AlreadyExists

CannotRemoveFromERC721TransferExempt

DecimalsTooLow

InsufficientAllowance

InvalidApproval

InvalidId

InvalidOperator

InvalidRecipient

InvalidSender

InvalidSigner

InvalidSpender

NotFound

OwnedIndexOverflow

PermitDeadlineExpired

QueueEmpty

QueueFull

RecipientIsERC721TransferExempt

SenderIsERC721TransferExempt

Unauthorized

UnsafeRecipient

owner

operator

approved

ApprovalForAll

spender

value

ERC20Approval

from

amount

ERC20Transfer

ERC721Approval

ERC721Transfer

DOMAIN_SEPARATOR

allowance

spender_

valueOrId_

approve

balanceOf

decimals

owner_

erc20BalanceOf

erc20TotalSupply

erc721BalanceOf

erc721TokensBankedInQueue

erc721TotalSupply

erc721TransferExempt

getApproved

isApprovedForAll

name

nonces

owned

ownerOf

erc721Owner

value_

deadline_

permit

from_

safeTransferFrom

data_

operator_

approved_

setApprovalForAll

interfaceId

supportsInterface

symbol

tokenURI

totalSupply

transfer

transferFrom

units

account_

amount_

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {IERC165} from "../lib/interfaces/IERC165.sol";

interface IERC404 is IERC165 {
  event ERC20Approval(address owner, address spender, uint256 value);
  event ApprovalForAll(
    address indexed owner,
    address indexed operator,
    bool approved
  );
  event ERC721Approval(
    address indexed owner,
    address indexed spender,
    uint256 indexed id
  );
  event ERC20Transfer(address indexed from, address indexed to, uint256 amount);
  event ERC721Transfer(
    address indexed from,
    address indexed to,
    uint256 indexed id
  );

  error NotFound();
  error InvalidId();
  error AlreadyExists();
  error InvalidRecipient();
  error InvalidSender();
  error InvalidSpender();
  error InvalidOperator();
  error UnsafeRecipient();
  error RecipientIsERC721TransferExempt();
  error SenderIsERC721TransferExempt();
  error Unauthorized();
  error InsufficientAllowance();
  error DecimalsTooLow();
  error CannotRemoveFromERC721TransferExempt();
  error PermitDeadlineExpired();
  error InvalidSigner();
  error InvalidApproval();
  error OwnedIndexOverflow();

  function name() external view returns (string memory);
  function symbol() external view returns (string memory);
  function decimals() external view returns (uint8);
  function totalSupply() external view returns (uint256);
  function erc20TotalSupply() external view returns (uint256);
  function erc721TotalSupply() external view returns (uint256);
  function balanceOf(address owner_) external view returns (uint256);
  function erc721BalanceOf(address owner_) external view returns (uint256);
  function erc20BalanceOf(address owner_) external view returns (uint256);
  function erc721TransferExempt(address account_) external view returns (bool);
  function isApprovedForAll(
    address owner_,
    address operator_
  ) external view returns (bool);
  function allowance(
    address owner_,
    address spender_
  ) external view returns (uint256);
  function owned(address owner_) external view returns (uint256[] memory);
  function ownerOf(uint256 id_) external view returns (address erc721Owner);
  function tokenURI(uint256 id_) external view returns (string memory);
  function approve(
    address spender_,
    uint256 valueOrId_
  ) external returns (bool);
  function setApprovalForAll(address operator_, bool approved_) external;
  function transferFrom(
    address from_,
    address to_,
    uint256 valueOrId_
  ) external returns (bool);
  function transfer(address to_, uint256 amount_) external returns (bool);
  function erc721TokensBankedInQueue() external view returns (uint256);
  function safeTransferFrom(address from_, address to_, uint256 id_) external;
  function safeTransferFrom(
    address from_,
    address to_,
    uint256 id_,
    bytes calldata data_
  ) external;
  function DOMAIN_SEPARATOR() external view returns (bytes32);
  function permit(
    address owner_,
    address spender_,
    uint256 value_,
    uint256 deadline_,
    uint8 v_,
    bytes32 r_,
    bytes32 s_
  ) external;
}


QueueOutOfBounds

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (utils/structs/DoubleEndedQueue.sol)
// Modified by Pandora Labs to support native uint256 operations
pragma solidity ^0.8.20;

/**
 * @dev A sequence of items with the ability to efficiently push and pop items (i.e. insert and remove) on both ends of
 * the sequence (called front and back). Among other access patterns, it can be used to implement efficient LIFO and
 * FIFO queues. Storage use is optimized, and all operations are O(1) constant time. This includes {clear}, given that
 * the existing queue contents are left in storage.
 *
 * The struct is called `Bytes32Deque`. Other types can be cast to and from `bytes32`. This data structure can only be
 * used in storage, and not in memory.
 * ```solidity
 * DoubleEndedQueue.Bytes32Deque queue;
 * ```
 */
library DoubleEndedQueue {
  /**
   * @dev An operation (e.g. {front}) couldn't be completed due to the queue being empty.
   */
  error QueueEmpty();

