// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    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");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    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");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    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);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    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);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    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 {
            // 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);
            }
        }
    }
}

// SPDX-License-Identifier: BUSL-1.1

// https://github.com/ensdomains/buffer

pragma solidity ^0.7.0;

/**
 * @dev A library for working with mutable byte buffers in Solidity.
 *
 * Byte buffers are mutable and expandable, and provide a variety of primitives
 * for writing to them. At any time you can fetch a bytes object containing the
 * current contents of the buffer. The bytes object should not be stored between
 * operations, as it may change due to resizing of the buffer.
 */
library Buffer {
    /**
     * @dev Represents a mutable buffer. Buffers have a current value (buf) and
     *      a capacity. The capacity may be longer than the current value, in
     *      which case it can be extended without the need to allocate more memory.
     */
    struct buffer {
        bytes buf;
        uint capacity;
    }

    /**
     * @dev Initializes a buffer with an initial capacity.a co
     * @param buf The buffer to initialize.
     * @param capacity The number of bytes of space to allocate the buffer.
     * @return The buffer, for chaining.
     */
    function init(buffer memory buf, uint capacity) internal pure returns (buffer memory) {
        if (capacity % 32 != 0) {
            capacity += 32 - (capacity % 32);
        }
        // Allocate space for the buffer data
        buf.capacity = capacity;
        assembly {
            let ptr := mload(0x40)
            mstore(buf, ptr)
            mstore(ptr, 0)
            mstore(0x40, add(32, add(ptr, capacity)))
        }
        return buf;
    }

    /**
     * @dev Writes a byte string to a buffer. Resizes if doing so would exceed
     *      the capacity of the buffer.
     * @param buf The buffer to append to.
     * @param off The start offset to write to.
     * @param rawData The data to append.
     * @param len The number of bytes to copy.
     * @return The original buffer, for chaining.
     */
    function writeRawBytes(
        buffer memory buf,
        uint off,
        bytes memory rawData,
        uint offData,
        uint len
    ) internal pure returns (buffer memory) {
        if (off + len > buf.capacity) {
            resize(buf, max(buf.capacity, len + off) * 2);
        }

        uint dest;
        uint src;
        assembly {
            // Memory address of the buffer data
            let bufptr := mload(buf)
            // Length of existing buffer data
            let buflen := mload(bufptr)
            // Start address = buffer address + offset + sizeof(buffer length)
            dest := add(add(bufptr, 32), off)
            // Update buffer length if we're extending it
            if gt(add(len, off), buflen) {
                mstore(bufptr, add(len, off))
            }
            src := add(rawData, offData)
        }

        // Copy word-length chunks while possible
        for (; len >= 32; len -= 32) {
            assembly {
                mstore(dest, mload(src))
            }
            dest += 32;
            src += 32;
        }

        // Copy remaining bytes
        uint mask = 256 ** (32 - len) - 1;
        assembly {
            let srcpart := and(mload(src), not(mask))
            let destpart := and(mload(dest), mask)
            mstore(dest, or(destpart, srcpart))
        }

        return buf;
    }

    /**
     * @dev Writes a byte string to a buffer. Resizes if doing so would exceed
     *      the capacity of the buffer.
     * @param buf The buffer to append to.
     * @param off The start offset to write to.
     * @param data The data to append.
     * @param len The number of bytes to copy.
     * @return The original buffer, for chaining.
     */
    function write(buffer memory buf, uint off, bytes memory data, uint len) internal pure returns (buffer memory) {
        require(len <= data.length);

        if (off + len > buf.capacity) {
            resize(buf, max(buf.capacity, len + off) * 2);
        }

        uint dest;
        uint src;
        assembly {
            // Memory address of the buffer data
            let bufptr := mload(buf)
            // Length of existing buffer data
            let buflen := mload(bufptr)
            // Start address = buffer address + offset + sizeof(buffer length)
            dest := add(add(bufptr, 32), off)
            // Update buffer length if we're extending it
            if gt(add(len, off), buflen) {
                mstore(bufptr, add(len, off))
            }
            src := add(data, 32)
        }

        // Copy word-length chunks while possible
        for (; len >= 32; len -= 32) {
            assembly {
                mstore(dest, mload(src))
            }
            dest += 32;
            src += 32;
        }

        // Copy remaining bytes
        uint mask = 256 ** (32 - len) - 1;
        assembly {
            let srcpart := and(mload(src), not(mask))
            let destpart := and(mload(dest), mask)
            mstore(dest, or(destpart, srcpart))
        }

        return buf;
    }

    function append(buffer memory buf, bytes memory data) internal pure returns (buffer memory) {
        return write(buf, buf.buf.length, data, data.length);
    }

    function resize(buffer memory buf, uint capacity) private pure {
        bytes memory oldbuf = buf.buf;
        init(buf, capacity);
        append(buf, oldbuf);
    }

    function max(uint a, uint b) private pure returns (uint) {
        if (a > b) {
            return a;
        }
        return b;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <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 GSN 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 payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

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

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * 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 `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// SPDX-License-Identifier: BUSL-1.1

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 receiver 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: BUSL-1.1

pragma solidity >=0.7.0;

import "./ILayerZeroUserApplicationConfig.sol";

interface ILayerZeroMessagingLibrary {
    // send(), messages will be inflight.
    function send(
        address _userApplication,
        uint64 _lastNonce,
        uint16 _chainId,
        bytes calldata _destination,
        bytes calldata _payload,
        address payable refundAddress,
        address _zroPaymentAddress,
        bytes calldata _adapterParams
    ) external payable;

