pragma solidity 0.6.6;

import { ERC1155Upgradeable } from "../lib/ERC1155Upgradeable.sol";
import {
	IERC1155Upgradeable
} from "@openzeppelin/contracts-upgradeable/token/ERC1155/IERC1155Upgradeable.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { AccessControlMixin } from "../common/AccessControlMixin.sol";
import { IChildToken } from "../interfaces/IChildToken.sol";
import { NativeMetaTransaction } from "../common/NativeMetaTransaction.sol";
import { ContextMixin } from "../common/ContextMixin.sol";

contract ChildMintableERC1155 is
	ERC1155Upgradeable,
	IChildToken,
	AccessControlMixin,
	NativeMetaTransaction,
	ContextMixin
{
	bytes32 public constant DEPOSITOR_ROLE = keccak256("DEPOSITOR_ROLE");

	string public name;

	/**
	 * @notice This function replace the constructor and should be called  once after contact creation
	 * @dev setting up collection info and permissions
	 * @param _name collection name
	 * @param uri_ basic URI for collection
	 * @param owner_ the owner of collection which have DEFAULT_ADMIN_ROLE
	 * @param childChainManager abi encoded ids array and amounts array
	 */
	function initialize(
		string memory _name,
		string memory uri_,
		address owner_,
		address childChainManager
	) public initializer {
		name = _name;

		__ERC1155_init(uri_);

		_setupContractId("ChildMintableERC1155");
		_setupRole(DEFAULT_ADMIN_ROLE, owner_);
		_setupRole(DEPOSITOR_ROLE, childChainManager);
		_initializeEIP712(uri_);
	}

	/**
	 * @notice called when tokens are deposited on root chain
	 * @dev Should be callable only by ChildChainManager
	 * Should handle deposit by minting the required tokens for user
	 * Make sure minting is done only by this function
	 * @param user user address for whom deposit is being done
	 * @param depositData abi encoded ids array and amounts array
	 */
	function deposit(address user, bytes calldata depositData)
		external
		override
		only(DEPOSITOR_ROLE)
	{
		(uint256[] memory ids, uint256[] memory amounts, bytes memory data) =
			abi.decode(depositData, (uint256[], uint256[], bytes));
		require(user != address(0), "ChildMintableERC1155: INVALID_DEPOSIT_USER");
		_mintBatch(user, ids, amounts, data);
	}

	/**
	 * @notice called when user wants to withdraw single token back to root chain
	 * @dev Should burn user's tokens. This transaction will be verified when exiting on root chain
	 * @param id id to withdraw
	 * @param amount amount to withdraw
	 */
	function withdrawSingle(uint256 id, uint256 amount) external override {
		_burn(_msgSender(), id, amount);
	}

	/**
	 * @notice called when user wants to batch withdraw tokens back to root chain
	 * @dev Should burn user's tokens. This transaction will be verified when exiting on root chain
	 * @param ids ids to withdraw
	 * @param amounts amounts to withdraw
	 */
	function withdrawBatch(uint256[] calldata ids, uint256[] calldata amounts) external override {
		_burnBatch(_msgSender(), ids, amounts);
	}

	/**
	 * @notice See definition of `_mint` in ERC1155 contract
	 * @dev This implementation only allows admins to mint tokens
	 * but can be changed as per requirement
	 */
	function mint(
		address account,
		uint256 id,
		uint256 amount,
		bytes calldata data
	) external override only(DEFAULT_ADMIN_ROLE) {
		_mint(account, id, amount, data);
	}

	/**
	 * @notice See definition of `_mintBatch` in ERC1155 contract
	 * @dev This implementation only allows admins to mint tokens
	 * but can be changed as per requirement
	 */
	function mintBatch(
		address to,
		uint256[] calldata ids,
		uint256[] calldata amounts,
		bytes calldata data
	) external override only(DEFAULT_ADMIN_ROLE) {
		_mintBatch(to, ids, amounts, data);
	}

	/**
	 * @notice See definition of `_burn` in ERC1155 contract
	 * @dev This implementation only allows user to burn only own or approved token
	 */
	function burn(
		address account,
		uint256 id,
		uint256 value
	) public virtual override {
		require(
			account == _msgSender() || isApprovedForAll(account, _msgSender()),
			"ChildMintableERC1155: caller is not owner nor approved"
		);
		_burn(account, id, value);
	}

