Highrise Contracts

Introduction

• This repo contains contracts to support:
  • Highrise land and estates
  • Funding contract to run the sales on our webpage

Contracts functionality

Land and Estate

• HighriseLand and HighriseEstate contracts are ERC721 tokens representing parts of Highrise world that inherit following openzeppelin contracts:

  • ERC721Upgradeable
  • ERC721EnumerableUpgradeable
  • ERC721RoyaltyUpgradeable
  • AccessControlUpgradeable
  • Initializable

• Both of these are supported to work on OpenSea.

  • Owner of the contract for opensea is defined by OWNER_ROLE in access control.
  • Gas-less listing is supported by overriding isApprovedForAll method

• Estates can be constructed/deconstructed from/to land parcels. Supported shapes are 3x3, 6x6, 9x9 and 12x12

• To create estates from land parcels user must first approve estate contract for transferring. This is achieved by ERC721 approve function in HighriseLand contract and in custom batch approval function approveForTransfer function in HighriseLandV2

• Both Land and Estate contracts are intended to be upgradeable. This is done by using OpenZeppelin TransparentUpgradeableProxy to separate the proxy and implementation contracts. This provides us with flexibility to add new logic and storage variables to the contracts in the future.

Token IDs and Coordinates

• Land coordinates are in range (-250, 250)
• Token ID is generated on Highrise backend with the following logic:

from struct import pack

def coordinates_to_token_id(coords: tuple[int, int]) -> int:
    """X and Y are 2 bytes each."""
    as_bytes = pack(">hh", coords[0], coords[1])
    return int.from_bytes(as_bytes, "big")

• See https://docs.python.org/3/library/struct.html for more understanding.
• Estate contract has token_id>coordinates conversion function implemented. In that way estate contract can validate that parcels passed for estate creation have valid shape.
• Two tests are implemented to validate token_id<>coordinates conversion works:
  • test_coordinates_parsing - generates token id from coordinates in python and calls estate contract parse function. Compares that function returned coordinates match the ones initially used for token_id generation
  • test_full_map_to_estates - All land parcels in the map are merged into 3x3 estates
  • these tests are skipped when running brownie test due to long execution time

Funding contract

• HighriseLandFund contract is a temporary contract used for sale purposes. It collects users payments and mints the Land tokens to the users.
• Contract States:
  • ENABLED - contract accepts payments and mints Land
  • DISABLED - contract does not accept payments, owner can enable the contract or withdraw funds
• Entrypoint to the contract from the user perspective is the fund function, which accepts a payload signed with a wallet key on our backend.
• When the payload signature is confirmed the payload is unpacked into tokenId, expiry and cost for minting purposes. After requirements are met Land NFT is minted to the user
• FundLandEvent is emitted when funding transaction is successful. Pending potential removal - not required anymore since we can track ERC721 Transfer events directly.
• Contract is granted MINTER_ROLE for HighriseLand

Prerequisites

• Install ganache - https://trufflesuite.com/ganache/
• Install brownie (pipx is also required to install it)

  # `pipx` install
  python3 -m pip install --user pipx
  python3 -m pipx ensurepath
  # install `brownie` with `pipx`
  pipx install eth-brownie

• Setup .env file and include the following variables
  • DEV_ACCOUNT_NAME - account stored in brownie used for deploying to testnets
  • WEB3_INFURA_PROJECT_ID - gateway to blockchain development - set up your account here https://infura.io/
  • ETHERSCAN_TOKEN - create account on https://etherscan.io/ - used for verifying and publishing smart contracts
  • ENVIRONMENT_NAME - Highrise environment that contracts will be used on

Brownie commands

• brownie init - initializes the project and creates project structure
• brownie compile - compiles all contracts within contracts/
• brownie run <script> - runs custom python script
• brownie test - runs tests
• brownie accounts list - lists all stored accounts
• brownie accounts new <account-name> - import existing account via private key. Stored accounts are in encrypted JSON files known as keystores
• brownie networks list - list all available networks to connect
• brownie networks add - add new network

Ethereum Theory

• Why to emit events
  • There are two types of Solidity event parameters: indexed and not indexed,
  • Events are used for return values from the transaction and as a cheap data storage,
  • Blockchain keeps event parameters in transaction logsEvents can be filtered by name and by contract address