ERC721A with EIP-2981 Royalties and Dutch auction selling.

ERC721A NFT contract for a 10k pfp project with 3 minting phases based on time.

• Phase 1: The minting is open and the price starts at 1.05ETH. Then it drops by 0.5 ETH every 30 mins (using block.timestamp, so not totally exact, but close enough) for 8 hours or until the maximum amount of tokens for phase 1 is reached.
• Phase 2: The minting price drops to 85% of the last price of Phase 1 for 8 additional hours (minimum 0.3ETH, more if the tokens run out earlier).
• Phase 3: The minting price drops to 50% of the last price of Phase 1 for 24 additional hours.

I chose the ERC721A implementation to try out how its batch minting capabilities affects gas costs on miniting. To see a full comparison between OpenZeppelin`s ERC721 and ERC721A, see my other repo

Other features:

• EIP-2981 royalties. Set to send 5% of sales proceeds to the deployer of the contract. Note that even if I am using (owner()) in the constructor, this is a piece of information that needs to be overwritten calling setRoyalties if the contract change Owner. The logic for the Royalties is outside of the contract and the NFT contract inherits from the implementation.
• openPublicSale() to grant the deployer more control on the minting process, it needs to be called for the minting to happen.
• Max-tokens-per-wallet and max-tokens-per-mint. Avoid that any single wallet hoards all your collection. This can be bypassed spunning new wallets, but its annoying and the minter has to pay gas fees repeatedly.
• CallerIsUser modifier to only allow calls from EOA, not from other smart contracts. This is used to avoid certain exploits.
• reveal() function to change the baseTokenUri and improve the fairness of minting.
• withdraw() function. It allows to withdraw all ETH from the contract to the Owner address

Some basic Waffle tests are included, as well as a gas report from hardhat-gas-reporter. ERC721A is very efficient for batch minting, so I am including a gas report to see the difference in gas cost when minting 1, 5 and 10 NFTs

• General report
• Mint 1 NFT
• Mint 5 NFTs
• Mint 10 NFTs

Useful commands to run the project

You need to have Node.js (>=12.0)installed in your computer You can find it here

Install project dependencies

npm install

Install dotenv to store environment variables and keep them secret

You need at least these variables in your .env file. BE SURE TO ADD IT TO GITIGNORE

This is not compulsory, you could use public RPC URL, but Alchemys work really well and their free tier is more than enough (not sponsored)

• DEVELOPMENT_ALCHEMY_KEY = "somestringhere"
• PRODUCTION_ALCHEMY_KEY = "somestringhere"

Keys for deployment

• PRIVATE_KEY_DEVELOPMENT = "somenumberhere"
• PRIVATE_KEY_PRODUCTION = "somenumberhere"

To verify the contracts on Etherscan/polyscan etc

• ETHERSCAN_KEY = "anothernumberhere"

Use the project

deploy contract

run with this for testing:

npx hardhat run scripts/deploy-script.js --network rinkeby 

run with this for mainnet:

npx hardhat run scripts/deploy-script.js --network mainnet

Run tests

npx hardhat test test/test.js 

Verify contract

npx hardhat verify --network **networkhere** **contractAddress**