Contract

/**
 *Submitted for verification at Etherscan.io on 2022-07-01
*/

// Dependency file: openzeppelin-solidity/contracts/introspection/IERC165.sol

// SPDX-License-Identifier: GPL-3.0

// 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 IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// Dependency file: openzeppelin-solidity/contracts/math/SafeMath.sol



// 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;
    }
}

// Dependency file: openzeppelin-solidity/contracts/cryptography/ECDSA.sol



// pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature`. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * // importANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     */
    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
        // Check the signature length
        if (signature.length != 65) {
            revert("ECDSA: invalid signature length");
        }

        // Divide the signature in r, s and v variables
        bytes32 r;
        bytes32 s;
        uint8 v;

        // ecrecover takes the signature parameters, and the only way to get them
        // currently is to use assembly.
        // solhint-disable-next-line no-inline-assembly
        assembly {
            r := mload(add(signature, 0x20))
            s := mload(add(signature, 0x40))
            v := byte(0, mload(add(signature, 0x60)))
        }

        return recover(hash, v, r, s);
    }

    /**
     * @dev Overload of {ECDSA-recover-bytes32-bytes-} that receives the `v`,
     * `r` and `s` signature fields separately.
     */
    function recover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal pure returns (address) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        require(uint256(s) <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, "ECDSA: invalid signature 's' value");
        require(v == 27 || v == 28, "ECDSA: invalid signature 'v' value");

        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(hash, v, r, s);
        require(signer != address(0), "ECDSA: invalid signature");

        return signer;
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * replicates the behavior of the
     * https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign[`eth_sign`]
     * JSON-RPC method.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
        // 32 is the length in bytes of hash,
        // enforced by the type signature above
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
    }
}

// Dependency file: contracts/storage/LinkdropStorage.sol

// pragma solidity >=0.6.0 <0.8.0;

contract LinkdropStorage {

    // Address of owner deploying this contract (usually factory)
    address public owner;

    // Address corresponding to linkdrop master key
    address payable public linkdropMaster;

    // Version of mastercopy contract
    uint public version;

    // Network id
    uint public chainId;

    // Indicates whether an address corresponds to linkdrop signing key
    mapping (address => bool) public isLinkdropSigner;

    // Indicates who the link is claimed to
    mapping (address => address) public claimedTo;

    // Indicates whether the link is canceled or not
    mapping (address => bool) internal _canceled;

    // Indicates whether the initializer function has been called or not
    bool public initialized;

    // Indicates whether the contract is paused or not
    bool internal _paused;

    address payable public constant feeReceiver = 0xbE9ad35449A5822B0863D2DeB3147c2a42e07C06;
    uint256 public constant sponsoredFeeAmount = 0.02 ether; // per sponsored claim
    
    // Events
    event Canceled(address linkId);
    event Claimed(address indexed linkId, uint ethAmount, address indexed token, uint tokenAmount, address receiver);
    event ClaimedERC721(address indexed linkId, uint ethAmount, address indexed nft, uint tokenId, address receiver);
    event ClaimedERC1155(address indexed linkId, uint ethAmount, address indexed nft, uint tokenId, uint tokenAmount, address receiver);    
    event Paused();
    event Unpaused();
    event AddedSigningKey(address linkdropSigner);
    event RemovedSigningKey(address linkdropSigner);

}

// Dependency file: contracts/interfaces/ILinkdropCommon.sol

// pragma solidity >=0.6.0 <0.8.0;

interface ILinkdropCommon {

    function initialize
    (
        address _owner,
        address payable _linkdropMaster,
        uint _version,
        uint _chainId
    )
    external returns (bool);

    function isClaimedLink(address _linkId) external view returns (bool);
    function isCanceledLink(address _linkId) external view returns (bool);
    function paused() external view returns (bool);
    function cancel(address _linkId) external  returns (bool);
    function withdraw() external returns (bool);
    function pause() external returns (bool);
    function unpause() external returns (bool);
    function addSigner(address _linkdropSigner) external payable returns (bool);
    function removeSigner(address _linkdropSigner) external returns (bool);
    function destroy() external;
    function getMasterCopyVersion() external view returns (uint);
    function verifyReceiverSignature( address _linkId,
                                      address _receiver,
                                      bytes calldata _signature
                                      )  external view returns (bool);
    receive() external payable;

