// File: Angelz.sol



// SPDX-License-Identifier: MIT LICENSE

pragma solidity ^0.8.10;

import "Strings.sol";
import "MerkleProof.sol";
import "ERC721Enum.sol";
import "Grace.sol";
import "IAngelz.sol";
import "ISanctuary.sol";

contract Angelz is IAngelz, ERC721Enum {
  using Strings for uint256;
  // mint price
  uint256 public constant MINT_PRICE = .0543 ether;
  // max number of tokens that can be minted - 30,616
  uint256 public immutable MAX_TOKENS;
  // number of tokens pay with eth - 25% of MAX_TOKENS
  uint256 public PAID_TOKENS;
  // number of tokens have been minted so far
  uint16 public minted;
  string public baseURI;
  bytes32 private rootWL;
  string internal constant baseExtension = ".json";
  bool public pauseMint = true;
  bool public pausePreMint = true;
  address public immutable owner;
  uint256 public freeMint = 500;

  address private constant addressOne =
    0xD70Ee431F074Fb835132ddE35255F8274A51D90b;
  address private constant addressTwo =
    0x13542174BA72e443450926Ea7fC15ED6D66491e0;
  address private constant addressThree =
    0xcC187E04A67c5601693dB7F25E4309D066512a24;

  // mapping from tokenId to a struct containing the token's traits
  mapping(uint256 => AngelHuman) public tokenTraits;
  // reference to the Sanctuary for choosing random Angel thieves
  ISanctuary public sanctuary;
  // reference to $GRACE for burning on mint
  GRACE public grace;

  /**
   * instantiates contract and rarity tables
   */
  constructor(address _grace, string memory _initBaseURI)
    ERC721P("AngelzGame", "AG")
  {
    owner = msg.sender;
    grace = GRACE(_grace);
    setBaseURI(_initBaseURI);
    MAX_TOKENS = 30616;
    PAID_TOKENS = MAX_TOKENS / 4;
  }

  modifier mintOpen() {
    require(!pauseMint, "PauseMint");
    _;
  }

  modifier preMintOpen() {
    require(!pausePreMint, "PausePreMint");
    _;
  }

  modifier onlyOwner() {
    _onlyOwner();
    _;
  }

  function _onlyOwner() private view {
    require(msg.sender == owner, "onlyOwner");
  }

  /** EXTERNAL */

  /**
   * mint a token - 90% Human, 10% Angel
   * The first 25% are 0.0543 eth, the remaining cost $GRACE
   */
  function mint(uint256 amount, bool stake) external payable mintOpen {
    require(tx.origin == msg.sender, "Only EOA");
    require(minted + amount <= MAX_TOKENS, "Allminted");
    require(amount > 0 && amount <= 10, "nomorethan10");
    if (minted < PAID_TOKENS) {
      if (minted < freeMint) {
        require(amount <= 2, "freelimit2pertx");
        require(msg.value == 0, "bruh its free");
      } else {
        require(minted + amount <= PAID_TOKENS, "Allonsaleminted");
        require(msg.value >= amount * MINT_PRICE, "notenougheth");
      }
    } else {
      require(msg.value == 0, "payinGRACE");
    }

    uint256 totalGraceTokenCost = 0;
    uint16[] memory tokenIds = stake ? new uint16[](amount) : new uint16[](0);
    uint256 seed;
    for (uint256 i = 0; i < amount; i++) {
      seed = random(minted);
      generate(minted, seed);
      address recipient = selectRecipient(seed);
      if (!stake || recipient != _msgSender()) {
        _safeMint(recipient, minted);
      } else {
        _safeMint(address(sanctuary), minted);
        tokenIds[i] = minted;
      }
      minted++;
      totalGraceTokenCost += mintCost(minted);
    }

    if (totalGraceTokenCost > 0) grace.burn(_msgSender(), totalGraceTokenCost);
    if (stake) sanctuary.addManyToSanctuaryAndHeaven(_msgSender(), tokenIds);
  }

  function preMint(
    uint256 amount,
    bool stake,
    bytes32[] calldata proof,
    uint256 _number
  ) external payable preMintOpen {
    require(tx.origin == msg.sender, "Only EOA");
    uint16 eligibilitySender = isEligible(proof, _number);
    if (eligibilitySender == 0) {
      revert("notWL");
    }
    require(minted + amount <= PAID_TOKENS, "Allminted");
    require(amount > 0 && amount <= 10, "nomorethan10");
    if (minted < freeMint) {
      require(amount <= 2, "freelimit2pertx");
      require(msg.value == 0, "bruh its free");
    } else {
      require(msg.value >= amount * MINT_PRICE, "notenougheth");
    }

