Tangible

Introduction

Tangible is a Real-World-Asset (RWA) DeFi Protocol for Real-Estate Auctions and Mortgage Lending.
I developed it as a member of the City Builders Network of Prospera (the world's premier private city).

What Tangible accomplishes:

• Allows lenders worldwide to earn yields, by supplying and lending their mortgage capital to the residents of a city/jurisdiction.
• Brings mortgage access to residents of a city/juridiction (such as Prospera) who are blocked from TradFi alternatives, through the power of Blockchain and Web3.

Links

• MVP

• MVP Demo

• On-Chain Gas-Efficient Amortization Schedule Mathematics:

• 
  • Explanation (in progress)
  • Desmos Implementation

Features

• NFTs: Legally Compliant NFTs, capable of representing RWA (property disputes can also be solved on-chain via arbitrator multisig)
• Lending Pool: Allows anyone to supply capital to the protocol and earn yeilds from mortgages. Includes tUSDC an SEC Compliant interest-bearing token (unavailable to US Citizens)
• On-Chain Mortgages: Gas-Efficient Amortization Schedule
• Auctions: Bidding mechanism to allow seamless real estate transactions. A user with an active mortgage can accept a bid, sell his house, pay off any mortgage debt, and keep the difference (all in one transaction).
• etc

Architecture

• protocol
  • state
    • State.sol (holds all protocol state vars. the proxy and all logic contracts inherit from it, to avoid storage collisions)
    • TargetManager.sol (handles upgrade and delegatecall logic)
    • Roles.sol
  • proxy
    • ProtocolProxy.sol: (the proxy responsible for mapping each function selector to the appropriate implementation)
  • logic (all non-abstract implementations inherit from State.sol)
    • Auctions.sol
    • Borrowing.sol
    • Info.sol (originally made to contain all external getters, and reduce size of other implementations. might get rid of it. under review)
    • Initializer.sol
    • Lending.sol
    • Residents.sol (Tracks who are the legitimate residents of the jurisdiction, which are the only eligible receivers of the NFT)
    • Setter.sol (originally made to contain all external setters, and reduce size of other implementations. might get rid of it. under review)
    • interest
      • InterestConstant.sol: Implementation of a Fixed/Constant Interest Rate Model
      • Interest2Slopes.sol: Implementation of an Two-Slope Interest Rate Model
      • InterestCurve.sol: Implementation of a Smooth Curve Interest Rate Model
    • loanStatus
      • Amortization.sol (holds implementation of a flexible & gas-efficient amortization schedule)
      • LoanStatus.sol (inherits from Amortization.sol, to differentiate Active Mortgages from Defaults, and so on)
• tokens
  • TangibleNft.sol
  • tUSDC.sol

TODOs/Fixes

• Main
  • Add safety mechanism to protect against clashing function selectors
  • Improve state initialization
  • Finish test suite (to reach full coverage)
  • Replace PRB with my own Fixed Point Math
  • Foundry supports stateful fuzzing. Use it to replace GeneralFuzz.t.sol
  • TargetManager upgrades should be behind a dao with a timelock
  • Improve usage of environment variables
  • Improve Gas-Expensive Functions:
    • highestActionableBid() (max heap?)
    • _defaultTime() (should be able to have the user pass in the defaultTime as a param, and only have the smart contract sanity check the preceding and subsequent month)
• Other
  • Expected vars in tests aren't being used
  • Implement foundry scripts/tasks with vm.broadcast
  • NatSpec comments
  • Improve contract and variable naming
  • Figure out how to simplify and shorten selector setting scripts
  • Slippage Protection
  • Tokenized Vault Inflation Vulnerabilities (maybe implement ERC4626)
  • Replace error strings with custom errors for gas efficiency

Future Features

• Mortgage Refinancing
• Fractionalization
  • Fractional Real Estate Ownership (ERC 1155 with nested mappings)
  • Ability to take out mortgage to purchase a fraction of a property
  • Build an exchange allowing users to buy in/out of real estate fractions

Frameworks

• Foundry
• Hardhat