	/**
	 * @notice Return the owner of contract, the who create collection and have DEFAULT_ADMIN_ROLE
	 * @dev This function required by opensea.io to correctly shown the owner of collection
	 */
	function owner() public view override returns (address) {
		return getRoleMember(DEFAULT_ADMIN_ROLE, 0);
	}

	// This is to support Native meta transactions
	// never use msg.sender directly, use _msgSender() instead
	function _msgSender() internal view override returns (address payable sender) {
		return ContextMixin.msgSender();
	}
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.6;

import "@openzeppelin/contracts-upgradeable/token/ERC1155/IERC1155Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/token/ERC1155/IERC1155MetadataURIUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/token/ERC1155/IERC1155ReceiverUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/utils/ContextUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/introspection/ERC165Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/math/SafeMathUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/utils/AddressUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/utils/StringsUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/Initializable.sol";

/**
 * @title Extended ERC1155Upgradeable
 * @author Bondly Finance
 * @notice This is basic ERC1155Upgradeable writen by OpenZeppelin team, with extended functionality
 * @dev Changes to the contract: overriden function uri():
 *     return concatination of _uri and _id,
 *     for converting uint to string we are used library Strings from OpenZeppelin.
 */

/**
 *
 * @dev Implementation of the basic standard multi-token.
 * See https://eips.ethereum.org/EIPS/eip-1155
 * Originally based on code by Enjin: https://github.com/enjin/erc-1155
 *
 * _Available since v3.1._
 */
contract ERC1155Upgradeable is
	Initializable,
	ContextUpgradeable,
	ERC165Upgradeable,
	IERC1155Upgradeable,
	IERC1155MetadataURIUpgradeable
{
	using SafeMathUpgradeable for uint256;
	using AddressUpgradeable for address;
	using StringsUpgradeable for uint256;

	// Mapping from token ID to account balances
	mapping(uint256 => mapping(address => uint256)) private _balances;

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

	// Used as the URI for all token types by relying on ID substitution, e.g. https://token-cdn-domain/{id}.json
	string private _uri;

	/*
	 *     bytes4(keccak256('balanceOf(address,uint256)')) == 0x00fdd58e
	 *     bytes4(keccak256('balanceOfBatch(address[],uint256[])')) == 0x4e1273f4
	 *     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
	 *     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5
	 *     bytes4(keccak256('safeTransferFrom(address,address,uint256,uint256,bytes)')) == 0xf242432a
	 *     bytes4(keccak256('safeBatchTransferFrom(address,address,uint256[],uint256[],bytes)')) == 0x2eb2c2d6
	 *
	 *     => 0x00fdd58e ^ 0x4e1273f4 ^ 0xa22cb465 ^
	 *        0xe985e9c5 ^ 0xf242432a ^ 0x2eb2c2d6 == 0xd9b67a26
	 */
	bytes4 private constant _INTERFACE_ID_ERC1155 = 0xd9b67a26;

	/*
	 *     bytes4(keccak256('uri(uint256)')) == 0x0e89341c
	 */
	bytes4 private constant _INTERFACE_ID_ERC1155_METADATA_URI = 0x0e89341c;

	/**
	 * @dev See {_setURI}.
	 */
	function __ERC1155_init(string memory uri_) internal initializer {
		__Context_init_unchained();
		__ERC165_init_unchained();
		__ERC1155_init_unchained(uri_);
	}

	function __ERC1155_init_unchained(string memory uri_) internal initializer {
		_setURI(uri_);

		// register the supported interfaces to conform to ERC1155 via ERC165
		_registerInterface(_INTERFACE_ID_ERC1155);

		// register the supported interfaces to conform to ERC1155MetadataURI via ERC165
		_registerInterface(_INTERFACE_ID_ERC1155_METADATA_URI);
	}

	/**
	 * @dev See {IERC1155MetadataURI-uri}.
	 *
	 * This implementation returns the same URI for *all* token types. It relies
	 * on the token type ID substitution mechanism
	 * https://eips.ethereum.org/EIPS/eip-1155#metadata[defined in the EIP].
	 *
	 * Clients calling this function must replace the `\{id\}` substring with the
	 * actual token type ID.
	 */
	function uri(uint256 _id) external view virtual override returns (string memory) {
		return string(abi.encodePacked(_uri, _id.toString()));
	}

