// SPDX-License-Identifier: Unlicense
/*
 * @title Solidity Bytes Arrays Utils
 * @author Gonçalo Sá <goncalo.sa@consensys.net>
 *
 * @dev Bytes tightly packed arrays utility library for ethereum contracts written in Solidity.
 *      The library lets you concatenate, slice and type cast bytes arrays both in memory and storage.
 */
pragma solidity >=0.8.0 <0.9.0;


library BytesLib {
    function concat(
        bytes memory _preBytes,
        bytes memory _postBytes
    )
    internal
    pure
    returns (bytes memory)
    {
        bytes memory tempBytes;

        assembly {
        // Get a location of some free memory and store it in tempBytes as
        // Solidity does for memory variables.
            tempBytes := mload(0x40)

        // Store the length of the first bytes array at the beginning of
        // the memory for tempBytes.
            let length := mload(_preBytes)
            mstore(tempBytes, length)

        // Maintain a memory counter for the current write location in the
        // temp bytes array by adding the 32 bytes for the array length to
        // the starting location.
            let mc := add(tempBytes, 0x20)
        // Stop copying when the memory counter reaches the length of the
        // first bytes array.
            let end := add(mc, length)

            for {
            // Initialize a copy counter to the start of the _preBytes data,
            // 32 bytes into its memory.
                let cc := add(_preBytes, 0x20)
            } lt(mc, end) {
            // Increase both counters by 32 bytes each iteration.
                mc := add(mc, 0x20)
                cc := add(cc, 0x20)
            } {
            // Write the _preBytes data into the tempBytes memory 32 bytes
            // at a time.
                mstore(mc, mload(cc))
            }

        // Add the length of _postBytes to the current length of tempBytes
        // and store it as the new length in the first 32 bytes of the
        // tempBytes memory.
            length := mload(_postBytes)
            mstore(tempBytes, add(length, mload(tempBytes)))

        // Move the memory counter back from a multiple of 0x20 to the
        // actual end of the _preBytes data.
            mc := end
        // Stop copying when the memory counter reaches the new combined
        // length of the arrays.
            end := add(mc, length)

            for {
                let cc := add(_postBytes, 0x20)
            } lt(mc, end) {
                mc := add(mc, 0x20)
                cc := add(cc, 0x20)
            } {
                mstore(mc, mload(cc))
            }

        // Update the free-memory pointer by padding our last write location
        // to 32 bytes: add 31 bytes to the end of tempBytes to move to the
        // next 32 byte block, then round down to the nearest multiple of
        // 32. If the sum of the length of the two arrays is zero then add
        // one before rounding down to leave a blank 32 bytes (the length block with 0).
            mstore(0x40, and(
            add(add(end, iszero(add(length, mload(_preBytes)))), 31),
            not(31) // Round down to the nearest 32 bytes.
            ))
        }

        return tempBytes;
    }

    function concatStorage(bytes storage _preBytes, bytes memory _postBytes) internal {
        assembly {
        // Read the first 32 bytes of _preBytes storage, which is the length
        // of the array. (We don't need to use the offset into the slot
        // because arrays use the entire slot.)
            let fslot := sload(_preBytes.slot)
        // Arrays of 31 bytes or less have an even value in their slot,
        // while longer arrays have an odd value. The actual length is
        // the slot divided by two for odd values, and the lowest order
        // byte divided by two for even values.
        // If the slot is even, bitwise and the slot with 255 and divide by
        // two to get the length. If the slot is odd, bitwise and the slot
        // with -1 and divide by two.
            let slength := div(and(fslot, sub(mul(0x100, iszero(and(fslot, 1))), 1)), 2)
            let mlength := mload(_postBytes)
            let newlength := add(slength, mlength)
        // slength can contain both the length and contents of the array
        // if length < 32 bytes so let's prepare for that
        // v. http://solidity.readthedocs.io/en/latest/miscellaneous.html#layout-of-state-variables-in-storage
            switch add(lt(slength, 32), lt(newlength, 32))
            case 2 {
            // Since the new array still fits in the slot, we just need to
            // update the contents of the slot.
            // uint256(bytes_storage) = uint256(bytes_storage) + uint256(bytes_memory) + new_length
                sstore(
                _preBytes.slot,
                // all the modifications to the slot are inside this
                // next block
                add(
                // we can just add to the slot contents because the
                // bytes we want to change are the LSBs
                fslot,
                add(
                mul(
                div(
                // load the bytes from memory
                mload(add(_postBytes, 0x20)),
                // zero all bytes to the right
                exp(0x100, sub(32, mlength))
                ),
                // and now shift left the number of bytes to
                // leave space for the length in the slot
                exp(0x100, sub(32, newlength))
                ),
                // increase length by the double of the memory
                // bytes length
                mul(mlength, 2)
                )
                )
                )
            }
            case 1 {
            // The stored value fits in the slot, but the combined value
            // will exceed it.
            // get the keccak hash to get the contents of the array
                mstore(0x0, _preBytes.slot)
                let sc := add(keccak256(0x0, 0x20), div(slength, 32))

            // save new length
                sstore(_preBytes.slot, add(mul(newlength, 2), 1))

            // The contents of the _postBytes array start 32 bytes into
            // the structure. Our first read should obtain the `submod`
            // bytes that can fit into the unused space in the last word
            // of the stored array. To get this, we read 32 bytes starting
            // from `submod`, so the data we read overlaps with the array
            // contents by `submod` bytes. Masking the lowest-order
            // `submod` bytes allows us to add that value directly to the
            // stored value.

                let submod := sub(32, slength)
                let mc := add(_postBytes, submod)
                let end := add(_postBytes, mlength)
                let mask := sub(exp(0x100, submod), 1)

                sstore(
                sc,
                add(
                and(
                fslot,
                0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00
                ),
                and(mload(mc), mask)
                )
                )

                for {
                    mc := add(mc, 0x20)
                    sc := add(sc, 1)
                } lt(mc, end) {
                    sc := add(sc, 1)
                    mc := add(mc, 0x20)
                } {
                    sstore(sc, mload(mc))
                }

                mask := exp(0x100, sub(mc, end))

                sstore(sc, mul(div(mload(mc), mask), mask))
            }
            default {
            // get the keccak hash to get the contents of the array
                mstore(0x0, _preBytes.slot)
            // Start copying to the last used word of the stored array.
                let sc := add(keccak256(0x0, 0x20), div(slength, 32))

            // save new length
                sstore(_preBytes.slot, add(mul(newlength, 2), 1))

