// File: contracts/inft/ERC721Drop.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "../interfaces/ERC721Spec.sol";
import "../interfaces/AletheaERC721Spec.sol";
import "../utils/AccessControl.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

/**
 * @title ERC721 Airdrop
 *
 * @notice During the release 2.0 distribution event of 10,000 personality pods,
 *      it became clear there is a need to distribute around 10% for free, as an Airdrop.
 *
 * @notice ERC721Drop contract introduces a scalable mechanism to mint NFTs to an arbitrary
 *      amount of addresses by leveraging the power of Merkle trees to "compress" minting data.
 *
 * @notice The input data is an array of (address, tokenId) pairs; Merkle tree is built out
 *      from this array, and the tree root is stored on the contract by its data manager.
 *      When minting (address, tokenId), executor specifies also the Merkle proof for an
 *      element (address, tokenId) to mint.
 */
contract ERC721Drop is AccessControl {
	// Use Zeppelin MerkleProof Library to verify Merkle proofs
	using MerkleProof for bytes32[];

	/**
	 * @notice Input data root, Merkle tree root for an array of (address, tokenId) pairs,
	 *      available for minting
	 *
	 * @notice Merkle root effectively "compresses" the (potentially) huge array of data elements
	 *      and allows to store it in a single 256-bits storage slot on-chain
	 */
	bytes32 public root;

	/**
	 * @dev Mintable ERC721 contract address to mint tokens of
	 */
	address public immutable targetContract;

	/**
	 * @notice Enables the airdrop, redeeming the tokens
	 *
	 * @dev Feature FEATURE_REDEEM_ACTIVE must be enabled in order for
	 *      `mint()` function to succeed
	 */
	uint32 public constant FEATURE_REDEEM_ACTIVE = 0x0000_0001;

	/**
	 * @notice Data manager is responsible for supplying the valid input data array
	 *      Merkle root which then can be used to mint tokens, meaning effectively,
	 *      that data manager may act as a minter on the target NFT contract
	 *
	 * @dev Role ROLE_DATA_MANAGER allows setting the Merkle tree root via setInputDataRoot()
	 */
	uint32 public constant ROLE_DATA_MANAGER = 0x0001_0000;

	/**
	 * @dev Fired in setInputDataRoot()
	 *
	 * @param _by an address which executed the operation
	 * @param _root new Merkle root value
	 */
	event RootChanged(address indexed _by, bytes32 _root);

	/**
	 * @dev Fired in redeem()
	 *
	 * @param _by an address which executed the operation
	 * @param _to an address the token was minted to
	 * @param _tokenId token ID minted
	 * @param _proof Merkle proof for the (_to, _tokenId) pair
	 */
	event Redeemed(address indexed _by, address indexed _to, uint256 indexed _tokenId, bytes32[] _proof);

	/**
	 * @dev Creates/deploys ERC721Drop and binds it to ERC721 smart contract on construction
	 *
	 * @param _target deployed Mintable ERC721 smart contract; contract will mint NFTs of that type
	 */
	constructor(address _target) {
		// verify the input is set
		require(_target != address(0), "target contract is not set");

		// verify the input is valid smart contract of the expected interfaces
		require(
			ERC165(_target).supportsInterface(type(ERC721).interfaceId)
			&& ERC165(_target).supportsInterface(type(MintableERC721).interfaceId),
			"unexpected target type"
		);

		// assign the address
		targetContract = _target;
	}

	/**
	 * @notice Restricted access function to update input data root (Merkle tree root),
	 *       and to define, effectively, the tokens to be created by this smart contract
	 *
	 * @dev Requires executor to have `ROLE_DATA_MANAGER` permission
	 *
	 * @param _root Merkle tree root for the input data array
	 */
	function setInputDataRoot(bytes32 _root) public {
		// verify the access permission
		require(isSenderInRole(ROLE_DATA_MANAGER), "access denied");

		// update input data Merkle tree root
		root = _root;

