// SPDX-License-Identifier: MIT

pragma solidity ^0.8.20;

import { IERC20Metadata, IERC20 } from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import { OFTAltCore } from "./OFTAltCore.sol";

/**
 * @title OFTAdapter Contract
 * @dev OFTAdapter is a contract that adapts an ERC-20 token to the OFT functionality.
 *
 * @dev For existing ERC20 tokens, this can be used to convert the token to crosschain compatibility.
 * @dev WARNING: ONLY 1 of these should exist for a given global mesh,
 * unless you make a NON-default implementation of OFT and needs to be done very carefully.
 * @dev WARNING: The default OFTAdapter implementation assumes LOSSLESS transfers, ie. 1 token in, 1 token out.
 * IF the 'innerToken' applies something like a transfer fee, the default will NOT work...
 * a pre/post balance check will need to be done to calculate the amountSentLD/amountReceivedLD.
 */
abstract contract OFTAdapterAlt is OFTAltCore {
    using SafeERC20 for IERC20;

    IERC20 internal immutable innerToken;

    /**
     * @dev Constructor for the OFTAdapter contract.
     * @param _token The address of the ERC-20 token to be adapted.
     * @param _lzEndpoint The LayerZero endpoint address.
     * @param _delegate The delegate capable of making OApp configurations inside of the endpoint.
     */
    constructor(
        address _token,
        address _lzEndpoint,
        address _delegate
    ) OFTAltCore(IERC20Metadata(_token).decimals(), _lzEndpoint, _delegate) {
        innerToken = IERC20(_token);
    }

    /**
     * @dev Retrieves the address of the underlying ERC20 implementation.
     * @return The address of the adapted ERC-20 token.
     *
     * @dev In the case of OFTAdapter, address(this) and erc20 are NOT the same contract.
     */
    function token() public view returns (address) {
        return address(innerToken);
    }

    /**
     * @notice Indicates whether the OFT contract requires approval of the 'token()' to send.
     * @return requiresApproval Needs approval of the underlying token implementation.
     *
     * @dev In the case of default OFTAdapter, approval is required.
     * @dev In non-default OFTAdapter contracts with something like mint and burn privileges, it would NOT need approval.
     */
    function approvalRequired() external pure virtual returns (bool) {
        return true;
    }

    /**
     * @dev Locks tokens from the sender's specified balance in this contract.
     * @param _from The address to debit from.
     * @param _amountLD The amount of tokens to send in local decimals.
     * @param _minAmountLD The minimum amount to send in local decimals.
     * @param _dstEid The destination chain ID.
     * @return amountSentLD The amount sent in local decimals.
     * @return amountReceivedLD The amount received in local decimals on the remote.
     *
     * @dev msg.sender will need to approve this _amountLD of tokens to be locked inside of the contract.
     * @dev WARNING: The default OFTAdapter implementation assumes LOSSLESS transfers, ie. 1 token in, 1 token out.
     * IF the 'innerToken' applies something like a transfer fee, the default will NOT work...
     * a pre/post balance check will need to be done to calculate the amountReceivedLD.
     */
    function _debit(
        address _from,
        uint256 _amountLD,
        uint256 _minAmountLD,
        uint32 _dstEid
    ) internal virtual override returns (uint256 amountSentLD, uint256 amountReceivedLD) {
        (amountSentLD, amountReceivedLD) = _debitView(_amountLD, _minAmountLD, _dstEid);
        // @dev Lock tokens by moving them into this contract from the caller.
        innerToken.safeTransferFrom(_from, address(this), amountSentLD);
    }

    /**
     * @dev Credits tokens to the specified address.
     * @param _to The address to credit the tokens to.
     * @param _amountLD The amount of tokens to credit in local decimals.
     * @dev _srcEid The source chain ID.
     * @return amountReceivedLD The amount of tokens ACTUALLY received in local decimals.
     *
     * @dev WARNING: The default OFTAdapter implementation assumes LOSSLESS transfers, ie. 1 token in, 1 token out.
     * IF the 'innerToken' applies something like a transfer fee, the default will NOT work...
     * a pre/post balance check will need to be done to calculate the amountReceivedLD.
     */
    function _credit(
        address _to,
        uint256 _amountLD,
        uint32 /*_srcEid*/
    ) internal virtual override returns (uint256 amountReceivedLD) {
        // @dev Unlock the tokens and transfer to the recipient.
        innerToken.safeTransfer(_to, _amountLD);
        // @dev In the case of NON-default OFTAdapter, the amountLD MIGHT not be == amountReceivedLD.
        return _amountLD;
    }
}