// SPDX-License-Identifier: LZBL-1.2

pragma solidity ^0.8.20;

import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";

import { MessagingFee, MessagingParams, MessagingReceipt, Origin, ILayerZeroEndpointV2 } from "./interfaces/ILayerZeroEndpointV2.sol";
import { ISendLib, Packet } from "./interfaces/ISendLib.sol";
import { ILayerZeroReceiver } from "./interfaces/ILayerZeroReceiver.sol";
import { Errors } from "./libs/Errors.sol";
import { GUID } from "./libs/GUID.sol";
import { Transfer } from "./libs/Transfer.sol";
import { MessagingChannel } from "./MessagingChannel.sol";
import { MessagingComposer } from "./MessagingComposer.sol";
import { MessageLibManager } from "./MessageLibManager.sol";
import { MessagingContext } from "./MessagingContext.sol";

// LayerZero EndpointV2 is fully backward compatible with LayerZero Endpoint(V1), but it also supports additional
// features that Endpoint(V1) does not support now and may not in the future. We have also changed some terminology
// to clarify pre-existing language that might have been confusing.
//
// The following is a list of terminology changes:
//     -chainId -> eid
//          - Rationale: chainId was a term we initially used to describe an endpoint on a specific chain. Since
//          LayerZero supports non-EVMs we could not map the classic EVM chainIds to the LayerZero chainIds, making it
//          confusing for developers. With the addition of EndpointV2 and its backward compatible nature, we would have
//          two chainIds per chain that has Endpoint(V1), further confusing developers. We have decided to change the
//          name to Endpoint Id, or eid, for simplicity and clarity.
//     -adapterParams -> options
//     -userApplication -> oapp. Omnichain Application
//     -srcAddress -> sender
//     -dstAddress -> receiver
//          - Rationale: The sender/receiver on EVM is the address. However, on non-EVM chains, the sender/receiver could
//          represented as a public key, or some other identifier. The term sender/receiver is more generic
//     -payload -> message.
//          - Rationale: The term payload is used in the context of a packet, which is a combination of the message and GUID
contract EndpointV2 is ILayerZeroEndpointV2, MessagingChannel, MessageLibManager, MessagingComposer, MessagingContext {
    address public lzToken;

    mapping(address oapp => address delegate) public delegates;

    /// @param _eid the unique Endpoint Id for this deploy that all other Endpoints can use to send to it
    constructor(uint32 _eid, address _owner) MessagingChannel(_eid) {
        _transferOwnership(_owner);
    }

    /// @dev MESSAGING STEP 0
    /// @notice This view function gives the application built on top of LayerZero the ability to requests a quote
    /// with the same parameters as they would to send their message. Since the quotes are given on chain there is a
    /// race condition in which the prices could change between the time the user gets their quote and the time they
    /// submit their message. If the price moves up and the user doesn't send enough funds the transaction will revert,
    /// if the price goes down the _refundAddress provided by the app will be refunded the difference.
    /// @param _params the messaging parameters
    /// @param _sender the sender of the message
    function quote(MessagingParams calldata _params, address _sender) external view returns (MessagingFee memory) {
        // lzToken must be set to support payInLzToken
        if (_params.payInLzToken && lzToken == address(0x0)) revert Errors.LZ_LzTokenUnavailable();

        // get the correct outbound nonce
        uint64 nonce = outboundNonce[_sender][_params.dstEid][_params.receiver] + 1;

        // construct the packet with a GUID
        Packet memory packet = Packet({
            nonce: nonce,
            srcEid: eid,
            sender: _sender,
            dstEid: _params.dstEid,
            receiver: _params.receiver,
            guid: GUID.generate(nonce, eid, _sender, _params.dstEid, _params.receiver),
            message: _params.message
        });

        // get the send library by sender and dst eid
        // use _ to avoid variable shadowing
        address _sendLibrary = getSendLibrary(_sender, _params.dstEid);

        return ISendLib(_sendLibrary).quote(packet, _params.options, _params.payInLzToken);
    }