    uint16[] memory tokenIds = stake ? new uint16[](amount) : new uint16[](0);
    uint256 seed;
    for (uint256 i = 0; i < amount; i++) {
      seed = random(minted);
      generate(minted, seed);
      address recipient = selectRecipient(seed);
      if (!stake || recipient != _msgSender()) {
        _safeMint(recipient, minted);
      } else {
        _safeMint(address(sanctuary), minted);
        tokenIds[i] = minted;
      }
      minted++;
    }
    if (stake) sanctuary.addManyToSanctuaryAndHeaven(_msgSender(), tokenIds);
  }

  /**
   * the first 25% are 0.0543 ETH
   * the next 25% are 10000 $GRACE
   * the next 25% are 20000 $GRACE
   * the final 25% are 40000 $GRACE
   * @param tokenId the ID to check the cost of to mint
   * @return the cost of the given token ID
   */
  function mintCost(uint256 tokenId) public view returns (uint256) {
    if (tokenId <= PAID_TOKENS) return 0;
    if (tokenId <= (MAX_TOKENS * 2) / 4) return 10000 ether;
    if (tokenId <= (MAX_TOKENS * 3) / 4) return 20000 ether;
    return 40000 ether;
  }

  function transferFrom(
    address from,
    address to,
    uint256 tokenId
  ) public virtual override {
    // Hardcode the Sanctuary's approval so that users don't have to waste gas approving
    if (_msgSender() != address(sanctuary))
      require(
        _isApprovedOrOwner(_msgSender(), tokenId),
        "Not owner nor approved"
      );
    _transfer(from, to, tokenId);
  }

  /** INTERNAL */

  function _baseURI() internal view virtual returns (string memory) {
    return baseURI;
  }

  /**
   * generates traits for a specific token, checking to make sure it's unique
   * @param tokenId the id of the token to generate traits for
   * @param seed a pseudorandom 256 bit number to derive traits from
   * @return t - a struct of traits for the given token ID
   */
  function generate(uint256 tokenId, uint256 seed)
    internal
    returns (AngelHuman memory t)
  {
    t = selectTraits(seed);
    tokenTraits[tokenId] = t;
    return t;
  }

  function selectTraits(uint256 seed)
    internal
    view
    returns (AngelHuman memory t)
  {
    t.human = (seed & 0xFFFF) % 10 != 0;
    seed >>= 16;
    if (t.human) {
      t.angelicIndex = 0;
      return t;
    }

    uint16 randomAngelicValue = uint16(seed & 0xFFFF) % 10;
    if (randomAngelicValue == 0) {
      t.angelicIndex = 8;
    } else if (randomAngelicValue == 1 || randomAngelicValue == 2) {
      t.angelicIndex = 7;
    } else if (
      randomAngelicValue == 3 ||
      randomAngelicValue == 4 ||
      randomAngelicValue == 5
    ) {
      t.angelicIndex = 6;
    } else {
      t.angelicIndex = 5;
    }
  }

  /**
   * the first 25% (ETH purchases) go to the minter
   * the remaining 75% have a 10% chance to be given to a random staked angel
   * @param seed a random value to select a recipient from
   * @return the address of the recipient (either the minter or the Angel thief's owner)
   */
  function selectRecipient(uint256 seed) internal view returns (address) {
    if (minted <= PAID_TOKENS || ((seed >> 245) % 10) != 0) return _msgSender(); // top 10 bits haven't been used
    address thief = sanctuary.randomAngelOwner(seed >> 144); // 144 bits reserved for trait selection
    if (thief == address(0x0)) return _msgSender();
    return thief;
  }

  /**
   * generates a pseudorandom number
   * @param seed a value ensure different outcomes for different sources in the same block
   * @return a pseudorandom value
   */
  function random(uint256 seed) internal view returns (uint256) {
    return
      uint256(
        keccak256(
          abi.encodePacked(
            tx.origin,
            blockhash(block.number - 1),
            block.timestamp,
            seed
          )
        )
      );
  }

