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82 lines
2.7 KiB
82 lines
2.7 KiB
4 years ago
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# Open Auction
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# Auction params
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# Beneficiary receives money from the highest bidder
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beneficiary: public(address)
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auctionStart: public(uint256)
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auctionEnd: public(uint256)
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# Current state of auction
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highestBidder: public(address)
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highestBid: public(uint256)
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# Set to true at the end, disallows any change
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ended: public(bool)
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# Keep track of refunded bids so we can follow the withdraw pattern
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pendingReturns: public(HashMap[address, uint256])
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# Create a simple auction with `_bidding_time`
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# seconds bidding time on behalf of the
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# beneficiary address `_beneficiary`.
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@external
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def __init__(_beneficiary: address, _bidding_time: uint256):
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self.beneficiary = _beneficiary
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self.auctionStart = block.timestamp
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self.auctionEnd = self.auctionStart + _bidding_time
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# Bid on the auction with the value sent
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# together with this transaction.
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# The value will only be refunded if the
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# auction is not won.
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@external
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@payable
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def bid():
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# Check if bidding period is over.
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assert block.timestamp < self.auctionEnd
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# Check if bid is high enough
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assert msg.value > self.highestBid
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# Track the refund for the previous high bidder
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self.pendingReturns[self.highestBidder] += self.highestBid
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# Track new high bid
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self.highestBidder = msg.sender
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self.highestBid = msg.value
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# Withdraw a previously refunded bid. The withdraw pattern is
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# used here to avoid a security issue. If refunds were directly
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# sent as part of bid(), a malicious bidding contract could block
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# those refunds and thus block new higher bids from coming in.
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@external
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def withdraw():
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pending_amount: uint256 = self.pendingReturns[msg.sender]
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self.pendingReturns[msg.sender] = 0
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send(msg.sender, pending_amount)
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# End the auction and send the highest bid
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# to the beneficiary.
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@external
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def endAuction():
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# It is a good guideline to structure functions that interact
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# with other contracts (i.e. they call functions or send Ether)
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# into three phases:
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# 1. checking conditions
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# 2. performing actions (potentially changing conditions)
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# 3. interacting with other contracts
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# If these phases are mixed up, the other contract could call
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# back into the current contract and modify the state or cause
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# effects (Ether payout) to be performed multiple times.
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# If functions called internally include interaction with external
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# contracts, they also have to be considered interaction with
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# external contracts.
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# 1. Conditions
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# Check if auction endtime has been reached
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assert block.timestamp >= self.auctionEnd
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# Check if this function has already been called
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assert not self.ended
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# 2. Effects
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self.ended = True
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# 3. Interaction
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send(self.beneficiary, self.highestBid)
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