// File: contracts/LootItems.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/access/Ownable.sol";
import "./interfaces/ERC1155/ERC1155Tradable.sol";

contract LootItems is ERC1155Tradable {
    /**
     * @dev Initialize LootItems
     */
    constructor(string memory baseURI, address proxyRegistryAddress)
        public
        ERC1155Tradable("Loot", "ITEMS", proxyRegistryAddress)
    {
        super._setBaseMetadataURI(baseURI);
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

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

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

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

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

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

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

// File: contracts/interfaces/ERC1155/ERC1155Tradable.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

// OpenSea ProxyRegistry Interface
// import {IProxyRegistry} from "../IProxyRegistry.sol";
import "../IProxyRegistry.sol";

// ERC1155 Interfaces
import "./ERC1155.sol";
import "./ERC1155MintBurn.sol";
import "./ERC1155Metadata.sol";

contract ERC1155Tradable is
    ERC1155,
    ERC1155MintBurn,
    ERC1155Metadata,
    AccessControl
{
    /***********************************|
    |   Constants                       |
    |__________________________________*/
    // Items Metadata
    string public name;
    string public symbol;

    // Access Control
    bytes32 public constant CONTROLLER_ROLE = keccak256("CONTROLLER_ROLE");
    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");

    // Internals
    uint256 internal _currentTokenID = 0;

    // Token Metadata
    mapping(uint256 => address) public creators;
    mapping(uint256 => uint256) public tokenSupply;
    mapping(uint256 => uint256) public tokenMaxSupply;

    // Native IPFS Support
    bool public ipfsURIs = false;
    mapping(uint256 => string) public ipfs;

    // OpenSea Integration
    address proxyRegistryAddress;

    constructor(
        string memory _name,
        string memory _symbol,
        address _proxyRegistryAddress
    ) public {
        name = _name;
        symbol = _symbol;
        proxyRegistryAddress = _proxyRegistryAddress;

        // Setup Role Management
        _setRoleAdmin(CONTROLLER_ROLE, CONTROLLER_ROLE);
        _setRoleAdmin(MINTER_ROLE, CONTROLLER_ROLE);

        // Set Initial Controller as Contract Deployer
        _setupRole(CONTROLLER_ROLE, msg.sender);
    }

    /***********************************|
    |   Events                          |
    |__________________________________*/
    /**
     * @dev A new item is created.
     */
    event ItemCreated(
        uint256 id,
        uint256 tokenInitialSupply,
        uint256 tokenMaxSupply,
        string ipfs
    );

    /**
     * @dev An item is updated.
     */
    event ItemUpdated(uint256 id, string ipfs);

    /***********************************|
    |   Items                           |
    |__________________________________*/

    /**
     * @dev Returns the total quantity for a token ID
     * @param _id uint256 ID of the token to query
     * @return amount of token in existence
     */
    function totalSupply(uint256 _id) public view returns (uint256) {
        return tokenSupply[_id];
    }

    /**
     * @dev Returns the max quantity for a token ID
     * @param _id uint256 ID of the token to query
     * @return amount of token in existence
     */
    function maxSupply(uint256 _id) public view returns (uint256) {
        return tokenMaxSupply[_id];
    }

    /**
     * @dev Creates a new token type and assigns _initialSupply to an address
     * @param _maxSupply max supply allowed
     * @param _initialSupply Optional amount to supply the first owner
     * @param _uri Optional URI for this token type
     * @param _data Optional data to pass if receiver is contract
     * @return _id The newly created token ID
     */
    function create(
        uint256 _initialSupply,
        uint256 _maxSupply,
        string calldata _uri,
        bytes calldata _data,
        string calldata _ipfs
    ) public returns (uint256 _id) {
        // Minter Role Required
        require(hasRole(MINTER_ROLE, msg.sender), "Unauthorized");

        // Sanity Check
        require(0 < _maxSupply, "Insufficient Max Supply");
        require(_initialSupply <= _maxSupply, "Invalid Initial Supply");

        // Calculate Token ID
        _id = _getNextTokenID();
        _incrementTokenTypeId();

        // Unique Item URI
        if (bytes(_uri).length > 0) {
            emit URI(_uri, _id);
        }

        // Mint Token if Initial Supply Above Zero
        if (_initialSupply != 0) {
            super._mint(msg.sender, _id, _initialSupply, _data);
        }