  /** READ */

  function isEligible(bytes32[] calldata proof, uint256 _number)
    public
    view
    returns (uint16 eligibility)
  {
    bytes32 leaf = keccak256(abi.encodePacked(_number, msg.sender));
    if (MerkleProof.verify(proof, rootWL, leaf)) return 1;
    return 0;
  }

  function getTokenTraits(uint256 tokenId)
    external
    view
    override
    returns (AngelHuman memory)
  {
    return tokenTraits[tokenId];
  }

  function getPaidTokens() external view override returns (uint256) {
    return PAID_TOKENS;
  }

  /** ADMIN */

  /**
   * called after deployment so that the contract can get random angel thieves
   * @param _sanctuary the address of the Sanctuary
   */
  function setSanctuary(address _sanctuary) external onlyOwner {
    sanctuary = ISanctuary(_sanctuary);
  }

  function setBaseURI(string memory _newBaseURI) public onlyOwner {
    baseURI = _newBaseURI;
  }

  function setRoot(bytes32 _rootWL) external onlyOwner {
    rootWL = _rootWL;
  }

  /**
   * allows owner to withdraw funds from minting
   */
  function withdrawAll() external onlyOwner {
    uint256 balance = address(this).balance;
    require(balance > 0, "No money");
    _withdraw(addressOne, (balance * 30) / 100);
    _withdraw(addressTwo, (balance * 30) / 100);
    _withdraw(addressThree, (balance * 30) / 100);
    _withdraw(msg.sender, address(this).balance);
  }

  function _withdraw(address _address, uint256 _amount) private {
    (bool success, ) = _address.call{ value: _amount }("");
    require(success, "Transfer failed");
  }

  /**
   * updates the number of tokens for sale
   */
  function setPaidTokens(uint256 _paidTokens) external onlyOwner {
    PAID_TOKENS = _paidTokens;
  }

  function setNumFreeMint(uint256 _freeMint) external onlyOwner {
    freeMint = _freeMint;
  }

  function setPauseMint(bool _setPauseMint) external onlyOwner {
    if (_setPauseMint) {
      pauseMint = true;
    } else {
      pauseMint = false;
    }
  }

  function setPausePreMint(bool _setPausePreMint) external onlyOwner {
    if (_setPausePreMint) {
      pausePreMint = true;
    } else {
      pausePreMint = false;
    }
  }

  /** RENDER */

  function tokenURI(uint256 tokenId)
    public
    view
    virtual
    override
    returns (string memory)
  {
    require(_exists(tokenId), "DNE");

    string memory currentBaseURI = _baseURI();

    return (
      bytes(currentBaseURI).length > 0
        ? string(
          abi.encodePacked(currentBaseURI, tokenId.toString(), baseExtension)
        )
        : ""
    );
  }
}

// File: Strings.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/Strings.sol)

pragma solidity ^0.8.0;

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

    /**
     * @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);
    }
}

// File: MerkleProof.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/cryptography/MerkleProof.sol)

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Trees proofs.
 *
 * The proofs can be generated using the JavaScript library
 * https://github.com/miguelmota/merkletreejs[merkletreejs].
 * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
 *
 * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merklee tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
            }
        }
        return computedHash;
    }
}

// File: ERC721Enum.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.10;
import "ERC721P.sol";
import "IERC721Enumerable.sol";

abstract contract ERC721Enum is ERC721P, IERC721Enumerable {
  function supportsInterface(bytes4 interfaceId)
    public
    view
    virtual
    override(IERC165, ERC721P)
    returns (bool)
  {
    return
      interfaceId == type(IERC721Enumerable).interfaceId ||
      super.supportsInterface(interfaceId);
  }

  function tokenOfOwnerByIndex(address owner, uint256 index)
    public
    view
    override
    returns (uint256 tokenId)
  {
    require(index < ERC721P.balanceOf(owner), "ERC721Enum: owner ioob");
    uint256 count;
    for (uint256 i; i < _owners.length; ++i) {
      if (owner == _owners[i]) {
        if (count == index) return i;
        else ++count;
      }
    }
    require(false, "ERC721Enum: owner ioob");
  }

  function tokensOfOwner(address owner) public view returns (uint256[] memory) {
    require(0 < ERC721P.balanceOf(owner), "ERC721Enum: owner ioob");
    uint256 tokenCount = balanceOf(owner);
    uint256[] memory tokenIds = new uint256[](tokenCount);
    for (uint256 i = 0; i < tokenCount; i++) {
      tokenIds[i] = tokenOfOwnerByIndex(owner, i);
    }
    return tokenIds;
  }

  function totalSupply() public view virtual override returns (uint256) {
    return _owners.length;
  }

  function tokenByIndex(uint256 index)
    public
    view
    virtual
    override
    returns (uint256)
  {
    require(index < ERC721Enum.totalSupply(), "ERC721Enum: global ioob");
    return index;
  }
}