            // Copy over the first `submod` bytes of the new data as in
            // case 1 above.
                let slengthmod := mod(slength, 32)
                let mlengthmod := mod(mlength, 32)
                let submod := sub(32, slengthmod)
                let mc := add(_postBytes, submod)
                let end := add(_postBytes, mlength)
                let mask := sub(exp(0x100, submod), 1)

                sstore(sc, add(sload(sc), and(mload(mc), mask)))

                for {
                    sc := add(sc, 1)
                    mc := add(mc, 0x20)
                } lt(mc, end) {
                    sc := add(sc, 1)
                    mc := add(mc, 0x20)
                } {
                    sstore(sc, mload(mc))
                }

                mask := exp(0x100, sub(mc, end))

                sstore(sc, mul(div(mload(mc), mask), mask))
            }
        }
    }

    function slice(
        bytes memory _bytes,
        uint256 _start,
        uint256 _length
    )
    internal
    pure
    returns (bytes memory)
    {
        require(_length + 31 >= _length, "slice_overflow");
        require(_bytes.length >= _start + _length, "slice_outOfBounds");

        bytes memory tempBytes;

        assembly {
            switch iszero(_length)
            case 0 {
            // Get a location of some free memory and store it in tempBytes as
            // Solidity does for memory variables.
                tempBytes := mload(0x40)

            // The first word of the slice result is potentially a partial
            // word read from the original array. To read it, we calculate
            // the length of that partial word and start copying that many
            // bytes into the array. The first word we copy will start with
            // data we don't care about, but the last `lengthmod` bytes will
            // land at the beginning of the contents of the new array. When
            // we're done copying, we overwrite the full first word with
            // the actual length of the slice.
                let lengthmod := and(_length, 31)

            // The multiplication in the next line is necessary
            // because when slicing multiples of 32 bytes (lengthmod == 0)
            // the following copy loop was copying the origin's length
            // and then ending prematurely not copying everything it should.
                let mc := add(add(tempBytes, lengthmod), mul(0x20, iszero(lengthmod)))
                let end := add(mc, _length)

                for {
                // The multiplication in the next line has the same exact purpose
                // as the one above.
                    let cc := add(add(add(_bytes, lengthmod), mul(0x20, iszero(lengthmod))), _start)
                } lt(mc, end) {
                    mc := add(mc, 0x20)
                    cc := add(cc, 0x20)
                } {
                    mstore(mc, mload(cc))
                }

                mstore(tempBytes, _length)

            //update free-memory pointer
            //allocating the array padded to 32 bytes like the compiler does now
                mstore(0x40, and(add(mc, 31), not(31)))
            }
            //if we want a zero-length slice let's just return a zero-length array
            default {
                tempBytes := mload(0x40)
            //zero out the 32 bytes slice we are about to return
            //we need to do it because Solidity does not garbage collect
                mstore(tempBytes, 0)

                mstore(0x40, add(tempBytes, 0x20))
            }
        }

        return tempBytes;
    }

    function toAddress(bytes memory _bytes, uint256 _start) internal pure returns (address) {
        require(_bytes.length >= _start + 20, "toAddress_outOfBounds");
        address tempAddress;

        assembly {
            tempAddress := div(mload(add(add(_bytes, 0x20), _start)), 0x1000000000000000000000000)
        }

        return tempAddress;
    }

    function toUint8(bytes memory _bytes, uint256 _start) internal pure returns (uint8) {
        require(_bytes.length >= _start + 1 , "toUint8_outOfBounds");
        uint8 tempUint;

        assembly {
            tempUint := mload(add(add(_bytes, 0x1), _start))
        }

        return tempUint;
    }

    function toUint16(bytes memory _bytes, uint256 _start) internal pure returns (uint16) {
        require(_bytes.length >= _start + 2, "toUint16_outOfBounds");
        uint16 tempUint;

        assembly {
            tempUint := mload(add(add(_bytes, 0x2), _start))
        }

        return tempUint;
    }

    function toUint32(bytes memory _bytes, uint256 _start) internal pure returns (uint32) {
        require(_bytes.length >= _start + 4, "toUint32_outOfBounds");
        uint32 tempUint;

        assembly {
            tempUint := mload(add(add(_bytes, 0x4), _start))
        }

        return tempUint;
    }

    function toUint64(bytes memory _bytes, uint256 _start) internal pure returns (uint64) {
        require(_bytes.length >= _start + 8, "toUint64_outOfBounds");
        uint64 tempUint;

        assembly {
            tempUint := mload(add(add(_bytes, 0x8), _start))
        }

        return tempUint;
    }

    function toUint96(bytes memory _bytes, uint256 _start) internal pure returns (uint96) {
        require(_bytes.length >= _start + 12, "toUint96_outOfBounds");
        uint96 tempUint;

        assembly {
            tempUint := mload(add(add(_bytes, 0xc), _start))
        }

        return tempUint;
    }

    function toUint128(bytes memory _bytes, uint256 _start) internal pure returns (uint128) {
        require(_bytes.length >= _start + 16, "toUint128_outOfBounds");
        uint128 tempUint;

        assembly {
            tempUint := mload(add(add(_bytes, 0x10), _start))
        }

        return tempUint;
    }

    function toUint256(bytes memory _bytes, uint256 _start) internal pure returns (uint256) {
        require(_bytes.length >= _start + 32, "toUint256_outOfBounds");
        uint256 tempUint;

        assembly {
            tempUint := mload(add(add(_bytes, 0x20), _start))
        }

        return tempUint;
    }

    function toBytes32(bytes memory _bytes, uint256 _start) internal pure returns (bytes32) {
        require(_bytes.length >= _start + 32, "toBytes32_outOfBounds");
        bytes32 tempBytes32;

        assembly {
            tempBytes32 := mload(add(add(_bytes, 0x20), _start))
        }

        return tempBytes32;
    }

    function equal(bytes memory _preBytes, bytes memory _postBytes) internal pure returns (bool) {
        bool success = true;

        assembly {
            let length := mload(_preBytes)

        // if lengths don't match the arrays are not equal
            switch eq(length, mload(_postBytes))
            case 1 {
            // cb is a circuit breaker in the for loop since there's
            //  no said feature for inline assembly loops
            // cb = 1 - don't breaker
            // cb = 0 - break
                let cb := 1

                let mc := add(_preBytes, 0x20)
                let end := add(mc, length)

                for {
                    let cc := add(_postBytes, 0x20)
                // the next line is the loop condition:
                // while(uint256(mc < end) + cb == 2)
                } eq(add(lt(mc, end), cb), 2) {
                    mc := add(mc, 0x20)
                    cc := add(cc, 0x20)
                } {
                // if any of these checks fails then arrays are not equal
                    if iszero(eq(mload(mc), mload(cc))) {
                    // unsuccess:
                        success := 0
                        cb := 0
                    }
                }
            }
            default {
            // unsuccess:
                success := 0
            }
        }

        return success;
    }

    function equalStorage(
        bytes storage _preBytes,
        bytes memory _postBytes
    )
    internal
    view
    returns (bool)
    {
        bool success = true;

        assembly {
        // we know _preBytes_offset is 0
            let fslot := sload(_preBytes.slot)
        // Decode the length of the stored array like in concatStorage().
            let slength := div(and(fslot, sub(mul(0x100, iszero(and(fslot, 1))), 1)), 2)
            let mlength := mload(_postBytes)