  /**
   * @dev A push operation couldn't be completed due to the queue being full.
   */
  error QueueFull();

  /**
   * @dev An operation (e.g. {at}) couldn't be completed due to an index being out of bounds.
   */
  error QueueOutOfBounds();

  /**
   * @dev Indices are 128 bits so begin and end are packed in a single storage slot for efficient access.
   *
   * Struct members have an underscore prefix indicating that they are "private" and should not be read or written to
   * directly. Use the functions provided below instead. Modifying the struct manually may violate assumptions and
   * lead to unexpected behavior.
   *
   * The first item is at data[begin] and the last item is at data[end - 1]. This range can wrap around.
   */
  struct Uint256Deque {
    uint128 _begin;
    uint128 _end;
    mapping(uint128 index => uint256) _data;
  }

  /**
   * @dev Inserts an item at the end of the queue.
   *
   * Reverts with {QueueFull} if the queue is full.
   */
  function pushBack(Uint256Deque storage deque, uint256 value) internal {
    unchecked {
      uint128 backIndex = deque._end;
      if (backIndex + 1 == deque._begin) revert QueueFull();
      deque._data[backIndex] = value;
      deque._end = backIndex + 1;
    }
  }

  /**
   * @dev Removes the item at the end of the queue and returns it.
   *
   * Reverts with {QueueEmpty} if the queue is empty.
   */
  function popBack(
    Uint256Deque storage deque
  ) internal returns (uint256 value) {
    unchecked {
      uint128 backIndex = deque._end;
      if (backIndex == deque._begin) revert QueueEmpty();
      --backIndex;
      value = deque._data[backIndex];
      delete deque._data[backIndex];
      deque._end = backIndex;
    }
  }

  /**
   * @dev Inserts an item at the beginning of the queue.
   *
   * Reverts with {QueueFull} if the queue is full.
   */
  function pushFront(Uint256Deque storage deque, uint256 value) internal {
    unchecked {
      uint128 frontIndex = deque._begin - 1;
      if (frontIndex == deque._end) revert QueueFull();
      deque._data[frontIndex] = value;
      deque._begin = frontIndex;
    }
  }

  /**
   * @dev Removes the item at the beginning of the queue and returns it.
   *
   * Reverts with `QueueEmpty` if the queue is empty.
   */
  function popFront(
    Uint256Deque storage deque
  ) internal returns (uint256 value) {
    unchecked {
      uint128 frontIndex = deque._begin;
      if (frontIndex == deque._end) revert QueueEmpty();
      value = deque._data[frontIndex];
      delete deque._data[frontIndex];
      deque._begin = frontIndex + 1;
    }
  }

  /**
   * @dev Returns the item at the beginning of the queue.
   *
   * Reverts with `QueueEmpty` if the queue is empty.
   */
  function front(
    Uint256Deque storage deque
  ) internal view returns (uint256 value) {
    if (empty(deque)) revert QueueEmpty();
    return deque._data[deque._begin];
  }

  /**
   * @dev Returns the item at the end of the queue.
   *
   * Reverts with `QueueEmpty` if the queue is empty.
   */
  function back(
    Uint256Deque storage deque
  ) internal view returns (uint256 value) {
    if (empty(deque)) revert QueueEmpty();
    unchecked {
      return deque._data[deque._end - 1];
    }
  }

  /**
   * @dev Return the item at a position in the queue given by `index`, with the first item at 0 and last item at
   * `length(deque) - 1`.
   *
   * Reverts with `QueueOutOfBounds` if the index is out of bounds.
   */
  function at(
    Uint256Deque storage deque,
    uint256 index
  ) internal view returns (uint256 value) {
    if (index >= length(deque)) revert QueueOutOfBounds();
    // By construction, length is a uint128, so the check above ensures that index can be safely downcast to uint128
    unchecked {
      return deque._data[deque._begin + uint128(index)];
    }
  }

  /**
   * @dev Resets the queue back to being empty.
   *
   * NOTE: The current items are left behind in storage. This does not affect the functioning of the queue, but misses
   * out on potential gas refunds.
   */
  function clear(Uint256Deque storage deque) internal {
    deque._begin = 0;
    deque._end = 0;
  }

  /**
   * @dev Returns the number of items in the queue.
   */
  function length(Uint256Deque storage deque) internal view returns (uint256) {
    unchecked {
      return uint256(deque._end - deque._begin);
    }
  }

  /**
   * @dev Returns true if the queue is empty.
   */
  function empty(Uint256Deque storage deque) internal view returns (bool) {
    return deque._end == deque._begin;
  }
}


onERC721Received

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

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


// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (utils/introspection/IERC165.sol)

pragma solidity ^0.8.20;

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


This contract is a hybrid ERC-404, combining ERC-721 and ERC-20 features. It allows token ownership tracking, ERC-20/ERC-721 transfers, approvals, and EIP-2612 permits. It supports minting/burning, with a queue for banking ERC-721s. It handles ERC-721 exemptions and maintains a dual representation of tokens.