    /// @dev MESSAGING STEP 1 - OApp need to transfer the fees to the endpoint before sending the message
    /// @param _params the messaging parameters
    /// @param _refundAddress the address to refund both the native and lzToken
    function send(
        MessagingParams calldata _params,
        address _refundAddress
    ) external payable sendContext(_params.dstEid, msg.sender) returns (MessagingReceipt memory) {
        if (_params.payInLzToken && lzToken == address(0x0)) revert Errors.LZ_LzTokenUnavailable();

        // send message
        (MessagingReceipt memory receipt, address _sendLibrary) = _send(msg.sender, _params);

        // OApp can simulate with 0 native value it will fail with error including the required fee, which can be provided in the actual call
        // this trick can be used to avoid the need to write the quote() function
        // however, without the quote view function it will be hard to compose an oapp on chain
        uint256 suppliedNative = _suppliedNative();
        uint256 suppliedLzToken = _suppliedLzToken(_params.payInLzToken);
        _assertMessagingFee(receipt.fee, suppliedNative, suppliedLzToken);

        // handle lz token fees
        _payToken(lzToken, receipt.fee.lzTokenFee, suppliedLzToken, _sendLibrary, _refundAddress);

        // handle native fees
        _payNative(receipt.fee.nativeFee, suppliedNative, _sendLibrary, _refundAddress);

        return receipt;
    }

    /// @dev internal function for sending the messages used by all external send methods
    /// @param _sender the address of the application sending the message to the destination chain
    /// @param _params the messaging parameters
    function _send(
        address _sender,
        MessagingParams calldata _params
    ) internal returns (MessagingReceipt memory, address) {
        // get the correct outbound nonce
        uint64 latestNonce = _outbound(_sender, _params.dstEid, _params.receiver);

        // construct the packet with a GUID
        Packet memory packet = Packet({
            nonce: latestNonce,
            srcEid: eid,
            sender: _sender,
            dstEid: _params.dstEid,
            receiver: _params.receiver,
            guid: GUID.generate(latestNonce, eid, _sender, _params.dstEid, _params.receiver),
            message: _params.message
        });

        // get the send library by sender and dst eid
        address _sendLibrary = getSendLibrary(_sender, _params.dstEid);

        // messageLib always returns encodedPacket with guid
        (MessagingFee memory fee, bytes memory encodedPacket) = ISendLib(_sendLibrary).send(
            packet,
            _params.options,
            _params.payInLzToken
        );

        // Emit packet information for DVNs, Executors, and any other offchain infrastructure to only listen
        // for this one event to perform their actions.
        emit PacketSent(encodedPacket, _params.options, _sendLibrary);

        return (MessagingReceipt(packet.guid, latestNonce, fee), _sendLibrary);
    }

    /// @dev MESSAGING STEP 2 - on the destination chain
    /// @dev configured receive library verifies a message
    /// @param _origin a struct holding the srcEid, nonce, and sender of the message
    /// @param _receiver the receiver of the message
    /// @param _payloadHash the payload hash of the message
    function verify(Origin calldata _origin, address _receiver, bytes32 _payloadHash) external {
        if (!isValidReceiveLibrary(_receiver, _origin.srcEid, msg.sender)) revert Errors.LZ_InvalidReceiveLibrary();

        uint64 lazyNonce = lazyInboundNonce[_receiver][_origin.srcEid][_origin.sender];
        if (!_initializable(_origin, _receiver, lazyNonce)) revert Errors.LZ_PathNotInitializable();
        if (!_verifiable(_origin, _receiver, lazyNonce)) revert Errors.LZ_PathNotVerifiable();

        // insert the message into the message channel
        _inbound(_receiver, _origin.srcEid, _origin.sender, _origin.nonce, _payloadHash);
        emit PacketVerified(_origin, _receiver, _payloadHash);
    }