	/**
	 * @dev See {IERC1155-balanceOf}.
	 *
	 * Requirements:
	 *
	 * - `account` cannot be the zero address.
	 */
	function balanceOf(address account, uint256 id)
		public
		view
		virtual
		override
		returns (uint256)
	{
		require(account != address(0), "ERC1155: balance query for the zero address");
		return _balances[id][account];
	}

	/**
	 * @dev See {IERC1155-balanceOfBatch}.
	 *
	 * Requirements:
	 *
	 * - `accounts` and `ids` must have the same length.
	 */
	function balanceOfBatch(address[] memory accounts, uint256[] memory ids)
		public
		view
		virtual
		override
		returns (uint256[] memory)
	{
		require(accounts.length == ids.length, "ERC1155: accounts and ids length mismatch");

		uint256[] memory batchBalances = new uint256[](accounts.length);

		for (uint256 i = 0; i < accounts.length; ++i) {
			batchBalances[i] = balanceOf(accounts[i], ids[i]);
		}

		return batchBalances;
	}

	/**
	 * @dev See {IERC1155-setApprovalForAll}.
	 */
	function setApprovalForAll(address operator, bool approved) public virtual override {
		require(_msgSender() != operator, "ERC1155: setting approval status for self");

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

	/**
	 * @dev See {IERC1155-isApprovedForAll}.
	 */
	function isApprovedForAll(address account, address operator)
		public
		view
		virtual
		override
		returns (bool)
	{
		return _operatorApprovals[account][operator];
	}

	/**
	 * @dev See {IERC1155-safeTransferFrom}.
	 */
	function safeTransferFrom(
		address from,
		address to,
		uint256 id,
		uint256 amount,
		bytes memory data
	) public virtual override {
		require(to != address(0), "ERC1155: transfer to the zero address");
		require(
			from == _msgSender() || isApprovedForAll(from, _msgSender()),
			"ERC1155: caller is not owner nor approved"
		);

		address operator = _msgSender();

		_beforeTokenTransfer(
			operator,
			from,
			to,
			_asSingletonArray(id),
			_asSingletonArray(amount),
			data
		);

		_balances[id][from] = _balances[id][from].sub(
			amount,
			"ERC1155: insufficient balance for transfer"
		);
		_balances[id][to] = _balances[id][to].add(amount);

		emit TransferSingle(operator, from, to, id, amount);

		_doSafeTransferAcceptanceCheck(operator, from, to, id, amount, data);
	}

	/**
	 * @dev See {IERC1155-safeBatchTransferFrom}.
	 */
	function safeBatchTransferFrom(
		address from,
		address to,
		uint256[] memory ids,
		uint256[] memory amounts,
		bytes memory data
	) public virtual override {
		require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");
		require(to != address(0), "ERC1155: transfer to the zero address");
		require(
			from == _msgSender() || isApprovedForAll(from, _msgSender()),
			"ERC1155: transfer caller is not owner nor approved"
		);

		address operator = _msgSender();

		_beforeTokenTransfer(operator, from, to, ids, amounts, data);

		for (uint256 i = 0; i < ids.length; ++i) {
			uint256 id = ids[i];
			uint256 amount = amounts[i];

			_balances[id][from] = _balances[id][from].sub(
				amount,
				"ERC1155: insufficient balance for transfer"
			);
			_balances[id][to] = _balances[id][to].add(amount);
		}

		emit TransferBatch(operator, from, to, ids, amounts);

		_doSafeBatchTransferAcceptanceCheck(operator, from, to, ids, amounts, data);
	}

	/**
	 * @dev Sets a new URI for all token types, by relying on the token type ID
	 * substitution mechanism
	 * https://eips.ethereum.org/EIPS/eip-1155#metadata[defined in the EIP].
	 *
	 * By this mechanism, any occurrence of the `\{id\}` substring in either the
	 * URI or any of the amounts in the JSON file at said URI will be replaced by
	 * clients with the token type ID.
	 *
	 * For example, the `https://token-cdn-domain/\{id\}.json` URI would be
	 * interpreted by clients as
	 * `https://token-cdn-domain/000000000000000000000000000000000000000000000000000000000004cce0.json`
	 * for token type ID 0x4cce0.
	 *
	 * See {uri}.
	 *
	 * Because these URIs cannot be meaningfully represented by the {URI} event,
	 * this function emits no events.
	 */
	function _setURI(string memory newuri) internal virtual {
		_uri = newuri;
	}

