// File: contracts/Base64.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

/// [MIT License]
/// @title Base64
/// @notice Provides a function for encoding some bytes in base64
/// @author Brecht Devos <brecht@loopring.org>
library Base64 {
    bytes internal constant TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    /// @notice Encodes some bytes to the base64 representation
    function encode(bytes memory data) internal pure returns (string memory) {
        uint256 len = data.length;
        if (len == 0) return "";

        // multiply by 4/3 rounded up
        uint256 encodedLen = 4 * ((len + 2) / 3);

        // Add some extra buffer at the end
        bytes memory result = new bytes(encodedLen + 32);

        bytes memory table = TABLE;

        assembly {
            let tablePtr := add(table, 1)
            let resultPtr := add(result, 32)

            for {
                let i := 0
            } lt(i, len) {

            } {
                i := add(i, 3)
                let input := and(mload(add(data, i)), 0xffffff)

                let out := mload(add(tablePtr, and(shr(18, input), 0x3F)))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(12, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(6, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(input, 0x3F))), 0xFF))
                out := shl(224, out)

                mstore(resultPtr, out)

                resultPtr := add(resultPtr, 4)
            }

            switch mod(len, 3)
            case 1 {
                mstore(sub(resultPtr, 2), shl(240, 0x3d3d))
            }
            case 2 {
                mstore(sub(resultPtr, 1), shl(248, 0x3d))
            }

            mstore(result, encodedLen)
        }

        return string(result);
    }
}
// File: contracts/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/INS20/ERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the INS20 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 `to`.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transfer(address to, 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;

  /**
   * @dev Moves `amount` tokens from `from` to `to` 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 from,
    address to,
    uint256 amount
  ) external returns (bool);
}

// File: contracts/ERC721/ERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC721/ERC721.sol)

pragma solidity ^0.8.0;

import "./IERC721Metadata.sol";
import "./IERC721Receiver.sol";
import "../utils/Address.sol";
import "../utils/Context.sol";
import "../utils/Strings.sol";
import "../utils/introspection/ERC165.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721Metadata {
  using Strings for uint256;
  using Address for address;

  // Token name
  string private _name;

  // Token symbol
  string private _symbol;

  // Mapping from token ID to owner address
  mapping(uint256 => address) internal _owners;

  // Mapping from token ID to approved address
  mapping(uint256 => address) private _tokenApprovals;

  // Mapping from owner to operator approvals
  mapping(address => mapping(address => bool)) private _operatorApprovals;

  /**
   * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
   */
  constructor(string memory name_, string memory symbol_) {
    _name = name_;
    _symbol = symbol_;
  }

  /**
   * @dev See {IERC721Metadata-name}.
   */
  function name() public view virtual override returns (string memory) {
    return _name;
  }

  /**
   * @dev See {IERC721Metadata-symbol}.
   */
  function symbol() public view virtual override returns (string memory) {
    return _symbol;
  }

  /**
   * @dev See {IERC165-supportsInterface}.
   */
  function supportsInterface(
    bytes4 interfaceId
  ) public view virtual override(ERC165, IERC165) returns (bool) {
    return
      interfaceId == type(IERC721).interfaceId ||
      super.supportsInterface(interfaceId);
  }

  /**
   * @dev See {IERC721-balanceOf}.
   */
  function balanceOf(
    address owner
  ) public view virtual override returns (uint256) {}

  /**
   * @dev See {IERC721-ownerOf}.
   */
  function ownerOf(
    uint256 tokenId
  ) public view virtual override returns (address) {
    address owner = _owners[tokenId];
    require(owner != address(0), "ERC721: invalid token ID");
    return owner;
  }

  /**
   * @dev See {IERC721Metadata-tokenURI}.
   */
  function tokenURI(
    uint256 tokenId
  ) public view virtual override returns (string memory) {}

  /**
   * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
   * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
   * by default, can be overridden in child contracts.
   */
  function _baseURI() internal view virtual returns (string memory) {
    return "";
  }

