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contracts...SimpleSale.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity 0.8.0;

/**
 * @dev This is an example contract implementation of NFToken with metadata extension.
 */
import "/contracts/MyCIHEAMToken.sol";

contract SimpleSale {

    MyCIHEAMToken myToken;
    
    uint public NFTid;
    uint public weiPrice;
    address payable public beneficiary;
    bool ended = false;


    // Events that will be emitted on changes.
    event SaleEnded(address winner, uint amount);


    constructor(
        uint _weiPrice,
        uint _NFTid,
        address _tokenSC
    ) {
        weiPrice = _weiPrice;
        NFTid = _NFTid;
        myToken = MyCIHEAMToken(_tokenSC);
        beneficiary = payable (myToken.ownerOf(NFTid));

    }

    function pay() public payable {

        require(
            msg.value == weiPrice,
            "Il prezzo non coincide"
        );
        
        require(!ended, "auctionEnd has already been called.");

        // 2. Effects
        ended = true;
        emit SaleEnded(msg.sender,msg.value);

        // 3. Interaction
        beneficiary.transfer(msg.value);
        myToken.safeTransferFrom(beneficiary, msg.sender, NFTid);

    }

    
}