}

// Dependency file: openzeppelin-solidity/contracts/token/ERC1155/IERC1155.sol



// pragma solidity >=0.6.2 <0.8.0;

// import "../../introspection/IERC165.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 IERC1155 is IERC165 {
    /**
     * @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;
}

// Dependency file: interfaces/ILinkdropERC1155.sol

// pragma solidity >=0.6.0 <0.8.0;

interface ILinkdropERC1155 {

    function verifyLinkdropSignerSignatureERC1155
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes calldata _signature
    )
    external view returns (bool);

    function checkClaimParamsERC1155
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _tokenAmount,        
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address _receiver,
        bytes calldata _receiverSignature
     )
    external view returns (bool);

    function claimERC1155
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address payable _receiver,
        bytes calldata _receiverSignature
    )
    external returns (bool);

}

// Dependency file: openzeppelin-solidity/contracts/token/ERC721/IERC721.sol



// pragma solidity >=0.6.2 <0.8.0;

// import "../../introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
      * @dev Safely transfers `tokenId` token from `from` to `to`.
      *
      * Requirements:
      *
      * - `from` cannot be the zero address.
      * - `to` cannot be the zero address.
      * - `tokenId` token must exist and be owned by `from`.
      * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
      * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
      *
      * Emits a {Transfer} event.
      */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
}

// Dependency file: interfaces/ILinkdropERC721.sol

// pragma solidity >=0.6.0 <0.8.0;

interface ILinkdropERC721 {

    function verifyLinkdropSignerSignatureERC721
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _expiration,
        address _linkId,
        bytes calldata _signature
    )
    external view returns (bool);

    function verifyReceiverSignatureERC721
    (
        address _linkId,
	    address _receiver,
		bytes calldata _signature
    )
    external view returns (bool);

    function checkClaimParamsERC721
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address _receiver,
        bytes calldata _receiverSignature
    )
    external view returns (bool);

    function claimERC721
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address payable _receiver,
        bytes calldata _receiverSignature
    )
    external returns (bool);

}

// Dependency file: contracts/linkdrop/LinkdropCommon.sol

// pragma solidity >=0.6.0 <0.8.0;

// import "../interfaces/ILinkdropCommon.sol";
// import "../storage/LinkdropStorage.sol";
// import "openzeppelin-solidity/contracts/cryptography/ECDSA.sol";
// import "openzeppelin-solidity/contracts/math/SafeMath.sol";

contract LinkdropCommon is ILinkdropCommon, LinkdropStorage {

    /**
    * @dev Function called only once to set owner, linkdrop master, contract version and chain id
    * @param _owner Owner address
    * @param _linkdropMaster Address corresponding to master key
    * @param _version Contract version
    * @param _chainId Network id
    */
    function initialize
    (
        address _owner,
        address payable _linkdropMaster,
        uint _version,
        uint _chainId
    )
    public
    override      
    returns (bool)
    {
        require(!initialized, "LINKDROP_PROXY_CONTRACT_ALREADY_INITIALIZED");
        owner = _owner;
        linkdropMaster = _linkdropMaster;
        isLinkdropSigner[linkdropMaster] = true;
        version = _version;
        chainId = _chainId;
        initialized = true;
        return true;
    }

    modifier onlyLinkdropMaster() {
        require(msg.sender == linkdropMaster, "ONLY_LINKDROP_MASTER");
        _;
    }

    modifier onlyLinkdropMasterOrFactory() {
        require (msg.sender == linkdropMaster || msg.sender == owner, "ONLY_LINKDROP_MASTER_OR_FACTORY");
        _;
    }

    modifier onlyFactory() {
        require(msg.sender == owner, "ONLY_FACTORY");
        _;
    }

    modifier whenNotPaused() {
        require(!paused(), "LINKDROP_PROXY_CONTRACT_PAUSED");
        _;
    }

