Swappable Collections

pragma solidity ^0.5.16;


/**
 * Utility library of inline functions on addresses
 */
library Address {

  // Default hash for EOA accounts returned by extcodehash
  bytes32 constant internal ACCOUNT_HASH = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;

  /**
   * Returns whether the target address is a contract
   * @dev This function will return false if invoked during the constructor of a contract.
   * @param _address address of the account to check
   * @return Whether the target address is a contract
   */
  function isContract(address _address) internal view returns (bool) {
    bytes32 codehash;

    // Currently there is no better way to check if there is a contract in an address
    // than to check the size of the code at that address or if it has a non-zero code hash or account hash
    assembly { codehash := extcodehash(_address) }
    return (codehash != 0x0 && codehash != ACCOUNT_HASH);
  }
}

pragma solidity ^0.5.0;

/*
 * @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.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

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

pragma solidity ^0.5.16;

import "../../interfaces/IERC165.sol";
import "../../utils/SafeMath.sol";
import "../../interfaces/IERC1155TokenReceiver.sol";
import "../../interfaces/IERC1155.sol";
import "../../utils/Address.sol";


/**
 * @dev Implementation of Multi-Token Standard contract
 */
contract ERC1155 is IERC165, IERC1155 {
  using SafeMath for uint256;
  using Address for address;

  /***********************************|
  |        Variables and Events       |
  |__________________________________*/

  // onReceive function signatures
  bytes4 constant internal ERC1155_RECEIVED_VALUE = 0xf23a6e61;
  bytes4 constant internal 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
  {
    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
  {
    // 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
  {
    // 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 True if the operator is approved, false if not
   */
  function isApprovedForAll(address _owner, address _operator)
    public view 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 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 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         |
  |__________________________________*/

  /**
   * INTERFACE_SIGNATURE_ERC165 = bytes4(keccak256("supportsInterface(bytes4)"));
   */
  bytes4 constant private INTERFACE_SIGNATURE_ERC165 = 0x01ffc9a7;

  /**
   * INTERFACE_SIGNATURE_ERC1155 =
   * bytes4(keccak256("safeTransferFrom(address,address,uint256,uint256,bytes)")) ^
   * bytes4(keccak256("safeBatchTransferFrom(address,address,uint256[],uint256[],bytes)")) ^
   * bytes4(keccak256("balanceOf(address,uint256)")) ^
   * bytes4(keccak256("balanceOfBatch(address[],uint256[])")) ^
   * bytes4(keccak256("setApprovalForAll(address,bool)")) ^
   * bytes4(keccak256("isApprovedForAll(address,address)"));
   */
  bytes4 constant private INTERFACE_SIGNATURE_ERC1155 = 0xd9b67a26;

  /**
   * @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) external view returns (bool) {
    if (_interfaceID == INTERFACE_SIGNATURE_ERC165 ||
        _interfaceID == INTERFACE_SIGNATURE_ERC1155) {
      return true;
    }
    return false;
  }
}

pragma solidity ^0.5.16;
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 Functions           |
  |_______________________________________*/

  /**
   * @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 Functions           |
  |_______________________________________*/

  /**
   * @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);
  }
}

pragma solidity ^0.5.16;


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           True if the operator is approved, false if not
   */
  function isApprovedForAll(address _owner, address _operator) external view returns (bool isOperator);
}

pragma solidity ^0.5.16;

/**
 * @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);

  /**
   * @notice Indicates whether a contract implements the `ERC1155TokenReceiver` functions and so can accept ERC1155 token types.
   * @param  interfaceID The ERC-165 interface ID that is queried for support.s
   * @dev This function MUST return true if it implements the ERC1155TokenReceiver interface and ERC-165 interface.
   *      This function MUST NOT consume more than 5,000 gas.
   * @return Whether ERC-165 or ERC1155TokenReceiver interfaces are supported.
   */
  function supportsInterface(bytes4 interfaceID) external view returns (bool);
}

pragma solidity ^0.5.16;


/**
 * @title ERC165
 * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
 */
interface IERC165 {

    /**
     * @notice Query if a contract implements an interface
     * @dev Interface identification is specified in ERC-165. This function
     * uses less than 30,000 gas
     * @param _interfaceId The interface identifier, as specified in ERC-165
     */
    function supportsInterface(bytes4 _interfaceId)
    external
    view
    returns (bool);
}

pragma solidity ^0.5.0;

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.
 *
 * 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(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _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 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 onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

pragma solidity ^0.5.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 *
 * _Since v2.5.0:_ this module is now much more gas efficient, given net gas
 * metering changes introduced in the Istanbul hardfork.
 */
contract ReentrancyGuard {
    bool private _notEntered;

    constructor () internal {
        // Storing an initial non-zero value makes deployment a bit more
        // expensive, but in exchange the refund on every call to nonReentrant
        // will be lower in amount. Since refunds are capped to a percetange of
        // the total transaction's gas, it is best to keep them low in cases
        // like this one, to increase the likelihood of the full refund coming
        // into effect.
        _notEntered = true;
    }

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

        // Any calls to nonReentrant after this point will fail
        _notEntered = false;

        _;

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

pragma solidity ^0.5.16;


/**
 * @title SafeMath
 * @dev Unsigned math operations with safety checks that revert on error
 */
library SafeMath {

  /**
   * @dev Multiplies two unsigned integers, reverts on 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-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b, "SafeMath#mul: OVERFLOW");

    return c;
  }

  /**
   * @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // Solidity only automatically asserts when dividing by 0
    require(b > 0, "SafeMath#div: DIVISION_BY_ZERO");
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold

    return c;
  }

  /**
   * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b <= a, "SafeMath#sub: UNDERFLOW");
    uint256 c = a - b;

    return c;
  }

  /**
   * @dev Adds two unsigned integers, reverts on overflow.
   */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, "SafeMath#add: OVERFLOW");

    return c; 
  }

  /**
   * @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
   * reverts when dividing by zero.
   */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0, "SafeMath#mod: DIVISION_BY_ZERO");
    return a % b;
  }
}

{
  "compilationTarget": {
    "/Users/ronak/Developer/projects/tsgit/swappable-asset-contracts/contracts/AssetContractShared.sol": "AssetContractShared"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "optimizer": {
    "enabled": false,
    "runs": 200
  },
  "remappings": []
}