        // if lengths don't match the arrays are not equal
            switch eq(slength, mlength)
            case 1 {
            // slength can contain both the length and contents of the array
            // if length < 32 bytes so let's prepare for that
            // v. http://solidity.readthedocs.io/en/latest/miscellaneous.html#layout-of-state-variables-in-storage
                if iszero(iszero(slength)) {
                    switch lt(slength, 32)
                    case 1 {
                    // blank the last byte which is the length
                        fslot := mul(div(fslot, 0x100), 0x100)

                        if iszero(eq(fslot, mload(add(_postBytes, 0x20)))) {
                        // unsuccess:
                            success := 0
                        }
                    }
                    default {
                    // cb is a circuit breaker in the for loop since there's
                    //  no said feature for inline assembly loops
                    // cb = 1 - don't breaker
                    // cb = 0 - break
                        let cb := 1

                    // get the keccak hash to get the contents of the array
                        mstore(0x0, _preBytes.slot)
                        let sc := keccak256(0x0, 0x20)

                        let mc := add(_postBytes, 0x20)
                        let end := add(mc, mlength)

                    // the next line is the loop condition:
                    // while(uint256(mc < end) + cb == 2)
                        for {} eq(add(lt(mc, end), cb), 2) {
                            sc := add(sc, 1)
                            mc := add(mc, 0x20)
                        } {
                            if iszero(eq(sload(sc), mload(mc))) {
                            // unsuccess:
                                success := 0
                                cb := 0
                            }
                        }
                    }
                }
            }
            default {
            // unsuccess:
                success := 0
            }
        }

        return success;
    }
}

// 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;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.19;

import { OFT, IERC20, ERC20 } from "OFT.sol";
import { IERC3156FlashBorrower } from "IERC3156FlashBorrower.sol";
import "IPrismaCore.sol";

/**
    @title Prisma Debt Token "acUSD"
    @notice CDP minted against collateral deposits within `TroveManager`.
            This contract has a 1:n relationship with multiple deployments of `TroveManager`,
            each of which hold one collateral type which may be used to mint this token.
 */
contract DebtToken is OFT {
    string public constant version = "1";

    // --- ERC 3156 Data ---
    bytes32 private constant _RETURN_VALUE = keccak256("ERC3156FlashBorrower.onFlashLoan");
    uint256 public constant FLASH_LOAN_FEE = 9; // 1 = 0.0001%

    // --- Data for EIP2612 ---

    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant permitTypeHash = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    // keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)");
    bytes32 private constant _TYPE_HASH = 0x8b73c3c69bb8fe3d512ecc4cf759cc79239f7b179b0ffacaa9a75d522b39400f;

    // Cache the domain separator as an immutable value, but also store the chain id that it corresponds to, in order to
    // invalidate the cached domain separator if the chain id changes.
    bytes32 private immutable _CACHED_DOMAIN_SEPARATOR;
    uint256 private immutable _CACHED_CHAIN_ID;

    bytes32 private immutable _HASHED_NAME;
    bytes32 private immutable _HASHED_VERSION;

    mapping(address => uint256) private _nonces;

    // --- Addresses ---
    IPrismaCore private immutable _prismaCore;
    address public immutable stabilityPoolAddress;
    address public immutable borrowerOperationsAddress;
    address public immutable factory;
    address public immutable gasPool;

    mapping(address => bool) public troveManager;

    // Amount of debt to be locked in gas pool on opening troves
    uint256 public immutable DEBT_GAS_COMPENSATION;

    constructor(
        string memory _name,
        string memory _symbol,
        address _stabilityPoolAddress,
        address _borrowerOperationsAddress,
        IPrismaCore prismaCore_,
        address _layerZeroEndpoint,
        address _factory,
        address _gasPool,
        uint256 _gasCompensation
    ) OFT(_name, _symbol, _layerZeroEndpoint) {
        stabilityPoolAddress = _stabilityPoolAddress;
        _prismaCore = prismaCore_;
        borrowerOperationsAddress = _borrowerOperationsAddress;
        factory = _factory;
        gasPool = _gasPool;

        DEBT_GAS_COMPENSATION = _gasCompensation;

        bytes32 hashedName = keccak256(bytes(_name));
        bytes32 hashedVersion = keccak256(bytes(version));

        _HASHED_NAME = hashedName;
        _HASHED_VERSION = hashedVersion;
        _CACHED_CHAIN_ID = block.chainid;
        _CACHED_DOMAIN_SEPARATOR = _buildDomainSeparator(_TYPE_HASH, hashedName, hashedVersion);
    }

    function enableTroveManager(address _troveManager) external {
        require(msg.sender == factory, "!Factory");
        troveManager[_troveManager] = true;
    }

    // --- Functions for intra-Prisma calls ---

    function mintWithGasCompensation(address _account, uint256 _amount) external returns (bool) {
        require(msg.sender == borrowerOperationsAddress);
        _mint(_account, _amount);
        _mint(gasPool, DEBT_GAS_COMPENSATION);

        return true;
    }

    function burnWithGasCompensation(address _account, uint256 _amount) external returns (bool) {
        require(msg.sender == borrowerOperationsAddress);
        _burn(_account, _amount);
        _burn(gasPool, DEBT_GAS_COMPENSATION);

        return true;
    }

    function mint(address _account, uint256 _amount) external {
        require(msg.sender == borrowerOperationsAddress || troveManager[msg.sender], "Debt: Caller not BO/TM");
        _mint(_account, _amount);
    }

    function burn(address _account, uint256 _amount) external {
        require(troveManager[msg.sender], "Debt: Caller not TroveManager");
        _burn(_account, _amount);
    }

    function sendToSP(address _sender, uint256 _amount) external {
        require(msg.sender == stabilityPoolAddress, "Debt: Caller not StabilityPool");
        _transfer(_sender, msg.sender, _amount);
    }

    function returnFromPool(address _poolAddress, address _receiver, uint256 _amount) external {
        require(msg.sender == stabilityPoolAddress || troveManager[msg.sender], "Debt: Caller not TM/SP");
        _transfer(_poolAddress, _receiver, _amount);
    }

    // --- External functions ---

    function transfer(address recipient, uint256 amount) public override(IERC20, ERC20) returns (bool) {
        _requireValidRecipient(recipient);
        return super.transfer(recipient, amount);
    }

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public override(IERC20, ERC20) returns (bool) {
        _requireValidRecipient(recipient);
        return super.transferFrom(sender, recipient, amount);
    }

    // --- ERC 3156 Functions ---

    /**
     * @dev Returns the maximum amount of tokens available for loan.
     * @param token The address of the token that is requested.
     * @return The amount of token that can be loaned.
     */
    function maxFlashLoan(address token) public view returns (uint256) {
        return token == address(this) ? type(uint256).max - totalSupply() : 0;
    }

    /**
     * @dev Returns the fee applied when doing flash loans. This function calls
     * the {_flashFee} function which returns the fee applied when doing flash
     * loans.
     * @param token The token to be flash loaned.
     * @param amount The amount of tokens to be loaned.
     * @return The fees applied to the corresponding flash loan.
     */
    function flashFee(address token, uint256 amount) external view returns (uint256) {
        return token == address(this) ? _flashFee(amount) : 0;
    }