        // Item Mappings
        creators[_id] = msg.sender;
        tokenMaxSupply[_id] = _maxSupply;
        tokenSupply[_id] = _initialSupply;

        // IPFS Mapping
        ipfs[_id] = _ipfs;

        emit ItemCreated(_id, _initialSupply, _maxSupply, _ipfs);
        return _id;
    }

    /**
     * @dev Creates a new token type and assigns _initialSupply to an address
     * @param _maxSupply max supply allowed
     * @param _initialSupply Optional amount to supply the first owner
     * @param _uri Optional URI for this token type
     * @param _data Optional data to pass if receiver is contract
     * @return _id The newly created token ID
     */
    function createBatch(
        uint256[] calldata _initialSupply,
        uint256[] calldata _maxSupply,
        string[] calldata _uri,
        bytes[] calldata _data,
        string[] calldata _ipfs
    ) external returns (bool) {
        // Minter Role Required
        require(hasRole(MINTER_ROLE, msg.sender), "Unauthorized");

        // Iterate Items
        for (uint256 index = 0; index < _initialSupply.length; index++) {
            create(
                _initialSupply[index],
                _maxSupply[index],
                _uri[index],
                _data[index],
                _ipfs[index]
            );
        }

        return true;
    }

    /**
     * @dev Mint _value of tokens of a given id
     * @param _to The address to mint tokens to.
     * @param _id token id to mint
     * @param _amount The amount to be minted
     * @param _data Data to be passed if receiver is contract
     */
    function mint(
        address _to,
        uint256 _id,
        uint256 _amount,
        bytes memory _data
    ) public returns (bool) {
        // Minter Role Required
        require(hasRole(MINTER_ROLE, msg.sender), "Unauthorized");

        // Check Max Supply
        require(
            tokenSupply[_id].add(_amount) <= tokenMaxSupply[_id],
            "Max Supply Reached"
        );

        // Update Item Amount
        tokenSupply[_id] = tokenSupply[_id].add(_amount);

        // Mint Item
        super._mint(_to, _id, _amount, _data);

        return true;
    }

    /***********************************|
    |   Item Metadata                   |
    |__________________________________*/

    /**
     * @notice A distinct Uniform Resource Identifier (URI) for a given token.
     * @dev URIs are defined in RFC 3986.
     *      Override default URI specification for mapping to IPFS hash
     * @param _id item id
     * @return URI string
     */
    function uri(uint256 _id) public view returns (string memory) {
        require(_exists(_id), "ERC1155Tradable#uri: NONEXISTENT_TOKEN");
        return
            ipfsURIs
                ? string(abi.encodePacked("ipfs://", ipfs[_id]))
                : super._uri(_id);
    }

    /**
     * @notice Toggle IPFS mapping used as tokenURI
     * @dev Toggle IPFS mapping used as tokenURI
     * @return ipfsURIs bool
     */
    function toggleIPFS() external returns (bool) {
        require(hasRole(CONTROLLER_ROLE, msg.sender));
        ipfsURIs = ipfsURIs ? false : true;
        return ipfsURIs;
    }

    /**
     * @notice Batch Update Item URIs
     * @param _ids Array of item ids
     * @param _newBaseMetadataURI New base URL of token's URI
     */
    function updateItemsURI(
        uint256[] calldata _ids,
        string memory _newBaseMetadataURI
    ) external returns (bool) {
        require(hasRole(CONTROLLER_ROLE, msg.sender));
        if (bytes(_newBaseMetadataURI).length > 0) {
            super._setBaseMetadataURI(_newBaseMetadataURI);
        }
        super._logURIs(_ids);
    }

    /**
     * @dev Will update the base URL of token's URI
     * @param _newBaseMetadataURI New base URL of token's URI
     */
    function setBaseMetadataURI(string memory _newBaseMetadataURI) external {
        require(hasRole(CONTROLLER_ROLE, msg.sender));
        super._setBaseMetadataURI(_newBaseMetadataURI);
    }

    /***********************************|
    |   Item Transfers                  |
    |__________________________________*/

    /**
     * Override isApprovedForAll to whitelist user's OpenSea proxy accounts to enable gas-free listings.
     */
    function isApprovedForAll(address _owner, address _operator)
        public
        view
        override
        returns (bool isOperator)
    {
        // Whitelist OpenSea proxy contract for easy trading.
        IProxyRegistry proxyRegistry = IProxyRegistry(proxyRegistryAddress);
        if (address(proxyRegistry.proxies(_owner)) == _operator) {
            return true;
        }

        return ERC1155.isApprovedForAll(_owner, _operator);
    }

    /***********************************|
    |   Helpers                         |
    |__________________________________*/