		// emit an event
		emit RootChanged(msg.sender, _root);
	}

	/**
	 * @notice Verifies the validity of a `(_to, _tokenId)` pair supplied based on the Merkle root
	 *      of the entire `(_to, _tokenId)` data array (pre-stored in the contract), and the Merkle
	 *      proof `_proof` for the particular `(_to, _tokenId)` pair supplied
	 *
	 * @dev Merkle tree and proof can be constructed using the `web3-utils`, `merkletreejs`,
	 *      and `keccak256` npm packages:
	 *      1. Hash the original array data elements (_to, _tokenId) via `web3.utils.soliditySha3`,
	 *         making sure the packing order and types are exactly as in `mint()` signature
	 *      2. Create a sorted MerkleTree (`merkletreejs`) from the hashed array, use `keccak256`
	 *         from the `keccak256` npm package as a hashing function, do not hash leaves
	 *         (already hashed in step 1); Ex. MerkleTree options: {hashLeaves: false, sortPairs: true}
	 *      3. For any given data element (_to, _tokenId) the proof is constructed by hashing it
	 *         (as in step 1) and querying the MerkleTree for a proof, providing the hashed element
	 *         as a leaf
	 *
	 * @param _to an address to mint token to
	 * @param _tokenId token ID to mint
	 * @param _proof Merkle proof for the (_to, _tokenId) pair supplied
	 * @return true if Merkle proof is valid (data belongs to the original array), false otherwise
	 */
	function isTokenValid(address _to, uint256 _tokenId, bytes32[] memory _proof) public view returns(bool) {
		// construct Merkle tree leaf from the inputs supplied
		bytes32 leaf = keccak256(abi.encodePacked(_to, _tokenId));

		// verify the proof supplied, and return the verification result
		return _proof.verify(root, leaf);
	}

	/**
	 * @notice Mints token `_tokenId` to an address `_to`, verifying the validity
	 *      of a `(_to, _tokenId)` pair via the Merkle proof `_proof`
	 *
	 * @dev Merkle tree and proof can be constructed using the `web3-utils`, `merkletreejs`,
	 *      and `keccak256` npm packages:
	 *      1. Hash the original array data elements (_to, _tokenId) via `web3.utils.soliditySha3`,
	 *         making sure the packing order and types are exactly as in `mint()` signature
	 *      2. Create a sorted MerkleTree (`merkletreejs`) from the hashed array, use `keccak256`
	 *         from the `keccak256` npm package as a hashing function, do not hash leaves
	 *         (already hashed in step 1); Ex. MerkleTree options: {hashLeaves: false, sortPairs: true}
	 *      3. For any given data element (_to, _tokenId) the proof is constructed by hashing it
	 *         (as in step 1) and querying the MerkleTree for a proof, providing the hashed element
	 *         as a leaf
	 *
	 * @dev Throws is the data or merkle proof supplied is not valid
	 *
	 * @param _to an address to mint token to
	 * @param _tokenId token ID to mint
	 * @param _proof Merkle proof for the (_to, _tokenId) pair supplied
	 */
	function redeem(address _to, uint256 _tokenId, bytes32[] memory _proof) public {
		// verify airdrop is in active state
		require(isFeatureEnabled(FEATURE_REDEEM_ACTIVE), "redeems are disabled");

		// verify the `(_to, _tokenId)` pair is valid
		require(isTokenValid(_to, _tokenId, _proof), "invalid token");

		// mint the token
		MintableERC721(targetContract).safeMint(_to, _tokenId);

