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Contract Name:
SoulboundIdentity

Contract Source Code:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

import "./libraries/Errors.sol";
import "./interfaces/ISoulboundIdentity.sol";
import "./interfaces/ISoulName.sol";
import "./tokens/MasaSBTAuthority.sol";

/// @title Soulbound Identity
/// @author Masa Finance
/// @notice Soulbound token that represents an identity.
/// @dev Soulbound identity, that inherits from the SBT contract.
contract SoulboundIdentity is
    MasaSBTAuthority,
    ISoulboundIdentity,
    ReentrancyGuard
{
    /* ========== STATE VARIABLES =========================================== */

    ISoulName public soulName;

    /* ========== INITIALIZE ================================================ */

    /// @notice Creates a new soulbound identity
    /// @dev Creates a new soulbound identity, inheriting from the SBT contract.
    /// @param admin Administrator of the smart contract
    /// @param baseTokenURI Base URI of the token
    constructor(address admin, string memory baseTokenURI)
        MasaSBTAuthority(admin, "Masa Identity", "MID", baseTokenURI)
    {}

    /* ========== RESTRICTED FUNCTIONS ====================================== */

    /// @notice Sets the SoulName contract address linked to this identity
    /// @dev The caller must have the admin role to call this function
    /// @param _soulName Address of the SoulName contract
    function setSoulName(ISoulName _soulName)
        external
        onlyRole(DEFAULT_ADMIN_ROLE)
    {
        if (address(_soulName) == address(0)) revert ZeroAddress();
        if (soulName == _soulName) revert SameValue();
        soulName = _soulName;
    }

    /* ========== MUTATIVE FUNCTIONS ======================================== */

    /// @notice Mints a new soulbound identity
    /// @dev The caller can only mint one identity per address
    /// @param to Address of the admin of the new identity
    function mint(address to) public override returns (uint256) {
        // Soulbound identity already created!
        if (balanceOf(to) > 0) revert IdentityAlreadyCreated(to);

        return _mintWithCounter(to);
    }

    /// @notice Mints a new soulbound identity with a SoulName associated to it
    /// @dev The caller can only mint one identity per address, and the name must be unique
    /// @param to Address of the admin of the new identity
    /// @param name Name of the new identity
    /// @param yearsPeriod Years of validity of the name
    /// @param _tokenURI URI of the NFT
    function mintIdentityWithName(
        address to,
        string memory name,
        uint256 yearsPeriod,
        string memory _tokenURI
    ) external override soulNameAlreadySet nonReentrant returns (uint256) {
        uint256 identityId = mint(to);
        soulName.mint(to, name, yearsPeriod, _tokenURI);

        return identityId;
    }

    /* ========== VIEWS ===================================================== */

    /// @notice Returns the address of the SoulName contract linked to this identity
    /// @dev This function returns the address of the SoulName contract linked to this identity
    /// @return Address of the SoulName contract
    function getSoulName() external view override returns (ISoulName) {
        return soulName;
    }

    /// @notice Returns the extension of the soul name
    /// @dev This function returns the extension of the soul name
    /// @return Extension of the soul name
    function getExtension() external view returns (string memory) {
        return soulName.getExtension();
    }

    /// @notice Returns the owner address of an identity
    /// @dev This function returns the owner address of the identity specified by the tokenId
    /// @param tokenId TokenId of the identity
    /// @return Address of the owner of the identity
    function ownerOf(uint256 tokenId)
        public
        view
        override(SBT, ISBT)
        returns (address)
    {
        return super.ownerOf(tokenId);
    }

    /// @notice Returns the owner address of a soul name
    /// @dev This function returns the owner address of the soul name identity specified by the name
    /// @param name Name of the soul name
    /// @return Address of the owner of the identity
    function ownerOf(string memory name)
        external
        view
        soulNameAlreadySet
        returns (address)
    {
        (, , uint256 identityId, , , ) = soulName.getTokenData(name);
        return super.ownerOf(identityId);
    }