  /**
   * @dev See {IERC721-approve}.
   */
  function approve(address to, uint256 tokenId) public virtual override {
    address owner = ERC721.ownerOf(tokenId);
    require(to != owner, "ERC721: approval to current owner");

    require(
      _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
      "ERC721: approve caller is not token owner nor approved for all"
    );

    _approve(to, tokenId);
  }

  /**
   * @dev See {IERC721-getApproved}.
   */
  function getApproved(
    uint256 tokenId
  ) public view virtual override returns (address) {
    _requireMinted(tokenId);

    return _tokenApprovals[tokenId];
  }

  /**
   * @dev See {IERC721-setApprovalForAll}.
   */
  function setApprovalForAll(
    address operator,
    bool approved
  ) public virtual override {
    _setApprovalForAll(_msgSender(), operator, approved);
  }

  /**
   * @dev See {IERC721-isApprovedForAll}.
   */
  function isApprovedForAll(
    address owner,
    address operator
  ) public view virtual override returns (bool) {
    return _operatorApprovals[owner][operator];
  }

  /**
   * @dev See {IERC721-transferFrom}.
   */
  function transferFrom(
    address from,
    address to,
    uint256 tokenId
  ) public virtual override returns (bool) {
    return true;
  }

  /**
   * @dev See {IERC721-safeTransferFrom}.
   */
  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId
  ) public virtual override {}

  /**
   * @dev See {IERC721-safeTransferFrom}.
   */
  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes memory data
  ) public virtual override {}

  /**
   * @dev Returns whether `tokenId` exists.
   *
   * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
   *
   * Tokens start existing when they are minted (`_mint`),
   * and stop existing when they are burned (`_burn`).
   */
  function _exists(uint256 tokenId) internal view virtual returns (bool) {
    return _owners[tokenId] != address(0);
  }

  /**
   * @dev Returns whether `spender` is allowed to manage `tokenId`.
   *
   * Requirements:
   *
   * - `tokenId` must exist.
   */
  function _isApprovedOrOwner(
    address spender,
    uint256 tokenId
  ) internal view virtual returns (bool) {
    address owner = ERC721.ownerOf(tokenId);
    return (spender == owner ||
      isApprovedForAll(owner, spender) ||
      getApproved(tokenId) == spender);
  }

  /**
   * @dev Mints `tokenId` and transfers it to `to`.
   *
   * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
   *
   * Requirements:
   *
   * - `tokenId` must not exist.
   * - `to` cannot be the zero address.
   *
   * Emits a {Transfer} event.
   */
  function _mint(address to, uint256 tokenId) internal virtual {}

  function _transfer(
    address from,
    address to,
    uint256 tokenId
  ) internal virtual {
    require(
      ERC721.ownerOf(tokenId) == from,
      "ERC721: transfer from incorrect owner"
    );

    _owners[tokenId] = to;
  }

  /**
   * @dev Approve `to` to operate on `tokenId`
   *
   * Emits an {Approval} event.
   */
  function _approve(address to, uint256 tokenId) internal virtual {
    _tokenApprovals[tokenId] = to;
    emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
  }

  /**
   * @dev Approve `operator` to operate on all of `owner` tokens
   *
   * Emits an {ApprovalForAll} event.
   */
  function _setApprovalForAll(
    address owner,
    address operator,
    bool approved
  ) internal virtual {
    require(owner != operator, "ERC721: approve to caller");
    _operatorApprovals[owner][operator] = approved;
    emit ApprovalForAll(owner, operator, approved);
  }

  /**
   * @dev Reverts if the `tokenId` has not been minted yet.
   */
  function _requireMinted(uint256 tokenId) internal view virtual {
    require(_exists(tokenId), "ERC721: invalid token ID");
  }

  function _checkOnERC721Received(
    address from,
    address to,
    uint256 tokenId,
    bytes memory data
  ) internal returns (bool) {
    if (to.isContract()) {
      try
        IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, data)
      returns (bytes4 retval) {
        return retval == IERC721Receiver.onERC721Received.selector;
      } catch (bytes memory reason) {
        if (reason.length == 0) {
          revert("ERC721: transfer to non ERC721Receiver implementer");
        } else {
          /// @solidity memory-safe-assembly
          assembly {
            revert(add(32, reason), mload(reason))
          }
        }
      }
    } else {
      return true;
    }
  }

  function _beforeTokenTransfer(
    address from,
    address to,
    uint256 tokenId
  ) internal virtual {}

  function _afterTokenTransfer(
    address from,
    address to,
    uint256 tokenId
  ) internal virtual {}
}