    /**
     * @notice Check item exists using creators
     * @dev Returns whether the specified token exists by checking to see if it has a creator
     * @param _id uint256 ID of the token to query the existence of
     * @return bool whether the token exists
     */
    function _exists(uint256 _id) internal view returns (bool) {
        return creators[_id] != address(0);
    }

    /**
     * @dev calculates the next token ID based on value of _currentTokenID
     * @return uint256 for the next token ID
     */
    function _getNextTokenID() internal view returns (uint256) {
        return _currentTokenID.add(1);
    }

    /**
     * @dev increments the value of _currentTokenID
     */
    function _incrementTokenTypeId() internal {
        _currentTokenID++;
    }

    /***********************************|
    |   ERC165                          |
    |__________________________________*/
    bytes4 private constant INTERFACE_SIGNATURE_ERC165 = 0x01ffc9a7;
    bytes4 private constant INTERFACE_SIGNATURE_ERC1155 = 0xd9b67a26;

    function supportsInterface(bytes4 _interfaceID)
        public
        pure
        override(ERC1155, ERC1155Metadata)
        returns (bool)
    {
        if (
            _interfaceID == INTERFACE_SIGNATURE_ERC165 ||
            _interfaceID == INTERFACE_SIGNATURE_ERC1155
        ) {
            return true;
        }
        return false;
    }
}

// File: @openzeppelin/contracts/GSN/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/*
 * @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 GSN 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 payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/AccessControl.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../utils/EnumerableSet.sol";
import "../utils/Address.sol";
import "../GSN/Context.sol";

/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * 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 {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;

    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }

    mapping (bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @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 {_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) public view returns (bool) {
        return _roles[role].members.contains(account);
    }

    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }

    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }

    /**
     * @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 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.
     */
    function grantRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");

        _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.
     */
    function revokeRole(bytes32 role, address account) public virtual {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");

        _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 granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual {
        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.
     *
     * [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}.
     * ====
     */
    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 {
        emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }

    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }

    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// File: contracts/interfaces/IProxyRegistry.sol



// SPDX-License-Identifier: WTFPL
pragma solidity ^0.6.0;

contract OwnableDelegateProxy {}

contract IProxyRegistry {
    mapping(address => OwnableDelegateProxy) public proxies;
}

// File: contracts/interfaces/ERC1155/ERC1155.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;

import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "./interfaces/IERC1155TokenReceiver.sol";
import "./interfaces/IERC1155.sol";
import "./ERC165.sol";

/**
 * @dev Implementation of Multi-Token Standard contract
 */
contract ERC1155 is IERC1155, ERC165 {
    using Address for address;
    using SafeMath for uint256;

    // onReceive function signatures
    bytes4 internal constant ERC1155_RECEIVED_VALUE = 0xf23a6e61;
    bytes4 internal constant ERC1155_BATCH_RECEIVED_VALUE = 0xbc197c81;

    // Objects balances
    mapping(address => mapping(uint256 => uint256)) internal balances;

    // Operator Functions
    mapping(address => mapping(address => bool)) internal operators;

    /***********************************|
    |     Public Transfer Functions     |
    |__________________________________*/
    /**
     * @notice Transfers amount amount of an _id from the _from address to the _to address specified
     * @param _from    Source address
     * @param _to      Target address
     * @param _id      ID of the token type
     * @param _amount  Transfered amount
     * @param _data    Additional data with no specified format, sent in call to `_to`
     */
    function safeTransferFrom(
        address _from,
        address _to,
        uint256 _id,
        uint256 _amount,
        bytes memory _data
    ) public override {
        require(
            (msg.sender == _from) || isApprovedForAll(_from, msg.sender),
            "ERC1155#safeTransferFrom: INVALID_OPERATOR"
        );
        require(
            _to != address(0),
            "ERC1155#safeTransferFrom: INVALID_RECIPIENT"
        );
        // require(_amount <= balances[_from][_id]) is not necessary since checked with safemath operations

        _safeTransferFrom(_from, _to, _id, _amount);
        _callonERC1155Received(_from, _to, _id, _amount, gasleft(), _data);
    }