    /// @dev MESSAGING STEP 3 - the last step
    /// @dev execute a verified message to the designated receiver
    /// @dev the execution provides the execution context (caller, extraData) to the receiver. the receiver can optionally assert the caller and validate the untrusted extraData
    /// @dev cant reentrant because the payload is cleared before execution
    /// @param _origin the origin of the message
    /// @param _receiver the receiver of the message
    /// @param _guid the guid of the message
    /// @param _message the message
    /// @param _extraData the extra data provided by the executor. this data is untrusted and should be validated.
    function lzReceive(
        Origin calldata _origin,
        address _receiver,
        bytes32 _guid,
        bytes calldata _message,
        bytes calldata _extraData
    ) external payable {
        // clear the payload first to prevent reentrancy, and then execute the message
        _clearPayload(_receiver, _origin.srcEid, _origin.sender, _origin.nonce, abi.encodePacked(_guid, _message));
        ILayerZeroReceiver(_receiver).lzReceive{ value: msg.value }(_origin, _guid, _message, msg.sender, _extraData);
        emit PacketDelivered(_origin, _receiver);
    }

    /// @param _origin the origin of the message
    /// @param _receiver the receiver of the message
    /// @param _guid the guid of the message
    /// @param _message the message
    /// @param _extraData the extra data provided by the executor.
    /// @param _reason the reason for failure
    function lzReceiveAlert(
        Origin calldata _origin,
        address _receiver,
        bytes32 _guid,
        uint256 _gas,
        uint256 _value,
        bytes calldata _message,
        bytes calldata _extraData,
        bytes calldata _reason
    ) external {
        emit LzReceiveAlert(_receiver, msg.sender, _origin, _guid, _gas, _value, _message, _extraData, _reason);
    }

    /// @dev Oapp uses this interface to clear a message.
    /// @dev this is a PULL mode versus the PUSH mode of lzReceive
    /// @dev the cleared message can be ignored by the app (effectively burnt)
    /// @dev authenticated by oapp
    /// @param _origin the origin of the message
    /// @param _guid the guid of the message
    /// @param _message the message
    function clear(address _oapp, Origin calldata _origin, bytes32 _guid, bytes calldata _message) external {
        _assertAuthorized(_oapp);

        bytes memory payload = abi.encodePacked(_guid, _message);
        _clearPayload(_oapp, _origin.srcEid, _origin.sender, _origin.nonce, payload);
        emit PacketDelivered(_origin, _oapp);
    }

    /// @dev allows reconfiguration to recover from wrong configurations
    /// @dev users should never approve the EndpointV2 contract to spend their non-layerzero tokens
    /// @dev override this function if the endpoint is charging ERC20 tokens as native
    /// @dev only owner
    /// @param _lzToken the new layer zero token address
    function setLzToken(address _lzToken) public virtual onlyOwner {
        lzToken = _lzToken;
        emit LzTokenSet(_lzToken);
    }

    /// @dev recover the token sent to this contract by mistake
    /// @dev only owner
    /// @param _token the token to recover. if 0x0 then it is native token
    /// @param _to the address to send the token to
    /// @param _amount the amount to send
    function recoverToken(address _token, address _to, uint256 _amount) external onlyOwner {
        Transfer.nativeOrToken(_token, _to, _amount);
    }

    /// @dev handling token payments on endpoint. the sender must approve the endpoint to spend the token
    /// @dev internal function
    /// @param _token the token to pay
    /// @param _required the amount required
    /// @param _supplied the amount supplied
    /// @param _receiver the receiver of the token
    function _payToken(
        address _token,
        uint256 _required,
        uint256 _supplied,
        address _receiver,
        address _refundAddress
    ) internal {
        if (_required > 0) {
            Transfer.token(_token, _receiver, _required);
        }
        if (_required < _supplied) {
            unchecked {
                // refund the excess
                Transfer.token(_token, _refundAddress, _supplied - _required);
            }
        }
    }