    /**
     * @dev Returns the fee applied when doing flash loans. By default this
     * implementation has 0 fees. This function can be overloaded to make
     * the flash loan mechanism deflationary.
     * @param amount The amount of tokens to be loaned.
     * @return The fees applied to the corresponding flash loan.
     */
    function _flashFee(uint256 amount) internal pure returns (uint256) {
        return (amount * FLASH_LOAN_FEE) / 10000;
    }

    /**
     * @dev Performs a flash loan. New tokens are minted and sent to the
     * `receiver`, who is required to implement the {IERC3156FlashBorrower}
     * interface. By the end of the flash loan, the receiver is expected to own
     * amount + fee tokens and have them approved back to the token contract itself so
     * they can be burned.
     * @param receiver The receiver of the flash loan. Should implement the
     * {IERC3156FlashBorrower-onFlashLoan} interface.
     * @param token The token to be flash loaned. Only `address(this)` is
     * supported.
     * @param amount The amount of tokens to be loaned.
     * @param data An arbitrary datafield that is passed to the receiver.
     * @return `true` if the flash loan was successful.
     */
    // This function can reenter, but it doesn't pose a risk because it always preserves the property that the amount
    // minted at the beginning is always recovered and burned at the end, or else the entire function will revert.
    // slither-disable-next-line reentrancy-no-eth
    function flashLoan(
        IERC3156FlashBorrower receiver,
        address token,
        uint256 amount,
        bytes calldata data
    ) external returns (bool) {
        require(token == address(this), "ERC20FlashMint: wrong token");
        require(amount <= maxFlashLoan(token), "ERC20FlashMint: amount exceeds maxFlashLoan");
        uint256 fee = _flashFee(amount);
        _mint(address(receiver), amount);
        require(
            receiver.onFlashLoan(msg.sender, token, amount, fee, data) == _RETURN_VALUE,
            "ERC20FlashMint: invalid return value"
        );
        _spendAllowance(address(receiver), address(this), amount + fee);
        _burn(address(receiver), amount);
        _transfer(address(receiver), _prismaCore.feeReceiver(), fee);
        return true;
    }

    // --- EIP 2612 Functionality ---

    function domainSeparator() public view returns (bytes32) {
        if (block.chainid == _CACHED_CHAIN_ID) {
            return _CACHED_DOMAIN_SEPARATOR;
        } else {
            return _buildDomainSeparator(_TYPE_HASH, _HASHED_NAME, _HASHED_VERSION);
        }
    }

    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        require(deadline >= block.timestamp, "Debt: expired deadline");
        bytes32 digest = keccak256(
            abi.encodePacked(
                "\x19\x01",
                domainSeparator(),
                keccak256(abi.encode(permitTypeHash, owner, spender, amount, _nonces[owner]++, deadline))
            )
        );
        address recoveredAddress = ecrecover(digest, v, r, s);
        require(recoveredAddress == owner, "Debt: invalid signature");
        _approve(owner, spender, amount);
    }

    function nonces(address owner) external view returns (uint256) {
        // FOR EIP 2612
        return _nonces[owner];
    }

    // --- Internal operations ---

    function _buildDomainSeparator(bytes32 typeHash, bytes32 name_, bytes32 version_) private view returns (bytes32) {
        return keccak256(abi.encode(typeHash, name_, version_, block.chainid, address(this)));
    }

    // --- 'require' functions ---

    function _requireValidRecipient(address _recipient) internal view {
        require(
            _recipient != address(0) && _recipient != address(this),
            "Debt: Cannot transfer tokens directly to the Debt token contract or the zero address"
        );
        require(
            _recipient != stabilityPoolAddress && !troveManager[_recipient] && _recipient != borrowerOperationsAddress,
            "Debt: Cannot transfer tokens directly to the StabilityPool, TroveManager or BorrowerOps"
        );
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)

pragma solidity ^0.8.0;

import "IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "IERC20.sol";
import "IERC20Metadata.sol";
import "Context.sol";

/**
 * @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 {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead 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 Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        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}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, 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 virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, spender) + 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 virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * This 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:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
            // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
            // decrementing then incrementing.
            _balances[to] += amount;
        }

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, 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:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

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

        _totalSupply += amount;
        unchecked {
            // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
            _balances[account] += amount;
        }
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `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 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

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

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
            // Overflow not possible: amount <= accountBalance <= totalSupply.
            _totalSupply -= amount;
        }

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This 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 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);
    }

    /**
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.7.6;

library ExcessivelySafeCall {
    uint256 constant LOW_28_MASK =
    0x00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff;

    /// @notice Use when you _really_ really _really_ don't trust the called
    /// contract. This prevents the called contract from causing reversion of
    /// the caller in as many ways as we can.
    /// @dev The main difference between this and a solidity low-level call is
    /// that we limit the number of bytes that the callee can cause to be
    /// copied to caller memory. This prevents stupid things like malicious
    /// contracts returning 10,000,000 bytes causing a local OOG when copying
    /// to memory.
    /// @param _target The address to call
    /// @param _gas The amount of gas to forward to the remote contract
    /// @param _maxCopy The maximum number of bytes of returndata to copy
    /// to memory.
    /// @param _calldata The data to send to the remote contract
    /// @return success and returndata, as `.call()`. Returndata is capped to
    /// `_maxCopy` bytes.
    function excessivelySafeCall(
        address _target,
        uint256 _gas,
        uint16 _maxCopy,
        bytes memory _calldata
    ) internal returns (bool, bytes memory) {
        // set up for assembly call
        uint256 _toCopy;
        bool _success;
        bytes memory _returnData = new bytes(_maxCopy);
        // dispatch message to recipient
        // by assembly calling "handle" function
        // we call via assembly to avoid memcopying a very large returndata
        // returned by a malicious contract
        assembly {
            _success := call(
            _gas, // gas
            _target, // recipient
            0, // ether value
            add(_calldata, 0x20), // inloc
            mload(_calldata), // inlen
            0, // outloc
            0 // outlen
            )
        // limit our copy to 256 bytes
            _toCopy := returndatasize()
            if gt(_toCopy, _maxCopy) {
                _toCopy := _maxCopy
            }
        // Store the length of the copied bytes
            mstore(_returnData, _toCopy)
        // copy the bytes from returndata[0:_toCopy]
            returndatacopy(add(_returnData, 0x20), 0, _toCopy)
        }
        return (_success, _returnData);
    }