    /**
     * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
     * @param _from     Source addresses
     * @param _to       Target addresses
     * @param _ids      IDs of each token type
     * @param _amounts  Transfer amounts per token type
     * @param _data     Additional data with no specified format, sent in call to `_to`
     */
    function safeBatchTransferFrom(
        address _from,
        address _to,
        uint256[] memory _ids,
        uint256[] memory _amounts,
        bytes memory _data
    ) public override {
        // Requirements
        require(
            (msg.sender == _from) || isApprovedForAll(_from, msg.sender),
            "ERC1155#safeBatchTransferFrom: INVALID_OPERATOR"
        );
        require(
            _to != address(0),
            "ERC1155#safeBatchTransferFrom: INVALID_RECIPIENT"
        );

        _safeBatchTransferFrom(_from, _to, _ids, _amounts);
        _callonERC1155BatchReceived(
            _from,
            _to,
            _ids,
            _amounts,
            gasleft(),
            _data
        );
    }

    /***********************************|
  |    Internal Transfer Functions    |
  |__________________________________*/

    /**
     * @notice Transfers amount amount of an _id from the _from address to the _to address specified
     * @param _from    Source address
     * @param _to      Target address
     * @param _id      ID of the token type
     * @param _amount  Transfered amount
     */
    function _safeTransferFrom(
        address _from,
        address _to,
        uint256 _id,
        uint256 _amount
    ) internal {
        // Update balances
        balances[_from][_id] = balances[_from][_id].sub(_amount); // Subtract amount
        balances[_to][_id] = balances[_to][_id].add(_amount); // Add amount

        // Emit event
        emit TransferSingle(msg.sender, _from, _to, _id, _amount);
    }

    /**
     * @notice Verifies if receiver is contract and if so, calls (_to).onERC1155Received(...)
     */
    function _callonERC1155Received(
        address _from,
        address _to,
        uint256 _id,
        uint256 _amount,
        uint256 _gasLimit,
        bytes memory _data
    ) internal {
        // Check if recipient is contract
        if (_to.isContract()) {
            bytes4 retval =
                IERC1155TokenReceiver(_to).onERC1155Received{gas: _gasLimit}(
                    msg.sender,
                    _from,
                    _id,
                    _amount,
                    _data
                );
            require(
                retval == ERC1155_RECEIVED_VALUE,
                "ERC1155#_callonERC1155Received: INVALID_ON_RECEIVE_MESSAGE"
            );
        }
    }

    /**
     * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
     * @param _from     Source addresses
     * @param _to       Target addresses
     * @param _ids      IDs of each token type
     * @param _amounts  Transfer amounts per token type
     */
    function _safeBatchTransferFrom(
        address _from,
        address _to,
        uint256[] memory _ids,
        uint256[] memory _amounts
    ) internal {
        require(
            _ids.length == _amounts.length,
            "ERC1155#_safeBatchTransferFrom: INVALID_ARRAYS_LENGTH"
        );

        // Number of transfer to execute
        uint256 nTransfer = _ids.length;

        // Executing all transfers
        for (uint256 i = 0; i < nTransfer; i++) {
            // Update storage balance of previous bin
            balances[_from][_ids[i]] = balances[_from][_ids[i]].sub(
                _amounts[i]
            );
            balances[_to][_ids[i]] = balances[_to][_ids[i]].add(_amounts[i]);
        }

        // Emit event
        emit TransferBatch(msg.sender, _from, _to, _ids, _amounts);
    }

    /**
     * @notice Verifies if receiver is contract and if so, calls (_to).onERC1155BatchReceived(...)
     */
    function _callonERC1155BatchReceived(
        address _from,
        address _to,
        uint256[] memory _ids,
        uint256[] memory _amounts,
        uint256 _gasLimit,
        bytes memory _data
    ) internal {
        // Pass data if recipient is contract
        if (_to.isContract()) {
            bytes4 retval =
                IERC1155TokenReceiver(_to).onERC1155BatchReceived{
                    gas: _gasLimit
                }(msg.sender, _from, _ids, _amounts, _data);
            require(
                retval == ERC1155_BATCH_RECEIVED_VALUE,
                "ERC1155#_callonERC1155BatchReceived: INVALID_ON_RECEIVE_MESSAGE"
            );
        }
    }

    /***********************************|
  |         Operator Functions        |
  |__________________________________*/

    /**
     * @notice Enable or disable approval for a third party ("operator") to manage all of caller's tokens
     * @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
        override
    {
        // Update operator status
        operators[msg.sender][_operator] = _approved;
        emit ApprovalForAll(msg.sender, _operator, _approved);
    }