    // estimate native fee at the send side
    function estimateFees(
        uint16 _chainId,
        address _userApplication,
        bytes calldata _payload,
        bool _payInZRO,
        bytes calldata _adapterParam
    ) external view returns (uint nativeFee, uint zroFee);

    //---------------------------------------------------------------------------
    // setConfig / getConfig are User Application (UA) functions to specify Oracle, Relayer, blockConfirmations, libraryVersion
    function setConfig(uint16 _chainId, address _userApplication, uint _configType, bytes calldata _config) external;

    function getConfig(
        uint16 _chainId,
        address _userApplication,
        uint _configType
    ) external view returns (bytes memory);
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;

import "./ILayerZeroUserApplicationConfig.sol";
import "./ILayerZeroMessagingLibrary.sol";

interface ILayerZeroMessagingLibraryV2 is ILayerZeroMessagingLibrary {
    function getOutboundNonce(uint16 _chainId, bytes calldata _path) external view returns (uint64);
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;

interface ILayerZeroOracleV2 {
    // @notice query price and assign jobs at the same time
    // @param _dstChainId - the destination endpoint identifier
    // @param _outboundProofType - the proof type identifier to specify proof to be relayed
    // @param _outboundBlockConfirmation - block confirmation delay before relaying blocks
    // @param _userApplication - the source sending contract address
    function assignJob(
        uint16 _dstChainId,
        uint16 _outboundProofType,
        uint64 _outboundBlockConfirmation,
        address _userApplication
    ) external returns (uint price);

    // @notice query the oracle price for relaying block information to the destination chain
    // @param _dstChainId the destination endpoint identifier
    // @param _outboundProofType the proof type identifier to specify the data to be relayed
    // @param _outboundBlockConfirmation - block confirmation delay before relaying blocks
    // @param _userApplication - the source sending contract address
    function getFee(
        uint16 _dstChainId,
        uint16 _outboundProofType,
        uint64 _outboundBlockConfirmation,
        address _userApplication
    ) external view returns (uint price);

    // @notice withdraw the accrued fee in ultra light node
    // @param _to - the fee receiver
    // @param _amount - the withdrawal amount
    function withdrawFee(address payable _to, uint _amount) external;
}

// SPDX-License-Identifier: BUSL-1.1

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: BUSL-1.1

pragma solidity >=0.7.0;

interface ILayerZeroRelayerV2 {
    // @notice query price and assign jobs at the same time
    // @param _dstChainId - the destination endpoint identifier
    // @param _outboundProofType - the proof type identifier to specify proof to be relayed
    // @param _userApplication - the source sending contract address. relayers may apply price discrimination to user apps
    // @param _payloadSize - the length of the payload. it is an indicator of gas usage for relaying cross-chain messages
    // @param _adapterParams - optional parameters for extra service plugins, e.g. sending dust tokens at the destination chain
    function assignJob(
        uint16 _dstChainId,
        uint16 _outboundProofType,
        address _userApplication,
        uint _payloadSize,
        bytes calldata _adapterParams
    ) external returns (uint price);

    // @notice query the relayer price for relaying the payload and its proof to the destination chain
    // @param _dstChainId - the destination endpoint identifier
    // @param _outboundProofType - the proof type identifier to specify proof to be relayed
    // @param _userApplication - the source sending contract address. relayers may apply price discrimination to user apps
    // @param _payloadSize - the length of the payload. it is an indicator of gas usage for relaying cross-chain messages
    // @param _adapterParams - optional parameters for extra service plugins, e.g. sending dust tokens at the destination chain
    function getFee(
        uint16 _dstChainId,
        uint16 _outboundProofType,
        address _userApplication,
        uint _payloadSize,
        bytes calldata _adapterParams
    ) external view returns (uint price);

    // @notice withdraw the accrued fee in ultra light node
    // @param _to - the fee receiver
    // @param _amount - the withdrawal amount
    function withdrawFee(address payable _to, uint _amount) external;
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.5.0;

interface ILayerZeroTreasury {
    function getFees(bool payInZro, uint relayerFee, uint oracleFee) external view returns (uint);
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;
pragma abicoder v2;

interface ILayerZeroUltraLightNodeV2 {
    // Relayer functions
    function validateTransactionProof(
        uint16 _srcChainId,
        address _dstAddress,
        uint _gasLimit,
        bytes32 _lookupHash,
        bytes32 _blockData,
        bytes calldata _transactionProof
    ) external;

    // an Oracle delivers the block data using updateHash()
    function updateHash(uint16 _srcChainId, bytes32 _lookupHash, uint _confirmations, bytes32 _blockData) external;

    // can only withdraw the receivable of the msg.sender
    function withdrawNative(address payable _to, uint _amount) external;

    function withdrawZRO(address _to, uint _amount) external;

    // view functions
    function getAppConfig(
        uint16 _remoteChainId,
        address _userApplicationAddress
    ) external view returns (ApplicationConfiguration memory);

    function accruedNativeFee(address _address) external view returns (uint);

    struct ApplicationConfiguration {
        uint16 inboundProofLibraryVersion;
        uint64 inboundBlockConfirmations;
        address relayer;
        uint16 outboundProofType;
        uint64 outboundBlockConfirmations;
        address oracle;
    }

