The core directory contains the AMM trading infrastructure and yield tokenization system — the two pillars of the Fira protocol.
The core module houses the contracts users interact with (through the router) to trade, provide liquidity, and split yield into fixed and floating components.
How Market and YieldContracts interact
The two subsystems are tightly coupled. A FiraMarket is parameterized by a BT address, and every swap queries the associated CT contract for the current BC index (via CT.newIndex()). The BC index determines how BT (denominated in asset units) should price against FW.
When the BC index rises (because the underlying vault earns yield), BT becomes cheaper in FW terms. The AMM incorporates this automatically: getMarketPreCompute converts FW reserves to asset terms before computing the exchange rate, so the pricing curve always reflects the current yield environment.
At expiry, the market freezes: swaps and new deposits revert. Burns still work, letting LPs exit. Post-expiry exits go through CT.redeemBC() rather than AMM swaps.
State management pattern
Both the market and yield contracts use a read-modify-write pattern with in-memory structs. The market loads MarketState into memory via readState, mutates it through MarketMathCore library calls, and persists it through _writeState. This avoids repeated SLOAD/SSTORE operations and keeps the math library pure.