    /**
     * @notice Queries the approval status of an operator for a given owner
     * @param _owner     The owner of the Tokens
     * @param _operator  Address of authorized operator
     * @return isOperator True if the operator is approved, false if not
     */
    function isApprovedForAll(address _owner, address _operator)
        public
        view
        virtual
        override
        returns (bool isOperator)
    {
        return operators[_owner][_operator];
    }

    /***********************************|
  |         Balance Functions         |
  |__________________________________*/

    /**
     * @notice Get the balance of an account's Tokens
     * @param _owner  The address of the token holder
     * @param _id     ID of the Token
     * @return The _owner's balance of the Token type requested
     */
    function balanceOf(address _owner, uint256 _id)
        public
        view
        override
        returns (uint256)
    {
        return balances[_owner][_id];
    }

    /**
     * @notice Get the balance of multiple account/token pairs
     * @param _owners The addresses of the token holders
     * @param _ids    ID of the Tokens
     * @return        The _owner's balance of the Token types requested (i.e. balance for each (owner, id) pair)
     */
    function balanceOfBatch(address[] memory _owners, uint256[] memory _ids)
        public
        view
        override
        returns (uint256[] memory)
    {
        require(
            _owners.length == _ids.length,
            "ERC1155#balanceOfBatch: INVALID_ARRAY_LENGTH"
        );

        // Variables
        uint256[] memory batchBalances = new uint256[](_owners.length);

        // Iterate over each owner and token ID
        for (uint256 i = 0; i < _owners.length; i++) {
            batchBalances[i] = balances[_owners[i]][_ids[i]];
        }

        return batchBalances;
    }

    /***********************************|
  |          ERC165 Functions         |
  |__________________________________*/

    /**
     * @notice Query if a contract implements an interface
     * @param _interfaceID  The interface identifier, as specified in ERC-165
     * @return `true` if the contract implements `_interfaceID` and
     */
    function supportsInterface(bytes4 _interfaceID)
        public
        pure
        virtual
        override
        returns (bool)
    {
        if (_interfaceID == type(IERC1155).interfaceId) {
            return true;
        }
        return super.supportsInterface(_interfaceID);
    }
}

// File: contracts/interfaces/ERC1155/ERC1155MintBurn.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;
import "./ERC1155.sol";

/**
 * @dev Multi-Fungible Tokens with minting and burning methods. These methods assume
 *      a parent contract to be executed as they are `internal` functions
 */
contract ERC1155MintBurn is ERC1155 {
    /****************************************|
    |   Minting                              |
    |_______________________________________*/

    /**
     * @notice Mint _amount of tokens of a given id
     * @param _to      The address to mint tokens to
     * @param _id      Token id to mint
     * @param _amount  The amount to be minted
     * @param _data    Data to pass if receiver is contract
     */
    function _mint(
        address _to,
        uint256 _id,
        uint256 _amount,
        bytes memory _data
    ) internal {
        // Add _amount
        balances[_to][_id] = balances[_to][_id].add(_amount);

        // Emit event
        emit TransferSingle(msg.sender, address(0x0), _to, _id, _amount);

        // Calling onReceive method if recipient is contract
        _callonERC1155Received(
            address(0x0),
            _to,
            _id,
            _amount,
            gasleft(),
            _data
        );
    }

    /**
     * @notice Mint tokens for each ids in _ids
     * @param _to       The address to mint tokens to
     * @param _ids      Array of ids to mint
     * @param _amounts  Array of amount of tokens to mint per id
     * @param _data    Data to pass if receiver is contract
     */
    function _batchMint(
        address _to,
        uint256[] memory _ids,
        uint256[] memory _amounts,
        bytes memory _data
    ) internal {
        require(
            _ids.length == _amounts.length,
            "ERC1155MintBurn#batchMint: INVALID_ARRAYS_LENGTH"
        );

        // Number of mints to execute
        uint256 nMint = _ids.length;

        // Executing all minting
        for (uint256 i = 0; i < nMint; i++) {
            // Update storage balance
            balances[_to][_ids[i]] = balances[_to][_ids[i]].add(_amounts[i]);
        }

        // Emit batch mint event
        emit TransferBatch(msg.sender, address(0x0), _to, _ids, _amounts);

        // Calling onReceive method if recipient is contract
        _callonERC1155BatchReceived(
            address(0x0),
            _to,
            _ids,
            _amounts,
            gasleft(),
            _data
        );
    }