    /// @notice Use when you _really_ really _really_ don't trust the called
    /// contract. This prevents the called contract from causing reversion of
    /// the caller in as many ways as we can.
    /// @dev The main difference between this and a solidity low-level call is
    /// that we limit the number of bytes that the callee can cause to be
    /// copied to caller memory. This prevents stupid things like malicious
    /// contracts returning 10,000,000 bytes causing a local OOG when copying
    /// to memory.
    /// @param _target The address to call
    /// @param _gas The amount of gas to forward to the remote contract
    /// @param _maxCopy The maximum number of bytes of returndata to copy
    /// to memory.
    /// @param _calldata The data to send to the remote contract
    /// @return success and returndata, as `.call()`. Returndata is capped to
    /// `_maxCopy` bytes.
    function excessivelySafeStaticCall(
        address _target,
        uint256 _gas,
        uint16 _maxCopy,
        bytes memory _calldata
    ) internal view returns (bool, bytes memory) {
        // set up for assembly call
        uint256 _toCopy;
        bool _success;
        bytes memory _returnData = new bytes(_maxCopy);
        // dispatch message to recipient
        // by assembly calling "handle" function
        // we call via assembly to avoid memcopying a very large returndata
        // returned by a malicious contract
        assembly {
            _success := staticcall(
            _gas, // gas
            _target, // recipient
            add(_calldata, 0x20), // inloc
            mload(_calldata), // inlen
            0, // outloc
            0 // outlen
            )
        // limit our copy to 256 bytes
            _toCopy := returndatasize()
            if gt(_toCopy, _maxCopy) {
                _toCopy := _maxCopy
            }
        // Store the length of the copied bytes
            mstore(_returnData, _toCopy)
        // copy the bytes from returndata[0:_toCopy]
            returndatacopy(add(_returnData, 0x20), 0, _toCopy)
        }
        return (_success, _returnData);
    }

    /**
     * @notice Swaps function selectors in encoded contract calls
     * @dev Allows reuse of encoded calldata for functions with identical
     * argument types but different names. It simply swaps out the first 4 bytes
     * for the new selector. This function modifies memory in place, and should
     * only be used with caution.
     * @param _newSelector The new 4-byte selector
     * @param _buf The encoded contract args
     */
    function swapSelector(bytes4 _newSelector, bytes memory _buf)
    internal
    pure
    {
        require(_buf.length >= 4);
        uint256 _mask = LOW_28_MASK;
        assembly {
        // load the first word of
            let _word := mload(add(_buf, 0x20))
        // mask out the top 4 bytes
        // /x
            _word := and(_word, _mask)
            _word := or(_newSelector, _word)
            mstore(add(_buf, 0x20), _word)
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (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);
}

// 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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (interfaces/IERC3156FlashBorrower.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC3156 FlashBorrower, as defined in
 * https://eips.ethereum.org/EIPS/eip-3156[ERC-3156].
 *
 * _Available since v4.1._
 */
interface IERC3156FlashBorrower {
    /**
     * @dev Receive a flash loan.
     * @param initiator The initiator of the loan.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @param fee The additional amount of tokens to repay.
     * @param data Arbitrary data structure, intended to contain user-defined parameters.
     * @return The keccak256 hash of "IERC3156FlashBorrower.onFlashLoan"
     */
    function onFlashLoan(
        address initiator,
        address token,
        uint256 amount,
        uint256 fee,
        bytes calldata data
    ) external returns (bytes32);
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.5.0;

import "ILayerZeroUserApplicationConfig.sol";

interface ILayerZeroEndpoint is ILayerZeroUserApplicationConfig {
    // @notice send a LayerZero message to the specified address at a LayerZero endpoint.
    // @param _dstChainId - the destination chain identifier
    // @param _destination - the address on destination chain (in bytes). address length/format may vary by chains
    // @param _payload - a custom bytes payload to send to the destination contract
    // @param _refundAddress - if the source transaction is cheaper than the amount of value passed, refund the additional amount to this address
    // @param _zroPaymentAddress - the address of the ZRO token holder who would pay for the transaction
    // @param _adapterParams - parameters for custom functionality. e.g. receive airdropped native gas from the relayer on destination
    function send(uint16 _dstChainId, bytes calldata _destination, bytes calldata _payload, address payable _refundAddress, address _zroPaymentAddress, bytes calldata _adapterParams) external payable;

    // @notice used by the messaging library to publish verified payload
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source contract (as bytes) at the source chain
    // @param _dstAddress - the address on destination chain
    // @param _nonce - the unbound message ordering nonce
    // @param _gasLimit - the gas limit for external contract execution
    // @param _payload - verified payload to send to the destination contract
    function receivePayload(uint16 _srcChainId, bytes calldata _srcAddress, address _dstAddress, uint64 _nonce, uint _gasLimit, bytes calldata _payload) external;

    // @notice get the inboundNonce of a lzApp from a source chain which could be EVM or non-EVM chain
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source chain contract address
    function getInboundNonce(uint16 _srcChainId, bytes calldata _srcAddress) external view returns (uint64);

    // @notice get the outboundNonce from this source chain which, consequently, is always an EVM
    // @param _srcAddress - the source chain contract address
    function getOutboundNonce(uint16 _dstChainId, address _srcAddress) external view returns (uint64);

    // @notice gets a quote in source native gas, for the amount that send() requires to pay for message delivery
    // @param _dstChainId - the destination chain identifier
    // @param _userApplication - the user app address on this EVM chain
    // @param _payload - the custom message to send over LayerZero
    // @param _payInZRO - if false, user app pays the protocol fee in native token
    // @param _adapterParam - parameters for the adapter service, e.g. send some dust native token to dstChain
    function estimateFees(uint16 _dstChainId, address _userApplication, bytes calldata _payload, bool _payInZRO, bytes calldata _adapterParam) external view returns (uint nativeFee, uint zroFee);

    // @notice get this Endpoint's immutable source identifier
    function getChainId() external view returns (uint16);

    // @notice the interface to retry failed message on this Endpoint destination
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source chain contract address
    // @param _payload - the payload to be retried
    function retryPayload(uint16 _srcChainId, bytes calldata _srcAddress, bytes calldata _payload) external;

    // @notice query if any STORED payload (message blocking) at the endpoint.
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source chain contract address
    function hasStoredPayload(uint16 _srcChainId, bytes calldata _srcAddress) external view returns (bool);

    // @notice query if the _libraryAddress is valid for sending msgs.
    // @param _userApplication - the user app address on this EVM chain
    function getSendLibraryAddress(address _userApplication) external view returns (address);

    // @notice query if the _libraryAddress is valid for receiving msgs.
    // @param _userApplication - the user app address on this EVM chain
    function getReceiveLibraryAddress(address _userApplication) external view returns (address);

    // @notice query if the non-reentrancy guard for send() is on
    // @return true if the guard is on. false otherwise
    function isSendingPayload() external view returns (bool);

    // @notice query if the non-reentrancy guard for receive() is on
    // @return true if the guard is on. false otherwise
    function isReceivingPayload() external view returns (bool);

    // @notice get the configuration of the LayerZero messaging library of the specified version
    // @param _version - messaging library version
    // @param _chainId - the chainId for the pending config change
    // @param _userApplication - the contract address of the user application
    // @param _configType - type of configuration. every messaging library has its own convention.
    function getConfig(uint16 _version, uint16 _chainId, address _userApplication, uint _configType) external view returns (bytes memory);

