# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## What this is

Jungfraujoch is the data-acquisition and analysis system for the PSI JUNGFRAU and EIGER
X-ray detectors. It receives detector data, runs it through an FPGA-accelerated pipeline
(spot finding, azimuthal/ROI integration, compression), streams images out over ZeroMQ for
writing to HDF5, and runs crystallographic analysis (indexing, integration, scaling/merging).
Most authoritative documentation lives in `docs/` and on Read The Docs
(https://jungfraujoch.readthedocs.io). When changing CLI behaviour, the program's own
usage message is the source of truth, not the docs.

## Build

Out-of-source CMake build, C++20, heavy use of `FetchContent` (spdlog, zstd, HDF5,
slsDetectorPackage, Catch2, cpp-httplib, libzmq, libtiff, FFTW, Ceres, fast-feedback-indexer are
downloaded and statically linked — the **first configure needs network access** and is slow).
Two dependencies are deliberately **not** vendored and must come from the system: **ZLIB** and
**Eigen3 ≥ 3.4**, both resolved with `find_package` (see the Eigen note in `CMakeLists.txt` for why).
libjpeg-turbo is built via `ExternalProject` in `preview/`; libcurl is fetched only for viewer builds.

```
mkdir build && cd build
cmake -DCMAKE_BUILD_TYPE=Release ..
make -j$(nproc) jfjoch_broker      # the main service; build other targets by name
```

Key CMake options:
- `JFJOCH_USE_CUDA` (default ON) — GPU path. Needs CUDA ≥ 12.8 (older is warned about and
  ignored). Provides the `ffbidx` and `fft` GPU indexers; without it only the CPU `fftw` indexer is
  available. FFTW is fetched and `JFJOCH_USE_FFTW` defined unconditionally, so `fftw` is always
  there. CUDA absence is not a build error — nvcc is looked for on `PATH`, `CUDA_PATH` and
  `/usr/local/cuda`.
- `JFJOCH_WRITER_ONLY` (default OFF) — builds only the HDF5 writer; skips broker, FPGA,
  receiver, analysis, tests, frontend.
- `JFJOCH_VIEWER_BUILD` (default OFF) — builds the Qt6 `jfjoch_viewer` desktop app in addition to
  the server stack.
- `JFJOCH_VIEWER_ONLY` (default OFF on Linux, **forced ON on Windows/macOS**) — builds only
  `jfjoch_viewer`, `rugnux` and the libraries they link; skips receiver, FPGA, detector control,
  tests and the frontend.
- `SLS9` (default OFF) — build against slsDetectorPackage 9.2.0 instead of 8.0.2.
- `JFJOCH_INSTALL_DRIVER_SOURCE` (default OFF) — install the PCIe driver source for DKMS/RPM.

### `-march` and LTO are deliberately NOT set in CMakeLists

The build system sets no architecture or LTO flags, so a site can pick its own — `x86-64-v4` on an
AVX-512 cluster, `-march=native`, or the plain baseline. **CI passes them explicitly**
(`.gitea/workflows/build_and_test.yml`): every Linux configure gets `LINUX_CMAKE_FLAGS`
(`-march=x86-64-v3 -flto=auto`), and the MSVC viewer job gets `/arch:AVX` (MSVC has no x86-64-v2
spelling; `/arch:AVX` is the nearest and implies SSE4.1/4.2). LTO is CI-only on purpose: measured on
rugnux it removes 7–10% of retired instructions and 9% of the binary but only ~1.5% of the wall
clock (the pipeline is GPU- and I/O-bound), while costing ~3× on an incremental rebuild — a bad
trade for a developer, a fine one for a build that happens once and is shipped.

**This matters when profiling.** A plain `cmake -DCMAKE_BUILD_TYPE=Release ..` produces a
*baseline* binary that is not what CI or production runs, and the difference is not uniform:
GPU-bound work is unaffected, but the CPU/Eigen-bound phases — first-pass indexing and
scaling/merging — are **~26% slower** without the flags (measured). Eigen in particular has no
vectorised `round` below SSE4.1 and falls back to a libm call per element, which can make
rounding look like ~10% of all cycles when it is nearly free in a real build. Pass the CI flags
when measuring anything CPU-side, or the profile will point at the wrong code:

```
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-march=x86-64-v3" \
      -DCMAKE_C_FLAGS="-march=x86-64-v3" ..
```

The frontend is a separate custom target: `make frontend` (in `frontend/`: `npm ci`,
`npm run build`, plus the third-party-licenses, Redoc and Sphinx-docs bundling steps). It is never
built automatically — `make install` only copies whatever already sits in `frontend/dist/`.