    event HashReceived(
        uint16 indexed srcChainId,
        address indexed oracle,
        bytes32 lookupHash,
        bytes32 blockData,
        uint confirmations
    );
    event RelayerParams(bytes adapterParams, uint16 outboundProofType);
    event Packet(bytes payload);
    event InvalidDst(
        uint16 indexed srcChainId,
        bytes srcAddress,
        address indexed dstAddress,
        uint64 nonce,
        bytes32 payloadHash
    );
    event PacketReceived(
        uint16 indexed srcChainId,
        bytes srcAddress,
        address indexed dstAddress,
        uint64 nonce,
        bytes32 payloadHash
    );
    event AppConfigUpdated(address indexed userApplication, uint indexed configType, bytes newConfig);
    event AddInboundProofLibraryForChain(uint16 indexed chainId, address lib);
    event EnableSupportedOutboundProof(uint16 indexed chainId, uint16 proofType);
    event SetChainAddressSize(uint16 indexed chainId, uint size);
    event SetDefaultConfigForChainId(
        uint16 indexed chainId,
        uint16 inboundProofLib,
        uint64 inboundBlockConfirm,
        address relayer,
        uint16 outboundProofType,
        uint64 outboundBlockConfirm,
        address oracle
    );
    event SetDefaultAdapterParamsForChainId(uint16 indexed chainId, uint16 indexed proofType, bytes adapterParams);
    event SetLayerZeroToken(address indexed tokenAddress);
    event SetRemoteUln(uint16 indexed chainId, bytes32 uln);
    event SetTreasury(address indexed treasuryAddress);
    event WithdrawZRO(address indexed msgSender, address indexed to, uint amount);
    event WithdrawNative(address indexed msgSender, address indexed to, uint amount);
}

// SPDX-License-Identifier: BUSL-1.1

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: BUSL-1.1

pragma solidity >=0.7.0;
pragma abicoder v2;

import "../proof/utility/LayerZeroPacket.sol";

interface ILayerZeroValidationLibrary {
    function validateProof(
        bytes32 blockData,
        bytes calldata _data,
        uint _remoteAddressSize
    ) external returns (LayerZeroPacket.Packet memory packet);
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "./Buffer.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";

library LayerZeroPacket {
    using Buffer for Buffer.buffer;
    using SafeMath for uint;

    struct Packet {
        uint16 srcChainId;
        uint16 dstChainId;
        uint64 nonce;
        address dstAddress;
        bytes srcAddress;
        bytes32 ulnAddress;
        bytes payload;
    }

    function getPacket(
        bytes memory data,
        uint16 srcChain,
        uint sizeOfSrcAddress,
        bytes32 ulnAddress
    ) internal pure returns (LayerZeroPacket.Packet memory) {
        uint16 dstChainId;
        address dstAddress;
        uint size;
        uint64 nonce;

        // The log consists of the destination chain id and then a bytes payload
        //      0--------------------------------------------31
        // 0   |  total bytes size
        // 32  |  destination chain id
        // 64  |  bytes offset
        // 96  |  bytes array size
        // 128 |  payload
        assembly {
            dstChainId := mload(add(data, 32))
            size := mload(add(data, 96)) /// size of the byte array
            nonce := mload(add(data, 104)) // offset to convert to uint64  128  is index -24
            dstAddress := mload(add(data, sub(add(128, sizeOfSrcAddress), 4))) // offset to convert to address 12 -8
        }

        Buffer.buffer memory srcAddressBuffer;
        srcAddressBuffer.init(sizeOfSrcAddress);
        srcAddressBuffer.writeRawBytes(0, data, 136, sizeOfSrcAddress); // 128 + 8

        uint payloadSize = size.sub(28).sub(sizeOfSrcAddress);
        Buffer.buffer memory payloadBuffer;
        payloadBuffer.init(payloadSize);
        payloadBuffer.writeRawBytes(0, data, sizeOfSrcAddress.add(156), payloadSize); // 148 + 8
        return
            LayerZeroPacket.Packet(
                srcChain,
                dstChainId,
                nonce,
                dstAddress,
                srcAddressBuffer.buf,
                ulnAddress,
                payloadBuffer.buf
            );
    }

    function getPacketV2(
        bytes memory data,
        uint sizeOfSrcAddress,
        bytes32 ulnAddress
    ) internal pure returns (LayerZeroPacket.Packet memory) {
        // packet def: abi.encodePacked(nonce, srcChain, srcAddress, dstChain, dstAddress, payload);
        // data def: abi.encode(packet) = offset(32) + length(32) + packet
        //              if from EVM
        // 0 - 31       0 - 31          |  total bytes size
        // 32 - 63      32 - 63         |  location
        // 64 - 95      64 - 95         |  size of the packet
        // 96 - 103     96 - 103        |  nonce
        // 104 - 105    104 - 105       |  srcChainId
        // 106 - P      106 - 125       |  srcAddress, where P = 106 + sizeOfSrcAddress - 1,
        // P+1 - P+2    126 - 127       |  dstChainId
        // P+3 - P+22   128 - 147       |  dstAddress
        // P+23 - END   148 - END       |  payload

        // decode the packet
        uint256 realSize;
        uint64 nonce;
        uint16 srcChain;
        uint16 dstChain;
        address dstAddress;
        assembly {
            realSize := mload(add(data, 64))
            nonce := mload(add(data, 72)) // 104 - 32
            srcChain := mload(add(data, 74)) // 106 - 32
            dstChain := mload(add(data, add(76, sizeOfSrcAddress))) // P + 3 - 32 = 105 + size + 3 - 32 = 76 + size
            dstAddress := mload(add(data, add(96, sizeOfSrcAddress))) // P + 23 - 32 = 105 + size + 23 - 32 = 96 + size
        }

        require(srcChain != 0, "LayerZeroPacket: invalid packet");