    // @notice get the send() LayerZero messaging library version
    // @param _userApplication - the contract address of the user application
    function getSendVersion(address _userApplication) external view returns (uint16);

    // @notice get the lzReceive() LayerZero messaging library version
    // @param _userApplication - the contract address of the user application
    function getReceiveVersion(address _userApplication) external view returns (uint16);
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.5.0;

interface ILayerZeroReceiver {
    // @notice LayerZero endpoint will invoke this function to deliver the message on the destination
    // @param _srcChainId - the source endpoint identifier
    // @param _srcAddress - the source sending contract address from the source chain
    // @param _nonce - the ordered message nonce
    // @param _payload - the signed payload is the UA bytes has encoded to be sent
    function lzReceive(uint16 _srcChainId, bytes calldata _srcAddress, uint64 _nonce, bytes calldata _payload) external;
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.5.0;

interface ILayerZeroUserApplicationConfig {
    // @notice set the configuration of the LayerZero messaging library of the specified version
    // @param _version - messaging library version
    // @param _chainId - the chainId for the pending config change
    // @param _configType - type of configuration. every messaging library has its own convention.
    // @param _config - configuration in the bytes. can encode arbitrary content.
    function setConfig(uint16 _version, uint16 _chainId, uint _configType, bytes calldata _config) external;

    // @notice set the send() LayerZero messaging library version to _version
    // @param _version - new messaging library version
    function setSendVersion(uint16 _version) external;

    // @notice set the lzReceive() LayerZero messaging library version to _version
    // @param _version - new messaging library version
    function setReceiveVersion(uint16 _version) external;

    // @notice Only when the UA needs to resume the message flow in blocking mode and clear the stored payload
    // @param _srcChainId - the chainId of the source chain
    // @param _srcAddress - the contract address of the source contract at the source chain
    function forceResumeReceive(uint16 _srcChainId, bytes calldata _srcAddress) external;
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.5.0;

import "IOFTCore.sol";
import "IERC20.sol";

/**
 * @dev Interface of the OFT standard
 */
interface IOFT is IOFTCore, IERC20 {

}

// SPDX-License-Identifier: MIT

pragma solidity >=0.5.0;

import "IERC165.sol";

/**
 * @dev Interface of the IOFT core standard
 */
interface IOFTCore is IERC165 {
    /**
     * @dev estimate send token `_tokenId` to (`_dstChainId`, `_toAddress`)
     * _dstChainId - L0 defined chain id to send tokens too
     * _toAddress - dynamic bytes array which contains the address to whom you are sending tokens to on the dstChain
     * _amount - amount of the tokens to transfer
     * _useZro - indicates to use zro to pay L0 fees
     * _adapterParam - flexible bytes array to indicate messaging adapter services in L0
     */
    function estimateSendFee(uint16 _dstChainId, bytes calldata _toAddress, uint _amount, bool _useZro, bytes calldata _adapterParams) external view returns (uint nativeFee, uint zroFee);

    /**
     * @dev send `_amount` amount of token to (`_dstChainId`, `_toAddress`) from `_from`
     * `_from` the owner of token
     * `_dstChainId` the destination chain identifier
     * `_toAddress` can be any size depending on the `dstChainId`.
     * `_amount` the quantity of tokens in wei
     * `_refundAddress` the address LayerZero refunds if too much message fee is sent
     * `_zroPaymentAddress` set to address(0x0) if not paying in ZRO (LayerZero Token)
     * `_adapterParams` is a flexible bytes array to indicate messaging adapter services
     */
    function sendFrom(address _from, uint16 _dstChainId, bytes calldata _toAddress, uint _amount, address payable _refundAddress, address _zroPaymentAddress, bytes calldata _adapterParams) external payable;

    /**
     * @dev returns the circulating amount of tokens on current chain
     */
    function circulatingSupply() external view returns (uint);

    /**
     * @dev returns the address of the ERC20 token
     */
    function token() external view returns (address);

    /**
     * @dev Emitted when `_amount` tokens are moved from the `_sender` to (`_dstChainId`, `_toAddress`)
     * `_nonce` is the outbound nonce
     */
    event SendToChain(uint16 indexed _dstChainId, address indexed _from, bytes _toAddress, uint _amount);

    /**
     * @dev Emitted when `_amount` tokens are received from `_srcChainId` into the `_toAddress` on the local chain.
     * `_nonce` is the inbound nonce.
     */
    event ReceiveFromChain(uint16 indexed _srcChainId, address indexed _to, uint _amount);

    event SetUseCustomAdapterParams(bool _useCustomAdapterParams);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IPrismaCore {
    event FeeReceiverSet(address feeReceiver);
    event GuardianSet(address guardian);
    event NewOwnerAccepted(address oldOwner, address owner);
    event NewOwnerCommitted(address owner, address pendingOwner, uint256 deadline);
    event NewOwnerRevoked(address owner, address revokedOwner);
    event Paused();
    event PriceFeedSet(address priceFeed);
    event Unpaused();

    function acceptTransferOwnership() external;

    function commitTransferOwnership(address newOwner) external;

    function revokeTransferOwnership() external;

    function setFeeReceiver(address _feeReceiver) external;

    function setGuardian(address _guardian) external;

    function setPaused(bool _paused) external;

    function setPriceFeed(address _priceFeed) external;

    function OWNERSHIP_TRANSFER_DELAY() external view returns (uint256);

    function feeReceiver() external view returns (address);

    function guardian() external view returns (address);

    function owner() external view returns (address);

    function ownershipTransferDeadline() external view returns (uint256);

    function paused() external view returns (bool);

    function pendingOwner() external view returns (address);

    function priceFeed() external view returns (address);

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

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "Ownable.sol";
import "ILayerZeroReceiver.sol";
import "ILayerZeroUserApplicationConfig.sol";
import "ILayerZeroEndpoint.sol";
import "BytesLib.sol";

/*
 * a generic LzReceiver implementation
 */
abstract contract LzApp is Ownable, ILayerZeroReceiver, ILayerZeroUserApplicationConfig {
    using BytesLib for bytes;

    // ua can not send payload larger than this by default, but it can be changed by the ua owner
    uint constant public DEFAULT_PAYLOAD_SIZE_LIMIT = 10000;

    ILayerZeroEndpoint public immutable lzEndpoint;
    mapping(uint16 => bytes) public trustedRemoteLookup;
    mapping(uint16 => mapping(uint16 => uint)) public minDstGasLookup;
    mapping(uint16 => uint) public payloadSizeLimitLookup;
    address public precrime;

    event SetPrecrime(address precrime);
    event SetTrustedRemote(uint16 _remoteChainId, bytes _path);
    event SetTrustedRemoteAddress(uint16 _remoteChainId, bytes _remoteAddress);
    event SetMinDstGas(uint16 _dstChainId, uint16 _type, uint _minDstGas);

    constructor(address _endpoint) {
        lzEndpoint = ILayerZeroEndpoint(_endpoint);
    }

    function lzReceive(uint16 _srcChainId, bytes calldata _srcAddress, uint64 _nonce, bytes calldata _payload) public virtual override {
        // lzReceive must be called by the endpoint for security
        require(_msgSender() == address(lzEndpoint), "LzApp: invalid endpoint caller");

        bytes memory trustedRemote = trustedRemoteLookup[_srcChainId];
        // if will still block the message pathway from (srcChainId, srcAddress). should not receive message from untrusted remote.
        require(_srcAddress.length == trustedRemote.length && trustedRemote.length > 0 && keccak256(_srcAddress) == keccak256(trustedRemote), "LzApp: invalid source sending contract");