    /// @notice Returns the URI of a soul name
    /// @dev This function returns the token URI of the soul name identity specified by the name
    /// @param name Name of the soul name
    /// @return URI of the identity associated to a soul name
    function tokenURI(string memory name)
        external
        view
        soulNameAlreadySet
        returns (string memory)
    {
        (, , uint256 identityId, , , ) = soulName.getTokenData(name);
        return super.tokenURI(identityId);
    }

    /// @notice Returns the URI of the owner of an identity
    /// @dev This function returns the token URI of the identity owned by an account
    /// @param owner Address of the owner of the identity
    /// @return URI of the identity owned by the account
    function tokenURI(address owner) external view returns (string memory) {
        uint256 tokenId = tokenOfOwner(owner);
        return super.tokenURI(tokenId);
    }

    /// @notice Returns the identity id of an account
    /// @dev This function returns the tokenId of the identity owned by an account
    /// @param owner Address of the owner of the identity
    /// @return TokenId of the identity owned by the account
    function tokenOfOwner(address owner)
        public
        view
        override
        returns (uint256)
    {
        return super.tokenOfOwnerByIndex(owner, 0);
    }

    /// @notice Checks if a soul name is available
    /// @dev This function queries if a soul name already exists and is in the available state
    /// @param name Name of the soul name
    /// @return available `true` if the soul name is available, `false` otherwise
    function isAvailable(string memory name)
        external
        view
        soulNameAlreadySet
        returns (bool available)
    {
        return soulName.isAvailable(name);
    }

    /// @notice Returns the information of a soul name
    /// @dev This function queries the information of a soul name
    /// @param name Name of the soul name
    /// @return sbtName Soul name, in upper/lower case and extension
    /// @return linked `true` if the soul name is linked, `false` otherwise
    /// @return identityId Identity id of the soul name
    /// @return tokenId SoulName id of the soul name
    /// @return expirationDate Expiration date of the soul name
    /// @return active `true` if the soul name is active, `false` otherwise
    function getTokenData(string memory name)
        external
        view
        soulNameAlreadySet
        returns (
            string memory sbtName,
            bool linked,
            uint256 identityId,
            uint256 tokenId,
            uint256 expirationDate,
            bool active
        )
    {
        return soulName.getTokenData(name);
    }

    /// @notice Returns all the active soul names of an account
    /// @dev This function queries all the identity names of the specified account
    /// @param owner Address of the owner of the identities
    /// @return sbtNames Array of soul names associated to the account
    function getSoulNames(address owner)
        external
        view
        soulNameAlreadySet
        returns (string[] memory sbtNames)
    {
        return soulName.getSoulNames(owner);
    }

    // SoulName -> SoulboundIdentity.tokenId
    // SoulName -> account -> SoulboundIdentity.tokenId

    /// @notice Returns all the active soul names of an account
    /// @dev This function queries all the identity names of the specified identity Id
    /// @param tokenId TokenId of the identity
    /// @return sbtNames Array of soul names associated to the identity Id
    function getSoulNames(uint256 tokenId)
        external
        view
        soulNameAlreadySet
        returns (string[] memory sbtNames)
    {
        return soulName.getSoulNames(tokenId);
    }

    /* ========== PRIVATE FUNCTIONS ========================================= */

    /* ========== MODIFIERS ================================================= */

    modifier soulNameAlreadySet() {
        if (address(soulName) == address(0)) revert SoulNameContractNotSet();
        _;
    }