## Test

Tests use **Catch2** and are collected into a single binary `tests/jfjoch_test`.

```
make -j$(nproc) jfjoch_test
cd tests
./jfjoch_test "<test name>"         # one test case (exact name in TEST_CASE)
./jfjoch_test "Prefix*"             # by name prefix
./jfjoch_test "[tag]"               # by tag
./jfjoch_test -r junit -o report.xml
```

**Do not run the whole suite** (`./jfjoch_test` with no filter). It takes far too long to be worth
running locally, and **CI runs it on every push anyway**. Run only the cases or tags covering the
code you changed and stop there; a bare `./jfjoch_test` is justified only for a genuinely sweeping
change. The same applies to the 37-crystal rotation battery (`rugnux_vs_xds.py`) — run it when a
change plausibly moves merged results, not as a reflex.

**Do not `git push`.** Commit when asked; pushing is a separate decision that belongs to the
maintainer.

`make jfjoch_hdf5_test` builds the HDF5 write-speed benchmark (it lives in `tools/`, so the binary
is `build/tools/jfjoch_hdf5_test`); CI also uses it to produce files that are validated against XDS
(Durin/Neggia), DIALS and CrystFEL. `jfjoch_hdf5_enospc_test` + the `enospc_shim` module test
out-of-space handling.

There is no lint config in the repo (no `.clang-tidy`/`.clang-format`, no CI lint step) — follow the
conventions the code already uses: namespaces lower_case, classes CamelCase, global constants
UPPER_CASE.

## Code style

The overriding principle is **simple, readable code** — favour the smallest, most direct
implementation that a reader can verify at a glance. Extra abstraction, speculative guards, and
clever-but-dense constructs are treated as actively harmful, not as polish. When torn between a
tidy abstraction and a flat, obvious version, pick the obvious one.

This matters most in the experimental analysis code under `image_analysis/`, where readability is
how the physics gets verified — keep those parts especially plain. **Do not add
defensive/unrequested code** (extra validation, rejection heuristics, "just in case" branches)
without asking first; if a guard isn't clearly needed, leave it out.

Match the surrounding code's idiom, naming, and comment density rather than importing a different
style.

## No sample identities in the repository

**Never put sample names or sample-specific measured values into source code, comments,
documentation, commit messages, or test fixtures.** Datasets belong to users and may be
confidential or embargoed; anything committed can leak outside the group working on them. This is
a hard rule, not a preference.

- **Forbidden**: sample/dataset names or internal codes (a protein name, a beamline dataset ID, a
  run label), and **measured unit-cell parameters tied to a real sample** (this is the most
  sensitive — never hardcode "protein X has cell a,b,c").
- **Fine**: general crystallographic descriptors — space group / Laue class ("a P2₁ crystal", "a
  holohedral 422 case"), lattice centering, twinning, "a crystal whose true axis is reported as its
  3× harmonic", pseudo-symmetry, etc. Describe the *crystallographic situation*, not the specimen.
- **Exception — plain lysozyme.** Lysozyme (HEWL) is the field's universal standard test specimen,
  not a user's confidential dataset, so naming it and using its well-known reference cell
  (tetragonal ~79/79/38, P4₃2₁2) in tests, docs and comments is allowed. This carve-out is only for
  generic lysozyme as a benchmark; a *named user dataset* that happens to be lysozyme is still off
  limits, and every other real sample remains forbidden.
- **Tests** must otherwise use neutral names (e.g. `tetragonal_uc`, not a specimen-named variable)
  and, where a cell is needed, a synthetic cell chosen for the test — not a real dataset's parameters.

When a bug was found on a specific dataset, commit the *behaviour* ("de-novo indexing adopted a
spurious axis-multiple supercell"), never the dataset.

## Local end-to-end run (no detector / no FPGA)

The FPGA HLS logic can be simulated on the CPU (`HLSSimulatedDevice`), so the full software
stack runs without hardware (slowly — fixed-point math on CPU). See
`docs/JFJOCH_BROKER.md` for the canonical walkthrough.

```
cd build/broker
./jfjoch_broker ../../etc/broker_local.json 5232      # config JSON + HTTP port
# then, separately:
cd tests/test_data && python jfjoch_broker_test.py     # feeds a test image, starts collection
# observe at http://localhost:5232 ; HDF5 is written under build/broker
```

`etc/broker_local.json`, `broker_eiger.json`, `broker_crmx.json` are example broker configs
(schema = `jfjoch_settings` in `broker/jfjoch_api.yaml`).