    /**
    * @dev Indicates whether a link is claimed or not
    * @param _linkId Address corresponding to link key
    * @return True if claimed
    */
    function isClaimedLink(address _linkId) public override view returns (bool) {
        return claimedTo[_linkId] != address(0);
    }

    /**
    * @dev Indicates whether a link is canceled or not
    * @param _linkId Address corresponding to link key
    * @return True if canceled
    */
    function isCanceledLink(address _linkId) public override view returns (bool) {
        return _canceled[_linkId];
    }

    /**
    * @dev Indicates whether a contract is paused or not
    * @return True if paused
    */
    function paused() public override view returns (bool) {
        return _paused;
    }

    /**
    * @dev Function to cancel a link, can only be called by linkdrop master
    * @param _linkId Address corresponding to link key
    * @return True if success
    */
    function cancel(address _linkId) external override onlyLinkdropMaster returns (bool) {
        require(!isClaimedLink(_linkId), "LINK_CLAIMED");
        _canceled[_linkId] = true;
        emit Canceled(_linkId);
        return true;
    }

    /**
    * @dev Function to withdraw eth to linkdrop master, can only be called by linkdrop master
    * @return True if success
    */
    function withdraw() external override onlyLinkdropMaster returns (bool) {
        linkdropMaster.transfer(address(this).balance);
        return true;
    }

    /**
    * @dev Function to pause contract, can only be called by linkdrop master
    * @return True if success
    */
    function pause() external override onlyLinkdropMaster whenNotPaused returns (bool) {
        _paused = true;
        emit Paused();
        return true;
    }

    /**
    * @dev Function to unpause contract, can only be called by linkdrop master
    * @return True if success
    */
    function unpause() external override onlyLinkdropMaster returns (bool) {
        require(paused(), "LINKDROP_CONTRACT_ALREADY_UNPAUSED");
        _paused = false;
        emit Unpaused();
        return true;
    }

    /**
    * @dev Function to add new signing key, can only be called by linkdrop master or owner (factory contract)
    * @param _linkdropSigner Address corresponding to signing key
    * @return True if success
    */
    function addSigner(address _linkdropSigner) external override payable onlyLinkdropMasterOrFactory returns (bool) {
        require(_linkdropSigner != address(0), "INVALID_LINKDROP_SIGNER_ADDRESS");
        isLinkdropSigner[_linkdropSigner] = true;
        return true;
    }

    /**
    * @dev Function to remove signing key, can only be called by linkdrop master
    * @param _linkdropSigner Address corresponding to signing key
    * @return True if success
    */
    function removeSigner(address _linkdropSigner) external override onlyLinkdropMaster returns (bool) {
        require(_linkdropSigner != address(0), "INVALID_LINKDROP_SIGNER_ADDRESS");
        isLinkdropSigner[_linkdropSigner] = false;
        return true;
    }

    /**
    * @dev Function to destroy this contract, can only be called by owner (factory) or linkdrop master
    * Withdraws all the remaining ETH to linkdrop master
    */
    function destroy() external override onlyLinkdropMasterOrFactory {
        selfdestruct(linkdropMaster);
    }

    /**
    * @dev Function for other contracts to be able to fetch the mastercopy version
    * @return Master copy version
    */
    function getMasterCopyVersion() external override view returns (uint) {
        return version;
    }