    /* ========== EVENTS ==================================================== */
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

error AddressDoesNotHaveIdentity(address to);
error AlreadyAdded();
error AuthorityNotExists(address authority);
error CallerNotOwner(address caller);
error CallerNotReader(address caller);
error CreditScoreAlreadyCreated(address to);
error IdentityAlreadyCreated(address to);
error IdentityOwnerIsReader(uint256 readerIdentityId);
error InsufficientEthAmount(uint256 amount);
error IdentityOwnerNotTokenOwner(uint256 tokenId, uint256 ownerIdentityId);
error InvalidPaymentMethod(address paymentMethod);
error InvalidSignature();
error InvalidSignatureDate(uint256 signatureDate);
error InvalidToken(address token);
error InvalidTokenURI(string tokenURI);
error LinkAlreadyExists(
    address token,
    uint256 tokenId,
    uint256 readerIdentityId,
    uint256 signatureDate
);
error LinkAlreadyRevoked();
error LinkDoesNotExist();
error NameAlreadyExists(string name);
error NameNotFound(string name);
error NameRegisteredByOtherAccount(string name, uint256 tokenId);
error NotAuthorized(address signer);
error NonExistingErc20Token(address erc20token);
error RefundFailed();
error SameValue();
error SBTAlreadyLinked(address token);
error SoulNameContractNotSet();
error TokenNotFound(uint256 tokenId);
error TransferFailed();
error URIAlreadyExists(string tokenURI);
error ValidPeriodExpired(uint256 expirationDate);
error ZeroAddress();
error ZeroLengthName(string name);
error ZeroYearsPeriod(uint256 yearsPeriod);

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "../tokens/SBT/ISBT.sol";

import "./ISoulName.sol";

interface ISoulboundIdentity is ISBT {
    function mint(address to) external returns (uint256);

    function mintIdentityWithName(
        address to,
        string memory name,
        uint256 yearsPeriod,
        string memory _tokenURI
    ) external returns (uint256);

    function getSoulName() external view returns (ISoulName);

    function tokenOfOwner(address owner) external view returns (uint256);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

interface ISoulName {
    function mint(
        address to,
        string memory name,
        uint256 yearsPeriod,
        string memory _tokenURI
    ) external returns (uint256);

    function getExtension() external view returns (string memory);

    function isAvailable(string memory name)
        external
        view
        returns (bool available);

    function getTokenData(string memory name)
        external
        view
        returns (
            string memory sbtName,
            bool linked,
            uint256 identityId,
            uint256 tokenId,
            uint256 expirationDate,
            bool active
        );

    function getTokenId(string memory name) external view returns (uint256);

    function getSoulNames(address owner)
        external
        view
        returns (string[] memory sbtNames);

    function getSoulNames(uint256 identityId)
        external
        view
        returns (string[] memory sbtNames);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/utils/Counters.sol";

import "./MasaSBT.sol";

/// @title MasaSBT
/// @author Masa Finance
/// @notice Soulbound token. Non-fungible token that is not transferable.
/// @dev Implementation of https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4105763 Soulbound token.
abstract contract MasaSBTAuthority is MasaSBT {
    /* ========== STATE VARIABLES =========================================== */

    using Counters for Counters.Counter;

    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
    Counters.Counter private _tokenIdCounter;

    /* ========== INITIALIZE ================================================ */

    /// @notice Creates a new soulbound token
    /// @dev Creates a new soulbound token
    /// @param admin Administrator of the smart contract
    /// @param name Name of the token
    /// @param symbol Symbol of the token
    /// @param baseTokenURI Base URI of the token
    constructor(
        address admin,
        string memory name,
        string memory symbol,
        string memory baseTokenURI
    ) MasaSBT(admin, name, symbol, baseTokenURI) {
        _grantRole(MINTER_ROLE, admin);
    }

    /* ========== RESTRICTED FUNCTIONS ====================================== */

    function _mintWithCounter(address to)
        internal
        virtual
        onlyRole(MINTER_ROLE)
        returns (uint256)
    {
        uint256 tokenId = _tokenIdCounter.current();
        _tokenIdCounter.increment();
        _mint(to, tokenId);

        return tokenId;
    }

    /* ========== MUTATIVE FUNCTIONS ======================================== */

    /* ========== VIEWS ===================================================== */

    /* ========== PRIVATE FUNCTIONS ========================================= */

    /* ========== MODIFIERS ================================================= */

    /* ========== EVENTS ==================================================== */
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/utils/introspection/IERC165.sol";

interface ISBT is IERC165 {
    /// @dev This emits when an SBT is newly minted.
    ///  This event emits when SBTs are created
    event Mint(address indexed _owner, uint256 indexed _tokenId);

