reasampler/CLAUDE.md

# CLAUDE.md

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

## Repo identity and current state

The CMake project and binary are now named `reaper_reasampler`. This is **ReaSampler** — a per-project audio sample-bank capture tool. The MPE modules (`mpe_model`, `mpe_view`) have been removed. M0–M4 are complete: `bank_model` (Sample metadata + BankIndex with JSON round-trip), `peaks` (waveform min/max bin computation), the `capture` shell's offline-render path (DAW-verified spike: master-mix / time-selection capture to a project-relative bank at 32-bit float WAV, non-destructive), and `persist` (BankIndex ↔ project ext state: `SetProjExtState`/`GetProjExtState` under namespace `"reasampler"`, GUID-based project identity, project-relative path resolution, Save-As bank relocation with copy semantics) are all implemented and tested. The remaining REAPER-facing shells (`insert`, `bank_panel`, `actions`) and the realtime backend are being built out per CONTEXT.md / PLAN.md. The *discipline* — pure REAPER-free testable core split from REAPER-facing shells — is **preserved** throughout.

CONTEXT.md is the authoritative spec and build roadmap. Read it first for any non-trivial task. Every REAPER API name cited there is correct-by-intent; verify argument order, types, and flag values against `vendor/reaper-sdk/sdk/reaper_plugin_functions.h` before use.

## One-time submodule setup

    git submodule update --init

Vendors two submodules (see `.gitmodules`):
- `vendor/reaper-sdk` — `sdk/reaper_plugin.h`, `sdk/reaper_plugin_functions.h`, SWELL headers
- `vendor/WDL` — WDL utilities and the SWELL cross-platform Win32 layer

## Build and test

    cmake -B build -S .
    cmake --build build
    ctest --test-dir build

Eight targets:

| Target | Kind | Purpose |
|---|---|---|
| `bank_model_tests` | executable | Pure unit tests for `bank_model` — no REAPER, no DAW. |
| `peaks_tests` | executable | Pure unit tests for `peaks` — no REAPER, no DAW. |
| `capture_paths_tests` | executable | Pure unit tests for `capture_paths` — no REAPER, no DAW. |
| `view_mode_model_tests` | executable | Pure unit tests for `view_mode_model` — no REAPER, no DAW. |
| `view_tree_tests` | executable | Pure unit tests for `view_tree` — no REAPER, no DAW. |
| `mode_switch_tests` | executable | Pure unit tests for `mode_switch` — no REAPER, no DAW. |
| `bank_book_tests` | executable | Pure unit tests for `bank_book` — no REAPER, no DAW. |
| `reaper_reasampler` | loadable module | The actual extension binary (`.dll` / `.dylib` / `.so`). |

### macOS / Linux: SWELL dialog resources

`src/resource.rc` must be pre-processed by SWELL's resgen once per platform:

    php vendor/WDL/WDL/swell/mac_resgen.php src/resource.rc   # macOS; Linux reuses the output

Add the generated file to the appropriate `APPLE` / Linux `target_sources` block in CMakeLists.txt. The SWS extension build is the canonical reference for this step.

### Install / reload

There is no hot-reload. Copy the built binary into REAPER's `UserPlugins/` folder (Options → Show REAPER resource path) and restart REAPER. Extensions load at startup only.

## Architecture: the load-bearing split

**Pure core (no REAPER types, unit-testable outside the DAW):**
- `bank_model` — `Sample` metadata struct + `BankIndex` (add/remove/query/tier/dedup-by-hash + JSON round-trip). Test it hard — it is the heart.
- `peaks` — waveform min/max bin computation from raw PCM. Fed a known signal, asserts envelope. Does not depend on REAPER's peak API.
- `view_mode_model` — Design View mode system: mode registry, GUID-keyed membership, folder-tree-aware visibility derivation, snapshot-based park/restore planner, JSON round-trip. Mirror of `bank_model` for the Design View phase.
- `view_tree` — pure `I_FOLDERDEPTH`→FolderTree helper for the Design View shell; no REAPER types at the boundary.
- `mode_switch` — REAPER-free segment layout + hit-test math for the bank_panel's Design View mode switch; divides a header rectangle into N equal segments and hit-tests a point to a segment. Mirror of `bank_grid`.
- `bank_book` — multi-bank registry (Phase B): an ordered set of banks (pool seeded as bank-zero + named banks), each wrapping a `BankIndex`. Owns create/rename/reorder/delete of named banks, pool privileges (un-deletable/un-renamable/un-evacuable, never zero banks) enforced in-model, active-bank id, index-only move/copy of a sample between banks, JSON round-trip + legacy-`bank_index`→pool migration. Wraps `BankIndex` (bank_model untouched; no `bankId` on `Sample`).