        Buffer.buffer memory srcAddressBuffer;
        srcAddressBuffer.init(sizeOfSrcAddress);
        srcAddressBuffer.writeRawBytes(0, data, 106, sizeOfSrcAddress);

        uint nonPayloadSize = sizeOfSrcAddress.add(32); // 2 + 2 + 8 + 20, 32 + 20 = 52 if sizeOfSrcAddress == 20
        uint payloadSize = realSize.sub(nonPayloadSize);
        Buffer.buffer memory payloadBuffer;
        payloadBuffer.init(payloadSize);
        payloadBuffer.writeRawBytes(0, data, nonPayloadSize.add(96), payloadSize);

        return
            LayerZeroPacket.Packet(
                srcChain,
                dstChain,
                nonce,
                dstAddress,
                srcAddressBuffer.buf,
                ulnAddress,
                payloadBuffer.buf
            );
    }

    function getPacketV3(
        bytes memory data,
        uint sizeOfSrcAddress,
        bytes32 ulnAddress
    ) internal pure returns (LayerZeroPacket.Packet memory) {
        // data def: abi.encodePacked(nonce, srcChain, srcAddress, dstChain, dstAddress, payload);
        //              if from EVM
        // 0 - 31       0 - 31          |  total bytes size
        // 32 - 39      32 - 39         |  nonce
        // 40 - 41      40 - 41         |  srcChainId
        // 42 - P       42 - 61         |  srcAddress, where P = 41 + sizeOfSrcAddress,
        // P+1 - P+2    62 - 63         |  dstChainId
        // P+3 - P+22   64 - 83         |  dstAddress
        // P+23 - END   84 - END        |  payload

        // decode the packet
        uint256 realSize = data.length;
        uint nonPayloadSize = sizeOfSrcAddress.add(32); // 2 + 2 + 8 + 20, 32 + 20 = 52 if sizeOfSrcAddress == 20
        require(realSize >= nonPayloadSize, "LayerZeroPacket: invalid packet");
        uint payloadSize = realSize - nonPayloadSize;

        uint64 nonce;
        uint16 srcChain;
        uint16 dstChain;
        address dstAddress;
        assembly {
            nonce := mload(add(data, 8)) // 40 - 32
            srcChain := mload(add(data, 10)) // 42 - 32
            dstChain := mload(add(data, add(12, sizeOfSrcAddress))) // P + 3 - 32 = 41 + size + 3 - 32 = 12 + size
            dstAddress := mload(add(data, add(32, sizeOfSrcAddress))) // P + 23 - 32 = 41 + size + 23 - 32 = 32 + size
        }

        require(srcChain != 0, "LayerZeroPacket: invalid packet");

        Buffer.buffer memory srcAddressBuffer;
        srcAddressBuffer.init(sizeOfSrcAddress);
        srcAddressBuffer.writeRawBytes(0, data, 42, sizeOfSrcAddress);

        Buffer.buffer memory payloadBuffer;
        if (payloadSize > 0) {
            payloadBuffer.init(payloadSize);
            payloadBuffer.writeRawBytes(0, data, nonPayloadSize.add(32), payloadSize);
        }

        return
            LayerZeroPacket.Packet(
                srcChain,
                dstChain,
                nonce,
                dstAddress,
                srcAddressBuffer.buf,
                ulnAddress,
                payloadBuffer.buf
            );
    }
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "./interfaces/ILayerZeroEndpoint.sol";

contract NonceContract {
    ILayerZeroEndpoint public immutable endpoint;
    // outboundNonce = [dstChainId][remoteAddress + localAddress]
    mapping(uint16 => mapping(bytes => uint64)) public outboundNonce;

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

    function increment(uint16 _chainId, address _ua, bytes calldata _path) external returns (uint64) {
        require(
            endpoint.getSendLibraryAddress(_ua) == msg.sender,
            "NonceContract: msg.sender is not valid sendlibrary"
        );
        return ++outboundNonce[_chainId][_path];
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

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

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        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 {
        emit OwnershipTransferred(_owner, address(0));
        _owner = 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");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;
pragma abicoder v2;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";

import "./interfaces/ILayerZeroValidationLibrary.sol";
import "./interfaces/ILayerZeroReceiver.sol";
import "./interfaces/ILayerZeroTreasury.sol";
import "./interfaces/ILayerZeroEndpoint.sol";
// v2
import "./interfaces/ILayerZeroMessagingLibraryV2.sol";
import "./interfaces/ILayerZeroOracleV2.sol";
import "./interfaces/ILayerZeroUltraLightNodeV2.sol";
import "./interfaces/ILayerZeroRelayerV2.sol";
import "./NonceContract.sol";

contract UltraLightNodeV2 is ILayerZeroMessagingLibraryV2, ILayerZeroUltraLightNodeV2, ReentrancyGuard, Ownable {
    using SafeERC20 for IERC20;
    using SafeMath for uint;

    // Application config
    uint public constant CONFIG_TYPE_INBOUND_PROOF_LIBRARY_VERSION = 1;
    uint public constant CONFIG_TYPE_INBOUND_BLOCK_CONFIRMATIONS = 2;
    uint public constant CONFIG_TYPE_RELAYER = 3;
    uint public constant CONFIG_TYPE_OUTBOUND_PROOF_TYPE = 4;
    uint public constant CONFIG_TYPE_OUTBOUND_BLOCK_CONFIRMATIONS = 5;
    uint public constant CONFIG_TYPE_ORACLE = 6;

    // Token and Contracts
    IERC20 public layerZeroToken;
    ILayerZeroTreasury public treasuryContract;

    mapping(address => uint) public nativeFees;
    uint public treasuryZROFees;

    // User Application
    mapping(address => mapping(uint16 => ApplicationConfiguration)) public appConfig; // app address => chainId => config
    mapping(uint16 => ApplicationConfiguration) public defaultAppConfig; // default UA settings if no version specified
    mapping(uint16 => mapping(uint16 => bytes)) public defaultAdapterParams;