    /// @dev This emits when an SBT is burned
    ///  This event emits when SBTs are destroyed
    event Burn(address indexed _owner, uint256 indexed _tokenId);

    /// @notice Count all SBTs assigned to an owner
    /// @dev SBTs 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 SBTs owned by `_owner`, possibly zero
    function balanceOf(address _owner) external view returns (uint256);

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

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

pragma solidity ^0.8.0;

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

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

pragma solidity ^0.8.0;

/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 */
library Counters {
    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        unchecked {
            counter._value += 1;
        }
    }

    function decrement(Counter storage counter) internal {
        uint256 value = counter._value;
        require(value > 0, "Counter: decrement overflow");
        unchecked {
            counter._value = value - 1;
        }
    }

    function reset(Counter storage counter) internal {
        counter._value = 0;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/utils/Strings.sol";

import "../libraries/Errors.sol";
import "../interfaces/ILinkableSBT.sol";
import "./SBT/SBT.sol";
import "./SBT/extensions/SBTEnumerable.sol";
import "./SBT/extensions/SBTBurnable.sol";

/// @title MasaSBT
/// @author Masa Finance
/// @notice Soulbound token. Non-fungible token that is not transferable.
/// @dev Implementation of https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4105763 Soulbound token.
abstract contract MasaSBT is
    SBT,
    SBTEnumerable,
    AccessControl,
    SBTBurnable,
    ILinkableSBT
{
    /* ========== STATE VARIABLES =========================================== */

    using Strings for uint256;

    string private _baseTokenURI;

    uint256 public override addLinkPrice; // price in stable coin
    uint256 public override addLinkPriceMASA; // price in MASA
    uint256 public override queryLinkPrice; // price in stable coin
    uint256 public override queryLinkPriceMASA; // price in MASA

    /* ========== INITIALIZE ================================================ */

    /// @notice Creates a new soulbound token
    /// @dev Creates a new soulbound token
    /// @param admin Administrator of the smart contract
    /// @param name Name of the token
    /// @param symbol Symbol of the token
    /// @param baseTokenURI Base URI of the token
    constructor(
        address admin,
        string memory name,
        string memory symbol,
        string memory baseTokenURI
    ) SBT(name, symbol) {
        _grantRole(DEFAULT_ADMIN_ROLE, admin);

        _baseTokenURI = baseTokenURI;
    }

    /* ========== RESTRICTED FUNCTIONS ====================================== */

    /// @notice Sets the price for adding the link in SoulLinker in stable coin
    /// @dev The caller must have the admin role to call this function
    /// @param _addLinkPrice New price for adding the link in SoulLinker in stable coin
    function setAddLinkPrice(uint256 _addLinkPrice)
        external
        onlyRole(DEFAULT_ADMIN_ROLE)
    {
        if (addLinkPrice == _addLinkPrice) revert SameValue();
        addLinkPrice = _addLinkPrice;
    }

    /// @notice Sets the price for adding the link in SoulLinker in MASA
    /// @dev The caller must have the admin role to call this function
    /// @param _addLinkPriceMASA New price for adding the link in SoulLinker in MASA
    function setAddLinkPriceMASA(uint256 _addLinkPriceMASA)
        external
        onlyRole(DEFAULT_ADMIN_ROLE)
    {
        if (addLinkPriceMASA == _addLinkPriceMASA) revert SameValue();
        addLinkPriceMASA = _addLinkPriceMASA;
    }

    /// @notice Sets the price for reading data in SoulLinker in stable coin
    /// @dev The caller must have the admin role to call this function
    /// @param _queryLinkPrice New price for reading data in SoulLinker in stable coin
    function setQueryLinkPrice(uint256 _queryLinkPrice)
        external
        onlyRole(DEFAULT_ADMIN_ROLE)
    {
        if (queryLinkPrice == _queryLinkPrice) revert SameValue();
        queryLinkPrice = _queryLinkPrice;
    }