## Architecture

**Data flow (online):** detector → FPGA acquisition (`fpga/`, `acquisition_device/`) →
`receiver/` builds full images from per-module FPGA output → `image_pusher/` streams CBOR-encoded
images over ZeroMQ (or TCP) → the consuming side (`image_puller/`) feeds `jfjoch_writer`
(`writer/`), which writes NXmx HDF5. The broker also emits a low-rate preview stream and a
metadata stream (`preview/`).

**Writer file split:** one acquisition produces one `_master.h5` plus many `_data_NNNNNN.h5`
files. Dataset-wide metadata (geometry, detector config, ROI/azimuthal definitions — anything
fixed for the whole run) is written to the **master** file in `writer/HDF5NXmx.cpp` (the `NXmx`
class). Per-image arrays (one entry per frame) are written to the **data** files by the
`HDF5DataFilePlugin` subclasses in `writer/`. Put shared metadata in `NXmx`, not in a data-file
plugin.

The HDF5 master/data layout is one of three `FileWriterFormat`s (`common/JFJochMessages.h`),
all NXmx: **`NXmxLegacy`** (master + `_data_NNNNNN.h5` joined by external links),
**`NXmxVDS`** (master + data joined by HDF5 virtual datasets — the default), and
**`NXmxIntegrated`** (a single self-contained file, no separate data files). Per-image plugins
must work for all three; with `NXmxIntegrated` "master" and "data" are the same file. (The enum
also has non-NXmx `DataOnly` and `NoFile`; values 4/5 are retired CBF/TIFF, kept only in the
OpenAPI enum for back compatibility.)

**Two acquisition workflows:** the FPGA-accelerated path (JUNGFRAU at PSI; FPGA does masking,
summation, spot finding, ROI/azimuthal integration, compression) and the DECTRIS SIMPLON path
(EIGER), which has no FPGA — masking/ROI/azimuthal analysis then runs on CPU through the shared
`image_analysis/` library. Treat ROI and azimuthal features as available in **both** workflows,
not FPGA-only.

**`jfjoch_broker`** (`broker/`) is the central online service: HTTP/REST + OpenAPI control plane,
FPGA configuration, image building, ZeroMQ output. `JFJochStateMachine` drives acquisition state;
`JFJochServices` wires the pieces; `OpenAPIConvert`/`JFJochBrokerParser` translate between the
generated API model and internal types.

**Three analysis frontends share one analysis library** (`image_analysis/`, built as
`JFJochImageAnalysis`):
- `jfjoch_broker` — online, real-time (FPGA + GPU).
- `jfjoch_viewer` — interactive Qt desktop (`viewer/`), results not persisted.
- `rugnux` (`rugnux/rugnux_cli.cpp`, built on the `Rugnux` library in the same directory) — offline
  batch over a stored HDF5, invoked as `rugnux {<options>} <input.h5>` (it has **no `--help`**; run
  it with no arguments to print the usage, which is the authority on its flags). Rotation vs stills
  is auto-detected from the goniometer axis. Merging is on by default (`--no-merge` to disable);
  merging writes `.mtz`/`.cif`/`.hkl` and skips the bulky `_process.h5` unless `--write-process-h5`,
  while `--no-merge` writes only `_process.h5`. `--azint-only` runs only azimuthal integration, and
  `--scale` re-scales/merges the already-integrated reflections in a `_process.h5`. (rugnux = the
  data-processing half of the system; see `docs/NAMING.md`.)

**`image_analysis/` pipeline** (subdirs): `spot_finding`, `indexing` (`ffbidx`/`fft` GPU,
`fftw` CPU), `lattice_search`, `geom_refinement`, `bragg_prediction`, `bragg_integration`,
`image_preprocessing`, `azint`, `roi`, `scale_merge`, plus `rotation_indexer/` and
`dark_mask_analysis/` compiled straight into `JFJochImageAnalysis`. (`beam_stop/` is an unbuilt
prototype — it is in no `CMakeLists.txt`.) Least-squares refinement uses **Ceres** (fetched in
`image_analysis/CMakeLists.txt`, built with miniglog, no MKL, no Ceres-CUDA, CXX_THREADS).
The indexer is chosen with `-X` (`FFBIDX|FFT|FFTW|Auto|None`, default `Auto`, which resolves to a
GPU indexer when one is present and `fftw` otherwise): `ffbidx` wants a known cell (`-C`) and suits
sparse serial stills; `fft`/`fftw` index de novo and suit strong rotation data.

**FPGA** (`fpga/`): `hls/` is the Vitis HLS source (image-analysis kernels), `hls_simulation/`
runs that same HLS on CPU for hardware-free testing, `hdl/` is the Verilog RTL, `host_library/` is
the host-side driver, `pcie_driver/` is the kernel module. The HLS algorithms are documented in
`docs/FPGA_DATA_ANALYSIS.md`.