	/**
	 * @dev Creates `amount` tokens of token type `id`, and assigns them to `account`.
	 *
	 * Emits a {TransferSingle} event.
	 *
	 * Requirements:
	 *
	 * - `account` cannot be the zero address.
	 * - If `account` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155Received} and return the
	 * acceptance magic value.
	 */
	function _mint(
		address account,
		uint256 id,
		uint256 amount,
		bytes memory data
	) internal virtual {
		require(account != address(0), "ERC1155: mint to the zero address");

		address operator = _msgSender();

		_beforeTokenTransfer(
			operator,
			address(0),
			account,
			_asSingletonArray(id),
			_asSingletonArray(amount),
			data
		);

		_balances[id][account] = _balances[id][account].add(amount);
		emit TransferSingle(operator, address(0), account, id, amount);

		_doSafeTransferAcceptanceCheck(operator, address(0), account, id, amount, data);
	}

	/**
	 * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {_mint}.
	 *
	 * Requirements:
	 *
	 * - `ids` and `amounts` must have the same length.
	 * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155BatchReceived} and return the
	 * acceptance magic value.
	 */
	function _mintBatch(
		address to,
		uint256[] memory ids,
		uint256[] memory amounts,
		bytes memory data
	) internal virtual {
		require(to != address(0), "ERC1155: mint to the zero address");
		require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");

		address operator = _msgSender();

		_beforeTokenTransfer(operator, address(0), to, ids, amounts, data);

		for (uint256 i = 0; i < ids.length; i++) {
			_balances[ids[i]][to] = amounts[i].add(_balances[ids[i]][to]);
		}

		emit TransferBatch(operator, address(0), to, ids, amounts);

		_doSafeBatchTransferAcceptanceCheck(operator, address(0), to, ids, amounts, data);
	}

	/**
	 * @dev Destroys `amount` tokens of token type `id` from `account`
	 *
	 * Requirements:
	 *
	 * - `account` cannot be the zero address.
	 * - `account` must have at least `amount` tokens of token type `id`.
	 */
	function _burn(
		address account,
		uint256 id,
		uint256 amount
	) internal virtual {
		require(account != address(0), "ERC1155: burn from the zero address");

		address operator = _msgSender();

		_beforeTokenTransfer(
			operator,
			account,
			address(0),
			_asSingletonArray(id),
			_asSingletonArray(amount),
			""
		);

		_balances[id][account] = _balances[id][account].sub(
			amount,
			"ERC1155: burn amount exceeds balance"
		);

		emit TransferSingle(operator, account, address(0), id, amount);
	}

	/**
	 * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {_burn}.
	 *
	 * Requirements:
	 *
	 * - `ids` and `amounts` must have the same length.
	 */
	function _burnBatch(
		address account,
		uint256[] memory ids,
		uint256[] memory amounts
	) internal virtual {
		require(account != address(0), "ERC1155: burn from the zero address");
		require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");

		address operator = _msgSender();

		_beforeTokenTransfer(operator, account, address(0), ids, amounts, "");

		for (uint256 i = 0; i < ids.length; i++) {
			_balances[ids[i]][account] = _balances[ids[i]][account].sub(
				amounts[i],
				"ERC1155: burn amount exceeds balance"
			);
		}

		emit TransferBatch(operator, account, address(0), ids, amounts);
	}

	/**
	 * @dev Hook that is called before any token transfer. This includes minting
	 * and burning, as well as batched variants.
	 *
	 * The same hook is called on both single and batched variants. For single
	 * transfers, the length of the `id` and `amount` arrays will be 1.
	 *
	 * Calling conditions (for each `id` and `amount` pair):
	 *
	 * - When `from` and `to` are both non-zero, `amount` of ``from``'s tokens
	 * of token type `id` will be  transferred to `to`.
	 * - When `from` is zero, `amount` tokens of token type `id` will be minted
	 * for `to`.
	 * - when `to` is zero, `amount` of ``from``'s tokens of token type `id`
	 * will be burned.
	 * - `from` and `to` are never both zero.
	 * - `ids` and `amounts` have the same, non-zero length.
	 *
	 * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
	 */
	function _beforeTokenTransfer(
		address operator,
		address from,
		address to,
		uint256[] memory ids,
		uint256[] memory amounts,
		bytes memory data
	) internal virtual {}