    /****************************************|
    |   Burning                              |
    |_______________________________________*/

    /**
     * @notice Burn _amount of tokens of a given token id
     * @param _from    The address to burn tokens from
     * @param _id      Token id to burn
     * @param _amount  The amount to be burned
     */
    function _burn(
        address _from,
        uint256 _id,
        uint256 _amount
    ) internal {
        //Substract _amount
        balances[_from][_id] = balances[_from][_id].sub(_amount);

        // Emit event
        emit TransferSingle(msg.sender, _from, address(0x0), _id, _amount);
    }

    /**
     * @notice Burn tokens of given token id for each (_ids[i], _amounts[i]) pair
     * @param _from     The address to burn tokens from
     * @param _ids      Array of token ids to burn
     * @param _amounts  Array of the amount to be burned
     */
    function _batchBurn(
        address _from,
        uint256[] memory _ids,
        uint256[] memory _amounts
    ) internal {
        // Number of mints to execute
        uint256 nBurn = _ids.length;
        require(
            nBurn == _amounts.length,
            "ERC1155MintBurn#batchBurn: INVALID_ARRAYS_LENGTH"
        );

        // Executing all minting
        for (uint256 i = 0; i < nBurn; i++) {
            // Update storage balance
            balances[_from][_ids[i]] = balances[_from][_ids[i]].sub(
                _amounts[i]
            );
        }

        // Emit batch mint event
        emit TransferBatch(msg.sender, _from, address(0x0), _ids, _amounts);
    }
}

// File: contracts/interfaces/ERC1155/ERC1155Metadata.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;

import "./interfaces/IERC1155Metadata.sol";
import "./ERC165.sol";

/**
 * @notice Contract that handles metadata related methods.
 * @dev Methods assume a deterministic generation of URI based on token IDs.
 *      Methods also assume that URI uses hex representation of token IDs.
 */
contract ERC1155Metadata is ERC165 {
    // URI's default URI prefix
    string public baseMetadataURI;
    event URI(string _uri, uint256 indexed _id);

    /***********************************|
    |     Metadata Public Functions     |
    |__________________________________*/

    /**
     * @notice A distinct Uniform Resource Identifier (URI) for a given token.
     * @dev URIs are defined in RFC 3986.
     *      URIs are assumed to be deterministically generated based on token ID
     * @return URI string
     */
    function _uri(uint256 _id) internal view returns (string memory) {
        return
            string(abi.encodePacked(baseMetadataURI, _uint2str(_id), ".json"));
    }

    /***********************************|
    |    Metadata Internal Functions    |
    |__________________________________*/

    /**
     * @notice Will emit default URI log event for corresponding token _id
     * @param _tokenIDs Array of IDs of tokens to log default URI
     */
    function _logURIs(uint256[] memory _tokenIDs) internal {
        string memory baseURL = baseMetadataURI;
        string memory tokenURI;

        for (uint256 i = 0; i < _tokenIDs.length; i++) {
            tokenURI = string(
                abi.encodePacked(baseURL, _uint2str(_tokenIDs[i]), ".json")
            );
            emit URI(tokenURI, _tokenIDs[i]);
        }
    }

    /**
     * @notice Will update the base URL of token's URI
     * @param _newBaseMetadataURI New base URL of token's URI
     */
    function _setBaseMetadataURI(string memory _newBaseMetadataURI) internal {
        baseMetadataURI = _newBaseMetadataURI;
    }

    /**
     * @notice Query if a contract implements an interface
     * @param _interfaceID  The interface identifier, as specified in ERC-165
     * @return `true` if the contract implements `_interfaceID` and
     */
    function supportsInterface(bytes4 _interfaceID)
        public
        pure
        virtual
        override
        returns (bool)
    {
        if (_interfaceID == type(IERC1155Metadata).interfaceId) {
            return true;
        }
        return super.supportsInterface(_interfaceID);
    }

    /***********************************|
  |    Utility Internal Functions     |
  |__________________________________*/

    /**
     * @notice Convert uint256 to string
     * @param _i Unsigned integer to convert to string
     */
    function _uint2str(uint256 _i)
        internal
        pure
        returns (string memory _uintAsString)
    {
        if (_i == 0) {
            return "0";
        }

        uint256 j = _i;
        uint256 ii = _i;
        uint256 len;