        _blockingLzReceive(_srcChainId, _srcAddress, _nonce, _payload);
    }

    // abstract function - the default behaviour of LayerZero is blocking. See: NonblockingLzApp if you dont need to enforce ordered messaging
    function _blockingLzReceive(uint16 _srcChainId, bytes memory _srcAddress, uint64 _nonce, bytes memory _payload) internal virtual;

    function _lzSend(uint16 _dstChainId, bytes memory _payload, address payable _refundAddress, address _zroPaymentAddress, bytes memory _adapterParams, uint _nativeFee) internal virtual {
        bytes memory trustedRemote = trustedRemoteLookup[_dstChainId];
        require(trustedRemote.length != 0, "LzApp: destination chain is not a trusted source");
        _checkPayloadSize(_dstChainId, _payload.length);
        lzEndpoint.send{value: _nativeFee}(_dstChainId, trustedRemote, _payload, _refundAddress, _zroPaymentAddress, _adapterParams);
    }

    function _checkGasLimit(uint16 _dstChainId, uint16 _type, bytes memory _adapterParams, uint _extraGas) internal view virtual {
        uint providedGasLimit = _getGasLimit(_adapterParams);
        uint minGasLimit = minDstGasLookup[_dstChainId][_type] + _extraGas;
        require(minGasLimit > 0, "LzApp: minGasLimit not set");
        require(providedGasLimit >= minGasLimit, "LzApp: gas limit is too low");
    }

    function _getGasLimit(bytes memory _adapterParams) internal pure virtual returns (uint gasLimit) {
        require(_adapterParams.length >= 34, "LzApp: invalid adapterParams");
        assembly {
            gasLimit := mload(add(_adapterParams, 34))
        }
    }

    function _checkPayloadSize(uint16 _dstChainId, uint _payloadSize) internal view virtual {
        uint payloadSizeLimit = payloadSizeLimitLookup[_dstChainId];
        if (payloadSizeLimit == 0) { // use default if not set
            payloadSizeLimit = DEFAULT_PAYLOAD_SIZE_LIMIT;
        }
        require(_payloadSize <= payloadSizeLimit, "LzApp: payload size is too large");
    }

    //---------------------------UserApplication config----------------------------------------
    function getConfig(uint16 _version, uint16 _chainId, address, uint _configType) external view returns (bytes memory) {
        return lzEndpoint.getConfig(_version, _chainId, address(this), _configType);
    }

    // generic config for LayerZero user Application
    function setConfig(uint16 _version, uint16 _chainId, uint _configType, bytes calldata _config) external override onlyOwner {
        lzEndpoint.setConfig(_version, _chainId, _configType, _config);
    }

    function setSendVersion(uint16 _version) external override onlyOwner {
        lzEndpoint.setSendVersion(_version);
    }

    function setReceiveVersion(uint16 _version) external override onlyOwner {
        lzEndpoint.setReceiveVersion(_version);
    }

    function forceResumeReceive(uint16 _srcChainId, bytes calldata _srcAddress) external override onlyOwner {
        lzEndpoint.forceResumeReceive(_srcChainId, _srcAddress);
    }

    // _path = abi.encodePacked(remoteAddress, localAddress)
    // this function set the trusted path for the cross-chain communication
    function setTrustedRemote(uint16 _srcChainId, bytes calldata _path) external onlyOwner {
        trustedRemoteLookup[_srcChainId] = _path;
        emit SetTrustedRemote(_srcChainId, _path);
    }

    function setTrustedRemoteAddress(uint16 _remoteChainId, bytes calldata _remoteAddress) external onlyOwner {
        trustedRemoteLookup[_remoteChainId] = abi.encodePacked(_remoteAddress, address(this));
        emit SetTrustedRemoteAddress(_remoteChainId, _remoteAddress);
    }

    function getTrustedRemoteAddress(uint16 _remoteChainId) external view returns (bytes memory) {
        bytes memory path = trustedRemoteLookup[_remoteChainId];
        require(path.length != 0, "LzApp: no trusted path record");
        return path.slice(0, path.length - 20); // the last 20 bytes should be address(this)
    }

    function setPrecrime(address _precrime) external onlyOwner {
        precrime = _precrime;
        emit SetPrecrime(_precrime);
    }

    function setMinDstGas(uint16 _dstChainId, uint16 _packetType, uint _minGas) external onlyOwner {
        require(_minGas > 0, "LzApp: invalid minGas");
        minDstGasLookup[_dstChainId][_packetType] = _minGas;
        emit SetMinDstGas(_dstChainId, _packetType, _minGas);
    }

    // if the size is 0, it means default size limit
    function setPayloadSizeLimit(uint16 _dstChainId, uint _size) external onlyOwner {
        payloadSizeLimitLookup[_dstChainId] = _size;
    }

    //--------------------------- VIEW FUNCTION ----------------------------------------
    function isTrustedRemote(uint16 _srcChainId, bytes calldata _srcAddress) external view returns (bool) {
        bytes memory trustedSource = trustedRemoteLookup[_srcChainId];
        return keccak256(trustedSource) == keccak256(_srcAddress);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "LzApp.sol";
import "ExcessivelySafeCall.sol";

/*
 * the default LayerZero messaging behaviour is blocking, i.e. any failed message will block the channel
 * this abstract class try-catch all fail messages and store locally for future retry. hence, non-blocking
 * NOTE: if the srcAddress is not configured properly, it will still block the message pathway from (srcChainId, srcAddress)
 */
abstract contract NonblockingLzApp is LzApp {
    using ExcessivelySafeCall for address;

    constructor(address _endpoint) LzApp(_endpoint) {}

    mapping(uint16 => mapping(bytes => mapping(uint64 => bytes32))) public failedMessages;

    event MessageFailed(uint16 _srcChainId, bytes _srcAddress, uint64 _nonce, bytes _payload, bytes _reason);
    event RetryMessageSuccess(uint16 _srcChainId, bytes _srcAddress, uint64 _nonce, bytes32 _payloadHash);