    /**
    * @dev Function to verify linkdrop receiver's signature
    * @param _linkId Address corresponding to link key
    * @param _receiver Address of linkdrop receiver
    * @param _signature ECDSA signature of linkdrop receiver
    * @return True if signed with link key
    */
    function verifyReceiverSignature
    (
        address _linkId,
        address _receiver,
        bytes memory _signature
    )
    public view
    override       
    returns (bool)
    {
        bytes32 prefixedHash = ECDSA.toEthSignedMessageHash(keccak256(abi.encodePacked(_receiver)));
        address signer = ECDSA.recover(prefixedHash, _signature);
        return signer == _linkId;
    }
    
    /**
    * @dev Fallback function to accept ETH
    */
    receive() external override payable {}    
}

// Dependency file: contracts/interfaces/ILinkdropERC20.sol

// pragma solidity >=0.6.0 <0.8.0;

interface ILinkdropERC20 {

    function verifyLinkdropSignerSignature
    (
        uint _weiAmount,
        address _tokenAddress,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes calldata _signature
    )
    external view returns (bool);

    function checkClaimParams
    (
        uint _weiAmount,
        address _tokenAddress,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address _receiver,
        bytes calldata _receiverSignature
    )
    external view returns (bool);

    function claim
    (
        uint _weiAmount,
        address _tokenAddress,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address payable _receiver,
        bytes calldata _receiverSignature
    )
    external returns (bool);

}

// Dependency file: openzeppelin-solidity/contracts/token/ERC20/IERC20.sol



// 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);
}

// Dependency file: contracts/linkdrop/LinkdropERC1155.sol

// pragma solidity >=0.6.0 <0.8.0;

// import "./LinkdropCommon.sol";
// import "../../interfaces/ILinkdropERC1155.sol";
// import "openzeppelin-solidity/contracts/token/ERC1155/IERC1155.sol";

contract LinkdropERC1155 is ILinkdropERC1155, LinkdropCommon {
    using SafeMath for uint;
    /**
    * @dev Function to verify linkdrop signer's signature
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId Token id to be claimed
    * @param _tokenAmount Token amount to be claimed
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _signature ECDSA signature of linkdrop signer
    * @return True if signed with linkdrop signer's private key
    */
    function verifyLinkdropSignerSignatureERC1155
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes memory _signature
    )
    public view
    override       
    returns (bool)
    {
        bytes32 prefixedHash = ECDSA.toEthSignedMessageHash
        (
            keccak256
            (
                abi.encodePacked
                (
                    _weiAmount,
                    _nftAddress,
                    _tokenId,
                    _tokenAmount,
                    _expiration,
                    version,
                    chainId,
                    _linkId,
                    address(this)
                )
            )
        );
        address signer = ECDSA.recover(prefixedHash, _signature);
        return isLinkdropSigner[signer];
    }


    /**
    * @dev Function to verify claim params and make sure the link is not claimed or canceled
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId Token id to be claimed
    * @param _tokenAmount Token amount to be claimed
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _linkdropSignerSignature ECDSA signature of linkdrop signer
    * @param _receiver Address of linkdrop receiver
    * @param _receiverSignature ECDSA signature of linkdrop receiver
    * @return True if success
    */
    function checkClaimParamsERC1155
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes memory _linkdropSignerSignature,
        address _receiver,
        bytes memory _receiverSignature
    )
    public view
    override       
    whenNotPaused
    returns (bool)
    {
        // Make sure nft address is not equal to address(0)
        require(_nftAddress != address(0), "INVALID_NFT_ADDRESS");

        // Make sure link is not claimed
        require(isClaimedLink(_linkId) == false, "LINK_CLAIMED");

        // Make sure link is not canceled
        require(isCanceledLink(_linkId) == false, "LINK_CANCELED");

        // Make sure link is not expired
        require(_expiration >= now, "LINK_EXPIRED");

        // Make sure eth amount is available for this contract
        require(address(this).balance >= _weiAmount, "INSUFFICIENT_ETHERS");