// File: contracts/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "../utils/introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
  /**
   * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
   */
  event Transfer(
    address indexed from,
    address indexed to,
    uint256 indexed tokenIdOrAmount
  );

  /**
   * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
   */
  event Approval(
    address indexed owner,
    address indexed approved,
    uint256 indexed tokenIdOrAmount
  );

  /**
   * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
   */
  event ApprovalForAll(
    address indexed owner,
    address indexed operator,
    bool approved
  );

  /**
   * @dev Returns the number of tokens in ``owner``'s account.
   */
  function balanceOf(address owner) external view returns (uint256 balance);

  /**
   * @dev Returns the owner of the `tokenId` token.
   *
   * Requirements:
   *
   * - `tokenId` must exist.
   */
  function ownerOf(uint256 tokenId) external view returns (address owner);

  /**
   * @dev Safely transfers `tokenId` token from `from` to `to`.
   *
   * Requirements:
   *
   * - `from` cannot be the zero address.
   * - `to` cannot be the zero address.
   * - `tokenId` token must exist and be owned by `from`.
   * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
   * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
   *
   * Emits a {Transfer} event.
   */
  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes calldata data
  ) external;

  /**
   * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
   * are aware of the ERC721 protocol to prevent tokens from being forever locked.
   *
   * Requirements:
   *
   * - `from` cannot be the zero address.
   * - `to` cannot be the zero address.
   * - `tokenId` token must exist and be owned by `from`.
   * - If the caller is not `from`, it must have been allowed to move this token by either {approve} or {setApprovalForAll}.
   * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
   *
   * Emits a {Transfer} event.
   */
  function safeTransferFrom(address from, address to, uint256 tokenId) external;

  /**
   * @dev Transfers `tokenId` token from `from` to `to`.
   *
   * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
   *
   * Requirements:
   *
   * - `from` cannot be the zero address.
   * - `to` cannot be the zero address.
   * - `tokenId` token must be owned by `from`.
   * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
   *
   * Emits a {Transfer} event.
   */
  function transferFrom(
    address from,
    address to,
    uint256 tokenId
  ) external returns (bool);

  /**
   * @dev Gives permission to `to` to transfer `tokenId` token to another account.
   * The approval is cleared when the token is transferred.
   *
   * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
   *
   * Requirements:
   *
   * - The caller must own the token or be an approved operator.
   * - `tokenId` must exist.
   *
   * Emits an {Approval} event.
   */
  function approve(address to, uint256 tokenId) external;

  /**
   * @dev Approve or remove `operator` as an operator for the caller.
   * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
   *
   * Requirements:
   *
   * - The `operator` cannot be the caller.
   *
   * Emits an {ApprovalForAll} event.
   */
  function setApprovalForAll(address operator, bool _approved) external;

  /**
   * @dev Returns the account approved for `tokenId` token.
   *
   * Requirements:
   *
   * - `tokenId` must exist.
   */
  function getApproved(
    uint256 tokenId
  ) external view returns (address operator);

  /**
   * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
   *
   * See {setApprovalForAll}
   */
  function isApprovedForAll(
    address owner,
    address operator
  ) external view returns (bool);
}

// File: contracts/ERC721/IERC721Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Metadata.sol)

pragma solidity ^0.8.0;

import "./IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
  /**
   * @dev Returns the token collection name.
   */
  function name() external view returns (string memory);

  /**
   * @dev Returns the token collection symbol.
   */
  function symbol() external view returns (string memory);

  /**
   * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
   */
  function tokenURI(uint256 tokenId) external view returns (string memory);
}