    // Validation
    mapping(uint16 => mapping(uint16 => address)) public inboundProofLibrary; // chainId => library Id => inboundProofLibrary contract
    mapping(uint16 => uint16) public maxInboundProofLibrary; // chainId => inboundProofLibrary
    mapping(uint16 => mapping(uint16 => bool)) public supportedOutboundProof; // chainId => outboundProofType => enabled
    mapping(uint16 => uint) public chainAddressSizeMap;
    mapping(address => mapping(uint16 => mapping(bytes32 => mapping(bytes32 => uint)))) public hashLookup; //[oracle][srcChainId][blockhash][datahash] -> confirmation
    mapping(uint16 => bytes32) public ulnLookup; // remote ulns

    ILayerZeroEndpoint public immutable endpoint;
    uint16 public immutable localChainId;
    NonceContract public immutable nonceContract;

    constructor(address _endpoint, address _nonceContract, uint16 _localChainId) {
        require(_endpoint != address(0x0), "LayerZero: endpoint cannot be zero address");
        require(_nonceContract != address(0x0), "LayerZero: nonceContract cannot be zero address");
        ILayerZeroEndpoint lzEndpoint = ILayerZeroEndpoint(_endpoint);
        localChainId = _localChainId;
        endpoint = lzEndpoint;
        nonceContract = NonceContract(_nonceContract);
    }

    // only the endpoint can call SEND() and setConfig()
    modifier onlyEndpoint() {
        require(address(endpoint) == msg.sender, "LayerZero: only endpoint");
        _;
    }

    //----------------------------------------------------------------------------------
    // PROTOCOL
    function validateTransactionProof(
        uint16 _srcChainId,
        address _dstAddress,
        uint _gasLimit,
        bytes32 _lookupHash,
        bytes32 _blockData,
        bytes calldata _transactionProof
    ) external override {
        // retrieve UA's configuration using the _dstAddress from arguments.
        ApplicationConfiguration memory uaConfig = _getAppConfig(_srcChainId, _dstAddress);

        // assert that the caller == UA's relayer
        require(uaConfig.relayer == msg.sender, "LayerZero: invalid relayer");

        LayerZeroPacket.Packet memory _packet;
        uint remoteAddressSize = chainAddressSizeMap[_srcChainId];
        require(remoteAddressSize != 0, "LayerZero: incorrect remote address size");
        {
            // assert that the data submitted by UA's oracle have no fewer confirmations than UA's configuration
            uint storedConfirmations = hashLookup[uaConfig.oracle][_srcChainId][_lookupHash][_blockData];
            require(
                storedConfirmations > 0 && storedConfirmations >= uaConfig.inboundBlockConfirmations,
                "LayerZero: not enough block confirmations"
            );

            // decode
            address inboundProofLib = inboundProofLibrary[_srcChainId][uaConfig.inboundProofLibraryVersion];
            _packet = ILayerZeroValidationLibrary(inboundProofLib).validateProof(
                _blockData,
                _transactionProof,
                remoteAddressSize
            );
        }

        // packet content assertion
        require(
            ulnLookup[_srcChainId] == _packet.ulnAddress && _packet.ulnAddress != bytes32(0),
            "LayerZero: invalid _packet.ulnAddress"
        );
        require(_packet.srcChainId == _srcChainId, "LayerZero: invalid srcChain Id");
        // failsafe because the remoteAddress size being passed into validateProof trims the address this should not hit
        require(_packet.srcAddress.length == remoteAddressSize, "LayerZero: invalid srcAddress size");
        require(_packet.dstChainId == localChainId, "LayerZero: invalid dstChain Id");
        require(_packet.dstAddress == _dstAddress, "LayerZero: invalid dstAddress");

        // if the dst is not a contract, then emit and return early. This will break inbound nonces, but this particular
        // path is already broken and wont ever be able to deliver anyways
        if (!_isContract(_dstAddress)) {
            emit InvalidDst(
                _packet.srcChainId,
                _packet.srcAddress,
                _packet.dstAddress,
                _packet.nonce,
                keccak256(_packet.payload)
            );
            return;
        }

        bytes memory pathData = abi.encodePacked(_packet.srcAddress, _packet.dstAddress);
        emit PacketReceived(
            _packet.srcChainId,
            _packet.srcAddress,
            _packet.dstAddress,
            _packet.nonce,
            keccak256(_packet.payload)
        );
        endpoint.receivePayload(_srcChainId, pathData, _dstAddress, _packet.nonce, _gasLimit, _packet.payload);
    }

    function send(
        address _ua,
        uint64,
        uint16 _dstChainId,
        bytes calldata _path,
        bytes calldata _payload,
        address payable _refundAddress,
        address _zroPaymentAddress,
        bytes calldata _adapterParams
    ) external payable override onlyEndpoint {
        address ua = _ua;
        uint16 dstChainId = _dstChainId;
        require(ulnLookup[dstChainId] != bytes32(0), "LayerZero: dstChainId does not exist");

        bytes memory dstAddress;
        uint64 nonce;
        // code block for solving 'Stack Too Deep'
        {
            uint chainAddressSize = chainAddressSizeMap[dstChainId];
            // path = remoteAddress + localAddress
            require(
                chainAddressSize != 0 && _path.length == 20 + chainAddressSize,
                "LayerZero: incorrect remote address size"
            );
            address srcInPath;
            bytes memory path = _path; // copy to memory
            assembly {
                srcInPath := mload(add(add(path, 20), chainAddressSize)) // chainAddressSize + 20
            }
            require(ua == srcInPath, "LayerZero: wrong path data");
            dstAddress = _path[0:chainAddressSize];
            nonce = nonceContract.increment(dstChainId, ua, path);
        }

        bytes memory payload = _payload;
        ApplicationConfiguration memory uaConfig = _getAppConfig(dstChainId, ua);

