ISR/CLAUDE.md

# CLAUDE.md

Guidance for Claude Code when working in this repository.

## Rules

- **Always update `README.md`** when user-facing behaviour changes (flags, endpoints, Docker setup, features), and **commit it in the same commit** as the code change. README is the external reference; CLAUDE.md documents internals.
- Run `python -m pytest tests/` after changing `isr.py` or `web.py` (tests cover the recorder and the loud-section detector).

## Files

| File | Purpose |
|------|---------|
| `isr.py` | Recorder: streams (Icecast/HTTP) + ALSA soundcards, time-aligned file splits |
| `web.py` | Archive browser: HTTP server, file listing, RMS loudness analysis, cut/delete |
| `webui.html` | Single-page UI (HTML/CSS/JS), loaded by `web.py` at startup — must sit next to `web.py` and be copied in the Dockerfile |
| `config.ini` | Recording sources; copy from `config.example.ini`. `[general]` gives defaults, every other section is a source (`type = stream` or `type = soundcard`) |
| `asound.conf` | dsnoop device `shared_mic` so ISR and other ALSA apps can share a soundcard |

## Commands

```bash
python isr.py [config.ini]        # recorder; --list-devices to list ALSA inputs
python web.py                     # web UI on :8080 (--dir, --port, --margin, --min-gap, --min-duration, --analyses-dir)
python -m pytest tests/           # test suite
docker compose up -d / down       # web UI mapped to host port 8050
```

Dependencies: `requests` (streams), `numpy` + `soundfile` (FLAC output and FLAC analysis/clips — both optional, code degrades gracefully).

## Code map

`web.py`:
- Detection: `_compute_rms_windows_wav()` / `analyze_flac()` produce 100 ms RMS windows → `_noise_floor_db()` estimates the rolling floor → `_loud_sections()` emits scored sections → `_package_result()` shapes the `/api/analyze` payload.
- Clips: `_api_clip()` validates params, `_clip_wav()` / `_clip_flac()` stream the decoded slice, `_wav_header()` builds the 44-byte PCM header.
- Filenames as a clock: `_recording_start()` parses the start time out of a filename stem; `_cut_filename()` turns a (stem, ext, start, end) into a wall-clock-named cut. Both the listing `date` field and `_api_cut()` use them.
- Live headers: `_live_wav_header()`, `_live_flac_header()` (+ `_flac_frame_samples()`, CRC-8 verified).
- Serving: `_stream()` (Range support), `_copy_to_response()`, `_safe_path()` (path traversal guard).

`webui.html` (one `<script>` block):
- Clip review: `clipQueue`/`clipCursor` globals, `playClip()`, `playFileSection()`, `hideClipBar()`; markup is the `#clip-bar` div.
- Day review: `dayHighlights()` builds `dayActiveSections` (chronological); `jumpToDaySection()` arms the queue.
- J/K: single document-level `keydown` listener — clip queue takes priority, in-player `currentTime` stepping is the fallback when no queue is armed.
- Analysis: `fetchAnalysis()` (session `analysisCache`), `analyse()` (per-row render), `cachedParamsMatch()` (autoload guard).

## Verifying changes

- `python -m pytest tests/` covers the recorder (`test_isr.py`) and the detector (`test_web.py`).
- There is no JS toolchain and no `node` on the dev box. After editing `webui.html`, cross-check every `getElementById('x')` against an `id="x"` declaration, and smoke-test endpoints.
- Endpoint smoke pattern: write a temp WAV/FLAC with a known loud burst, subclass `web._Handler` with `recordings_dir`/`analyses_dir` pointing at the temp dir, serve `web._Server(('127.0.0.1', 0), H)` in a daemon thread, then hit `/api/analyze` and `/api/clip` with urllib — assert section start/score and that `Content-Length == len(body) == 44 + frames × channels × 2`.
- Dev box is Windows / PowerShell 5.1. Multi-line commit messages: use the Bash tool with `git commit -F - <<'EOF'` — PowerShell here-strings containing quotes get mangled into separate arguments.