		// emit an event
		emit Redeemed(msg.sender, _to, _tokenId, _proof);
	}
}

// File: contracts/interfaces/ERC721Spec.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "./ERC165Spec.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard
 *
 * @notice See https://eips.ethereum.org/EIPS/eip-721
 *
 * @dev Solidity issue #3412: The ERC721 interfaces include explicit mutability guarantees for each function.
 *      Mutability guarantees are, in order weak to strong: payable, implicit nonpayable, view, and pure.
 *      Implementation MUST meet the mutability guarantee in this interface and MAY meet a stronger guarantee.
 *      For example, a payable function in this interface may be implemented as nonpayable
 *      (no state mutability specified) in implementing contract.
 *      It is expected a later Solidity release will allow stricter contract to inherit from this interface,
 *      but current workaround is that we edit this interface to add stricter mutability before inheriting:
 *      we have removed all "payable" modifiers.
 *
 * @dev The ERC-165 identifier for this interface is 0x80ac58cd.
 *
 * @author William Entriken, Dieter Shirley, Jacob Evans, Nastassia Sachs
 */
interface ERC721 is ERC165 {
	/// @dev This emits when ownership of any NFT changes by any mechanism.
	///  This event emits when NFTs are created (`from` == 0) and destroyed
	///  (`to` == 0). Exception: during contract creation, any number of NFTs
	///  may be created and assigned without emitting Transfer. At the time of
	///  any transfer, the approved address for that NFT (if any) is reset to none.
	event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);

	/// @dev This emits when the approved address for an NFT is changed or
	///  reaffirmed. The zero address indicates there is no approved address.
	///  When a Transfer event emits, this also indicates that the approved
	///  address for that NFT (if any) is reset to none.
	event Approval(address indexed _owner, address indexed _approved, uint256 indexed _tokenId);

	/// @dev This emits when an operator is enabled or disabled for an owner.
	///  The operator can manage all NFTs of the owner.
	event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);

	/// @notice Count all NFTs assigned to an owner
	/// @dev NFTs assigned to the zero address are considered invalid, and this
	///  function throws for queries about the zero address.
	/// @param _owner An address for whom to query the balance
	/// @return The number of NFTs owned by `_owner`, possibly zero
	function balanceOf(address _owner) external view returns (uint256);

	/// @notice Find the owner of an NFT
	/// @dev NFTs assigned to zero address are considered invalid, and queries
	///  about them do throw.
	/// @param _tokenId The identifier for an NFT
	/// @return The address of the owner of the NFT
	function ownerOf(uint256 _tokenId) external view returns (address);

	/// @notice Transfers the ownership of an NFT from one address to another address
	/// @dev Throws unless `msg.sender` is the current owner, an authorized
	///  operator, or the approved address for this NFT. Throws if `_from` is
	///  not the current owner. Throws if `_to` is the zero address. Throws if
	///  `_tokenId` is not a valid NFT. When transfer is complete, this function
	///  checks if `_to` is a smart contract (code size > 0). If so, it calls
	///  `onERC721Received` on `_to` and throws if the return value is not
	///  `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
	/// @param _from The current owner of the NFT
	/// @param _to The new owner
	/// @param _tokenId The NFT to transfer
	/// @param _data Additional data with no specified format, sent in call to `_to`
	function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes calldata _data) external /*payable*/;

	/// @notice Transfers the ownership of an NFT from one address to another address
	/// @dev This works identically to the other function with an extra data parameter,
	///  except this function just sets data to "".
	/// @param _from The current owner of the NFT
	/// @param _to The new owner
	/// @param _tokenId The NFT to transfer
	function safeTransferFrom(address _from, address _to, uint256 _tokenId) external /*payable*/;

	/// @notice Transfer ownership of an NFT -- THE CALLER IS RESPONSIBLE
	///  TO CONFIRM THAT `_to` IS CAPABLE OF RECEIVING NFTS OR ELSE
	///  THEY MAY BE PERMANENTLY LOST
	/// @dev Throws unless `msg.sender` is the current owner, an authorized
	///  operator, or the approved address for this NFT. Throws if `_from` is
	///  not the current owner. Throws if `_to` is the zero address. Throws if
	///  `_tokenId` is not a valid NFT.
	/// @param _from The current owner of the NFT
	/// @param _to The new owner
	/// @param _tokenId The NFT to transfer
	function transferFrom(address _from, address _to, uint256 _tokenId) external /*payable*/;

	/// @notice Change or reaffirm the approved address for an NFT
	/// @dev The zero address indicates there is no approved address.
	///  Throws unless `msg.sender` is the current NFT owner, or an authorized
	///  operator of the current owner.
	/// @param _approved The new approved NFT controller
	/// @param _tokenId The NFT to approve
	function approve(address _approved, uint256 _tokenId) external /*payable*/;

