// File: contracts/sFlyzERC20.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

import './types/ERC20.sol';
import './types/Ownable.sol';

contract sFlyzERC20 is ERC20Permit, Ownable {
    using SafeMath for uint256;

    modifier onlyStakingContract() {
        require(msg.sender == stakingContract);
        _;
    }

    address public stakingContract;
    address public initializer;

    event LogSupply(
        uint256 indexed epoch,
        uint256 timestamp,
        uint256 totalSupply
    );
    event LogRebase(uint256 indexed epoch, uint256 rebase, uint256 index);
    event LogStakingContractUpdated(address stakingContract);

    struct Rebase {
        uint256 epoch;
        uint256 rebase; // 18 decimals
        uint256 totalStakedBefore;
        uint256 totalStakedAfter;
        uint256 amountRebased;
        uint256 index;
        uint256 blockNumberOccured;
    }
    Rebase[] public rebases;

    uint256 public INDEX;

    uint256 private constant MAX_UINT256 = ~uint256(0);
    uint256 private constant INITIAL_FRAGMENTS_SUPPLY = 5000000 * 10**9;

    // TOTAL_GONS is a multiple of INITIAL_FRAGMENTS_SUPPLY so that _gonsPerFragment is an integer.
    // Use the highest value that fits in a uint256 for max granularity.
    uint256 private constant TOTAL_GONS =
        MAX_UINT256 - (MAX_UINT256 % INITIAL_FRAGMENTS_SUPPLY);

    // MAX_SUPPLY = maximum integer < (sqrt(4*TOTAL_GONS + 1) - 1) / 2
    uint256 private constant MAX_SUPPLY = ~uint128(0); // (2^128) - 1

    uint256 private _gonsPerFragment;
    mapping(address => uint256) private _gonBalances;

    mapping(address => mapping(address => uint256)) private _allowedValue;

    constructor() ERC20('sFlyzERC20', 'sFLZ', 9) ERC20Permit() {
        initializer = msg.sender;
        _totalSupply = INITIAL_FRAGMENTS_SUPPLY;
        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);
    }

    function initialize(address stakingContract_) external returns (bool) {
        require(msg.sender == initializer);
        require(stakingContract_ != address(0));
        stakingContract = stakingContract_;
        _gonBalances[stakingContract] = TOTAL_GONS;

        emit Transfer(address(0x0), stakingContract, _totalSupply);
        emit LogStakingContractUpdated(stakingContract_);

        initializer = address(0);
        return true;
    }

    function setIndex(uint256 _INDEX) external onlyOwner returns (bool) {
        require(INDEX == 0);
        INDEX = gonsForBalance(_INDEX);
        return true;
    }

    /**
        @notice increases sFLYZ supply to increase staking balances relative to profit_
        @param profit_ uint256
        @return uint256
     */
    function rebase(uint256 profit_, uint256 epoch_)
        public
        onlyStakingContract
        returns (uint256)
    {
        uint256 rebaseAmount;
        uint256 circulatingSupply_ = circulatingSupply();

        if (profit_ == 0) {
            emit LogSupply(epoch_, block.timestamp, _totalSupply);
            emit LogRebase(epoch_, 0, index());
            return _totalSupply;
        } else if (circulatingSupply_ > 0) {
            rebaseAmount = profit_.mul(_totalSupply).div(circulatingSupply_);
        } else {
            rebaseAmount = profit_;
        }

        _totalSupply = _totalSupply.add(rebaseAmount);

        if (_totalSupply > MAX_SUPPLY) {
            _totalSupply = MAX_SUPPLY;
        }

        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);

        _storeRebase(circulatingSupply_, profit_, epoch_);

        return _totalSupply;
    }

    /**
        @notice emits event with data about rebase
        @param previousCirculating_ uint
        @param profit_ uint
        @param epoch_ uint
        @return bool
     */
    function _storeRebase(
        uint256 previousCirculating_,
        uint256 profit_,
        uint256 epoch_
    ) internal returns (bool) {
        uint256 rebasePercent = profit_.mul(1e18).div(previousCirculating_);

        rebases.push(
            Rebase({
                epoch: epoch_,
                rebase: rebasePercent, // 18 decimals
                totalStakedBefore: previousCirculating_,
                totalStakedAfter: circulatingSupply(),
                amountRebased: profit_,
                index: index(),
                blockNumberOccured: block.number
            })
        );

        emit LogSupply(epoch_, block.timestamp, _totalSupply);
        emit LogRebase(epoch_, rebasePercent, index());

        return true;
    }

    function balanceOf(address who) public view override returns (uint256) {
        return _gonBalances[who].div(_gonsPerFragment);
    }

    function gonsForBalance(uint256 amount) public view returns (uint256) {
        return amount.mul(_gonsPerFragment);
    }

    function balanceForGons(uint256 gons) public view returns (uint256) {
        return gons.div(_gonsPerFragment);
    }