        // compute all the fees
        uint relayerFee = _handleRelayer(dstChainId, uaConfig, ua, payload.length, _adapterParams);
        uint oracleFee = _handleOracle(dstChainId, uaConfig, ua);
        uint nativeProtocolFee = _handleProtocolFee(relayerFee, oracleFee, ua, _zroPaymentAddress);

        // total native fee, does not include ZRO protocol fee
        uint totalNativeFee = relayerFee.add(oracleFee).add(nativeProtocolFee);

        // assert the user has attached enough native token for this address
        require(totalNativeFee <= msg.value, "LayerZero: not enough native for fees");
        // refund if they send too much
        uint amount = msg.value.sub(totalNativeFee);
        if (amount > 0) {
            (bool success, ) = _refundAddress.call{value: amount}("");
            require(success, "LayerZero: failed to refund");
        }

        // emit the data packet
        bytes memory encodedPayload = abi.encodePacked(nonce, localChainId, ua, dstChainId, dstAddress, payload);
        emit Packet(encodedPayload);
    }

    function _handleRelayer(
        uint16 _dstChainId,
        ApplicationConfiguration memory _uaConfig,
        address _ua,
        uint _payloadSize,
        bytes memory _adapterParams
    ) internal returns (uint relayerFee) {
        if (_adapterParams.length == 0) {
            _adapterParams = defaultAdapterParams[_dstChainId][_uaConfig.outboundProofType];
        }
        address relayerAddress = _uaConfig.relayer;
        ILayerZeroRelayerV2 relayer = ILayerZeroRelayerV2(relayerAddress);
        relayerFee = relayer.assignJob(_dstChainId, _uaConfig.outboundProofType, _ua, _payloadSize, _adapterParams);

        _creditNativeFee(relayerAddress, relayerFee);

        // emit the param events
        emit RelayerParams(_adapterParams, _uaConfig.outboundProofType);
    }

    function _handleOracle(
        uint16 _dstChainId,
        ApplicationConfiguration memory _uaConfig,
        address _ua
    ) internal returns (uint oracleFee) {
        address oracleAddress = _uaConfig.oracle;
        oracleFee = ILayerZeroOracleV2(oracleAddress).assignJob(
            _dstChainId,
            _uaConfig.outboundProofType,
            _uaConfig.outboundBlockConfirmations,
            _ua
        );

        _creditNativeFee(oracleAddress, oracleFee);
    }

    function _handleProtocolFee(
        uint _relayerFee,
        uint _oracleFee,
        address _ua,
        address _zroPaymentAddress
    ) internal returns (uint protocolNativeFee) {
        // if no ZRO token or not specifying a payment address, pay in native token
        bool payInNative = _zroPaymentAddress == address(0x0) || address(layerZeroToken) == address(0x0);
        uint protocolFee = treasuryContract.getFees(!payInNative, _relayerFee, _oracleFee);

        if (protocolFee > 0) {
            if (payInNative) {
                address treasuryAddress = address(treasuryContract);
                _creditNativeFee(treasuryAddress, protocolFee);
                protocolNativeFee = protocolFee;
            } else {
                // zro payment address must equal the ua or the tx.origin otherwise the transaction reverts
                require(
                    _zroPaymentAddress == _ua || _zroPaymentAddress == tx.origin,
                    "LayerZero: must be paid by sender or origin"
                );

                // transfer the LayerZero token to this contract from the payee
                layerZeroToken.safeTransferFrom(_zroPaymentAddress, address(this), protocolFee);

                treasuryZROFees = treasuryZROFees.add(protocolFee);
            }
        }
    }

    function _creditNativeFee(address _receiver, uint _amount) internal {
        nativeFees[_receiver] = nativeFees[_receiver].add(_amount);
    }

    // Can be called by any address to update a block header
    // can only upload new block data or the same block data with more confirmations
    function updateHash(
        uint16 _srcChainId,
        bytes32 _lookupHash,
        uint _confirmations,
        bytes32 _blockData
    ) external override {
        uint storedConfirmations = hashLookup[msg.sender][_srcChainId][_lookupHash][_blockData];

        // if it has a record, requires a larger confirmation.
        require(
            storedConfirmations < _confirmations,
            "LayerZero: oracle data can only update if it has more confirmations"
        );

        // set the new information into storage
        hashLookup[msg.sender][_srcChainId][_lookupHash][_blockData] = _confirmations;

        emit HashReceived(_srcChainId, msg.sender, _lookupHash, _blockData, _confirmations);
    }

    //----------------------------------------------------------------------------------
    // Other Library Interfaces

    // default to DEFAULT setting if ZERO value
    function getAppConfig(
        uint16 _remoteChainId,
        address _ua
    ) external view override returns (ApplicationConfiguration memory) {
        return _getAppConfig(_remoteChainId, _ua);
    }

    function _getAppConfig(uint16 _remoteChainId, address _ua) internal view returns (ApplicationConfiguration memory) {
        ApplicationConfiguration memory config = appConfig[_ua][_remoteChainId];
        ApplicationConfiguration storage defaultConfig = defaultAppConfig[_remoteChainId];

        if (config.inboundProofLibraryVersion == 0) {
            config.inboundProofLibraryVersion = defaultConfig.inboundProofLibraryVersion;
        }

        if (config.inboundBlockConfirmations == 0) {
            config.inboundBlockConfirmations = defaultConfig.inboundBlockConfirmations;
        }

        if (config.relayer == address(0x0)) {
            config.relayer = defaultConfig.relayer;
        }

        if (config.outboundProofType == 0) {
            config.outboundProofType = defaultConfig.outboundProofType;
        }