	/// @notice Enable or disable approval for a third party ("operator") to manage
	///  all of `msg.sender`'s assets
	/// @dev Emits the ApprovalForAll event. The contract MUST allow
	///  multiple operators per owner.
	/// @param _operator Address to add to the set of authorized operators
	/// @param _approved True if the operator is approved, false to revoke approval
	function setApprovalForAll(address _operator, bool _approved) external;

	/// @notice Get the approved address for a single NFT
	/// @dev Throws if `_tokenId` is not a valid NFT.
	/// @param _tokenId The NFT to find the approved address for
	/// @return The approved address for this NFT, or the zero address if there is none
	function getApproved(uint256 _tokenId) external view returns (address);

	/// @notice Query if an address is an authorized operator for another address
	/// @param _owner The address that owns the NFTs
	/// @param _operator The address that acts on behalf of the owner
	/// @return True if `_operator` is an approved operator for `_owner`, false otherwise
	function isApprovedForAll(address _owner, address _operator) external view returns (bool);
}

/// @dev Note: the ERC-165 identifier for this interface is 0x150b7a02.
interface ERC721TokenReceiver {
	/// @notice Handle the receipt of an NFT
	/// @dev The ERC721 smart contract calls this function on the recipient
	///  after a `transfer`. This function MAY throw to revert and reject the
	///  transfer. Return of other than the magic value MUST result in the
	///  transaction being reverted.
	///  Note: the contract address is always the message sender.
	/// @param _operator The address which called `safeTransferFrom` function
	/// @param _from The address which previously owned the token
	/// @param _tokenId The NFT identifier which is being transferred
	/// @param _data Additional data with no specified format
	/// @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
	///  unless throwing
	function onERC721Received(address _operator, address _from, uint256 _tokenId, bytes calldata _data) external returns(bytes4);
}

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 *
 * @notice See https://eips.ethereum.org/EIPS/eip-721
 *
 * @dev The ERC-165 identifier for this interface is 0x5b5e139f.
 *
 * @author William Entriken, Dieter Shirley, Jacob Evans, Nastassia Sachs
 */
interface ERC721Metadata is ERC721 {
	/// @notice A descriptive name for a collection of NFTs in this contract
	function name() external view returns (string memory _name);

	/// @notice An abbreviated name for NFTs in this contract
	function symbol() external view returns (string memory _symbol);

	/// @notice A distinct Uniform Resource Identifier (URI) for a given asset.
	/// @dev Throws if `_tokenId` is not a valid NFT. URIs are defined in RFC
	///  3986. The URI may point to a JSON file that conforms to the "ERC721
	///  Metadata JSON Schema".
	function tokenURI(uint256 _tokenId) external view returns (string memory);
}

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 *
 * @notice See https://eips.ethereum.org/EIPS/eip-721
 *
 * @dev The ERC-165 identifier for this interface is 0x780e9d63.
 *
 * @author William Entriken, Dieter Shirley, Jacob Evans, Nastassia Sachs
 */
interface ERC721Enumerable is ERC721 {
	/// @notice Count NFTs tracked by this contract
	/// @return A count of valid NFTs tracked by this contract, where each one of
	///  them has an assigned and queryable owner not equal to the zero address
	function totalSupply() external view returns (uint256);

	/// @notice Enumerate valid NFTs
	/// @dev Throws if `_index` >= `totalSupply()`.
	/// @param _index A counter less than `totalSupply()`
	/// @return The token identifier for the `_index`th NFT,
	///  (sort order not specified)
	function tokenByIndex(uint256 _index) external view returns (uint256);

	/// @notice Enumerate NFTs assigned to an owner
	/// @dev Throws if `_index` >= `balanceOf(_owner)` or if
	///  `_owner` is the zero address, representing invalid NFTs.
	/// @param _owner An address where we are interested in NFTs owned by them
	/// @param _index A counter less than `balanceOf(_owner)`
	/// @return The token identifier for the `_index`th NFT assigned to `_owner`,
	///   (sort order not specified)
	function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256);
}

// File: contracts/interfaces/AletheaERC721Spec.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