	function _doSafeTransferAcceptanceCheck(
		address operator,
		address from,
		address to,
		uint256 id,
		uint256 amount,
		bytes memory data
	) private {
		if (to.isContract()) {
			try
				IERC1155ReceiverUpgradeable(to).onERC1155Received(operator, from, id, amount, data)
			returns (bytes4 response) {
				if (response != IERC1155ReceiverUpgradeable(to).onERC1155Received.selector) {
					revert("ERC1155: ERC1155Receiver rejected tokens");
				}
			} catch Error(string memory reason) {
				revert(reason);
			} catch {
				revert("ERC1155: transfer to non ERC1155Receiver implementer");
			}
		}
	}

	function _doSafeBatchTransferAcceptanceCheck(
		address operator,
		address from,
		address to,
		uint256[] memory ids,
		uint256[] memory amounts,
		bytes memory data
	) private {
		if (to.isContract()) {
			try
				IERC1155ReceiverUpgradeable(to).onERC1155BatchReceived(
					operator,
					from,
					ids,
					amounts,
					data
				)
			returns (bytes4 response) {
				if (response != IERC1155ReceiverUpgradeable(to).onERC1155BatchReceived.selector) {
					revert("ERC1155: ERC1155Receiver rejected tokens");
				}
			} catch Error(string memory reason) {
				revert(reason);
			} catch {
				revert("ERC1155: transfer to non ERC1155Receiver implementer");
			}
		}
	}

	function _asSingletonArray(uint256 element) private pure returns (uint256[] memory) {
		uint256[] memory array = new uint256[](1);
		array[0] = element;

		return array;
	}

	uint256[47] private __gap;
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

import "../../introspection/IERC165Upgradeable.sol";

/**
 * @dev Required interface of an ERC1155 compliant contract, as defined in the
 * https://eips.ethereum.org/EIPS/eip-1155[EIP].
 *
 * _Available since v3.1._
 */
interface IERC1155Upgradeable is IERC165Upgradeable {
    /**
     * @dev Emitted when `value` tokens of token type `id` are transferred from `from` to `to` by `operator`.
     */
    event TransferSingle(address indexed operator, address indexed from, address indexed to, uint256 id, uint256 value);

    /**
     * @dev Equivalent to multiple {TransferSingle} events, where `operator`, `from` and `to` are the same for all
     * transfers.
     */
    event TransferBatch(address indexed operator, address indexed from, address indexed to, uint256[] ids, uint256[] values);

    /**
     * @dev Emitted when `account` grants or revokes permission to `operator` to transfer their tokens, according to
     * `approved`.
     */
    event ApprovalForAll(address indexed account, address indexed operator, bool approved);

    /**
     * @dev Emitted when the URI for token type `id` changes to `value`, if it is a non-programmatic URI.
     *
     * If an {URI} event was emitted for `id`, the standard
     * https://eips.ethereum.org/EIPS/eip-1155#metadata-extensions[guarantees] that `value` will equal the value
     * returned by {IERC1155MetadataURI-uri}.
     */
    event URI(string value, uint256 indexed id);

    /**
     * @dev Returns the amount of tokens of token type `id` owned by `account`.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function balanceOf(address account, uint256 id) external view returns (uint256);

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {balanceOf}.
     *
     * Requirements:
     *
     * - `accounts` and `ids` must have the same length.
     */
    function balanceOfBatch(address[] calldata accounts, uint256[] calldata ids) external view returns (uint256[] memory);

    /**
     * @dev Grants or revokes permission to `operator` to transfer the caller's tokens, according to `approved`,
     *
     * Emits an {ApprovalForAll} event.
     *
     * Requirements:
     *
     * - `operator` cannot be the caller.
     */
    function setApprovalForAll(address operator, bool approved) external;

    /**
     * @dev Returns true if `operator` is approved to transfer ``account``'s tokens.
     *
     * See {setApprovalForAll}.
     */
    function isApprovedForAll(address account, address operator) external view returns (bool);

    /**
     * @dev Transfers `amount` tokens of token type `id` from `from` to `to`.
     *
     * Emits a {TransferSingle} event.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - If the caller is not `from`, it must be have been approved to spend ``from``'s tokens via {setApprovalForAll}.
     * - `from` must have a balance of tokens of type `id` of at least `amount`.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155Received} and return the
     * acceptance magic value.
     */
    function safeTransferFrom(address from, address to, uint256 id, uint256 amount, bytes calldata data) external;

