Lending Facility & DFC

[leeftk]

Overview

Implemented a lending facility that allows users to borrow collateral tokens against locked issuance tokens with dynamic fee calculation.

Key Changes

• Added lending facility logic module with borrow/repay functionality
• Integrated dynamic fee calculation based on utilization rates
• Added role-based access control for facility management
• Implemented borrowing limits and quotas

Technical Details

• Users lock issuance tokens as collateral to borrow collateral tokens
• Dynamic fees scale with system utilization
• Configurable individual and system-wide borrowing limits
• Automatic issuance token locking/unlocking during borrow/repay
• Fee collection and distribution to DBC FM

Formulas & Pricing

• Borrow Capacity: virtualIssuanceSupply × P_floor (where P_floor is first segment's initial price)
• Required Collateral: borrowAmount ÷ floorPrice (issuance tokens needed)
• Utilization Rate: currentlyBorrowedAmount ÷ borrowCapacity
• Dynamic Fee: requestedAmount × feeRate (feeRate from DynamicFeeCalculator based on utilization)
• Floor Liquidity Rate: (borrowableAmount - currentlyBorrowedAmount) ÷ borrowableAmount

Testing

• Borrow/repay flows verified with proper state management
• Fee calculation accuracy confirmed across utilization ranges
• Access control and limit enforcement tested

Missing

• Updates from tech specs and implementation that need to be made
• Looping feature for allowing multiple loops
• More fuzz tests
• Testing all unhappy paths
• Inverter Standard review
• Invariant tests