// File: contracts/ERC721/IERC721Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC721/IERC721Receiver.sol)

pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721Receiver.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// File: contracts/Inscription.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "contracts/ERC20/IERC20.sol";
import "contracts/ERC721/ERC721.sol";
import "contracts/ERC721/IERC721.sol";
import "./Base64.sol";

struct Tick {
  string op;
  uint256 amt;
}

contract INS20 is IERC20, ERC721 {
  uint64 public maxSupply; // 21,000,000
  uint64 public mintLimit; // 1000
  uint64 public lastBlock;
  uint64 public mintedPer;

  // bytes32 public immutable hashPre;
  bytes32 public immutable hash;

  bool public nft2ft;
  // number of tickets minted
  uint128 private tickNumber;
  uint128 internal _totalSupply;

  address public proxy;

  // -------- IERC20 --------
  mapping(address => uint256) internal _balances;
  mapping(address => uint256) internal _insBalances;
  mapping(address => mapping(address => uint256)) private _allowances;
  string private _tick;

  // for svg
  mapping(uint256 => Tick) internal _tickets;

  constructor(
    string memory tick,
    uint64 maxSupply_,
    uint64 mintLimit_,
    address proxy_
  ) ERC721("ins-20", tick) {
    _tick = tick;
    // hashPre = keccak256(
    //   string.concat(
    //     '{"p":"ins-20","op":"mint","tick":"',
    //     bytes(tick),
    //     '","amt":"'
    //   )
    // );
    // hashTail = keccak256(bytes('"}'));
    hash = keccak256(
      string.concat(
        '{"p":"ins-20","op":"mint","tick":"',
        bytes(tick),
        '","amt":"1000"}'
      )
    );
    maxSupply = maxSupply_;
    mintLimit = mintLimit_;
    proxy = proxy_;
  }

  event Inscribe(address indexed from, address indexed to, string data);

  /// @dev Inscribe your first EVM Inscriptions
  /// @dev Use Flashbots for your txes https://docs.flashbots.net/flashbots-protect/quick-start#adding-flashbots-protect-rpc-manually
  function inscribe(bytes calldata data) public {
    require(keccak256(data) == hash, "Inscribe data is wrong.");
    require(tx.origin == msg.sender, "Contracts are not allowed");

    if (block.number > lastBlock) {
      lastBlock = uint64(block.number);
      mintedPer = 0;
    } else {
      require(
        mintedPer < 10,
        "Only 10 ticks per block. Using Flashbots can prevent failed txes."
      );
      unchecked {
        mintedPer++;
      }
    }

    // string memory d = string(data);
    // uint256 amt = extractAmt(d);
    // For lower gas
    uint256 amt = 1000;

    require(amt <= mintLimit, "Exceeded mint limit");
    require(_totalSupply + amt < maxSupply, "Exceeded max supply");
    _mint(msg.sender, tickNumber, amt);

    emit Inscribe(
      address(0),
      msg.sender,
      string(string.concat("data:text/plain;charset=utf-8", data))
    );
  }

  function _mint(address to, uint256 tokenId, uint256 amount) internal {
    _beforeTokenTransfer(address(0), to, tokenId);

    unchecked {
      _totalSupply += uint128(amount);
      _balances[to] += amount;
      _insBalances[msg.sender]++;
    }
    _owners[tokenId] = to;
    _tickets[tokenId] = Tick("mint", amount);

    emit Transfer(address(0), to, tokenId);

    _afterTokenTransfer(address(0), to, tokenId);
  }

  /* function extractAmt(string memory json) internal view returns (uint256) {
    // index of amt's value
    uint amtStart = 47;

    bytes memory jsonBytes = bytes(json);
    require(
      jsonBytes.length == 53,
      'Inscribe data is wrong.'
    );

    // verify pre hash
    bytes memory pre = new bytes(amtStart);
    for (uint256 i = 0; i < amtStart; i++) {
      pre[i] = jsonBytes[i];
    }
    require(
      keccak256(pre) == hashPre,
      'Inscribe data is wrong.'
    );

    // index of amt's value end
    uint256 end = amtStart;
    while (end < jsonBytes.length && jsonBytes[end] != '"') {
      end++;
    }