**REAPER-facing shells:**
- `capture` — `ICaptureBackend` interface; `OfflineRenderBackend` (deterministic default) and `RealtimeRecordBackend`. Input: `CaptureRequest`. Output: finished file + populated `Sample` handed to `bank_model`.
- `insert` — placement via `InsertMedia`; conform-to-project-tempo is an explicit opt-in flag, never silent stretching.
- `bank_panel` — docked LICE-drawn grid: thumbnails, audition, multi-select, keyboard navigation.
- `persist` — project ext state (`SetProjExtState` / `GetProjExtState`, namespace `"reasampler"`) ↔ `bank_model` JSON + `ViewModeModel` JSON (`"view_state"` key); project-relative path resolution.
- `view` — Design View shell: reads the folder tree via `view_tree`, snapshots flag values before parking, drives hide + CPU-park on inactive-mode leaves (`B_SHOWINTCP`/`B_SHOWINMIXER`/`B_MAINSEND`/`I_FXEN` + per-FX offline) and derived visibility on parents; restores from snapshot. Never touches master or `B_MUTE`/`I_SOLO`.
- `track_guid` — shared `MediaTrack*` → canonical GUID-string formatter; single source of truth for membership keys used by both the view shell and the actions layer.
- `actions` — registers the capture/placement/slot action family and the Design View action family (toggle active mode, activate Arrange/Design, tag/untag selected tracks, show-both); routes each to the modules above via the `command_id`/`gaccel`/`hookcommand` contract.

## REAPER extension contract (src/main.cpp)

- Exactly **one** translation unit defines `REAPERAPI_IMPLEMENT` — that is `main.cpp`. Every other `.cpp` includes `reaper_plugin_functions.h` without the define and gets `extern` declarations for the global API function pointers.
- REAPER dlopen()s any `reaper_*.dll|dylib|so` found in `UserPlugins/` and calls the `ReaperPluginEntry` export (produced by `REAPER_PLUGIN_ENTRYPOINT`). `rec->GetFunc` resolves API pointers; `rec->Register` plugs extension callbacks in.
- Action registration pattern (preserve this for all new actions):
  1. `rec->Register("command_id", (void*)"STABLE_FOREVER_STRING")` — mints a persistent command id. **Never change this string after shipping**; user keybindings key off it.
  2. `rec->Register("gaccel", &accel)` — puts the action in the Actions list.
  3. `rec->Register("hookcommand", ...)` — receives every action fired; claim only your own id, return `false` otherwise.
  4. On unload (`rec == nullptr`), mirror-unregister everything with the same strings prefixed by `'-'`.

## The load-bearing principle

**Capture and placement are separate acts.** Capturing audio writes a file to the bank and adds an index entry. It **never** puts an item in the arrange view. Placement is a distinct, on-demand action (`insert` module / `InsertMedia`). Any code path that auto-inserts a capture into the timeline violates the purpose of the tool and **must be rejected in review**.

## Precision invariants — required before any feature ships

- **Null test:** a dry offline capture of a range, re-inserted at its source position, nulls to silence against the source. Ship as a verification action.
- **Bit-identical repeats:** identical offline capture requests produce identical files.
- **Non-destructive:** capture never mutates source items or tracks; the realtime backend's temp track is created and removed cleanly, and source routing is restored.
- **Exact bounds:** no rounding of the requested range; no added silence unless a tail is explicitly requested; channel count preserved (no silent stereo fold).
- **Relative paths only** in the persisted `BankIndex`.
- **Capture FX scope:** two scopes only — item = item/take FX only; track = item FX + the selected track's own track FX. There is no master scope (to capture the master, render a track instead). For both scopes, the out-of-scope chain (ancestors + master track, plus the item's own track for item scope) has its FX, gain, and pan/width/pan-law/mode neutralized to unity — the master track is bypassed as out-of-scope chain, not captured as a scope. Range (time selection or razor) is orthogonal.