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {safeTransferFrom}.
     *
     * Emits a {TransferBatch} event.
     *
     * Requirements:
     *
     * - `ids` and `amounts` must have the same length.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155BatchReceived} and return the
     * acceptance magic value.
     */
    function safeBatchTransferFrom(address from, address to, uint256[] calldata ids, uint256[] calldata amounts, bytes calldata data) external;
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

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

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

pragma solidity 0.6.6;

import {
	AccessControlUpgradeable
} from "@openzeppelin/contracts-upgradeable/access/AccessControlUpgradeable.sol";

contract AccessControlMixin is AccessControlUpgradeable {
	string private _revertMsg;

	function _setupContractId(string memory contractId) internal {
		_revertMsg = string(abi.encodePacked(contractId, ": INSUFFICIENT_PERMISSIONS"));
	}

	modifier only(bytes32 role) {
		require(hasRole(role, _msgSender()), _revertMsg);
		_;
	}
}

pragma solidity 0.6.6;

interface IChildToken {
	/**
	 * @notice called when tokens are deposited on root chain
	 * @dev Should be callable only by ChildChainManager
	 * Should handle deposit by minting the required tokens for user
	 * Make sure minting is done only by this function
	 * @param user user address for whom deposit is being done
	 * @param depositData abi encoded ids array and amounts array
	 */
	function deposit(address user, bytes calldata depositData) external;

	/**
	 * @notice called when user wants to withdraw single token back to root chain
	 * @dev Should burn user's tokens. This transaction will be verified when exiting on root chain
	 * @param id id to withdraw
	 * @param amount amount to withdraw
	 */
	function withdrawSingle(uint256 id, uint256 amount) external;

	/**
	 * @notice called when user wants to batch withdraw tokens back to root chain
	 * @dev Should burn user's tokens. This transaction will be verified when exiting on root chain
	 * @param ids ids to withdraw
	 * @param amounts amounts to withdraw
	 */
	function withdrawBatch(uint256[] calldata ids, uint256[] calldata amounts) external;

	/**
	 * @notice See definition of `_mint` in ERC1155 contract
	 * @dev This implementation only allows admins to mint tokens
	 * but can be changed as per requirement
	 */
	function mint(
		address account,
		uint256 id,
		uint256 amount,
		bytes calldata data
	) external;

	/**
	 * @notice See definition of `_mintBatch` in ERC1155 contract
	 * @dev This implementation only allows admins to mint tokens
	 * but can be changed as per requirement
	 */
	function mintBatch(
		address to,
		uint256[] calldata ids,
		uint256[] calldata amounts,
		bytes calldata data
	) external;

	/**
	 * @notice See definition of `_burn` in ERC1155 contract
	 * @dev This implementation only allows user to burn only own or approved token
	 */
	function burn(
		address account,
		uint256 id,
		uint256 value
	) external;

	/**
	 * @notice Return the owner of contract, the who create collection and have DEFAULT_ADMIN_ROLE
	 * @dev This function required by opensea.io to correctly shown the owner of collection
	 */
	function owner() external view returns (address);
}

pragma solidity 0.6.6;

import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
import { EIP712Base } from "./EIP712Base.sol";

contract NativeMetaTransaction is EIP712Base {
	using SafeMath for uint256;
	bytes32 private constant META_TRANSACTION_TYPEHASH =
		keccak256(bytes("MetaTransaction(uint256 nonce,address from,bytes functionSignature)"));
	event MetaTransactionExecuted(
		address userAddress,
		address payable relayerAddress,
		bytes functionSignature
	);
	mapping(address => uint256) nonces;

	struct MetaTransaction {
		uint256 nonce;
		address from;
		bytes functionSignature;
	}

	function executeMetaTransaction(
		address userAddress,
		bytes memory functionSignature,
		bytes32 sigR,
		bytes32 sigS,
		uint8 sigV
	) public payable returns (bytes memory) {
		MetaTransaction memory metaTx =
			MetaTransaction({
				nonce: nonces[userAddress],
				from: userAddress,
				functionSignature: functionSignature
			});

		require(
			verify(userAddress, metaTx, sigR, sigS, sigV),
			"Signer and signature do not match"
		);

		nonces[userAddress] = nonces[userAddress].add(1);

		emit MetaTransactionExecuted(userAddress, msg.sender, functionSignature);