## Non-obvious internals

- **Recorder/web coupling is one file:** `RecorderManager` atomically writes `recordings/status.json` every 2 s listing in-progress files; deleted on clean shutdown. `web.py` reads it to show REC badges and to refuse analyse/cut/delete on active files. In-progress WAV/FLAC headers are unfinalized, so durations are not read for active files.
- **Stream splits:** OGG/Opus/FLAC codec headers are extracted from the first ~16 KB of each connection and prepended to every split file so each file plays standalone. A new file is always opened on reconnect (gap in stream). MP3/AAC need no headers.
- **Split timing:** files split at clock-aligned boundaries (`get_next_split_time()`), e.g. `split_minutes = 60` → on the hour.
- **Filename is the clock — fixed format, not configurable.** Recordings are named `%Y%m%d_%H%M%S.<ext>` (the *start* time). This is hardcoded as `FILENAME_FORMAT`, defined in **both** `isr.py` (recorder writes it) and `web.py` (reads it back) — the two copies must stay in sync. There is no `filename_pattern` config option (removed; `web.py` can't see `config.ini`, so a configurable pattern would break parsing). `web.py` derives the displayed DATE column from the filename via `_recording_start()` (falling back to mtime only for non-standard names — mtime is the last write ≈ end, not the start). Cut downloads are named by the wall-clock span they cover via `_cut_filename()`: a 22:31:30→22:32:30 slice of `20260523_220000.flac` becomes `20260523_22-31-30_22-32-30.flac`; non-standard source names fall back to `<stem>_cut_<start>s-<end>s`.
- **ALSA:** capture spawns `arecord` as a subprocess, raw PCM read in 100 ms chunks by a thread. Device spec resolution: `default` → exact `hw:X,Y` → partial name → fallback to any literal ALSA PCM name (so `shared_mic` from asound.conf works without appearing in `arecord -l`).
- **Shutdown:** SIGTERM is converted to KeyboardInterrupt in `main()`; `RecorderManager.stop()` joins all threads against a single shared 25 s deadline to stay inside Docker's `stop_grace_period: 30s`.
- **Loud-section detection is adaptive — do not regress it to an absolute threshold.** Per-window dB is compared against a rolling noise floor (`NOISE_PERCENTILE`-th percentile per `NOISE_BLOCK_SECONDS` block, min-smoothed over ±2 blocks so events can't raise their own floor; clamped to ≥ `MIN_RMS`). A section needs `margin` dB of prominence and carries a `score` (peak dB above floor) used for ranking. Sections shorter than `min_duration` (default 0.5 s, after `min_gap` merging) are discarded — without this, isolated 100 ms pops (clicks, single raindrops) produced thousands of zero-length sections per day. The original fixed RMS threshold flagged every ambience change (passing cars, rain) and produced ~600 useless sections/day — that is why it was replaced. Known limitation: a short (~10 s) swell on a quiet street still flags because the floor blocks are 30 s; the planned fix is an onset/spectral filter or optional Silero VAD, **not** a higher margin. Tests in `tests/test_web.py`.
- **Analysis params are coupled in five places.** CLI `--margin`/`--min-gap`/`--min-duration` → `/api/config` → UI inputs `#margin-input`/`#min-gap-input`/`#min-duration-input` → `/api/analyze` query params → cache JSON head keys. Renaming or adding a param means touching all five plus `cachedParamsMatch()` and the `_cached_analysis_params()` regex (see the threshold→margin change `c84b7d8` and the min_duration addition).
- **Analysis cache:** results stored as `<analyses-dir>/<file>.analysis.json` keyed by margin+min_gap+min_duration; orphans pruned at web startup. In Docker the recordings mount is **read-only** for the web container, so docker-compose layers a read-write `./recordings/analyses` bind mount over it. The `margin`, `min_gap`, and `min_duration` keys MUST stay first in the cache JSON — `_cached_analysis_params()` reads only the first 256 bytes to avoid parsing the large embedded result. Caches written by older detector versions (missing a key) never match and get overwritten on the next analyse.
- **Analyze responses:** `/api/analyze` returns `rms_display` (~800 points), never the full per-window RMS list — the UI doesn't use it and it is ~45x larger.
- **Section playback uses clips, not seeks:** `/api/clip?file&start&end` decodes the slice server-side (wave/soundfile) and returns a standalone 16-bit WAV with exact Content-Length (capped at `CLIP_MAX_SECONDS`), `Cache-Control: private` so re-listening is free. The UI plays chips/J-K through the bottom clip bar (`clipQueue` in webui.html); seeking the full file only happens via "Open in file". Rationale (finding): libsndfile writes FLAC **without a SEEKTABLE**, so a browser seek bisects the whole multi-hundred-MB file with Range requests — seeking big FLACs in `<audio>` is inherently slow and must not be reintroduced as the primary navigation. Server-side `sf.SoundFile.seek()` on local disk is fast and frame-accurate.
- **HTTP/1.1 keep-alive:** `_Handler.protocol_version = 'HTTP/1.1'`; every response path must set an accurate `Content-Length`. `_copy_to_response()` force-closes the connection if it under-delivers (file truncated mid-serve).
- **Live playback:** for files listed in status.json, `/stream/` patches the header on the fly so the browser sees the duration recorded so far and can seek; responses get `Cache-Control: no-store`. WAV: `_live_wav_header` derives sizes from the byte count. FLAC: `_live_flac_header` parses the sample count out of the last frame header in the file tail (CRC-8-verified to reject false sync matches) and rewrites STREAMINFO total_samples — duration is NOT derivable from byte size for FLAC.
- **Path safety:** every file parameter in `web.py` goes through `_safe_path()`, which resolves and verifies the path stays inside the recordings dir.
- **dsnoop in Docker:** sharing the soundcard requires `asound.conf` on the host *and* `ipc: host` in docker-compose (dsnoop uses shared memory across the container boundary).