/**
 * @title Alethea Mintable ERC721
 *
 * @notice Defines mint capabilities for Alethea ERC721 tokens.
 *      This interface should be treated as a definition of what mintable means for ERC721
 */
interface MintableERC721 {
	/**
	 * @notice Checks if specified token exists
	 *
	 * @dev Returns whether the specified token ID has an ownership
	 *      information associated with it
	 *
	 * @param _tokenId ID of the token to query existence for
	 * @return whether the token exists (true - exists, false - doesn't exist)
	 */
	function exists(uint256 _tokenId) external view returns(bool);

	/**
	 * @dev Creates new token with token ID specified
	 *      and assigns an ownership `_to` for this token
	 *
	 * @dev Unsafe: doesn't execute `onERC721Received` on the receiver.
	 *      Prefer the use of `saveMint` instead of `mint`.
	 *
	 * @dev Should have a restricted access handled by the implementation
	 *
	 * @param _to an address to mint token to
	 * @param _tokenId ID of the token to mint
	 */
	function mint(address _to, uint256 _tokenId) external;

	/**
	 * @dev Creates new tokens starting with token ID specified
	 *      and assigns an ownership `_to` for these tokens
	 *
	 * @dev Token IDs to be minted: [_tokenId, _tokenId + n)
	 *
	 * @dev n must be greater or equal 2: `n > 1`
	 *
	 * @dev Unsafe: doesn't execute `onERC721Received` on the receiver.
	 *      Prefer the use of `saveMintBatch` instead of `mintBatch`.
	 *
	 * @dev Should have a restricted access handled by the implementation
	 *
	 * @param _to an address to mint tokens to
	 * @param _tokenId ID of the first token to mint
	 * @param n how many tokens to mint, sequentially increasing the _tokenId
	 */
	function mintBatch(address _to, uint256 _tokenId, uint256 n) external;

	/**
	 * @dev Creates new token with token ID specified
	 *      and assigns an ownership `_to` for this token
	 *
	 * @dev Checks if `_to` is a smart contract (code size > 0). If so, it calls
	 *      `onERC721Received` on `_to` and throws if the return value is not
	 *      `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
	 *
	 * @dev Should have a restricted access handled by the implementation
	 *
	 * @param _to an address to mint token to
	 * @param _tokenId ID of the token to mint
	 */
	function safeMint(address _to, uint256 _tokenId) external;

	/**
	 * @dev Creates new token with token ID specified
	 *      and assigns an ownership `_to` for this token
	 *
	 * @dev Checks if `_to` is a smart contract (code size > 0). If so, it calls
	 *      `onERC721Received` on `_to` and throws if the return value is not
	 *      `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
	 *
	 * @dev Should have a restricted access handled by the implementation
	 *
	 * @param _to an address to mint token to
	 * @param _tokenId ID of the token to mint
	 * @param _data additional data with no specified format, sent in call to `_to`
	 */
	function safeMint(address _to, uint256 _tokenId, bytes memory _data) external;

	/**
	 * @dev Creates new tokens starting with token ID specified
	 *      and assigns an ownership `_to` for these tokens
	 *
	 * @dev Token IDs to be minted: [_tokenId, _tokenId + n)
	 *
	 * @dev n must be greater or equal 2: `n > 1`
	 *
	 * @dev Checks if `_to` is a smart contract (code size > 0). If so, it calls
	 *      `onERC721Received` on `_to` and throws if the return value is not
	 *      `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
	 *
	 * @dev Should have a restricted access handled by the implementation
	 *
	 * @param _to an address to mint token to
	 * @param _tokenId ID of the token to mint
	 * @param n how many tokens to mint, sequentially increasing the _tokenId
	 */
	function safeMintBatch(address _to, uint256 _tokenId, uint256 n) external;

