Problem

In ArtistV4, we want to limit every address to only 1 token per edition. To do this, we give the buyer a requestedTokenId in a signed message that is validated on chain.

The problem is we are planning to start serving the metadata on chain in a future upgrade and we need a consecutive number to differentiate each token within the edition (ie: serial number). That number can be the numSold emitted by the EditionPurchased event when we’re serving the metadata, but that info is inaccessible when the metadata exists on chain. We also can’t use tokenId unless we can’t enforce all of the tokenIds will be consecutive, which is not the case with the current ArtistV4 plan.

Options

1. require a signature for every purchase of every edition

• can guarantee consecutive serial numbers, but only when the edition has sold out
• every purchase needs to happen via our app
• higher chance of failed transactions (if our backend gives out the same token id multiple times or one outside the valid range)
• lowest gas 👇
  • buyEdition = $23.3 @ 100 gwei (average-case)
  • createEdition = $31.50 @ 100 gwei (worse-case)

2. store each buyer’s address and increment id on chain

// editionId => buyer address => token id
    mapping(uint256 => mapping(address => uint256)) soldTokens;

• most simple
• most expensive 👇
  • buyEdition = $29.4 @ 100 gwei (average-case)
  • createEdition = $31.50 @ 100 gwei (worse-case)

3. ✅ Use “reserve ticket” idea

• less expensive than option 2 but more expensive than option 1
• adds variable cost to createEdition depending on how many unique buyers we want to guarantee for the edition (gas stats below are for 1024 unique buyers)