ERC404.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

abstract contract Ownable {
    event OwnershipTransferred(address indexed user, address indexed newOwner);

    error Unauthorized();
    error InvalidOwner();

    address public owner;

    modifier onlyOwner() virtual {
        if (msg.sender != owner) revert Unauthorized();

        _;
    }

    constructor(address _owner) {
        if (_owner == address(0)) revert InvalidOwner();
        owner = _owner;
        emit OwnershipTransferred(address(0), _owner);
    }

    function transferOwnership(address _owner) public virtual onlyOwner {
        if (_owner == address(0)) revert InvalidOwner();
        owner = _owner;
        emit OwnershipTransferred(msg.sender, _owner);
    }

    function revokeOwnership() public virtual onlyOwner {
        owner = address(0);
        emit OwnershipTransferred(msg.sender, address(0));
    }
}

abstract contract ERC721Receiver {
    function onERC721Received(
        address,
        address,
        uint256,
        bytes calldata
    ) external virtual returns (bytes4) {
        return ERC721Receiver.onERC721Received.selector;
    }
}

/// @notice ERC404
///         A gas-efficient, mixed ERC20 / ERC721 implementation
///         with native liquidity and fractionalization.
///
///         This is an experimental standard designed to integrate
///         with pre-existing ERC20 / ERC721 support as smoothly as
///         possible.
///
/// @dev    In order to support full functionality of ERC20 and ERC721
///         supply assumptions are made that slightly constraint usage.
///         Ensure decimals are sufficiently large (standard 18 recommended)
///         as ids are effectively encoded in the lowest range of amounts.
///
///         NFTs are spent on ERC20 functions in a FILO queue, this is by
///         design.
///
abstract contract ERC404 is Ownable {
    // Events
    event ERC20Transfer(
        address indexed from,
        address indexed to,
        uint256 amount
    );
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 amount
    );
    event Transfer(
        address indexed from,
        address indexed to,
        uint256 indexed id
    );
    event ERC721Approval(
        address indexed owner,
        address indexed spender,
        uint256 indexed id
    );
    event ApprovalForAll(
        address indexed owner,
        address indexed operator,
        bool approved
    );

    // Errors
    error NotFound();
    error AlreadyExists();
    error InvalidRecipient();
    error InvalidSender();
    error UnsafeRecipient();

    // Metadata
    /// @dev Token name
    string public name;

    /// @dev Token symbol
    string public symbol;

    /// @dev Decimals for fractional representation
    uint8 public immutable decimals;

    /// @dev Total supply in fractionalized representation
    uint256 public immutable totalSupply;

    /// @dev Current mint counter, monotonically increasing to ensure accurate ownership
    uint256 public minted;

    // Mappings
    /// @dev Balance of user in fractional representation
    mapping(address => uint256) public balanceOf;

    /// @dev Allowance of user in fractional representation
    mapping(address => mapping(address => uint256)) public allowance;

    /// @dev Approval in native representaion
    mapping(uint256 => address) public getApproved;

    /// @dev Approval for all in native representation
    mapping(address => mapping(address => bool)) public isApprovedForAll;

    /// @dev Owner of id in native representation
    mapping(uint256 => address) internal _ownerOf;

    /// @dev Array of owned ids in native representation
    mapping(address => uint256[]) internal _owned;

    /// @dev Tracks indices for the _owned mapping
    mapping(uint256 => uint256) internal _ownedIndex;

    /// @dev Addresses whitelisted from minting / burning for gas savings (pairs, routers, etc)
    mapping(address => bool) public exemptFee;

    /// @dev mint block
    mapping(uint256 => uint256) public mintedBlockNumber;

    /// @dev start mint one time
    bool internal started = false;

    // Constructor
    constructor(
        string memory _name,
        string memory _symbol,
        uint8 _decimals,
        uint256 _totalNativeSupply,
        address _owner
    ) Ownable(_owner) {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        totalSupply = _totalNativeSupply * (10 ** decimals);
    }

    /// @dev start mint after presale
    function startMint() public onlyOwner {
        require(started == false, "Mint has already been initiated!");
        started = true;
    }

    /// @notice Initialization function to set pairs / etc
    ///         saving gas by avoiding mint / burn on unnecessary targets
    function setExemptFee(address target, bool state) public onlyOwner {
        exemptFee[target] = state;
    }

    /// @notice Function to find owner of a given native token
    function ownerOf(uint256 id) public view virtual returns (address owner) {
        owner = _ownerOf[id];

        if (owner == address(0)) {
            revert NotFound();
        }
    }

    /// @notice tokenURI must be implemented by child contract
    function tokenURI(uint256 id) public view virtual returns (string memory);

    /// @notice Function for token approvals
    /// @dev This function assumes id / native if amount less than or equal to current max id
    function approve(
        address spender,
        uint256 amountOrId
    ) public virtual returns (bool) {
        if (amountOrId <= minted && amountOrId > 0) {
            address owner = _ownerOf[amountOrId];

            if (msg.sender != owner && !isApprovedForAll[owner][msg.sender]) {
                revert Unauthorized();
            }

            getApproved[amountOrId] = spender;

            emit Approval(owner, spender, amountOrId);
        } else {
            allowance[msg.sender][spender] = amountOrId;

            emit Approval(msg.sender, spender, amountOrId);
        }

        return true;
    }


    /// @notice Function native approvals
    function setApprovalForAll(address operator, bool approved) public virtual {
        isApprovedForAll[msg.sender][operator] = approved;
        emit ApprovalForAll(msg.sender, operator, approved);
    }