**Detector control** (`detector_control/`): wrappers for SLS (JUNGFRAU) and DECTRIS SIMPLON
(EIGER). **`jungfrau/`**: JUNGFRAU ADU→energy gain/pedestal calibration.

**Other libs:** `common/` (geometry, diffraction experiment, image buffer, CUDA wrappers — the
shared core, linked nearly everywhere), `compression/` (vendored bitshuffle + LZ4 + zstd; the
algorithms are `BSHUF_LZ4`, `BSHUF_ZSTD`, `BSHUF_ZSTD_RLE`, `BSHUF_ZSTD_RLE_HUFF`),
`frame_serialize/` (CBOR stream codec), `reader/` (HDF5 dataset read-back), `gemmi_gph/` (vendored
GEMMI for MTZ/XDS_ASCII I/O), `xds-plugin/` (XDS HDF5 read plugin).

## Portability (jfjoch_viewer)

Cross-platform support is a goal **only for `jfjoch_viewer` and its dependency tree** — keep that
code, and any shared library it transitively links (`common/`, `image_analysis/`, `reader/`,
`gemmi_gph/`, etc.), **MSVC-compatible** so the viewer can build on Windows. The rest of the
project (broker, receiver, FPGA host, detector control, …) is Linux-only and does not need to be
portable; don't constrain it for portability's sake.

- **Windows/MSVC** is the primary portability target. The end goal is a Windows viewer built
  with **MSVC *and* CUDA** (`JFJOCH_USE_CUDA=ON`): GPU processing is a wanted feature, not
  optional, so the intended Windows config is the full GPU path (`ffbidx`, GPU `fft`), not a
  CPU-only fallback. MSVC is required regardless, because CUDA on Windows requires it. Avoid
  GCC/Clang-only extensions, POSIX-only APIs, and other non-MSVC constructs in viewer-reachable
  code, and keep CUDA-reachable viewer code (`ffbidx`, GPU indexers) MSVC-buildable too.
- **macOS** is a nice-to-have for the viewer. It rules out CUDA, so anything the viewer depends on
  must also have a working CPU-only / non-CUDA path (the `JFJOCH_USE_CUDA=OFF`, `fftw`-indexer
  configuration). This non-CUDA path must keep working, but it is the macOS fallback — *not* the
  intended Windows configuration.

`JFJOCH_VIEWER_ONLY` is forced ON on Windows and macOS, so a plain configure there already builds
just the portable subset. libtiff, libjpeg-turbo (via `ExternalProject` in `preview/`) and libcurl
(viewer builds only) are now brought in by the build itself, so they need nothing from the host.
Two dependencies are still supplied externally on every platform, deliberately and by decision, not
as an open TODO: **ZLIB** and **Eigen** (header-only; needed by Ceres, by the analysis libs
directly, and by `ffbidx` under CUDA). Both are resolved with `find_package` — the system package on
Linux (`zlib-devel`, `eigen3-devel`), a build prefix pointed at by `CMAKE_PREFIX_PATH`/`Eigen3_DIR`
on Windows. Vendoring Eigen through `FetchContent` with `OVERRIDE_FIND_PACKAGE` is specifically
ruled out: it segfaults the CMake bundled with Visual Studio (see the long note in `CMakeLists.txt`).
Qt is supplied externally as before.

## OpenAPI is the single source of truth

`broker/jfjoch_api.yaml` defines the entire REST API **and the shared data schemas**. From it,
`update_version.sh` regenerates three clients — **do not hand-edit generated code**:
- C++ server model → `broker/gen/` (cpp-pistache-server generator; compiled as `JFJochAPI`).
- Python client → `python-client/` (and `gen_python_client.sh`, published as PyPI `jfjoch-client`).
- TypeScript frontend client → `frontend/src/client/` (hey-api `openapi-ts`, `npm run openapi`).

When you change `jfjoch_api.yaml`, regenerate the relevant client(s); for a version bump write the new version into `VERSION` and run
`update_version.sh` (which reads it and rewrites the `version:` in the YAML itself,
`frontend/src/version.ts`, `frontend/package.json`, `docs/conf.py`, the python client, the Redoc
html — and also the FPGA HDL and PCIe-driver version strings). It downloads
`openapi-generator-cli.jar` and runs `npm install`, so it needs network access.