    /// @notice Sets the price for reading data in SoulLinker in MASA
    /// @dev The caller must have the admin role to call this function
    /// @param _queryLinkPriceMASA New price for reading data in SoulLinker in MASA
    function setQueryLinkPriceMASA(uint256 _queryLinkPriceMASA)
        external
        onlyRole(DEFAULT_ADMIN_ROLE)
    {
        if (queryLinkPriceMASA == _queryLinkPriceMASA) revert SameValue();
        queryLinkPriceMASA = _queryLinkPriceMASA;
    }

    /* ========== MUTATIVE FUNCTIONS ======================================== */

    /* ========== VIEWS ===================================================== */

    /// @notice Returns true if the token exists
    /// @dev Returns true if the token has been minted
    /// @param tokenId Token to check
    /// @return True if the token exists
    function exists(uint256 tokenId) external view returns (bool) {
        return _exists(tokenId);
    }

    /// @notice A distinct Uniform Resource Identifier (URI) for a given asset.
    /// @dev Throws if `_tokenId` is not a valid SBT. URIs are defined in RFC
    ///  3986. The URI may point to a JSON file that conforms to the "ERC721
    ///  Metadata JSON Schema".
    /// @param tokenId SBT to get the URI of
    /// @return URI of the SBT
    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override
        returns (string memory)
    {
        _requireMinted(tokenId);

        string memory baseURI = _baseURI();
        return
            bytes(baseURI).length > 0
                ? string(abi.encodePacked(baseURI, tokenId.toString(), ".json"))
                : "";
    }

    /// @notice Query if a contract implements an interface
    /// @dev Interface identification is specified in ERC-165.
    /// @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)
        public
        view
        virtual
        override(SBT, SBTEnumerable, AccessControl, IERC165)
        returns (bool)
    {
        return super.supportsInterface(interfaceId);
    }

    /* ========== PRIVATE FUNCTIONS ========================================= */

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

    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual override(SBT, SBTEnumerable) {
        super._beforeTokenTransfer(from, to, tokenId);
    }

    /* ========== MODIFIERS ================================================= */

    /* ========== EVENTS ==================================================== */
}

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

pragma solidity ^0.8.0;

import "./IAccessControl.sol";
import "../utils/Context.sol";
import "../utils/Strings.sol";
import "../utils/introspection/ERC165.sol";

/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms. This is a lightweight version that doesn't allow enumerating role
 * members except through off-chain means by accessing the contract event logs. Some
 * applications may benefit from on-chain enumerability, for those cases see
 * {AccessControlEnumerable}.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context, IAccessControl, ERC165 {
    struct RoleData {
        mapping(address => bool) members;
        bytes32 adminRole;
    }

    mapping(bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @dev Modifier that checks that an account has a specific role. Reverts
     * with a standardized message including the required role.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     *
     * _Available since v4.1._
     */
    modifier onlyRole(bytes32 role) {
        _checkRole(role);
        _;
    }

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

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view virtual override returns (bool) {
        return _roles[role].members[account];
    }

    /**
     * @dev Revert with a standard message if `_msgSender()` is missing `role`.
     * Overriding this function changes the behavior of the {onlyRole} modifier.
     *
     * Format of the revert message is described in {_checkRole}.
     *
     * _Available since v4.6._
     */
    function _checkRole(bytes32 role) internal view virtual {
        _checkRole(role, _msgSender());
    }

    /**
     * @dev Revert with a standard message if `account` is missing `role`.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     */
    function _checkRole(bytes32 role, address account) internal view virtual {
        if (!hasRole(role, account)) {
            revert(
                string(
                    abi.encodePacked(
                        "AccessControl: account ",
                        Strings.toHexString(uint160(account), 20),
                        " is missing role ",
                        Strings.toHexString(uint256(role), 32)
                    )
                )
            );
        }
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view virtual override returns (bytes32) {
        return _roles[role].adminRole;
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     *
     * May emit a {RoleGranted} event.
     */
    function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
        _grantRole(role, account);
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     *
     * May emit a {RoleRevoked} event.
     */
    function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
        _revokeRole(role, account);
    }