    // overriding the virtual function in LzReceiver
    function _blockingLzReceive(uint16 _srcChainId, bytes memory _srcAddress, uint64 _nonce, bytes memory _payload) internal virtual override {
        (bool success, bytes memory reason) = address(this).excessivelySafeCall(gasleft(), 150, abi.encodeWithSelector(this.nonblockingLzReceive.selector, _srcChainId, _srcAddress, _nonce, _payload));
        // try-catch all errors/exceptions
        if (!success) {
            _storeFailedMessage(_srcChainId, _srcAddress, _nonce, _payload, reason);
        }
    }

    function _storeFailedMessage(uint16 _srcChainId, bytes memory _srcAddress, uint64 _nonce, bytes memory _payload, bytes memory _reason) internal virtual {
        failedMessages[_srcChainId][_srcAddress][_nonce] = keccak256(_payload);
        emit MessageFailed(_srcChainId, _srcAddress, _nonce, _payload, _reason);
    }

    function nonblockingLzReceive(uint16 _srcChainId, bytes calldata _srcAddress, uint64 _nonce, bytes calldata _payload) public virtual {
        // only internal transaction
        require(_msgSender() == address(this), "NonblockingLzApp: caller must be LzApp");
        _nonblockingLzReceive(_srcChainId, _srcAddress, _nonce, _payload);
    }

    //@notice override this function
    function _nonblockingLzReceive(uint16 _srcChainId, bytes memory _srcAddress, uint64 _nonce, bytes memory _payload) internal virtual;

    function retryMessage(uint16 _srcChainId, bytes calldata _srcAddress, uint64 _nonce, bytes calldata _payload) public payable virtual {
        // assert there is message to retry
        bytes32 payloadHash = failedMessages[_srcChainId][_srcAddress][_nonce];
        require(payloadHash != bytes32(0), "NonblockingLzApp: no stored message");
        require(keccak256(_payload) == payloadHash, "NonblockingLzApp: invalid payload");
        // clear the stored message
        failedMessages[_srcChainId][_srcAddress][_nonce] = bytes32(0);
        // execute the message. revert if it fails again
        _nonblockingLzReceive(_srcChainId, _srcAddress, _nonce, _payload);
        emit RetryMessageSuccess(_srcChainId, _srcAddress, _nonce, payloadHash);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "ERC20.sol";
import "IERC165.sol";
import "IOFT.sol";
import "OFTCore.sol";

// override decimal() function is needed
contract OFT is OFTCore, ERC20, IOFT {
    constructor(string memory _name, string memory _symbol, address _lzEndpoint) ERC20(_name, _symbol) OFTCore(_lzEndpoint) {}

    function supportsInterface(bytes4 interfaceId) public view virtual override(OFTCore, IERC165) returns (bool) {
        return interfaceId == type(IOFT).interfaceId || interfaceId == type(IERC20).interfaceId || super.supportsInterface(interfaceId);
    }

    function token() public view virtual override returns (address) {
        return address(this);
    }

    function circulatingSupply() public view virtual override returns (uint) {
        return totalSupply();
    }

    function _debitFrom(address _from, uint16, bytes memory, uint _amount) internal virtual override returns(uint) {
        address spender = _msgSender();
        if (_from != spender) _spendAllowance(_from, spender, _amount);
        _burn(_from, _amount);
        return _amount;
    }

    function _creditTo(uint16, address _toAddress, uint _amount) internal virtual override returns(uint) {
        _mint(_toAddress, _amount);
        return _amount;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "NonblockingLzApp.sol";
import "IOFTCore.sol";
import "ERC165.sol";

abstract contract OFTCore is NonblockingLzApp, ERC165, IOFTCore {
    using BytesLib for bytes;

    uint public constant NO_EXTRA_GAS = 0;

    // packet type
    uint16 public constant PT_SEND = 0;

    bool public useCustomAdapterParams;

    constructor(address _lzEndpoint) NonblockingLzApp(_lzEndpoint) {}

    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return interfaceId == type(IOFTCore).interfaceId || super.supportsInterface(interfaceId);
    }

    function estimateSendFee(uint16 _dstChainId, bytes calldata _toAddress, uint _amount, bool _useZro, bytes calldata _adapterParams) public view virtual override returns (uint nativeFee, uint zroFee) {
        // mock the payload for sendFrom()
        bytes memory payload = abi.encode(PT_SEND, _toAddress, _amount);
        return lzEndpoint.estimateFees(_dstChainId, address(this), payload, _useZro, _adapterParams);
    }

    function sendFrom(address _from, uint16 _dstChainId, bytes calldata _toAddress, uint _amount, address payable _refundAddress, address _zroPaymentAddress, bytes calldata _adapterParams) public payable virtual override {
        _send(_from, _dstChainId, _toAddress, _amount, _refundAddress, _zroPaymentAddress, _adapterParams);
    }

    function setUseCustomAdapterParams(bool _useCustomAdapterParams) public virtual onlyOwner {
        useCustomAdapterParams = _useCustomAdapterParams;
        emit SetUseCustomAdapterParams(_useCustomAdapterParams);
    }

    function _nonblockingLzReceive(uint16 _srcChainId, bytes memory _srcAddress, uint64 _nonce, bytes memory _payload) internal virtual override {
        uint16 packetType;
        assembly {
            packetType := mload(add(_payload, 32))
        }

        if (packetType == PT_SEND) {
            _sendAck(_srcChainId, _srcAddress, _nonce, _payload);
        } else {
            revert("OFTCore: unknown packet type");
        }
    }

    function _send(address _from, uint16 _dstChainId, bytes memory _toAddress, uint _amount, address payable _refundAddress, address _zroPaymentAddress, bytes memory _adapterParams) internal virtual {
        _checkAdapterParams(_dstChainId, PT_SEND, _adapterParams, NO_EXTRA_GAS);

        uint amount = _debitFrom(_from, _dstChainId, _toAddress, _amount);

        bytes memory lzPayload = abi.encode(PT_SEND, _toAddress, amount);
        _lzSend(_dstChainId, lzPayload, _refundAddress, _zroPaymentAddress, _adapterParams, msg.value);

        emit SendToChain(_dstChainId, _from, _toAddress, amount);
    }

    function _sendAck(uint16 _srcChainId, bytes memory, uint64, bytes memory _payload) internal virtual {
        (, bytes memory toAddressBytes, uint amount) = abi.decode(_payload, (uint16, bytes, uint));

        address to = toAddressBytes.toAddress(0);

        amount = _creditTo(_srcChainId, to, amount);
        emit ReceiveFromChain(_srcChainId, to, amount);
    }

    function _checkAdapterParams(uint16 _dstChainId, uint16 _pkType, bytes memory _adapterParams, uint _extraGas) internal virtual {
        if (useCustomAdapterParams) {
            _checkGasLimit(_dstChainId, _pkType, _adapterParams, _extraGas);
        } else {
            require(_adapterParams.length == 0, "OFTCore: _adapterParams must be empty.");
        }
    }

    function _debitFrom(address _from, uint16 _dstChainId, bytes memory _toAddress, uint _amount) internal virtual returns(uint);

    function _creditTo(uint16 _srcChainId, address _toAddress, uint _amount) internal virtual returns(uint);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "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 anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing 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);
    }
}

{
  "compilationTarget": {
    "DebtToken.sol": "DebtToken"
  },
  "evmVersion": "paris",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}