// File: ERC721P.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.10;
import "IERC721.sol";
import "IERC721Receiver.sol";
import "IERC721Metadata.sol";
import "Address.sol";
import "Context.sol";
import "ERC165.sol";

abstract contract ERC721P is Context, ERC165, IERC721, IERC721Metadata {
  using Address for address;
  string private _name;
  string private _symbol;
  address[] internal _owners;
  mapping(uint256 => address) private _tokenApprovals;
  mapping(address => mapping(address => bool)) private _operatorApprovals;

  constructor(string memory name_, string memory symbol_) {
    _name = name_;
    _symbol = symbol_;
  }

  function supportsInterface(bytes4 interfaceId)
    public
    view
    virtual
    override(ERC165, IERC165)
    returns (bool)
  {
    return
      interfaceId == type(IERC721).interfaceId ||
      interfaceId == type(IERC721Metadata).interfaceId ||
      super.supportsInterface(interfaceId);
  }

  function balanceOf(address owner)
    public
    view
    virtual
    override
    returns (uint256)
  {
    require(owner != address(0), "ERC721: balance query for the zero address");
    uint256 count = 0;
    uint256 length = _owners.length;
    for (uint256 i = 0; i < length; ++i) {
      if (owner == _owners[i]) {
        ++count;
      }
    }
    delete length;
    return count;
  }

  function ownerOf(uint256 tokenId)
    public
    view
    virtual
    override
    returns (address)
  {
    address owner = _owners[tokenId];
    require(owner != address(0), "ERC721: owner query for nonexistent token");
    return owner;
  }

  function name() public view virtual override returns (string memory) {
    return _name;
  }

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

  function approve(address to, uint256 tokenId) public virtual override {
    address owner = ERC721P.ownerOf(tokenId);
    require(to != owner, "ERC721: approval to current owner");

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

    _approve(to, tokenId);
  }

  function getApproved(uint256 tokenId)
    public
    view
    virtual
    override
    returns (address)
  {
    require(_exists(tokenId), "ERC721: approved query for nonexistent token");

    return _tokenApprovals[tokenId];
  }

  function setApprovalForAll(address operator, bool approved)
    public
    virtual
    override
  {
    require(operator != _msgSender(), "ERC721: approve to caller");

    _operatorApprovals[_msgSender()][operator] = approved;
    emit ApprovalForAll(_msgSender(), operator, approved);
  }

  function isApprovedForAll(address owner, address operator)
    public
    view
    virtual
    override
    returns (bool)
  {
    return _operatorApprovals[owner][operator];
  }

  function transferFrom(
    address from,
    address to,
    uint256 tokenId
  ) public virtual override {
    //solhint-disable-next-line max-line-length
    require(
      _isApprovedOrOwner(_msgSender(), tokenId),
      "ERC721: transfer caller is not owner nor approved"
    );

    _transfer(from, to, tokenId);
  }

  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId
  ) public virtual override {
    safeTransferFrom(from, to, tokenId, "");
  }

  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) public virtual override {
    require(
      _isApprovedOrOwner(_msgSender(), tokenId),
      "ERC721: transfer caller is not owner nor approved"
    );
    _safeTransfer(from, to, tokenId, _data);
  }

  function _safeTransfer(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) internal virtual {
    _transfer(from, to, tokenId);
    require(
      _checkOnERC721Received(from, to, tokenId, _data),
      "ERC721: transfer to non ERC721Receiver implementer"
    );
  }

  function _exists(uint256 tokenId) internal view virtual returns (bool) {
    return tokenId < _owners.length && _owners[tokenId] != address(0);
  }

  function _isApprovedOrOwner(address spender, uint256 tokenId)
    internal
    view
    virtual
    returns (bool)
  {
    require(_exists(tokenId), "ERC721: operator query for nonexistent token");
    address owner = ERC721P.ownerOf(tokenId);
    return (spender == owner ||
      getApproved(tokenId) == spender ||
      isApprovedForAll(owner, spender));
  }

  function _safeMint(address to, uint256 tokenId) internal virtual {
    _safeMint(to, tokenId, "");
  }

  function _safeMint(
    address to,
    uint256 tokenId,
    bytes memory _data
  ) internal virtual {
    _mint(to, tokenId);
    require(
      _checkOnERC721Received(address(0), to, tokenId, _data),
      "ERC721: transfer to non ERC721Receiver implementer"
    );
  }

  function _mint(address to, uint256 tokenId) internal virtual {
    require(to != address(0), "ERC721: mint to the zero address");
    require(!_exists(tokenId), "ERC721: token already minted");