        if (config.outboundBlockConfirmations == 0) {
            config.outboundBlockConfirmations = defaultConfig.outboundBlockConfirmations;
        }

        if (config.oracle == address(0x0)) {
            config.oracle = defaultConfig.oracle;
        }

        return config;
    }

    function setConfig(
        uint16 _remoteChainId,
        address _ua,
        uint _configType,
        bytes calldata _config
    ) external override onlyEndpoint {
        ApplicationConfiguration storage uaConfig = appConfig[_ua][_remoteChainId];
        if (_configType == CONFIG_TYPE_INBOUND_PROOF_LIBRARY_VERSION) {
            uint16 inboundProofLibraryVersion = abi.decode(_config, (uint16));
            require(
                inboundProofLibraryVersion <= maxInboundProofLibrary[_remoteChainId],
                "LayerZero: invalid inbound proof library version"
            );
            uaConfig.inboundProofLibraryVersion = inboundProofLibraryVersion;
        } else if (_configType == CONFIG_TYPE_INBOUND_BLOCK_CONFIRMATIONS) {
            uint64 blockConfirmations = abi.decode(_config, (uint64));
            uaConfig.inboundBlockConfirmations = blockConfirmations;
        } else if (_configType == CONFIG_TYPE_RELAYER) {
            address relayer = abi.decode(_config, (address));
            uaConfig.relayer = relayer;
        } else if (_configType == CONFIG_TYPE_OUTBOUND_PROOF_TYPE) {
            uint16 outboundProofType = abi.decode(_config, (uint16));
            require(
                supportedOutboundProof[_remoteChainId][outboundProofType] || outboundProofType == 0,
                "LayerZero: invalid outbound proof type"
            );
            uaConfig.outboundProofType = outboundProofType;
        } else if (_configType == CONFIG_TYPE_OUTBOUND_BLOCK_CONFIRMATIONS) {
            uint64 blockConfirmations = abi.decode(_config, (uint64));
            uaConfig.outboundBlockConfirmations = blockConfirmations;
        } else if (_configType == CONFIG_TYPE_ORACLE) {
            address oracle = abi.decode(_config, (address));
            uaConfig.oracle = oracle;
        } else {
            revert("LayerZero: Invalid config type");
        }

        emit AppConfigUpdated(_ua, _configType, _config);
    }

    function getConfig(
        uint16 _remoteChainId,
        address _ua,
        uint _configType
    ) external view override returns (bytes memory) {
        ApplicationConfiguration storage uaConfig = appConfig[_ua][_remoteChainId];

        if (_configType == CONFIG_TYPE_INBOUND_PROOF_LIBRARY_VERSION) {
            if (uaConfig.inboundProofLibraryVersion == 0) {
                return abi.encode(defaultAppConfig[_remoteChainId].inboundProofLibraryVersion);
            }
            return abi.encode(uaConfig.inboundProofLibraryVersion);
        } else if (_configType == CONFIG_TYPE_INBOUND_BLOCK_CONFIRMATIONS) {
            if (uaConfig.inboundBlockConfirmations == 0) {
                return abi.encode(defaultAppConfig[_remoteChainId].inboundBlockConfirmations);
            }
            return abi.encode(uaConfig.inboundBlockConfirmations);
        } else if (_configType == CONFIG_TYPE_RELAYER) {
            if (uaConfig.relayer == address(0x0)) {
                return abi.encode(defaultAppConfig[_remoteChainId].relayer);
            }
            return abi.encode(uaConfig.relayer);
        } else if (_configType == CONFIG_TYPE_OUTBOUND_PROOF_TYPE) {
            if (uaConfig.outboundProofType == 0) {
                return abi.encode(defaultAppConfig[_remoteChainId].outboundProofType);
            }
            return abi.encode(uaConfig.outboundProofType);
        } else if (_configType == CONFIG_TYPE_OUTBOUND_BLOCK_CONFIRMATIONS) {
            if (uaConfig.outboundBlockConfirmations == 0) {
                return abi.encode(defaultAppConfig[_remoteChainId].outboundBlockConfirmations);
            }
            return abi.encode(uaConfig.outboundBlockConfirmations);
        } else if (_configType == CONFIG_TYPE_ORACLE) {
            if (uaConfig.oracle == address(0x0)) {
                return abi.encode(defaultAppConfig[_remoteChainId].oracle);
            }
            return abi.encode(uaConfig.oracle);
        } else {
            revert("LayerZero: Invalid config type");
        }
    }

    // returns the native fee the UA pays to cover fees
    function estimateFees(
        uint16 _dstChainId,
        address _ua,
        bytes calldata _payload,
        bool _payInZRO,
        bytes calldata _adapterParams
    ) external view override returns (uint nativeFee, uint zroFee) {
        ApplicationConfiguration memory uaConfig = _getAppConfig(_dstChainId, _ua);

        // Relayer Fee
        bytes memory adapterParams;
        if (_adapterParams.length > 0) {
            adapterParams = _adapterParams;
        } else {
            adapterParams = defaultAdapterParams[_dstChainId][uaConfig.outboundProofType];
        }
        uint relayerFee = ILayerZeroRelayerV2(uaConfig.relayer).getFee(
            _dstChainId,
            uaConfig.outboundProofType,
            _ua,
            _payload.length,
            adapterParams
        );

        // Oracle Fee
        address ua = _ua; // stack too deep
        uint oracleFee = ILayerZeroOracleV2(uaConfig.oracle).getFee(
            _dstChainId,
            uaConfig.outboundProofType,
            uaConfig.outboundBlockConfirmations,
            ua
        );

