Functions
    function claimFees() external returns (bool);

    function claimOnBehalf(address claimingForAddress) external returns (bool);

    function closeCurrentFeePeriod() external;

    function closeSecondary(uint snxBackedDebt, uint debtShareSupply) external;

    function recordFeePaid(uint sUSDAmount) external;

    function setRewardsToDistribute(uint amount) external;
}


// Inheritance


// Libraires


// Internal references


// https://docs.synthetix.io/contracts/source/contracts/rewardsdistribution
contract RewardsDistribution is Owned, IRewardsDistribution {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /**
     * @notice Authorised address able to call distributeRewards
     */
    address public authority;

    /**
     * @notice Address of the Synthetix ProxyERC20
     */
    address public synthetixProxy;

    /**
     * @notice Address of the RewardEscrow contract
     */
    address public rewardEscrow;

    /**
     * @notice Address of the FeePoolProxy
     */
    address public feePoolProxy;

    /**
     * @notice An array of addresses and amounts to send
     */
    DistributionData[] public distributions;

    /**
     * @dev _authority maybe the underlying synthetix contract.
     * Remember to set the authority on a synthetix upgrade
     */
    constructor(
        address _owner,
        address _authority,
        address _synthetixProxy,
        address _rewardEscrow,
        address _feePoolProxy
    ) public Owned(_owner) {
        authority = _authority;
        synthetixProxy = _synthetixProxy;
        rewardEscrow = _rewardEscrow;
        feePoolProxy = _feePoolProxy;
    }

    // ========== EXTERNAL SETTERS ==========

    function setSynthetixProxy(address _synthetixProxy) external onlyOwner {
        synthetixProxy = _synthetixProxy;
    }

    function setRewardEscrow(address _rewardEscrow) external onlyOwner {
        rewardEscrow = _rewardEscrow;
    }

    function setFeePoolProxy(address _feePoolProxy) external onlyOwner {
        feePoolProxy = _feePoolProxy;
    }

    /**
     * @notice Set the address of the contract authorised to call distributeRewards()
     * @param _authority Address of the authorised calling contract.
     */
    function setAuthority(address _authority) external onlyOwner {
        authority = _authority;
    }

    // ========== EXTERNAL FUNCTIONS ==========

    /**
     * @notice Adds a Rewards DistributionData struct to the distributions
     * array. Any entries here will be iterated and rewards distributed to
     * each address when tokens are sent to this contract and distributeRewards()
     * is called by the autority.
     * @param destination An address to send rewards tokens too
     * @param amount The amount of rewards tokens to send
     */
    function addRewardDistribution(address destination, uint amount) external onlyOwner returns (bool) {
        require(destination != address(0), "Cant add a zero address");
        require(amount != 0, "Cant add a zero amount");

        DistributionData memory rewardsDistribution = DistributionData(destination, amount);
        distributions.push(rewardsDistribution);

        emit RewardDistributionAdded(distributions.length - 1, destination, amount);
        return true;
    }

    /**
     * @notice Deletes a RewardDistribution from the distributions
     * so it will no longer be included in the call to distributeRewards()
     * @param index The index of the DistributionData to delete
     */
    function removeRewardDistribution(uint index) external onlyOwner {
        require(index <= distributions.length - 1, "index out of bounds");

        // shift distributions indexes across
        for (uint i = index; i < distributions.length - 1; i++) {
            distributions[i] = distributions[i + 1];
        }
        distributions.length--;

        // Since this function must shift all later entries down to fill the
        // gap from the one it removed, it could in principle consume an
        // unbounded amount of gas. However, the number of entries will
        // presumably always be very low.
    }

    /**
     * @notice Edits a RewardDistribution in the distributions array.
     * @param index The index of the DistributionData to edit
     * @param destination The destination address. Send the same address to keep or different address to change it.
     * @param amount The amount of tokens to edit. Send the same number to keep or change the amount of tokens to send.
     */
    function editRewardDistribution(
        uint index,
        address destination,
        uint amount
    ) external onlyOwner returns (bool) {
        require(index <= distributions.length - 1, "index out of bounds");

        distributions[index].destination = destination;
        distributions[index].amount = amount;

        return true;
    }

    function distributeRewards(uint amount) external returns (bool) {
        require(amount > 0, "Nothing to distribute");
        require(msg.sender == authority, "Caller is not authorised");
        require(rewardEscrow != address(0), "RewardEscrow is not set");
        require(synthetixProxy != address(0), "SynthetixProxy is not set");
        require(feePoolProxy != address(0), "FeePoolProxy is not set");
        require(
            IERC20(synthetixProxy).balanceOf(address(this)) >= amount,
            "RewardsDistribution contract does not have enough tokens to distribute"
        );

        uint remainder = amount;

        // Iterate the array of distributions sending the configured amounts
        for (uint i = 0; i < distributions.length; i++) {
            if (distributions[i].destination != address(0) && distributions[i].amount != 0) {
                remainder = remainder.sub(distributions[i].amount);

                // Transfer the SNX
                IERC20(synthetixProxy).transfer(distributions[i].destination, distributions[i].amount);

                // If the contract implements RewardsDistributionRecipient.sol, inform it how many SNX its received.
                bytes memory payload = abi.encodeWithSignature("notifyRewardAmount(uint256)", distributions[i].amount);

                // solhint-disable avoid-low-level-calls
                (bool success, bytes memory result) = distributions[i].destination.call(payload);

                if (!success) {
                    // if the error was emitted by the destination contract, bubble
                    uint len = result.length;
                    assembly {
                        revert(add(result, 0x20), len)
                    }
                }
            }
        }

        // After all ditributions have been sent, send the remainder to the RewardsEscrow contract
        IERC20(synthetixProxy).transfer(rewardEscrow, remainder);

        // Tell the FeePool how much it has to distribute to the stakers
        IFeePool(feePoolProxy).setRewardsToDistribute(remainder);

        emit RewardsDistributed(amount);
        return true;
    }

    /* ========== VIEWS ========== */

    /**
     * @notice Retrieve the length of the distributions array
     */
    function distributionsLength() external view returns (uint) {
        return distributions.length;
    }

    /* ========== Events ========== */

    event RewardDistributionAdded(uint index, address destination, uint amount);
    event RewardsDistributed(uint amount);
}