> ## Documentation Index
> Fetch the complete documentation index at: https://pulse-hook.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# Structure
> How project code is composed
## General approach
When it comes to contract code, the main contract will seem small. All the real math happens in the libraries - there are five of them. The approach was to build things in such a way that further modification of the contract doesn't break the one really important thing: testing. So each library has its own test unit.
I hope this makes contributing easier for you too - you can rework a single unit without needing to explore the whole project. If you read it and think it is nice to try it out, check out [Contribute](/code/contribute) !
## Main code (`src/`)
`src/MPFHook.sol` - the Uniswap v4 hook itself. Holds all contract storage; contains no math of its own, only orchestration that feeds data into the libraries below.
`src/lib/FrugalMedianLibrary.sol` - pure math for a frugal-streaming approximate median estimator, letting the hook track a running median of priority fees without storing full history.
`src/lib/PenaltyFeeLibrary.sol` - pure math for the penalty curve plus its constants; given a swap's priority fee and the reference median, returns the LP fee to charge.
`src/lib/GetPriorityFeeLibrary.sol` - reads the current transaction's priority fee from *tx.gasprice / block.basefee*, floored at zero for legacy transactions.
`src/lib/SnapshotWindowLibrary.sol` - maintains a rolling per-block window of median snapshots and averages it, smoothing out single-block manipulation attempts before the fee decision is made.
`src/lib/TickCheckerLibrary.sol` - gates whether a swap is allowed to update the running median, requiring the pool's tick to have moved enough (scaled by liquidity) since the last accepted update.
## Tests (`test/`)
`test/unit/PenaltyFeeLibrary.t.sol` - checks the penalty curve's shape: no fee below threshold, monotonic increase, and saturation at the max.
`test/unit/FrugalMedianLibrary.t.sol` - isolates the median estimator's convergence and step-size behavior over a sequence of observations.
`test/unit/GetPriorityFeeLibrary.t.sol` - isolates priority-fee reading under different *vm.fee / vm.txGasPrice* combinations, including the legacy-transaction edge case.
`test/unit/SnapshotWindowLibrary.t.sol` - isolates the snapshot window's once-per-block recording, circular-buffer wraparound, and averaging.
`test/unit/TickCheckerLibrary.t.sol` - isolates the tick-movement gate, from baseline establishment through acceptance/rejection at different liquidity levels.
`test/integration/MPFHook.t.sol` - deploys the hook against a local *PoolManager* and drives it through real swaps, exercising all five libraries together via the hook's orchestration layer.
`test/fork/MPFHookForkIntegration.t.sol` - end-to-end test on a forked mainnet RPC against the real WETH/USDC pool, validating the assembled system under real liquidity conditions.
`test/utils/BaseTest.sol`**,** `Deployers.sol`**,** `libraries/EasyPosm.sol` - shared test infrastructure (pool/currency deployment helpers, liquidity-position minting) used by the integration tests.