		(bool success, bytes memory returnData) =
			address(this).call(abi.encodePacked(functionSignature, userAddress));
		require(success, "Function call not successful");

		return returnData;
	}

	function hashMetaTransaction(MetaTransaction memory metaTx) internal pure returns (bytes32) {
		return
			keccak256(
				abi.encode(
					META_TRANSACTION_TYPEHASH,
					metaTx.nonce,
					metaTx.from,
					keccak256(metaTx.functionSignature)
				)
			);
	}

	function getNonce(address user) public view returns (uint256 nonce) {
		nonce = nonces[user];
	}

	function verify(
		address signer,
		MetaTransaction memory metaTx,
		bytes32 sigR,
		bytes32 sigS,
		uint8 sigV
	) internal view returns (bool) {
		require(signer != address(0), "NativeMetaTransaction: INVALID_SIGNER");
		return
			signer == ecrecover(toTypedMessageHash(hashMetaTransaction(metaTx)), sigV, sigR, sigS);
	}
}

pragma solidity 0.6.6;

abstract contract ContextMixin {
	function msgSender() internal view returns (address payable sender) {
		if (msg.sender == address(this)) {
			bytes memory array = msg.data;
			uint256 index = msg.data.length;
			assembly {
				// Load the 32 bytes word from memory with the address on the lower 20 bytes, and mask those.
				sender := and(mload(add(array, index)), 0xffffffffffffffffffffffffffffffffffffffff)
			}
		} else {
			sender = msg.sender;
		}
		return sender;
	}
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

import "./IERC1155Upgradeable.sol";

/**
 * @dev Interface of the optional ERC1155MetadataExtension interface, as defined
 * in the https://eips.ethereum.org/EIPS/eip-1155#metadata-extensions[EIP].
 *
 * _Available since v3.1._
 */
interface IERC1155MetadataURIUpgradeable is IERC1155Upgradeable {
    /**
     * @dev Returns the URI for token type `id`.
     *
     * If the `\{id\}` substring is present in the URI, it must be replaced by
     * clients with the actual token type ID.
     */
    function uri(uint256 id) external view returns (string memory);
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../../introspection/IERC165Upgradeable.sol";

/**
 * _Available since v3.1._
 */
interface IERC1155ReceiverUpgradeable is IERC165Upgradeable {

    /**
        @dev Handles the receipt of a single ERC1155 token type. This function is
        called at the end of a `safeTransferFrom` after the balance has been updated.
        To accept the transfer, this must return
        `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
        (i.e. 0xf23a6e61, or its own function selector).
        @param operator The address which initiated the transfer (i.e. msg.sender)
        @param from The address which previously owned the token
        @param id The ID of the token being transferred
        @param value The amount of tokens being transferred
        @param data Additional data with no specified format
        @return `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))` if transfer is allowed
    */
    function onERC1155Received(
        address operator,
        address from,
        uint256 id,
        uint256 value,
        bytes calldata data
    )
        external
        returns(bytes4);

    /**
        @dev Handles the receipt of a multiple ERC1155 token types. This function
        is called at the end of a `safeBatchTransferFrom` after the balances have
        been updated. To accept the transfer(s), this must return
        `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
        (i.e. 0xbc197c81, or its own function selector).
        @param operator The address which initiated the batch transfer (i.e. msg.sender)
        @param from The address which previously owned the token
        @param ids An array containing ids of each token being transferred (order and length must match values array)
        @param values An array containing amounts of each token being transferred (order and length must match ids array)
        @param data Additional data with no specified format
        @return `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))` if transfer is allowed
    */
    function onERC1155BatchReceived(
        address operator,
        address from,
        uint256[] calldata ids,
        uint256[] calldata values,
        bytes calldata data
    )
        external
        returns(bytes4);
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;
import "../proxy/Initializable.sol";

/*
 * @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 ContextUpgradeable is Initializable {
    function __Context_init() internal initializer {
        __Context_init_unchained();
    }

    function __Context_init_unchained() internal initializer {
    }
    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;
    }
    uint256[50] private __gap;
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC165Upgradeable.sol";
import "../proxy/Initializable.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts may inherit from this and call {_registerInterface} to declare
 * their support of an interface.
 */
abstract contract ERC165Upgradeable is Initializable, IERC165Upgradeable {
    /*
     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
     */
    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;