        // LayerZero Fee
        uint protocolFee = treasuryContract.getFees(_payInZRO, relayerFee, oracleFee);
        _payInZRO ? zroFee = protocolFee : nativeFee = protocolFee;

        // return the sum of fees
        nativeFee = nativeFee.add(relayerFee).add(oracleFee);
    }

    //---------------------------------------------------------------------------
    // Claim Fees

    // universal withdraw ZRO token function
    function withdrawZRO(address _to, uint _amount) external override nonReentrant {
        require(msg.sender == address(treasuryContract), "LayerZero: only treasury");
        treasuryZROFees = treasuryZROFees.sub(_amount);
        layerZeroToken.safeTransfer(_to, _amount);
        emit WithdrawZRO(msg.sender, _to, _amount);
    }

    // universal withdraw native token function.
    // the source contract should perform all the authentication control
    function withdrawNative(address payable _to, uint _amount) external override nonReentrant {
        require(_to != address(0x0), "LayerZero: _to cannot be zero address");
        nativeFees[msg.sender] = nativeFees[msg.sender].sub(_amount);

        (bool success, ) = _to.call{value: _amount}("");
        require(success, "LayerZero: withdraw failed");
        emit WithdrawNative(msg.sender, _to, _amount);
    }

    //---------------------------------------------------------------------------
    // Owner calls, configuration only.
    function setLayerZeroToken(address _layerZeroToken) external onlyOwner {
        require(_layerZeroToken != address(0x0), "LayerZero: _layerZeroToken cannot be zero address");
        layerZeroToken = IERC20(_layerZeroToken);
        emit SetLayerZeroToken(_layerZeroToken);
    }

    function setTreasury(address _treasury) external onlyOwner {
        require(_treasury != address(0x0), "LayerZero: treasury cannot be zero address");
        treasuryContract = ILayerZeroTreasury(_treasury);
        emit SetTreasury(_treasury);
    }

    function addInboundProofLibraryForChain(uint16 _chainId, address _library) external onlyOwner {
        require(_library != address(0x0), "LayerZero: library cannot be zero address");
        uint16 libId = maxInboundProofLibrary[_chainId];
        require(libId < 65535, "LayerZero: can not add new library");
        maxInboundProofLibrary[_chainId] = ++libId;
        inboundProofLibrary[_chainId][libId] = _library;
        emit AddInboundProofLibraryForChain(_chainId, _library);
    }

    function enableSupportedOutboundProof(uint16 _chainId, uint16 _proofType) external onlyOwner {
        supportedOutboundProof[_chainId][_proofType] = true;
        emit EnableSupportedOutboundProof(_chainId, _proofType);
    }

    function setDefaultConfigForChainId(
        uint16 _chainId,
        uint16 _inboundProofLibraryVersion,
        uint64 _inboundBlockConfirmations,
        address _relayer,
        uint16 _outboundProofType,
        uint64 _outboundBlockConfirmations,
        address _oracle
    ) external onlyOwner {
        require(
            _inboundProofLibraryVersion <= maxInboundProofLibrary[_chainId] && _inboundProofLibraryVersion > 0,
            "LayerZero: invalid inbound proof library version"
        );
        require(_inboundBlockConfirmations > 0, "LayerZero: invalid inbound block confirmation");
        require(_relayer != address(0x0), "LayerZero: invalid relayer address");
        require(supportedOutboundProof[_chainId][_outboundProofType], "LayerZero: invalid outbound proof type");
        require(_outboundBlockConfirmations > 0, "LayerZero: invalid outbound block confirmation");
        require(_oracle != address(0x0), "LayerZero: invalid oracle address");
        defaultAppConfig[_chainId] = ApplicationConfiguration(
            _inboundProofLibraryVersion,
            _inboundBlockConfirmations,
            _relayer,
            _outboundProofType,
            _outboundBlockConfirmations,
            _oracle
        );
        emit SetDefaultConfigForChainId(
            _chainId,
            _inboundProofLibraryVersion,
            _inboundBlockConfirmations,
            _relayer,
            _outboundProofType,
            _outboundBlockConfirmations,
            _oracle
        );
    }

    function setDefaultAdapterParamsForChainId(
        uint16 _chainId,
        uint16 _proofType,
        bytes calldata _adapterParams
    ) external onlyOwner {
        defaultAdapterParams[_chainId][_proofType] = _adapterParams;
        emit SetDefaultAdapterParamsForChainId(_chainId, _proofType, _adapterParams);
    }

    function setRemoteUln(uint16 _remoteChainId, bytes32 _remoteUln) external onlyOwner {
        require(ulnLookup[_remoteChainId] == bytes32(0), "LayerZero: remote uln already set");
        ulnLookup[_remoteChainId] = _remoteUln;
        emit SetRemoteUln(_remoteChainId, _remoteUln);
    }

    function setChainAddressSize(uint16 _chainId, uint _size) external onlyOwner {
        require(chainAddressSizeMap[_chainId] == 0, "LayerZero: remote chain address size already set");
        chainAddressSizeMap[_chainId] = _size;
        emit SetChainAddressSize(_chainId, _size);
    }

    //----------------------------------------------------------------------------------
    // view functions

    function accruedNativeFee(address _address) external view override returns (uint) {
        return nativeFees[_address];
    }

    function getOutboundNonce(uint16 _chainId, bytes calldata _path) external view override returns (uint64) {
        return nonceContract.outboundNonce(_chainId, _path);
    }

    function _isContract(address addr) internal view returns (bool) {
        uint size;
        assembly {
            size := extcodesize(addr)
        }
        return size != 0;
    }
}

{
  "compilationTarget": {
    "contracts/UltraLightNodeV2.sol": "UltraLightNodeV2"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 10000
  },
  "remappings": []
}