## Frontend

React 19 + TypeScript + MUI 6 + Vite 7 (`frontend/`); charts are Plotly (`react-plotly.js`). Data
layer is generated from the OpenAPI spec (`@hey-api/openapi-ts` → fetch client + TanStack Query
hooks + zod schemas; config in `frontend/openapi-ts.config.ts`). Scripts:
`npm start` (dev server), `npm run build` (tsc + vite), `npm run openapi` (regen client),
`npm run redocly4broker` (regen `broker/redoc-static.html`).

## Adding a per-image scalar quantity

A per-image scalar (e.g. `ice_ring_score`, `bkg_estimate`, `mosaicity`) flows analysis → message → CBOR
→ HDF5 → scan-result/plot → API → viewer/frontend. To add one, mirror an existing float scalar
(`bkg_estimate` is a clean template) at every layer:

1. **Compute** where the azint profile is finalized: `image_analysis/MXAnalysisWithoutFPGA.cpp` (CPU),
   `receiver/JFJochReceiverFPGA.cpp` (FPGA), and the offline azint worker in `rugnux/Rugnux.cpp`.
2. **Message** (`common/JFJochMessages.h`): `std::optional<float> <name>` in `DataMessage`; in
   `EndMessage` **two** members — `std::vector<float> v_<name>` (the per-image array) and an
   `std::optional<float> <name>` run-mean scalar. Mind the `v_` prefix.
3. **CBOR**: encode in `frame_serialize/CBORStream2Serializer.cpp` — one key in the DataMessage block
   (`SerializeImageInternal`) *and* two in the END block (`SerializeSequenceEnd`: `<name>` and
   `v_<name>`); decode the same three in `CBORStream2Deserializer.cpp`. Optional fields are
   back-compatible — no version bump.
4. **HDF5** write: `writer/HDF5DataFilePluginMX.{h,cpp}` — an `AutoIncrVector<float>` with reserve /
   per-image write / `SaveVector("/entry/MX/<name>")` (per-image arrays live in the data-file plugin);
   plus the NXmx master writes in `writer/HDF5NXmx.cpp` (`SaveVectorIfMissing(..., end.v_<name>)` and
   a `SaveScalar(... "Mean", end.<name>)`). **HDF5 dataset names are camelCase even though the message
   fields are snake_case** — `bkg_estimate` is stored as `/entry/MX/bkgEstimate` (+ `bkgEstimateMean`).
   HDF5 **read-back** (so a stored file re-opens, e.g. in the viewer) is in
   `reader/HDF5MetadataSource.cpp`, NOT `JFJochHDF5Reader.cpp`: mirror the three `bkgEstimate` sites —
   master `ReadOptVector`, data-file `ReadVector` into the dataset, and the per-image message population.
5. **Scan result**: `common/ScanResult.h` (`ScanResultElem`) + `common/ScanResultGenerator.cpp`
   (copy in `Add`, resize+fill in `FillEndMessage`). The name is **not** preserved here — the
   `bkg_estimate` member is called just `bkg`, and so is the API property in step 7.
6. **Receiver plot**: `common/Plot.h` (`PlotType`) + `common/JFJochReceiverPlots.{h,cpp}` — a
   `StatusVector` member, cleared in `Setup`, fed in `Add`, plus the `GetPlots` / `GetPlotRaw` cases
   and (if the run-mean scalar of step 2 is wanted) a `GetBkgEstimate`-style accessor.
7. **API**: add to the `plot_type` enum and the `scan_result` images schema in `broker/jfjoch_api.yaml`,
   regenerate the C++ model (`java -jar openapi-generator-cli.jar generate -i broker/jfjoch_api.yaml -o
   broker/gen -g cpp-pistache-server`) and the frontend client (`cd frontend && npm run openapi`), then
   wire `broker/OpenAPIConvert.cpp` (`ConvertPlotType` string→enum and the `Convert(ScanResult)` setter).
8. **Reader/viewer**: `reader/JFJochReaderDataset.h` + `viewer/JFJochHttpReader.cpp` (`GetPlot_i`) and
   `viewer/JFJochViewerDatasetInfo.cpp` (combo item + `ExtractMetric`).
9. **Frontend**: `frontend/src/components/DataProcessingPlots.tsx` (`MenuItem`) + `DataProcessingPlot.tsx`
   in the same directory (y-axis label in `AxisTypeY`).
10. **Docs**: `docs/CBOR.md` and `docs/HDF5.md` name the fields literally; `docs/CPU_DATA_ANALYSIS.md`
    describes the quantity in prose.

Gotcha: an existing `build/` dir needs a `cmake .` reconfigure to pick up a newly-added
`broker/gen/model` source file — `broker/CMakeLists.txt` collects it with `AUX_SOURCE_DIRECTORY`,
a configure-time directory scan. (`gen/api` is include-path-only and needs no reconfigure.)