        // Make sure linkdrop master has enough tokens of corresponding tokenId
        require(IERC1155(_nftAddress).balanceOf(linkdropMaster, _tokenId) >= _tokenAmount, "LINKDROP_MASTER_DOES_NOT_HAVE_ENOUGH_TOKENS");

        // Verify that link key is legit and signed by linkdrop signer's private key
        require
        (
            verifyLinkdropSignerSignatureERC1155
            (
                _weiAmount,
                _nftAddress,
                _tokenId,
                _tokenAmount,
                _expiration,
                _linkId,
                _linkdropSignerSignature
            ),
            "INVALID_LINKDROP_SIGNER_SIGNATURE"
        );

        // Verify that receiver address is signed by ephemeral key assigned to claim link (link key)
        require
        (
            verifyReceiverSignature(_linkId, _receiver, _receiverSignature),
            "INVALID_RECEIVER_SIGNATURE"
        );

        return true;
    }

    /**
    * @dev Function to claim ETH and/or ERC1155 token. Can only be called when contract is not paused
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId Token id to be claimed
    * @param _tokenAmount Token amount to be claimed
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _linkdropSignerSignature ECDSA signature of linkdrop signer
    * @param _receiver Address of linkdrop receiver
    * @param _receiverSignature ECDSA signature of linkdrop receiver
    * @return True if success
    */
    function claimERC1155
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address payable _receiver,
        bytes calldata _receiverSignature
    )
    external
    override 
    whenNotPaused
    returns (bool)
    {

        // Make sure params are valid
        require
        (
            checkClaimParamsERC1155
            (
                _weiAmount,
                _nftAddress,
                _tokenId,
                _tokenAmount,
                _expiration,                
                _linkId,
                _linkdropSignerSignature,
                _receiver,
                _receiverSignature
            ),
            "INVALID_CLAIM_PARAMS"
        );

        // Mark link as claimed
        claimedTo[_linkId] = _receiver;

        // Make sure transfer succeeds
        require(_transferFundsERC1155(_weiAmount, _nftAddress, _tokenId, _tokenAmount, _receiver), "TRANSFER_FAILED");

        // Log claim
        emit ClaimedERC1155(_linkId, _weiAmount, _nftAddress, _tokenId, _tokenAmount, _receiver);

        return true;
    }

    /**
    * @dev Internal function to transfer ethers and/or ERC1155 tokens
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId token id to transfer
    * @param _tokenAmount Token amount to transfer
    * @param _receiver Address to transfer funds to
    * @return True if success
    */
    function _transferFundsERC1155
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _tokenAmount,
        address payable _receiver
    )
    internal returns (bool) {
      // should send fees to fee receiver
      if (tx.origin != _receiver) { 
        feeReceiver.transfer(sponsoredFeeAmount);
      }
      
      // Transfer ethers
      if (_weiAmount > 0) {
        _receiver.transfer(_weiAmount);
      }
      
      // Transfer NFT
      IERC1155(_nftAddress).safeTransferFrom(linkdropMaster, _receiver, _tokenId, _tokenAmount, new bytes(0));
      
      return true;
    }

}

// Dependency file: contracts/linkdrop/LinkdropERC721.sol

// pragma solidity >=0.6.0 <0.8.0;

// import "./LinkdropCommon.sol";
// import "../../interfaces/ILinkdropERC721.sol";
// import "openzeppelin-solidity/contracts/token/ERC721/IERC721.sol";

contract LinkdropERC721 is ILinkdropERC721, LinkdropCommon {
    using SafeMath for uint;
    /**
    * @dev Function to verify linkdrop signer's signature
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId Token id to be claimed
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _signature ECDSA signature of linkdrop signer
    * @return True if signed with linkdrop signer's private key
    */
    function verifyLinkdropSignerSignatureERC721
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _expiration,
        address _linkId,
        bytes memory _signature
    )
    public view
    override       
    returns (bool)
    {
        bytes32 prefixedHash = ECDSA.toEthSignedMessageHash
        (
            keccak256
            (
                abi.encodePacked
                (
                    _weiAmount,
                    _nftAddress,
                    _tokenId,
                    _expiration,
                    version,
                    chainId,
                    _linkId,
                    address(this)
                )
            )
        );
        address signer = ECDSA.recover(prefixedHash, _signature);
        return isLinkdropSigner[signer];
    }