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been revoked `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     *
     * May emit a {RoleRevoked} event.
     */
    function renounceRole(bytes32 role, address account) public virtual override {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");

        _revokeRole(role, account);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * May emit a {RoleGranted} event.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     *
     * NOTE: This function is deprecated in favor of {_grantRole}.
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        bytes32 previousAdminRole = getRoleAdmin(role);
        _roles[role].adminRole = adminRole;
        emit RoleAdminChanged(role, previousAdminRole, adminRole);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * Internal function without access restriction.
     *
     * May emit a {RoleGranted} event.
     */
    function _grantRole(bytes32 role, address account) internal virtual {
        if (!hasRole(role, account)) {
            _roles[role].members[account] = true;
            emit RoleGranted(role, account, _msgSender());
        }
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * Internal function without access restriction.
     *
     * May emit a {RoleRevoked} event.
     */
    function _revokeRole(bytes32 role, address account) internal virtual {
        if (hasRole(role, account)) {
            _roles[role].members[account] = false;
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

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

pragma solidity ^0.8.0;

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

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

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

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

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

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

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "../tokens/SBT/ISBT.sol";

interface ILinkableSBT is ISBT {
    function addLinkPrice() external view returns (uint256);

    function addLinkPriceMASA() external view returns (uint256);

    function queryLinkPrice() external view returns (uint256);

    function queryLinkPriceMASA() external view returns (uint256);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/utils/introspection/ERC165.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/utils/Strings.sol";

import "./ISBT.sol";
import "./extensions/ISBTMetadata.sol";

/// @title SBT
/// @author Masa Finance
/// @notice Soulbound token is an NFT token that is not transferable.
contract SBT is Context, ERC165, ISBT, ISBTMetadata {
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

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

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

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

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

    /**
     * @dev See {ISBT-balanceOf}.
     */
    function balanceOf(address owner)
        public
        view
        virtual
        override
        returns (uint256)
    {
        require(owner != address(0), "SBT: address zero is not a valid owner");
        return _balances[owner];
    }

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

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

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

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

        string memory baseURI = _baseURI();
        return
            bytes(baseURI).length > 0
                ? string(abi.encodePacked(baseURI, tokenId.toString()))
                : "";
    }

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

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

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

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Mint} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "SBT: mint to the zero address");
        require(!_exists(tokenId), "SBT: token already minted");

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

        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Mint(to, tokenId);

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

    /**
     * @dev Destroys `tokenId`.
     *
     * Requirements:
     * - `tokenId` must exist.
     *
     * Emits a {Burn} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = SBT.ownerOf(tokenId);

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

        _balances[owner] -= 1;
        delete _owners[tokenId];

        emit Burn(owner, tokenId);

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

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

    /**
     * @dev Hook that is called before any token minting/burning
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` 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,
        address,
        uint256
    ) internal virtual {}

    /**
     * @dev Hook that is called after any minting/burning of tokens
     *
     * Calling conditions:
     * - when `from` and `to` are both non-zero.
     * - `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,
        address,
        uint256
    ) internal virtual {}
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "../SBT.sol";
import "./ISBTEnumerable.sol";

/**
 * @dev This implements an optional extension of {SBT} defined in the EIP that adds
 * enumerability of all the token ids in the contract as well as all token ids owned by each
 * account.
 */
abstract contract SBTEnumerable is SBT, ISBTEnumerable {
    // Mapping from owner to list of owned token IDs
    mapping(address => mapping(uint256 => uint256)) private _ownedTokens;

    // Mapping from token ID to index of the owner tokens list
    mapping(uint256 => uint256) private _ownedTokensIndex;