    // Staking contract holds excess sFLYZ
    function circulatingSupply() public view returns (uint256) {
        return _totalSupply.sub(balanceOf(stakingContract));
    }

    function index() public view returns (uint256) {
        return balanceForGons(INDEX);
    }

    function transfer(address to, uint256 value)
        public
        override
        returns (bool)
    {
        uint256 gonValue = value.mul(_gonsPerFragment);
        _gonBalances[msg.sender] = _gonBalances[msg.sender].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(msg.sender, to, value);
        return true;
    }

    function allowance(address owner_, address spender)
        public
        view
        override
        returns (uint256)
    {
        return _allowedValue[owner_][spender];
    }

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) public override returns (bool) {
        _allowedValue[from][msg.sender] = _allowedValue[from][msg.sender].sub(
            value
        );
        emit Approval(from, msg.sender, _allowedValue[from][msg.sender]);

        uint256 gonValue = gonsForBalance(value);
        _gonBalances[from] = _gonBalances[from].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(from, to, value);

        return true;
    }

    function approve(address spender, uint256 value)
        public
        override
        returns (bool)
    {
        _allowedValue[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    // What gets called in a permit
    function _approve(
        address owner,
        address spender,
        uint256 value
    ) internal virtual override {
        _allowedValue[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    function increaseAllowance(address spender, uint256 addedValue)
        public
        override
        returns (bool)
    {
        _allowedValue[msg.sender][spender] = _allowedValue[msg.sender][spender]
            .add(addedValue);
        emit Approval(msg.sender, spender, _allowedValue[msg.sender][spender]);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue)
        public
        override
        returns (bool)
    {
        uint256 oldValue = _allowedValue[msg.sender][spender];
        if (subtractedValue >= oldValue) {
            _allowedValue[msg.sender][spender] = 0;
        } else {
            _allowedValue[msg.sender][spender] = oldValue.sub(subtractedValue);
        }
        emit Approval(msg.sender, spender, _allowedValue[msg.sender][spender]);
        return true;
    }
}

// File: contracts/types/ERC20.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

import '../interfaces/IERC20.sol';
import '../libraries/SafeMath.sol';
import '../libraries/Counters.sol';
import '../libraries/Address.sol';

abstract contract ERC20 is IERC20 {
    using SafeMath for uint256;

    // TODO comment actual hash value.
    bytes32 private constant ERC20TOKEN_ERC1820_INTERFACE_ID =
        keccak256('ERC20Token');

    mapping(address => uint256) internal _balances;

    mapping(address => mapping(address => uint256)) internal _allowances;

    uint256 internal _totalSupply;

    string internal _name;

    string internal _symbol;

    uint8 internal _decimals;

    constructor(
        string memory name_,
        string memory symbol_,
        uint8 decimals_
    ) {
        _name = name_;
        _symbol = symbol_;
        _decimals = decimals_;
    }

    function name() public view override returns (string memory) {
        return _name;
    }

    function symbol() public view override returns (string memory) {
        return _symbol;
    }

    function decimals() public view override returns (uint8) {
        return _decimals;
    }

    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }

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

    function transfer(address recipient, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function allowance(address owner, address spender)
        public
        view
        virtual
        override
        returns (uint256)
    {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(
            sender,
            msg.sender,
            _allowances[sender][msg.sender].sub(
                amount,
                'ERC20: transfer amount exceeds allowance'
            )
        );
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue)
        public
        virtual
        returns (bool)
    {
        _approve(
            msg.sender,
            spender,
            _allowances[msg.sender][spender].add(addedValue)
        );
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue)
        public
        virtual
        returns (bool)
    {
        _approve(
            msg.sender,
            spender,
            _allowances[msg.sender][spender].sub(
                subtractedValue,
                'ERC20: decreased allowance below zero'
            )
        );
        return true;
    }

    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), 'ERC20: transfer from the zero address');
        require(recipient != address(0), 'ERC20: transfer to the zero address');

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(
            amount,
            'ERC20: transfer amount exceeds balance'
        );
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    function _mint(address account_, uint256 ammount_) internal virtual {
        require(account_ != address(0), 'ERC20: mint to the zero address');
        _beforeTokenTransfer(address(this), account_, ammount_);
        _totalSupply = _totalSupply.add(ammount_);
        _balances[account_] = _balances[account_].add(ammount_);
        emit Transfer(address(this), account_, ammount_);
    }

    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), 'ERC20: burn from the zero address');

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(
            amount,
            'ERC20: burn amount exceeds balance'
        );
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), 'ERC20: approve from the zero address');
        require(spender != address(0), 'ERC20: approve to the zero address');

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function _beforeTokenTransfer(
        address from_,
        address to_,
        uint256 amount_
    ) internal virtual {}
}

interface IERC2612Permit {
    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    function nonces(address owner) external view returns (uint256);
}

abstract contract ERC20Permit is ERC20, IERC2612Permit {
    using Counters for Counters.Counter;

    mapping(address => Counters.Counter) private _nonces;

    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH =
        0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;

    bytes32 public DOMAIN_SEPARATOR;

    constructor() {
        uint256 chainID;
        assembly {
            chainID := chainid()
        }