    /**
    * @dev Function to verify linkdrop receiver's signature
    * @param _linkId Address corresponding to link key
    * @param _receiver Address of linkdrop receiver
    * @param _signature ECDSA signature of linkdrop receiver
    * @return True if signed with link key
    */
    function verifyReceiverSignatureERC721
    (
        address _linkId,
        address _receiver,
        bytes memory _signature
    )
    public view
    override       
    returns (bool)
    {
        bytes32 prefixedHash = ECDSA.toEthSignedMessageHash(keccak256(abi.encodePacked(_receiver)));
        address signer = ECDSA.recover(prefixedHash, _signature);
        return signer == _linkId;
    }

    /**
    * @dev Function to verify claim params and make sure the link is not claimed or canceled
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId Token id to be claimed
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _linkdropSignerSignature ECDSA signature of linkdrop signer
    * @param _receiver Address of linkdrop receiver
    * @param _receiverSignature ECDSA signature of linkdrop receiver
    * @return True if success
    */
    function checkClaimParamsERC721
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _expiration,
        address _linkId,
        bytes memory _linkdropSignerSignature,
        address _receiver,
        bytes memory _receiverSignature
    )
    public view
    override       
    whenNotPaused
    returns (bool)
    {
        // Make sure nft address is not equal to address(0)
        require(_nftAddress != address(0), "INVALID_NFT_ADDRESS");

        // Make sure link is not claimed
        require(isClaimedLink(_linkId) == false, "LINK_CLAIMED");

        // Make sure link is not canceled
        require(isCanceledLink(_linkId) == false, "LINK_CANCELED");

        // Make sure link is not expired
        require(_expiration >= now, "LINK_EXPIRED");

        // Make sure eth amount is available for this contract
        require(address(this).balance >= _weiAmount, "INSUFFICIENT_ETHERS");

        // Verify that link key is legit and signed by linkdrop signer's private key
        require
        (
            verifyLinkdropSignerSignatureERC721
            (
                _weiAmount,
                _nftAddress,
                _tokenId,
                _expiration,
                _linkId,
                _linkdropSignerSignature
            ),
            "INVALID_LINKDROP_SIGNER_SIGNATURE"
        );

        // Verify that receiver address is signed by ephemeral key assigned to claim link (link key)
        require
        (
            verifyReceiverSignatureERC721(_linkId, _receiver, _receiverSignature),
            "INVALID_RECEIVER_SIGNATURE"
        );

        return true;
    }

    /**
    * @dev Function to claim ETH and/or ERC721 token. Can only be called when contract is not paused
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId Token id to be claimed
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _linkdropSignerSignature ECDSA signature of linkdrop signer
    * @param _receiver Address of linkdrop receiver
    * @param _receiverSignature ECDSA signature of linkdrop receiver
    * @return True if success
    */
    function claimERC721
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address payable _receiver,
        bytes calldata _receiverSignature
    )
    external
    override 
    onlyFactory
    whenNotPaused
    returns (bool)
    {

        // Make sure params are valid
        require
        (
            checkClaimParamsERC721
            (
                _weiAmount,
                _nftAddress,
                _tokenId,
                _expiration,
                _linkId,
                _linkdropSignerSignature,
                _receiver,
                _receiverSignature
            ),
            "INVALID_CLAIM_PARAMS"
        );

        // Mark link as claimed
        claimedTo[_linkId] = _receiver;

        // Make sure transfer succeeds
        require(_transferFundsERC721(_weiAmount, _nftAddress, _tokenId, _receiver), "TRANSFER_FAILED");