    // get the value of amt
    bytes memory amtBytes = new bytes(end - amtStart);
    for (uint i; i < end - amtStart; i++) {
      amtBytes[i] = jsonBytes[amtStart + i];
    }

    // verify tail hash
    bytes memory tail = new bytes(2);
    tail[0] = jsonBytes[jsonBytes.length - 2];
    tail[1] = jsonBytes[jsonBytes.length - 1];
    require(
      keccak256(tail) == hashTail,
      'Inscribe data is wrong.'
    );

    // convert to uint
    uint result = 0;
    for (uint i = 0; i < amtBytes.length; i++) {
      uint256 amt = uint256(uint8(amtBytes[i]));
      // ASCII
      if (amt < 48 || amt > 57) {
        revert("Non-numeric character encountered");
      }

      result = result * 10 + (amt - 48);
    }
    return result;
  } */

  // -------- IERC20 --------

  function symbol() public view virtual override returns (string memory) {
    return _tick;
  }

  function decimals() public view virtual returns (uint8) {
    return 1;
  }

  function totalSupply() public view override returns (uint256) {
    return _totalSupply;
  }

  function balanceOf(
    address owner
  ) public view override(ERC721, IERC20) returns (uint256) {
    require(owner != address(0), "ERC20: address zero is not a valid owner");
    return nft2ft ? _balances[owner] : _insBalances[owner];
  }

  function allowance(
    address owner,
    address spender
  ) public view override returns (uint256) {
    return _allowances[owner][spender];
  }

  function approve(
    address spender,
    uint256 amountOrTokenID
  ) public override(ERC721, IERC20) {
    if (!nft2ft) {
      ERC721._approve(spender, amountOrTokenID);
    } else {
      address owner = msg.sender;
      _approve(owner, spender, amountOrTokenID);
    }
  }

  function setApprovalForAll(
    address operator,
    bool approved
  ) public override {
    if (!nft2ft) {
      ERC721.setApprovalForAll(operator,approved);
    }
  }

  // only for FT
  function transfer(
    address to,
    uint256 amount
  ) external override returns (bool) {
    if (nft2ft) {
      require(to != address(0), "ERC20: transfer to the zero address");
      _transfer20(msg.sender, to, amount);
    }
    return nft2ft;
  }

  function transferFrom(
    address from,
    address to,
    uint256 tokenIdOrAmount
  ) public override(ERC721, IERC20) returns (bool) {
    require(from != address(0), "INS20: transfer from the zero address");
    require(to != address(0), "INS20: transfer to the zero address");

    if (!nft2ft) {
      require(
        _isApprovedOrOwner(_msgSender(), tokenIdOrAmount),
        "ERC721: caller is not token owner nor approved"
      );
      _transfer721(from, to, tokenIdOrAmount);
    } else {
      _spendAllowance(from, msg.sender, tokenIdOrAmount);
      _transfer20(from, to, tokenIdOrAmount);
    }

    return true;
  }

  function _spendAllowance(
    address owner,
    address spender,
    uint256 amount
  ) internal virtual {
    uint256 currentAllowance = allowance(owner, spender);
    if (currentAllowance != type(uint256).max) {
      require(currentAllowance >= amount, "ERC20: insufficient allowance");
      unchecked {
        _approve(owner, spender, currentAllowance - amount);
      }
    }
  }

  function _approve(
    address owner,
    address spender,
    uint256 amount
  ) internal virtual {
    require(owner != address(0), "ERC20: approve from the zero address");
    require(spender != address(0), "ERC20: approve to the zero address");

    _allowances[owner][spender] = amount;
    if(nft2ft) emit Approval(owner, spender, amount);
  }

  function _transfer20(address from, address to, uint256 amount) internal {
    _beforeTokenTransfer(from, to, amount);
    // transfer like erc20
    uint256 fromBalance = _balances[from];
    require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
    unchecked {
      _balances[from] = fromBalance - amount;
    }
    _balances[to] += amount;

    string memory t = string(
      string.concat(
        '{"p":"ins-20","op":"transfer","tick":"INSC","amt":"',
        bytes(toString(amount)),
        '"}'
      )
    );
    emit Inscribe(
      from,
      to,
      string(string.concat("data:text/plain;charset=utf-8", bytes(t)))
    );
    _afterTokenTransfer(from, to, amount);
    if (nft2ft) emit Transfer(from, to, amount);
  }