        // Get number of bytes
        while (j != 0) {
            len++;
            j /= 10;
        }

        bytes memory bstr = new bytes(len);
        uint256 k = len - 1;

        // Get each individual ASCII
        while (ii != 0) {
            bstr[k--] = bytes1(uint8(48 + (ii % 10)));
            ii /= 10;
        }

        // Convert to string
        return string(bstr);
    }
}

// File: @openzeppelin/contracts/utils/EnumerableSet.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256`
 * (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.2;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: contracts/interfaces/ERC1155/interfaces/IERC1155TokenReceiver.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;

/**
 * @dev ERC-1155 interface for accepting safe transfers.
 */
interface IERC1155TokenReceiver {
    /**
     * @notice Handle the receipt of a single ERC1155 token type
     * @dev An ERC1155-compliant smart contract MUST call this function on the token recipient contract, at the end of a `safeTransferFrom` after the balance has been updated
     * This function MAY throw to revert and reject the transfer
     * Return of other amount than the magic value MUST result in the transaction being reverted
     * Note: The token contract address is always the message sender
     * @param _operator  The address which called the `safeTransferFrom` function
     * @param _from      The address which previously owned the token
     * @param _id        The id of the token being transferred
     * @param _amount    The amount of tokens being transferred
     * @param _data      Additional data with no specified format
     * @return           `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
     */
    function onERC1155Received(
        address _operator,
        address _from,
        uint256 _id,
        uint256 _amount,
        bytes calldata _data
    ) external returns (bytes4);

    /**
     * @notice Handle the receipt of multiple ERC1155 token types
     * @dev An ERC1155-compliant smart contract MUST call this function on the token recipient contract, at the end of a `safeBatchTransferFrom` after the balances have been updated
     * This function MAY throw to revert and reject the transfer
     * Return of other amount than the magic value WILL result in the transaction being reverted
     * Note: The token contract address is always the message sender
     * @param _operator  The address which called the `safeBatchTransferFrom` function
     * @param _from      The address which previously owned the token
     * @param _ids       An array containing ids of each token being transferred
     * @param _amounts   An array containing amounts of each token being transferred
     * @param _data      Additional data with no specified format
     * @return           `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
     */
    function onERC1155BatchReceived(
        address _operator,
        address _from,
        uint256[] calldata _ids,
        uint256[] calldata _amounts,
        bytes calldata _data
    ) external returns (bytes4);
}

// File: contracts/interfaces/ERC1155/interfaces/IERC1155.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;

interface IERC1155 {
    /****************************************|
  |                 Events                 |
  |_______________________________________*/

    /**
     * @dev Either TransferSingle or TransferBatch MUST emit when tokens are transferred, including zero amount transfers as well as minting or burning
     *   Operator MUST be msg.sender
     *   When minting/creating tokens, the `_from` field MUST be set to `0x0`
     *   When burning/destroying tokens, the `_to` field MUST be set to `0x0`
     *   The total amount transferred from address 0x0 minus the total amount transferred to 0x0 may be used by clients and exchanges to be added to the "circulating supply" for a given token ID
     *   To broadcast the existence of a token ID with no initial balance, the contract SHOULD emit the TransferSingle event from `0x0` to `0x0`, with the token creator as `_operator`, and a `_amount` of 0
     */
    event TransferSingle(
        address indexed _operator,
        address indexed _from,
        address indexed _to,
        uint256 _id,
        uint256 _amount
    );

    /**
     * @dev Either TransferSingle or TransferBatch MUST emit when tokens are transferred, including zero amount transfers as well as minting or burning
     *   Operator MUST be msg.sender
     *   When minting/creating tokens, the `_from` field MUST be set to `0x0`
     *   When burning/destroying tokens, the `_to` field MUST be set to `0x0`
     *   The total amount transferred from address 0x0 minus the total amount transferred to 0x0 may be used by clients and exchanges to be added to the "circulating supply" for a given token ID
     *   To broadcast the existence of multiple token IDs with no initial balance, this SHOULD emit the TransferBatch event from `0x0` to `0x0`, with the token creator as `_operator`, and a `_amount` of 0
     */
    event TransferBatch(
        address indexed _operator,
        address indexed _from,
        address indexed _to,
        uint256[] _ids,
        uint256[] _amounts
    );

    /**
     * @dev MUST emit when an approval is updated
     */
    event ApprovalForAll(
        address indexed _owner,
        address indexed _operator,
        bool _approved
    );

