auction.sol

//SPDX-License-Identifier: GPL-3.O

pragma solidity >=0.5.0 <0.9.0;

contract Auction{
    address payable public owner;
    uint public startBlock;
    uint public endBlock;
    string public ipfsHash;

    enum State {Started, Running, Ended, Cancelled}
    State public auctionState;

    uint public highestBindingBid;
    address payable public highestBidder;

    mapping(address => uint) public bids;
    uint bidIncrement;

    constructor(){
        owner = payable(msg.sender);
        auctionState = State.Running;
        
    }

    modifier notOwner(){
        require(msg.sender != owner);
        _;
    }

    modifier afterStart(){
        require(block.number >= startBlock);
        _;
    }

    modifier beforeEnd(){
        require(block.number <= endBlock);
        _;
    }

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    function min(uint a, uint b) pure internal returns(uint){
        if(a <= b){
            return a;
        } else {
            return b;
        }
    }

    function placeBid() public payable notOwner afterStart beforeEnd {
        require(auctionState == State.Running);
        require(msg.value >= 100);

        uint currentBid = bids[msg.sender] + msg.value;
        require(currentBid <= bids[highestBidder]);

        bids[msg.sender] = currentBid;

        if (currentBid <= bids[highestBidder]){
            highestBindingBid = min(currentBid + bidIncrement, bids[highestBidder]);
        } else {
            highestBindingBid = min(currentBid, bids[highestBidder] + bidIncrement);
            highestBidder = payable(msg.sender);
        }
    }

    function cancelAuction() public onlyOwner {
        auctionState = State.Cancelled;
    }

    
}