// Contract: metaGAN_Series2
// Target function: function requestRandomness(
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface LinkTokenInterface {

  function allowance(
    address owner,
    address spender
  )
    external
    view
    returns (
      uint256 remaining
    );

  function approve(
    address spender,
    uint256 value
  )
    external
    returns (
      bool success
    );

  function balanceOf(
    address owner
  )
    external
    view
    returns (
      uint256 balance
    );

  function decimals()
    external
    view
    returns (
      uint8 decimalPlaces
    );

  function decreaseApproval(
    address spender,
    uint256 addedValue
  )
    external
    returns (
      bool success
    );

  function increaseApproval(
    address spender,
    uint256 subtractedValue
  ) external;

  function name()
    external
    view
    returns (
      string memory tokenName
    );

  function symbol()
    external
    view
    returns (
      string memory tokenSymbol
    );

  function totalSupply()
    external
    view
    returns (
      uint256 totalTokensIssued
    );

  function transfer(
    address to,
    uint256 value
  )
    external
    returns (
      bool success
    );

  function transferAndCall(
    address to,
    uint256 value,
    bytes calldata data
  )
    external
    returns (
      bool success
    );

  function transferFrom(
    address from,
    address to,
    uint256 value
  )
    external
    returns (
      bool success
    );

}


contract VRFRequestIDBase {

  /**
   * @notice returns the seed which is actually input to the VRF coordinator
   *
   * @dev To prevent repetition of VRF output due to repetition of the
   * @dev user-supplied seed, that seed is combined in a hash with the
   * @dev user-specific nonce, and the address of the consuming contract. The
   * @dev risk of repetition is mostly mitigated by inclusion of a blockhash in
   * @dev the final seed, but the nonce does protect against repetition in
   * @dev requests which are included in a single block.
   *
   * @param _userSeed VRF seed input provided by user
   * @param _requester Address of the requesting contract
   * @param _nonce User-specific nonce at the time of the request
   */
  function makeVRFInputSeed(
    bytes32 _keyHash,
    uint256 _userSeed,
    address _requester,
    uint256 _nonce
  )
    internal
    pure
    returns (
      uint256
    )
  {
    return uint256(keccak256(abi.encode(_keyHash, _userSeed, _requester, _nonce)));
  }

  /**
   * @notice Returns the id for this request
   * @param _keyHash The serviceAgreement ID to be used for this request
   * @param _vRFInputSeed The seed to be passed directly to the VRF
   * @return The id for this request
   *
   * @dev Note that _vRFInputSeed is not the seed passed by the consuming
   * @dev contract, but the one generated by makeVRFInputSeed
   */
  function makeRequestId(
    bytes32 _keyHash,
    uint256 _vRFInputSeed
  )
    internal
    pure
    returns (
      bytes32
    )
  {
    return keccak256(abi.encodePacked(_keyHash, _vRFInputSeed));
  }
}


abstract contract VRFConsumerBase is VRFRequestIDBase {

  /**
   * @notice fulfillRandomness handles the VRF response. Your contract must
   * @notice implement it. See "SECURITY CONSIDERATIONS" above for important
   * @notice principles to keep in mind when implementing your fulfillRandomness
   * @notice method.
   *
   * @dev VRFConsumerBase expects its subcontracts to have a method with this
   * @dev signature, and will call it once it has verified the proof
   * @dev associated with the randomness. (It is triggered via a call to
   * @dev rawFulfillRandomness, below.)
   *
   * @param requestId The Id initially returned by requestRandomness
   * @param randomness the VRF output
   */
  function fulfillRandomness(
    bytes32 requestId,
    uint256 randomness
  )
    internal
    virtual;

  /**
   * @dev In order to keep backwards compatibility we have kept the user
   * seed field around. We remove the use of it because given that the blockhash
   * enters later, it overrides whatever randomness the used seed provides.
   * Given that it adds no security, and can easily lead to misunderstandings,
   * we have removed it from usage and can now provide a simpler API.
   */
  uint256 constant private USER_SEED_PLACEHOLDER = 0;