        // Log claim
        emit ClaimedERC721(_linkId, _weiAmount, _nftAddress, _tokenId, _receiver);

        return true;
    }

    /**
    * @dev Internal function to transfer ethers and/or ERC721 tokens
    * @param _weiAmount Amount of wei to be claimed
    * @param _nftAddress NFT address
    * @param _tokenId Amount of tokens to be claimed (in atomic value)
    * @param _receiver Address to transfer funds to
    * @return True if success
    */
    function _transferFundsERC721
    (
        uint _weiAmount,
        address _nftAddress,
        uint _tokenId,
        address payable _receiver
    )
    internal returns (bool)
    {

      // should send fees to fee receiver
      if (tx.origin != _receiver) { 
        feeReceiver.transfer(sponsoredFeeAmount);
      }
      
      // Transfer ethers
      if (_weiAmount > 0) {
        _receiver.transfer(_weiAmount);
      }

      // Transfer NFT
      IERC721(_nftAddress).transferFrom(linkdropMaster, _receiver, _tokenId);
      
      return true;
    }

}

// Dependency file: contracts/linkdrop/LinkdropERC20.sol

// pragma solidity >=0.6.0 <0.8.0;

// import "openzeppelin-solidity/contracts/token/ERC20/IERC20.sol";
// import "../interfaces/ILinkdropERC20.sol";
// import "./LinkdropCommon.sol";

contract LinkdropERC20 is ILinkdropERC20, LinkdropCommon {
  
    using SafeMath for uint;
    
    /**
    * @dev Function to verify linkdrop signer's signature
    * @param _weiAmount Amount of wei to be claimed
    * @param _tokenAddress Token address
    * @param _tokenAmount Amount of tokens to be claimed (in atomic value)
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _signature ECDSA signature of linkdrop signer
    * @return True if signed with linkdrop signer's private key
    */
    function verifyLinkdropSignerSignature
    (
        uint _weiAmount,
        address _tokenAddress,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes memory _signature
    )
    public view
      override 
    returns (bool)
    {
        bytes32 prefixedHash = ECDSA.toEthSignedMessageHash
        (
            keccak256
            (
                abi.encodePacked
                (
                    _weiAmount,
                    _tokenAddress,
                    _tokenAmount,
                    _expiration,
                    version,
                    chainId,
                    _linkId,
                    address(this)
                )
            )
        );
        address signer = ECDSA.recover(prefixedHash, _signature);
        return isLinkdropSigner[signer];
    }


    /**
    * @dev Function to verify claim params and make sure the link is not claimed or canceled
    * @param _weiAmount Amount of wei to be claimed
    * @param _tokenAddress Token address
    * @param _tokenAmount Amount of tokens to be claimed (in atomic value)
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _linkdropSignerSignature ECDSA signature of linkdrop signer
    * @param _receiver Address of linkdrop receiver
    * @param _receiverSignature ECDSA signature of linkdrop receiver,
    * @return True if success
    */
    function checkClaimParams
    (
        uint _weiAmount,
        address _tokenAddress,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes memory _linkdropSignerSignature,
        address _receiver,
        bytes memory _receiverSignature
     )
    public view
    override       
    whenNotPaused
    returns (bool)
    {
        // If tokens are being claimed
        if (_tokenAmount > 0) {
            require(_tokenAddress != address(0), "INVALID_TOKEN_ADDRESS");
        }

        // Make sure link is not claimed
        require(isClaimedLink(_linkId) == false, "LINK_CLAIMED");

        // Make sure link is not canceled
        require(isCanceledLink(_linkId) == false, "LINK_CANCELED");

        // Make sure link is not expired
        require(_expiration >= now, "LINK_EXPIRED");

        // Make sure eth amount is available for this contract
        require(address(this).balance >= _weiAmount, "INSUFFICIENT_ETHERS");