    _beforeTokenTransfer(address(0), to, tokenId);
    _owners.push(to);

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

  function _burn(uint256 tokenId) internal virtual {
    address owner = ERC721P.ownerOf(tokenId);

    _beforeTokenTransfer(owner, address(0), tokenId);

    // Clear approvals
    _approve(address(0), tokenId);
    _owners[tokenId] = address(0);

    emit Transfer(owner, address(0), tokenId);
  }

  function _transfer(
    address from,
    address to,
    uint256 tokenId
  ) internal virtual {
    require(
      ERC721P.ownerOf(tokenId) == from,
      "ERC721: transfer of token that is not own"
    );
    require(to != address(0), "ERC721: transfer to the zero address");

    _beforeTokenTransfer(from, to, tokenId);

    // Clear approvals from the previous owner
    _approve(address(0), tokenId);
    _owners[tokenId] = to;

    emit Transfer(from, to, tokenId);
  }

  function _approve(address to, uint256 tokenId) internal virtual {
    _tokenApprovals[tokenId] = to;
    emit Approval(ERC721P.ownerOf(tokenId), to, tokenId);
  }

  function _checkOnERC721Received(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) private 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 {
          assembly {
            revert(add(32, reason), mload(reason))
          }
        }
      }
    } else {
      return true;
    }
  }

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

// File: IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "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 tokenId);

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

    /**
     * @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`, 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 be 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;

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

    /**
     * @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 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);

    /**
     * @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;
}

// File: IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (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: IERC721Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (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 `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// File: IERC721Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (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: Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/Address.sol)

pragma solidity ^0.8.0;

/**
 * @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
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 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

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (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: ERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (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: IERC721Enumerable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC721/extensions/IERC721Enumerable.sol)

pragma solidity ^0.8.0;

import "IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

// File: Grace.sol



// SPDX-License-Identifier: MIT LICENSE

pragma solidity ^0.8.10;

import "ERC20.sol";
import "Ownable.sol";

contract GRACE is ERC20, Ownable {
  // a mapping from an address to whether or not it can mint / burn
  mapping(address => bool) controllers;

  constructor() ERC20("$GRACE", "GRACE") {}

  /**
   * mints $GRACE to a recipient
   * @param to the recipient of the $GRACE
   * @param amount the amount of $GRACE to mint
   */
  function mint(address to, uint256 amount) external {
    require(controllers[msg.sender], "Only controllers can mint");
    _mint(to, amount);
  }

  /**
   * burns $GRACE from a holder
   * @param from the holder of the $GRACE
   * @param amount the amount of $GRACE to burn
   */
  function burn(address from, uint256 amount) external {
    require(controllers[msg.sender], "Only controllers can burn");
    _burn(from, amount);
  }

  /**
   * enables an address to mint / burn
   * @param controller the address to enable
   */
  function addController(address controller) external onlyOwner {
    controllers[controller] = true;
  }

  /**
   * disables an address from minting / burning
   * @param controller the address to disbale
   */
  function removeController(address controller) external onlyOwner {
    controllers[controller] = false;
  }
}

// File: ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "IERC20.sol";
import "IERC20Metadata.sol";
import "Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }

        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);

        _afterTokenTransfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    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;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// File: IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 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 `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, 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 returns (bool);

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

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

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

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// File: Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (access/Ownable.sol)

pragma solidity ^0.8.0;

import "Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: IAngelz.sol



// SPDX-License-Identifier: MIT LICENSE

pragma solidity ^0.8.10;

interface IAngelz {
  // struct to store each token's traits
  struct AngelHuman {
    bool human;
    uint8 angelicIndex;
  }

  function getPaidTokens() external view returns (uint256);

  function getTokenTraits(uint256 tokenId)
    external
    view
    returns (AngelHuman memory);
}

// File: ISanctuary.sol



// SPDX-License-Identifier: MIT LICENSE

pragma solidity ^0.8.10;

interface ISanctuary {
  function addManyToSanctuaryAndHeaven(
    address account,
    uint16[] calldata tokenIds
  ) external;

  function randomAngelOwner(uint256 seed) external view returns (address);
}