    // Array with all token ids, used for enumeration
    uint256[] private _allTokens;

    // Mapping from token id to position in the allTokens array
    mapping(uint256 => uint256) private _allTokensIndex;

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

    /**
     * @dev See {ISBTEnumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index)
        public
        view
        virtual
        override
        returns (uint256)
    {
        require(
            index < SBT.balanceOf(owner),
            "SBTEnumerable: owner index out of bounds"
        );
        return _ownedTokens[owner][index];
    }

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

    /**
     * @dev See {ISBTEnumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index)
        public
        view
        virtual
        override
        returns (uint256)
    {
        require(
            index < SBTEnumerable.totalSupply(),
            "SBTEnumerable: global index out of bounds"
        );
        return _allTokens[index];
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual override {
        super._beforeTokenTransfer(from, to, tokenId);

        if (from == address(0)) {
            _addTokenToAllTokensEnumeration(tokenId);
        } else if (from != to) {
            _removeTokenFromOwnerEnumeration(from, tokenId);
        }
        if (to == address(0)) {
            _removeTokenFromAllTokensEnumeration(tokenId);
        } else if (to != from) {
            _addTokenToOwnerEnumeration(to, tokenId);
        }
    }

    /**
     * @dev Private function to add a token to this extension's ownership-tracking data structures.
     * @param to address representing the new owner of the given token ID
     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
     */
    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        uint256 length = SBT.balanceOf(to);
        _ownedTokens[to][length] = tokenId;
        _ownedTokensIndex[tokenId] = length;
    }

    /**
     * @dev Private function to add a token to this extension's token tracking data structures.
     * @param tokenId uint256 ID of the token to be added to the tokens list
     */
    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    /**
     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
     * @param from address representing the previous owner of the given token ID
     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
     */
    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId)
        private
    {
        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = SBT.balanceOf(from) - 1;
        uint256 tokenIndex = _ownedTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
        }

        // This also deletes the contents at the last position of the array
        delete _ownedTokensIndex[tokenId];
        delete _ownedTokens[from][lastTokenIndex];
    }

    /**
     * @dev Private function to remove a token from this extension's token tracking data structures.
     * This has O(1) time complexity, but alters the order of the _allTokens array.
     * @param tokenId uint256 ID of the token to be removed from the tokens list
     */
    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _allTokens.length - 1;
        uint256 tokenIndex = _allTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
        uint256 lastTokenId = _allTokens[lastTokenIndex];

        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        // This also deletes the contents at the last position of the array
        delete _allTokensIndex[tokenId];
        _allTokens.pop();
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/utils/Context.sol";

import "../SBT.sol";

/**
 * @title SBT Burnable Token
 * @dev SBT Token that can be burned (destroyed).
 */
abstract contract SBTBurnable is Context, SBT {
    /**
     * @dev Burns `tokenId`. See {SBT-_burn}.
     *
     * Requirements:
     *
     * - The caller must own `tokenId` or be an approved operator.
     */
    function burn(uint256 tokenId) public virtual {
        //solhint-disable-next-line max-line-length
        require(
            _isOwner(_msgSender(), tokenId),
            "SBT: caller is not token owner"
        );
        _burn(tokenId);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/IAccessControl.sol)

pragma solidity ^0.8.0;

/**
 * @dev External interface of AccessControl declared to support ERC165 detection.
 */
interface IAccessControl {
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {AccessControl-_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) external view returns (bool);

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {AccessControl-_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) external view returns (bytes32);

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) external;
}

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

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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

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

pragma solidity ^0.8.0;

import "./IERC165.sol";

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

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "../ISBT.sol";

/**
 * @title SBT Soulbound Token Standard, optional metadata extension
 */
interface ISBTMetadata is ISBT {
    /**
     * @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);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "../ISBT.sol";

/**
 * @title SBT Soulbound Token Standard, optional enumeration extension
 */
interface ISBTEnumerable is ISBT {
    /**
     * @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);

    /**
     * @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);
}

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