    /**
     * @dev Mapping of interface ids to whether or not it's supported.
     */
    mapping(bytes4 => bool) private _supportedInterfaces;

    function __ERC165_init() internal initializer {
        __ERC165_init_unchained();
    }

    function __ERC165_init_unchained() internal initializer {
        // Derived contracts need only register support for their own interfaces,
        // we register support for ERC165 itself here
        _registerInterface(_INTERFACE_ID_ERC165);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     *
     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev Registers the contract as an implementer of the interface defined by
     * `interfaceId`. Support of the actual ERC165 interface is automatic and
     * registering its interface id is not required.
     *
     * See {IERC165-supportsInterface}.
     *
     * Requirements:
     *
     * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
     */
    function _registerInterface(bytes4 interfaceId) internal virtual {
        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
    uint256[49] private __gap;
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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 SafeMathUpgradeable {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @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) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * 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);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * 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);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

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

        uint256 size;
        // 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");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

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

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev String operations.
 */
library StringsUpgradeable {
    /**
     * @dev Converts a `uint256` to its ASCII `string` 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);
        uint256 index = digits - 1;
        temp = value;
        while (temp != 0) {
            buffer[index--] = bytes1(uint8(48 + temp % 10));
            temp /= 10;
        }
        return string(buffer);
    }
}

// SPDX-License-Identifier: MIT

// solhint-disable-next-line compiler-version
pragma solidity >=0.4.24 <0.8.0;

import "../utils/AddressUpgradeable.sol";

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since a proxied contract can't have a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {UpgradeableProxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 */
abstract contract Initializable {

    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Modifier to protect an initializer function from being invoked twice.
     */
    modifier initializer() {
        require(_initializing || _isConstructor() || !_initialized, "Initializable: contract is already initialized");

        bool isTopLevelCall = !_initializing;
        if (isTopLevelCall) {
            _initializing = true;
            _initialized = true;
        }

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

    /// @dev Returns true if and only if the function is running in the constructor
    function _isConstructor() private view returns (bool) {
        return !AddressUpgradeable.isContract(address(this));
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <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 IERC165Upgradeable {
    /**
     * @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

pragma solidity >=0.6.0 <0.8.0;

import "../utils/EnumerableSetUpgradeable.sol";
import "../utils/AddressUpgradeable.sol";
import "../utils/ContextUpgradeable.sol";
import "../proxy/Initializable.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 AccessControlUpgradeable is Initializable, ContextUpgradeable {
    function __AccessControl_init() internal initializer {
        __Context_init_unchained();
        __AccessControl_init_unchained();
    }

    function __AccessControl_init_unchained() internal initializer {
    }
    using EnumerableSetUpgradeable for EnumerableSetUpgradeable.AddressSet;
    using AddressUpgradeable for address;

    struct RoleData {
        EnumerableSetUpgradeable.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());
        }
    }
    uint256[49] private __gap;
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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 v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSetUpgradeable {
    // 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];
    }

    // Bytes32Set

    struct Bytes32Set {
        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(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, 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(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set 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(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, 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(uint160(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(uint160(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(uint160(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(uint160(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));
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @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) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * 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);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * 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);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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;
    }
}

pragma solidity 0.6.6;

import { Initializable } from "@openzeppelin/contracts-upgradeable/proxy/Initializable.sol";

contract EIP712Base is Initializable {
	struct EIP712Domain {
		string name;
		string version;
		address verifyingContract;
		bytes32 salt;
	}

	string public constant ERC712_VERSION = "1";

	bytes32 internal constant EIP712_DOMAIN_TYPEHASH =
		keccak256(
			bytes(
				"EIP712Domain(string name,string version,address verifyingContract,bytes32 salt)"
			)
		);
	bytes32 internal domainSeperator;

	function _initializeEIP712(string memory name) internal initializer {
		_setDomainSeperator(name);
	}

	function _setDomainSeperator(string memory name) internal {
		domainSeperator = keccak256(
			abi.encode(
				EIP712_DOMAIN_TYPEHASH,
				keccak256(bytes(name)),
				keccak256(bytes(ERC712_VERSION)),
				address(this),
				bytes32(getChainId())
			)
		);
	}

	function getDomainSeperator() public view returns (bytes32) {
		return domainSeperator;
	}

	function getChainId() public pure returns (uint256) {
		uint256 id;
		assembly {
			id := chainid()
		}
		return id;
	}

	function toTypedMessageHash(bytes32 messageHash) internal view returns (bytes32) {
		return keccak256(abi.encodePacked("\x19\x01", getDomainSeperator(), messageHash));
	}
}