	/**
	 * @dev Creates new tokens starting with token ID specified
	 *      and assigns an ownership `_to` for these tokens
	 *
	 * @dev Token IDs to be minted: [_tokenId, _tokenId + n)
	 *
	 * @dev n must be greater or equal 2: `n > 1`
	 *
	 * @dev Checks if `_to` is a smart contract (code size > 0). If so, it calls
	 *      `onERC721Received` on `_to` and throws if the return value is not
	 *      `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
	 *
	 * @dev Should have a restricted access handled by the implementation
	 *
	 * @param _to an address to mint token to
	 * @param _tokenId ID of the token to mint
	 * @param n how many tokens to mint, sequentially increasing the _tokenId
	 * @param _data additional data with no specified format, sent in call to `_to`
	 */
	function safeMintBatch(address _to, uint256 _tokenId, uint256 n, bytes memory _data) external;
}

/**
 * @title Alethea Burnable ERC721
 *
 * @notice Defines burn capabilities for Alethea ERC721 tokens.
 *      This interface should be treated as a definition of what burnable means for ERC721
 */
interface BurnableERC721 {
	/**
	 * @notice Destroys the token with token ID specified
	 *
	 * @dev Should be accessible publicly by token owners.
	 *      May have a restricted access handled by the implementation
	 *
	 * @param _tokenId ID of the token to burn
	 */
	function burn(uint256 _tokenId) external;
}

/**
 * @title With Base URI
 *
 * @notice A marker interface for the contracts having the baseURI() function
 *      or public string variable named baseURI
 *      NFT implementations like TinyERC721, or ShortERC721 are example of such smart contracts
 */
interface WithBaseURI {
	/**
	 * @dev Usually used in NFT implementations to construct ERC721Metadata.tokenURI as
	 *      `base URI + token ID` if token URI is not set (not present in `_tokenURIs` mapping)
	 *
	 * @dev For example, if base URI is https://api.com/token/, then token #1
	 *      will have an URI https://api.com/token/1
	 */
	function baseURI() external view returns(string memory);
}

// File: contracts/utils/AccessControl.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

/**
 * @title Access Control List
 *
 * @notice Access control smart contract provides an API to check
 *      if specific operation is permitted globally and/or
 *      if particular user has a permission to execute it.
 *
 * @notice It deals with two main entities: features and roles.
 *
 * @notice Features are designed to be used to enable/disable specific
 *      functions (public functions) of the smart contract for everyone.
 * @notice User roles are designed to restrict access to specific
 *      functions (restricted functions) of the smart contract to some users.
 *
 * @notice Terms "role", "permissions" and "set of permissions" have equal meaning
 *      in the documentation text and may be used interchangeably.
 * @notice Terms "permission", "single permission" implies only one permission bit set.
 *
 * @notice Access manager is a special role which allows to grant/revoke other roles.
 *      Access managers can only grant/revoke permissions which they have themselves.
 *      As an example, access manager with no other roles set can only grant/revoke its own
 *      access manager permission and nothing else.
 *
 * @notice Access manager permission should be treated carefully, as a super admin permission:
 *      Access manager with even no other permission can interfere with another account by
 *      granting own access manager permission to it and effectively creating more powerful
 *      permission set than its own.
 *
 * @dev Both current and OpenZeppelin AccessControl implementations feature a similar API
 *      to check/know "who is allowed to do this thing".
 * @dev Zeppelin implementation is more flexible:
 *      - it allows setting unlimited number of roles, while current is limited to 256 different roles
 *      - it allows setting an admin for each role, while current allows having only one global admin
 * @dev Current implementation is more lightweight:
 *      - it uses only 1 bit per role, while Zeppelin uses 256 bits
 *      - it allows setting up to 256 roles at once, in a single transaction, while Zeppelin allows
 *        setting only one role in a single transaction
 *
 * @dev This smart contract is designed to be inherited by other
 *      smart contracts which require access control management capabilities.
 *
 * @dev Access manager permission has a bit 255 set.
 *      This bit must not be used by inheriting contracts for any other permissions/features.
 */
contract AccessControl {
	/**
	 * @notice Access manager is responsible for assigning the roles to users,
	 *      enabling/disabling global features of the smart contract
	 * @notice Access manager can add, remove and update user roles,
	 *      remove and update global features
	 *
	 * @dev Role ROLE_ACCESS_MANAGER allows modifying user roles and global features
	 * @dev Role ROLE_ACCESS_MANAGER has single bit at position 255 enabled
	 */
	uint256 public constant ROLE_ACCESS_MANAGER = 0x8000000000000000000000000000000000000000000000000000000000000000;

	/**
	 * @dev Bitmask representing all the possible permissions (super admin role)
	 * @dev Has all the bits are enabled (2^256 - 1 value)
	 */
	uint256 private constant FULL_PRIVILEGES_MASK = type(uint256).max; // before 0.8.0: uint256(-1) overflows to 0xFFFF...