    /// @dev handling native token payments on endpoint
    /// @dev override this if the endpoint is charging ERC20 tokens as native
    /// @dev internal function
    /// @param _required the amount required
    /// @param _supplied the amount supplied
    /// @param _receiver the receiver of the native token
    /// @param _refundAddress the address to refund the excess to
    function _payNative(
        uint256 _required,
        uint256 _supplied,
        address _receiver,
        address _refundAddress
    ) internal virtual {
        if (_required > 0) {
            Transfer.native(_receiver, _required);
        }
        if (_required < _supplied) {
            unchecked {
                // refund the excess
                Transfer.native(_refundAddress, _supplied - _required);
            }
        }
    }

    /// @dev get the balance of the lzToken as the supplied lzToken fee if payInLzToken is true
    function _suppliedLzToken(bool _payInLzToken) internal view returns (uint256 supplied) {
        if (_payInLzToken) {
            supplied = IERC20(lzToken).balanceOf(address(this));

            // if payInLzToken is true, the supplied fee must be greater than 0 to prevent a race condition
            // in which an oapp sending a message with lz token and the lz token is set to a new token between the tx
            // being sent and the tx being mined. if the required lz token fee is 0 and the old lz token would be
            // locked in the contract instead of being refunded
            if (supplied == 0) revert Errors.LZ_ZeroLzTokenFee();
        }
    }

    /// @dev override this if the endpoint is charging ERC20 tokens as native
    function _suppliedNative() internal view virtual returns (uint256) {
        return msg.value;
    }

    /// @dev Assert the required fees and the supplied fees are enough
    function _assertMessagingFee(
        MessagingFee memory _required,
        uint256 _suppliedNativeFee,
        uint256 _suppliedLzTokenFee
    ) internal pure {
        if (_required.nativeFee > _suppliedNativeFee || _required.lzTokenFee > _suppliedLzTokenFee) {
            revert Errors.LZ_InsufficientFee(
                _required.nativeFee,
                _suppliedNativeFee,
                _required.lzTokenFee,
                _suppliedLzTokenFee
            );
        }
    }

    /// @dev override this if the endpoint is charging ERC20 tokens as native
    /// @return 0x0 if using native. otherwise the address of the native ERC20 token
    function nativeToken() external view virtual returns (address) {
        return address(0x0);
    }

    /// @notice delegate is authorized by the oapp to configure anything in layerzero
    function setDelegate(address _delegate) external {
        delegates[msg.sender] = _delegate;
        emit DelegateSet(msg.sender, _delegate);
    }

    // ========================= Internal =========================
    function _initializable(
        Origin calldata _origin,
        address _receiver,
        uint64 _lazyInboundNonce
    ) internal view returns (bool) {
        return
            _lazyInboundNonce > 0 || // allowInitializePath already checked
            ILayerZeroReceiver(_receiver).allowInitializePath(_origin);
    }

    /// @dev bytes(0) payloadHash can never be submitted
    function _verifiable(
        Origin calldata _origin,
        address _receiver,
        uint64 _lazyInboundNonce
    ) internal view returns (bool) {
        return
            _origin.nonce > _lazyInboundNonce || // either initializing an empty slot or reverifying
            inboundPayloadHash[_receiver][_origin.srcEid][_origin.sender][_origin.nonce] != EMPTY_PAYLOAD_HASH; // only allow reverifying if it hasn't been executed
    }

    /// @dev assert the caller to either be the oapp or the delegate
    function _assertAuthorized(address _oapp) internal view override(MessagingChannel, MessageLibManager) {
        if (msg.sender != _oapp && msg.sender != delegates[_oapp]) revert Errors.LZ_Unauthorized();
    }

    // ========================= VIEW FUNCTIONS FOR OFFCHAIN ONLY =========================
    // Not involved in any state transition function.
    // ====================================================================================
    function initializable(Origin calldata _origin, address _receiver) external view returns (bool) {
        return _initializable(_origin, _receiver, lazyInboundNonce[_receiver][_origin.srcEid][_origin.sender]);
    }

    function verifiable(Origin calldata _origin, address _receiver) external view returns (bool) {
        return _verifiable(_origin, _receiver, lazyInboundNonce[_receiver][_origin.srcEid][_origin.sender]);
    }
}