        // Make sure tokens are available for this contract
        if (_tokenAddress != address(0)) {
            require
            (
                IERC20(_tokenAddress).balanceOf(linkdropMaster) >= _tokenAmount,
                "INSUFFICIENT_TOKENS"
            );

            require
            (
                IERC20(_tokenAddress).allowance(linkdropMaster, address(this)) >= _tokenAmount, "INSUFFICIENT_ALLOWANCE"
            );
        }

        // Verify that link key is legit and signed by linkdrop signer
        require
        (
            verifyLinkdropSignerSignature
            (
                _weiAmount,
                _tokenAddress,
                _tokenAmount,
                _expiration,
                _linkId,
                _linkdropSignerSignature
            ),
            "INVALID_LINKDROP_SIGNER_SIGNATURE"
        );

        // Verify that receiver address is signed by ephemeral key assigned to claim link (link key)
        require
        (
            verifyReceiverSignature(_linkId, _receiver, _receiverSignature),
            "INVALID_RECEIVER_SIGNATURE"
        );

        return true;
    }

    /**
    * @dev Function to claim ETH and/or ERC20 tokens. Can only be called when contract is not paused
    * @param _weiAmount Amount of wei to be claimed
    * @param _tokenAddress Token address
    * @param _tokenAmount Amount of tokens to be claimed (in atomic value)
    * @param _expiration Unix timestamp of link expiration time
    * @param _linkId Address corresponding to link key
    * @param _linkdropSignerSignature ECDSA signature of linkdrop signer
    * @param _receiver Address of linkdrop receiver
    * @param _receiverSignature ECDSA signature of linkdrop receiver
    * @return True if success
    */
    function claim
    (
        uint _weiAmount,
        address _tokenAddress,
        uint _tokenAmount,
        uint _expiration,
        address _linkId,
        bytes calldata _linkdropSignerSignature,
        address payable _receiver,
        bytes calldata _receiverSignature
    )
    external
    override       
    onlyFactory
    whenNotPaused
    returns (bool)
    {

        // Make sure params are valid
        require
        (
            checkClaimParams
            (
                _weiAmount,
                _tokenAddress,
                _tokenAmount,
                _expiration,
                _linkId,
                _linkdropSignerSignature,
                _receiver,
                _receiverSignature
            ),
            "INVALID_CLAIM_PARAMS"
        );

        // Mark link as claimed
        claimedTo[_linkId] = _receiver;

        // Make sure transfer succeeds
        require(_transferFunds(_weiAmount, _tokenAddress, _tokenAmount, _receiver), "TRANSFER_FAILED");

        // Emit claim event
        emit Claimed(_linkId, _weiAmount, _tokenAddress, _tokenAmount, _receiver);

        return true;
    }

    /**
    * @dev Internal function to transfer ethers and/or ERC20 tokens
    * @param _weiAmount Amount of wei to be claimed
    * @param _tokenAddress Token address
    * @param _tokenAmount Amount of tokens to be claimed (in atomic value)
    * @param _receiver Address to transfer funds to

    * @return True if success
    */
    function _transferFunds
    (
        uint _weiAmount,
        address _tokenAddress,
        uint _tokenAmount,
        address payable _receiver
    )
    internal returns (bool)
    {

      // should send fees to fee receiver
      if (tx.origin != _receiver) { 
        feeReceiver.transfer(sponsoredFeeAmount);
      }
      
        // Transfer ethers
        if (_weiAmount > 0) {
            _receiver.transfer(_weiAmount);
        }

        // Transfer tokens
        if (_tokenAmount > 0) {
            IERC20(_tokenAddress).transferFrom(linkdropMaster, _receiver, _tokenAmount);
        }

        return true;
    }

}

pragma solidity >=0.6.0 <0.8.0;

// import "./LinkdropERC20.sol";
// import "./LinkdropERC721.sol";
// import "./LinkdropERC1155.sol";

contract LinkdropMastercopy is LinkdropERC20, LinkdropERC721, LinkdropERC1155 {

}

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