	/**
	 * @notice Privileged addresses with defined roles/permissions
	 * @notice In the context of ERC20/ERC721 tokens these can be permissions to
	 *      allow minting or burning tokens, transferring on behalf and so on
	 *
	 * @dev Maps user address to the permissions bitmask (role), where each bit
	 *      represents a permission
	 * @dev Bitmask 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
	 *      represents all possible permissions
	 * @dev 'This' address mapping represents global features of the smart contract
	 */
	mapping(address => uint256) public userRoles;

	/**
	 * @dev Fired in updateRole() and updateFeatures()
	 *
	 * @param _by operator which called the function
	 * @param _to address which was granted/revoked permissions
	 * @param _requested permissions requested
	 * @param _actual permissions effectively set
	 */
	event RoleUpdated(address indexed _by, address indexed _to, uint256 _requested, uint256 _actual);

	/**
	 * @notice Creates an access control instance,
	 *      setting contract creator to have full privileges
	 */
	constructor() {
		// contract creator has full privileges
		userRoles[msg.sender] = FULL_PRIVILEGES_MASK;
	}

	/**
	 * @notice Retrieves globally set of features enabled
	 *
	 * @dev Effectively reads userRoles role for the contract itself
	 *
	 * @return 256-bit bitmask of the features enabled
	 */
	function features() public view returns(uint256) {
		// features are stored in 'this' address  mapping of `userRoles` structure
		return userRoles[address(this)];
	}

	/**
	 * @notice Updates set of the globally enabled features (`features`),
	 *      taking into account sender's permissions
	 *
	 * @dev Requires transaction sender to have `ROLE_ACCESS_MANAGER` permission
	 * @dev Function is left for backward compatibility with older versions
	 *
	 * @param _mask bitmask representing a set of features to enable/disable
	 */
	function updateFeatures(uint256 _mask) public {
		// delegate call to `updateRole`
		updateRole(address(this), _mask);
	}

	/**
	 * @notice Updates set of permissions (role) for a given user,
	 *      taking into account sender's permissions.
	 *
	 * @dev Setting role to zero is equivalent to removing an all permissions
	 * @dev Setting role to `FULL_PRIVILEGES_MASK` is equivalent to
	 *      copying senders' permissions (role) to the user
	 * @dev Requires transaction sender to have `ROLE_ACCESS_MANAGER` permission
	 *
	 * @param operator address of a user to alter permissions for or zero
	 *      to alter global features of the smart contract
	 * @param role bitmask representing a set of permissions to
	 *      enable/disable for a user specified
	 */
	function updateRole(address operator, uint256 role) public {
		// caller must have a permission to update user roles
		require(isSenderInRole(ROLE_ACCESS_MANAGER), "access denied");

		// evaluate the role and reassign it
		userRoles[operator] = evaluateBy(msg.sender, userRoles[operator], role);

		// fire an event
		emit RoleUpdated(msg.sender, operator, role, userRoles[operator]);
	}