    /// @notice walletOfOwner
    function walletOfOwner(address _owner) public view returns (uint256[] memory) {
        uint256 ownerTokenCount = 0;

        // Primeiro, contamos quantos NFTs o usuário possui
        for (uint256 i = 1; i <= minted; i++) {
            if (_ownerOf[i] == _owner) {
                ownerTokenCount++;
            }
        }

        // Inicializamos um array para armazenar os IDs dos NFTs do usuário
        uint256[] memory ownedTokenIds = new uint256[](ownerTokenCount);

        uint256 index = 0;
        // Agora, preenchemos o array com os IDs dos NFTs do usuário
        for (uint256 i = 1; i <= minted && index < ownerTokenCount; i++) {
            if (_ownerOf[i] == _owner) {
                ownedTokenIds[index] = i;
                index++;
            }
        }
        return ownedTokenIds;
    }

    /// @notice Function for mixed transfers
    /// @dev This function assumes id / native if amount less than or equal to current max id
    function transferFrom(
        address from,
        address to,
        uint256 amountOrId
    ) public virtual {
        if (amountOrId <= minted) {
            if (from != _ownerOf[amountOrId]) {
                revert InvalidSender();
            }

            if (to == address(0)) {
                revert InvalidRecipient();
            }

            if (
                msg.sender != from &&
                !isApprovedForAll[from][msg.sender] &&
                msg.sender != getApproved[amountOrId]
            ) {
                revert Unauthorized();
            }

            balanceOf[from] -= _getUnit();

            unchecked {
                balanceOf[to] += _getUnit();
            }

            _ownerOf[amountOrId] = to;
            delete getApproved[amountOrId];

            // update _owned for sender
            uint256 updatedId = _owned[from][_owned[from].length - 1];
            _owned[from][_ownedIndex[amountOrId]] = updatedId;
            // pop
            _owned[from].pop();
            // update index for the moved id
            _ownedIndex[updatedId] = _ownedIndex[amountOrId];
            // push token to to owned
            _owned[to].push(amountOrId);
            // update index for to owned
            _ownedIndex[amountOrId] = _owned[to].length - 1;

            emit Transfer(from, to, amountOrId);
            emit ERC20Transfer(from, to, _getUnit());
        } else {
            uint256 allowed = allowance[from][msg.sender];

            if (allowed != type(uint256).max)
                allowance[from][msg.sender] = allowed - amountOrId;

            _transfer(from, to, amountOrId);
        }
    }

    /// @notice Function for fractional transfers
    function transfer(
        address to,
        uint256 amount
    ) public virtual returns (bool) {
        return _transfer(msg.sender, to, amount);
    }

    /// @notice Function for native transfers with contract support
    function safeTransferFrom(
        address from,
        address to,
        uint256 id
    ) public virtual {
        transferFrom(from, to, id);

        if (
            to.code.length != 0 &&
            ERC721Receiver(to).onERC721Received(msg.sender, from, id, "") !=
            ERC721Receiver.onERC721Received.selector
        ) {
            revert UnsafeRecipient();
        }
    }

    /// @notice Function for native transfers with contract support and callback data
    function safeTransferFrom(
        address from,
        address to,
        uint256 id,
        bytes calldata data
    ) public virtual {
        transferFrom(from, to, id);

        if (
            to.code.length != 0 &&
            ERC721Receiver(to).onERC721Received(msg.sender, from, id, data) !=
            ERC721Receiver.onERC721Received.selector
        ) {
            revert UnsafeRecipient();
        }
    }

    /// @notice Internal function for fractional transfers
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal returns (bool) {
        uint256 unit = _getUnit();
        uint256 balanceBeforeSender = balanceOf[from];
        uint256 balanceBeforeReceiver = balanceOf[to];

        balanceOf[from] -= amount;

        unchecked {
            balanceOf[to] += amount;
        }


        // Check if start
        if (started == true) {
            // Skip burn for certain addresses to save gas
            if (!exemptFee[from]) {
                uint256 tokens_to_burn = (balanceBeforeSender / unit) -
                    (balanceOf[from] / unit);
                for (uint256 i = 0; i < tokens_to_burn; i++) {
                    _burn(from);
                }
            }

            // Skip minting for certain addresses to save gas
            if (!exemptFee[to]) {
                uint256 tokens_to_mint = (balanceOf[to] / unit) -
                    (balanceBeforeReceiver / unit);
                for (uint256 i = 0; i < tokens_to_mint; i++) {
                    _mint(to);
                }
            }
        }    

        emit ERC20Transfer(from, to, amount);
        return true;
    }

    // Internal utility logic
    function _getUnit() internal view returns (uint256) {
        return 10 ** decimals;
    }

    function _mint(address to) internal virtual {
        if (to == address(0)) {
            revert InvalidRecipient();
        }

        unchecked {
            minted++;
        }

        uint256 id = minted;

        if (_ownerOf[id] != address(0)) {
            revert AlreadyExists();
        }

        _ownerOf[id] = to;
        _owned[to].push(id);
        _ownedIndex[id] = _owned[to].length - 1;
        mintedBlockNumber[id] = block.number;

        emit Transfer(address(0), to, id);
    }

    function _burn(address from) internal virtual {
        if (from == address(0)) {
            revert InvalidSender();
        }

        uint256 id = _owned[from][_owned[from].length - 1];
        _owned[from].pop();
        delete _ownedIndex[id];
        delete _ownerOf[id];
        delete getApproved[id];

        emit Transfer(from, address(0), id);
    }

    function _setNameSymbol(
        string memory _name,
        string memory _symbol
    ) internal {
        name = _name;
        symbol = _symbol;
    }
}