        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256(
                    'EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'
                ),
                keccak256(bytes(name())),
                keccak256(bytes('1')), // Version
                chainID,
                address(this)
            )
        );
    }

    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public virtual override {
        require(block.timestamp <= deadline, 'Permit: expired deadline');

        bytes32 hashStruct = keccak256(
            abi.encode(
                PERMIT_TYPEHASH,
                owner,
                spender,
                amount,
                _nonces[owner].current(),
                deadline
            )
        );

        bytes32 _hash = keccak256(
            abi.encodePacked(uint16(0x1901), DOMAIN_SEPARATOR, hashStruct)
        );

        address signer = ecrecover(_hash, v, r, s);
        require(
            signer != address(0) && signer == owner,
            'ZeroSwapPermit: Invalid signature'
        );

        _nonces[owner].increment();
        _approve(owner, spender, amount);
    }

    function nonces(address owner) public view override returns (uint256) {
        return _nonces[owner].current();
    }
}

// File: contracts/types/Ownable.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

interface IOwnable {
    function owner() external view returns (address);

    function renounceManagement() external;

    function pushManagement(address newOwner_) external;

    function pullManagement() external;
}

contract Ownable is IOwnable {
    address internal _owner;
    address internal _newOwner;

    event OwnershipPushed(
        address indexed previousOwner,
        address indexed newOwner
    );
    event OwnershipPulled(
        address indexed previousOwner,
        address indexed newOwner
    );

    constructor() {
        _owner = msg.sender;
        emit OwnershipPushed(address(0), _owner);
    }

    function owner() public view override returns (address) {
        return _owner;
    }

    modifier onlyOwner() {
        require(_owner == msg.sender, 'Ownable: caller is not the owner');
        _;
    }

    function renounceManagement() public virtual override onlyOwner {
        emit OwnershipPushed(_owner, address(0));
        _owner = address(0);
    }

    function pushManagement(address newOwner_)
        public
        virtual
        override
        onlyOwner
    {
        require(
            newOwner_ != address(0),
            'Ownable: new owner is the zero address'
        );
        emit OwnershipPushed(_owner, newOwner_);
        _newOwner = newOwner_;
    }

    function pullManagement() public virtual override {
        require(msg.sender == _newOwner, 'Ownable: must be new owner to pull');
        emit OwnershipPulled(_owner, _newOwner);
        _owner = _newOwner;
    }
}

// File: contracts/interfaces/IERC20.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity >=0.5.0;

interface IERC20 {
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Transfer(address indexed from, address indexed to, uint256 value);

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

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

    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 value) external returns (bool);

    function transfer(address to, uint256 value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);
}

interface IERC20Mintable {
    function mint(uint256 amount_) external;

    function mint(address account_, uint256 ammount_) external;
}

// File: contracts/libraries/SafeMath.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, 'SafeMath: addition overflow');

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, 'SafeMath: subtraction overflow');
    }

    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    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;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, 'SafeMath: division by 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;
    }

    function sqrrt(uint256 a) internal pure returns (uint256 c) {
        if (a > 3) {
            c = a;
            uint256 b = add(div(a, 2), 1);
            while (b < c) {
                c = b;
                b = div(add(div(a, b), b), 2);
            }
        } else if (a != 0) {
            c = 1;
        }
    }
}

// File: contracts/libraries/Counters.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

import './SafeMath.sol';

library Counters {
    using SafeMath for uint256;

    struct Counter {
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}

// File: contracts/libraries/Address.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

library Address {
    function isContract(address account) internal view returns (bool) {
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    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'
        );
    }

    function functionCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return functionCall(target, data, 'Address: low-level call failed');
    }

    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    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'
            );
    }

    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'
        );
        require(isContract(target), 'Address: call to non-contract');

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{value: value}(
            data
        );
        return _verifyCallResult(success, returndata, 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);
            }
        }
    }

    function functionStaticCall(address target, bytes memory data)
        internal
        view
        returns (bytes memory)
    {
        return
            functionStaticCall(
                target,
                data,
                'Address: low-level static call failed'
            );
    }

    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), 'Address: static call to non-contract');

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function functionDelegateCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return
            functionDelegateCall(
                target,
                data,
                'Address: low-level delegate call failed'
            );
    }

    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), 'Address: delegate call to non-contract');

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            if (returndata.length > 0) {
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }

    function addressToString(address _address)
        internal
        pure
        returns (string memory)
    {
        bytes32 _bytes = bytes32(uint256(_address));
        bytes memory HEX = '0123456789abcdef';
        bytes memory _addr = new bytes(42);

        _addr[0] = '0';
        _addr[1] = 'x';

        for (uint256 i = 0; i < 20; i++) {
            _addr[2 + i * 2] = HEX[uint8(_bytes[i + 12] >> 4)];
            _addr[3 + i * 2] = HEX[uint8(_bytes[i + 12] & 0x0f)];
        }

        return string(_addr);
    }
}