	/**
	 * @notice Determines the permission bitmask an operator can set on the
	 *      target permission set
	 * @notice Used to calculate the permission bitmask to be set when requested
	 *     in `updateRole` and `updateFeatures` functions
	 *
	 * @dev Calculated based on:
	 *      1) operator's own permission set read from userRoles[operator]
	 *      2) target permission set - what is already set on the target
	 *      3) desired permission set - what do we want set target to
	 *
	 * @dev Corner cases:
	 *      1) Operator is super admin and its permission set is `FULL_PRIVILEGES_MASK`:
	 *        `desired` bitset is returned regardless of the `target` permission set value
	 *        (what operator sets is what they get)
	 *      2) Operator with no permissions (zero bitset):
	 *        `target` bitset is returned regardless of the `desired` value
	 *        (operator has no authority and cannot modify anything)
	 *
	 * @dev Example:
	 *      Consider an operator with the permissions bitmask     00001111
	 *      is about to modify the target permission set          01010101
	 *      Operator wants to set that permission set to          00110011
	 *      Based on their role, an operator has the permissions
	 *      to update only lowest 4 bits on the target, meaning that
	 *      high 4 bits of the target set in this example is left
	 *      unchanged and low 4 bits get changed as desired:      01010011
	 *
	 * @param operator address of the contract operator which is about to set the permissions
	 * @param target input set of permissions to operator is going to modify
	 * @param desired desired set of permissions operator would like to set
	 * @return resulting set of permissions given operator will set
	 */
	function evaluateBy(address operator, uint256 target, uint256 desired) public view returns(uint256) {
		// read operator's permissions
		uint256 p = userRoles[operator];

		// taking into account operator's permissions,
		// 1) enable the permissions desired on the `target`
		target |= p & desired;
		// 2) disable the permissions desired on the `target`
		target &= FULL_PRIVILEGES_MASK ^ (p & (FULL_PRIVILEGES_MASK ^ desired));

		// return calculated result
		return target;
	}

	/**
	 * @notice Checks if requested set of features is enabled globally on the contract
	 *
	 * @param required set of features to check against
	 * @return true if all the features requested are enabled, false otherwise
	 */
	function isFeatureEnabled(uint256 required) public view returns(bool) {
		// delegate call to `__hasRole`, passing `features` property
		return __hasRole(features(), required);
	}

	/**
	 * @notice Checks if transaction sender `msg.sender` has all the permissions required
	 *
	 * @param required set of permissions (role) to check against
	 * @return true if all the permissions requested are enabled, false otherwise
	 */
	function isSenderInRole(uint256 required) public view returns(bool) {
		// delegate call to `isOperatorInRole`, passing transaction sender
		return isOperatorInRole(msg.sender, required);
	}

	/**
	 * @notice Checks if operator has all the permissions (role) required
	 *
	 * @param operator address of the user to check role for
	 * @param required set of permissions (role) to check
	 * @return true if all the permissions requested are enabled, false otherwise
	 */
	function isOperatorInRole(address operator, uint256 required) public view returns(bool) {
		// delegate call to `__hasRole`, passing operator's permissions (role)
		return __hasRole(userRoles[operator], required);
	}

	/**
	 * @dev Checks if role `actual` contains all the permissions required `required`
	 *
	 * @param actual existent role
	 * @param required required role
	 * @return true if actual has required role (all permissions), false otherwise
	 */
	function __hasRole(uint256 actual, uint256 required) internal pure returns(bool) {
		// check the bitmask for the role required and return the result
		return actual & required == required;
	}
}

// File: @openzeppelin/contracts/utils/cryptography/MerkleProof.sol



// SPDX-License-Identifier: MIT

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) {
        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));
            }
        }

        // Check if the computed hash (root) is equal to the provided root
        return computedHash == root;
    }
}

// File: contracts/interfaces/ERC165Spec.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

/**
 * @title ERC-165 Standard Interface Detection
 *
 * @dev Interface of the ERC165 standard, as defined in the
 *       https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * @dev Implementers can declare support of contract interfaces,
 *      which can then be queried by others.
 *
 * @author Christian Reitwießner, Nick Johnson, Fabian Vogelsteller, Jordi Baylina, Konrad Feldmeier, William Entriken
 */
interface ERC165 {
	/**
	 * @notice Query if a contract implements an interface
	 *
	 * @dev Interface identification is specified in ERC-165.
	 *      This function uses less than 30,000 gas.
	 *
	 * @param interfaceID The interface identifier, as specified in ERC-165
	 * @return `true` if the contract implements `interfaceID` and
	 *      `interfaceID` is not 0xffffffff, `false` otherwise
	 */
	function supportsInterface(bytes4 interfaceID) external view returns (bool);
}