  // -------- IERC721 --------

  // just for erc721 transfer
  function _transfer721(address from, address to, uint256 tokenId) internal {
    // transfer like erc721
    ERC721._transfer(from, to, tokenId);

    // transfer like erc20
    _transfer20(from, to, _tickets[tokenId].amt);
    _insBalances[from] -= 1;
    _insBalances[to] += 1;

    emit Transfer(from, to, tokenId);

    ERC721._approve(address(0), tokenId);
  }

  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId
  ) public override {
    require(
      !nft2ft,
      "Not support ERC721 any more."
    );
    safeTransferFrom(from, to, tokenId, "");
  }

  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes memory data
  ) public override {
    require(
      !nft2ft,
      "Not support ERC721 any more."
    );
    require(
      _isApprovedOrOwner(_msgSender(), tokenId),
      "ERC721: caller is not token owner nor approved"
    );
    _transfer721(from, to, tokenId);
    require(
      _checkOnERC721Received(from, to, tokenId, data),
      "ERC721: transfer to non ERC721Receiver implementer"
    );
  }

  function toFT() public {
    require(!nft2ft && proxy == msg.sender, "Has done");
    nft2ft = true;
  }

  // metadata
  function tokenURI(
    uint256 tokenID
  ) public view virtual override returns (string memory) {
    require(
      !nft2ft,
      "Not support ERC721 any more."
    );
    string memory output = '<svg xmlns="http://www.w3.org/2000/svg" preserveAspectRatio="xMinYMin meet" viewBox="0 0 350 350"> <style>.base { fill: white; font-family: serif; font-size: 14px; }</style><rect width="100%" height="100%" fill="black" /><text x="100" y="100" class="base">{</text><text x="130" y="130" class="base">"p":"ins-20",</text><text x="130" y="160" class="base">"op":"';

    bytes memory data;


    data = abi.encodePacked(
      output,
      bytes(_tickets[tokenID].op),
      '",</text><text x="130" y="190" class="base">"tick":"insc",</text><text x="130" y="220" class="base">"amt":'
    );
    data = abi.encodePacked(
      data,
      bytes(toString(_tickets[tokenID].amt)),
      '</text><text x="100" y="250" class="base">}</text></svg>'
    );

    string memory json = Base64.encode(
      bytes(
        string(
          abi.encodePacked(
            '{"description": "INS20 is a social experiment, a first attempt to practice inscription within the EVM.", "image": "data:image/svg+xml;base64,',
            Base64.encode(data),
            '"}'
          )
        )
      )
    );
    output = string(abi.encodePacked("data:application/json;base64,", json));
    return output;
  }

  function _beforeTokenTransfer(
    address from,
    address to,
    uint256 amount
  ) internal override(ERC721) {
    if (from == address(0)) {
      tickNumber++;
    }
  }

  function _afterTokenTransfer(
    address from,
    address to,
    uint256 tokenId
  ) internal virtual override(ERC721) {}

  function toString(uint256 value) internal pure returns (string memory) {
    if (value == 0) {
      return "0";
    }
    uint256 temp = value;
    uint256 digits;
    while (temp != 0) {
      digits++;
      temp /= 10;
    }
    bytes memory buffer = new bytes(digits);
    while (value != 0) {
      digits -= 1;
      buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
      value /= 10;
    }
    return string(buffer);
  }
}

// File: contracts/utils/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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");

        (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");

        (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");

        (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");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal 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
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^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 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) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: contracts/utils/introspection/ERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// File: contracts/utils/introspection/IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * 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[EIP 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);
}

// File: contracts/utils/Strings.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/Strings.sol)

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";
    uint8 private constant _ADDRESS_LENGTH = 20;

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }

    /**
     * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
     */
    function toHexString(address addr) internal pure returns (string memory) {
        return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
    }
}