    /**
     * @dev MUST emit when the URI is updated for a token ID
     *   URIs are defined in RFC 3986
     *   The URI MUST point a JSON file that conforms to the "ERC-1155 Metadata JSON Schema"
     */
    event URI(string _amount, uint256 indexed _id);

    /****************************************|
  |                Functions               |
  |_______________________________________*/

    /**
     * @notice Transfers amount of an _id from the _from address to the _to address specified
     * @dev MUST emit TransferSingle event on success
     * Caller must be approved to manage the _from account's tokens (see isApprovedForAll)
     * MUST throw if `_to` is the zero address
     * MUST throw if balance of sender for token `_id` is lower than the `_amount` sent
     * MUST throw on any other error
     * When transfer is complete, this function MUST check if `_to` is a smart contract (code size > 0). If so, it MUST call `onERC1155Received` on `_to` and revert if the return amount is not `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
     * @param _from    Source address
     * @param _to      Target address
     * @param _id      ID of the token type
     * @param _amount  Transfered amount
     * @param _data    Additional data with no specified format, sent in call to `_to`
     */
    function safeTransferFrom(
        address _from,
        address _to,
        uint256 _id,
        uint256 _amount,
        bytes calldata _data
    ) external;

    /**
     * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
     * @dev MUST emit TransferBatch event on success
     * Caller must be approved to manage the _from account's tokens (see isApprovedForAll)
     * MUST throw if `_to` is the zero address
     * MUST throw if length of `_ids` is not the same as length of `_amounts`
     * MUST throw if any of the balance of sender for token `_ids` is lower than the respective `_amounts` sent
     * MUST throw on any other error
     * When transfer is complete, this function MUST check if `_to` is a smart contract (code size > 0). If so, it MUST call `onERC1155BatchReceived` on `_to` and revert if the return amount is not `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
     * Transfers and events MUST occur in the array order they were submitted (_ids[0] before _ids[1], etc)
     * @param _from     Source addresses
     * @param _to       Target addresses
     * @param _ids      IDs of each token type
     * @param _amounts  Transfer amounts per token type
     * @param _data     Additional data with no specified format, sent in call to `_to`
     */
    function safeBatchTransferFrom(
        address _from,
        address _to,
        uint256[] calldata _ids,
        uint256[] calldata _amounts,
        bytes calldata _data
    ) external;

    /**
     * @notice Get the balance of an account's Tokens
     * @param _owner  The address of the token holder
     * @param _id     ID of the Token
     * @return        The _owner's balance of the Token type requested
     */
    function balanceOf(address _owner, uint256 _id)
        external
        view
        returns (uint256);

    /**
     * @notice Get the balance of multiple account/token pairs
     * @param _owners The addresses of the token holders
     * @param _ids    ID of the Tokens
     * @return        The _owner's balance of the Token types requested (i.e. balance for each (owner, id) pair)
     */
    function balanceOfBatch(address[] calldata _owners, uint256[] calldata _ids)
        external
        view
        returns (uint256[] memory);

    /**
     * @notice Enable or disable approval for a third party ("operator") to manage all of caller's tokens
     * @dev MUST emit the ApprovalForAll event on success
     * @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 Queries the approval status of an operator for a given owner
     * @param _owner     The owner of the Tokens
     * @param _operator  Address of authorized operator
     * @return isOperator True if the operator is approved, false if not
     */
    function isApprovedForAll(address _owner, address _operator)
        external
        view
        returns (bool isOperator);
}

// File: contracts/interfaces/ERC1155/ERC165.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;

abstract contract ERC165 {
    /**
     * @notice Query if a contract implements an interface
     * @param _interfaceID The interface identifier, as specified in ERC-165
     * @return `true` if the contract implements `_interfaceID`
     */
    function supportsInterface(bytes4 _interfaceID)
        public
        pure
        virtual
        returns (bool)
    {
        return _interfaceID == this.supportsInterface.selector;
    }
}

// File: contracts/interfaces/ERC1155/interfaces/IERC1155Metadata.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.6.12;

interface IERC1155Metadata {
    /****************************************|
  |                Functions               |
  |_______________________________________*/

    /**
     * @notice A distinct Uniform Resource Identifier (URI) for a given token.
     * @dev URIs are defined in RFC 3986.
     *      URIs are assumed to be deterministically generated based on token ID
     *      Token IDs are assumed to be represented in their hex format in URIs
     * @return URI string
     */
    function uri(uint256 _id) external view returns (string memory);
}