Auction Demo

• Basic auction demo for learning purposes in Solidity for Ethereum.
• This contract aims to handle an auction from its start to its end.

Data Structures

Bid: Holds all data related to a single bid.

    // Bid related data
    struct Bid {
        address bidder;     // the bidder
        uint amount;        // the amount of the bid
        uint time;          // timestamp when this bid is made
        bool claimed;       // whether this bid has been claimed or not by the user
    }

AuctionData: all data of the auction. Who is the owner, when started, when finished, what bids its have, what claims has been done, if it is open or not.

    // Auction data structure
    struct AuctionData {
        address owner;        // the one who creates the auction
        uint auctionStart;    // auction start timestamp
        uint auctionEnd;      // when the auction will end
        bool auctionClosed;   // whether the auction is closed or not
        bool refundsDone;     // whether refunds have been processed
        uint feesCollected;   // accumulated fees collected
        Bid highestBid;       // the bid with the highest amount
        Bid[] bidHistory;     // all the bid history of this auction
    }

Constants: all fixed attributes used when the auction is created.

    uint public constant MINIMUM_BID = 1 ether;                // minimum bid amount
    uint public constant AUCTION_DURATION = 1 days;            // auction duration
    uint public constant AUCTION_FEE = 2;                      // fee % collected when refunding non-winners bids
    uint public constant EXTENSION_TIME_WINDOW = 10 minutes;   // time added when bid occurs near auction end
    uint public constant MIN_BID_INCREMENT_PCT = 5;            // required % increase over highest bid

Events

AuctionStart: indicates the auction is started. Is issued once contract is deployed.

    event AuctionStart(
        address indexed owner,
        uint startTime,
        uint endTime
    );

AuctionClosed: shows when an auction is closed. Is triggered by the owner anytime.

    event AuctionClosed(
        address winner,
        uint amount
    );

BidClaimed: issued by any bidder when he/she decides to claim their funds.

    event BidClaimed(
        address indexed bidder, 
        uint refundedAmount
    );

Modifiers

Modifiers exists to check is an auction is active or not and if the caller is the owner or not.

Auction Flow

Auction is Created

This occurs when contract is deployed. This auction accepts some fixed attributes:

a) Bids has a minimum of 1 ETH
b) Auction last for 1 day
c) When auction is closed and non-winning bids has not claimed their funds, those funds are refunded but keeping a fee of 2%
d) A window of 10 min is set, if a bid is accepted and auction is finalizing befor 10 min, auction ending is extended by 10 more minutes
e) A bid is accepted if is greater than maximum bid and exceeds a rate of 5%

All this setup is done in constructor.

Auction is Open

The following functions are applicable:

bid: Accepts a bid, anyone can bid

• Signature: function bid() external payable isAuctionOpen
• Parameters: None
• Returns: None

claimMyBid: Allow bidders to claim refundable bids when auction is still open, except for winning bid

• Signature: function claimMyBid() external isAuctionOpen
• Parameters: None
• Returns: None

getAuctionProgress: Show auction times and winning bid

• Signature: function getAuctionProgress() external view
• Parametes: None
• Returns:
  • uint auctionStartTime: auction's start time
  • uint auctionEndTime: auction's end time
  • uint timeRemaining: auction's remaining time
  • address highestBidder: address of winner bidder
  • uint highestBidAmount: amount of winner bidder
  • uint highestBidTime: timestamp when winner bid was accepted

getWinnerBid: Show highest bidder, amount of higher bid and timestamp of higher bid

• Signature: function getWinnerBid() external view isAuctionOpen
• Parameters: None
• Returns: None

showBidders: Show all bidders (addresses, amounts and timestamps)

• Signature: function showBidders() external view isAuctionOpen
• Parameters: None
• Returns:
  • bidders: array of bidder's addesses
  • amounts: array of bidder's amounts
  • times: array of bidder's timestamps when the bid was accepted

showBiddersData (privileged): Show all bidders (addresses, amounts, timestamps, claimed flag)

• Signature: function showBiddersData() external view isOwner isAuctionOpen
• Parameters: None
• Returns:
  • bidHistory: array of bid structure which holds address, amount, timestamp and claimed flag for all bidders

closeAuction (privileged): Owner could close auction, refunding all non-winning bids keeping a fee whenever he/she wants (in an open or closed auction)

• Signature: function closeAuction() external isOwner
• Parameters: None
• Returns: None

Auction is Closed

Withdraw (privileged): Owner get all remaining funds from the contract (winning bid amount plus fees of refunded non-winning bids

• Signature: function withdraw() external isOwner isAuctionClosed
• Parameters: None
• Returns: None