woodshop/MATERIALS_INVENTORY_PLAN.md

# Materials, Finish, Batch Builds & Shop Inventory — Plan (v2, reconciled)

Design plan for four related features, reconciled after a Codex review.
Nothing built yet. v2 changes vs v1 are marked **[v2]**.

## What changed in v2 (after Codex review)
- **[v2] Sanding never shrinks the design model.** Part dims = final/intended.
  Sanding becomes a *manufacturing allowance* in the CutPlan (rough vs final),
  not a scene mutation. (Codex #1.)
- **[v2] Rob's stock-reality refinement:** the allowance applies to dimensions we
  actually **cut** — length always, width only for rips/sheet goods. Dimensional
  lumber's fixed section (a 2x4 is 1.5×3.5 as delivered) is NOT padded. Final
  dims remain the truth for fit in v1.
- **[v2] Finish is first-class** (`material` + `finish` enum + `finish_color`),
  layered: stock shape → material/species → finish → visual → cost. A painted
  pine board is still pine for buying/cutting. (Codex #2, #9.) Single enum now,
  sheen later (simpler than Codex's kind+sheen split).
- **[v2] Inventory is an append-only event ledger**; current state is derived.
  (Codex #5.) Kept deliberately lean — minimal events, no undo/branching, raw
  events never shown to the user.
- **[v2] Offcuts are real stock pieces** behind one `AvailableStock` interface the
  planner consumes (reusing the seeded-packing from lock-aware reopt). (Codex #6.)
- **[v2] Sequence reordered** per Codex: materials/finish first; allowance and
  batch as CutPlan features; inventory last (model → workflows → window).

## Guiding principles
- Deterministic math, AI only for narrative. Easy, intuitive, useful — no
  complexity for its own sake.
- Additive, backward-compatible serialization (loader filters by known fields).
- Physical state (stock, offcuts, builds) is **shop-wide**, in the data dir.
- Reuse existing machinery (`_pack_lumber_seeded`, `_pack_plywood_seeded`,
  `_free_rects_sheet`).

## Data locations
- Scenes: `$XDG_DATA_HOME/woodshop/` (per project).
- Prices + estimate rates: `$XDG_CONFIG_HOME/woodshop/{prices,estimate}.json`.
- **New** ledger: `$XDG_DATA_HOME/woodshop/inventory.json` (shop-wide, append-only).

---

## Phase 1 — Material + finish fields + color resolver

**Goal:** parts carry a material and a finish; the viewer colors by them; sanded
raw wood reads lighter, painted boards show their color. Flat colors v1 (PyVista
textures are a future option).

**Data model (additive on `Part`):**
- `material: str = ""` — species/sheet: spruce, pine, oak, walnut, maple, birch,
  mdf, spruce-ply. Default derived from stock (`lumber.py`).
- `finish: str = "raw"` — one of `raw | sanded | clear | stain | paint`.
- `finish_color: str = ""` — hex, for paint/stain.
- **[v2] Migration:** old scenes store `finishes: ["sanded"]`; `from_dict` maps a
  non-empty list → `finish="sanded"` (or "paint" if a color is present).

**Color resolver (viewer), layered stock→material→finish→visual:**
- base = `MATERIAL_COLORS[material]` if set else positional palette (fallback).
- `paint` → `finish_color`; `stain` → blend base toward `finish_color`/darker;
  `clear` → base slightly richer; `sanded` → base ~15% lighter; `raw` → base.
- **Per-part subtle tint** (±~5% lightness keyed by `_stable_hash(id)`) so
  same-material boards stay distinguishable. Selection highlight unchanged.

**Scene ops / UI:** `scene.set_material(ref, m)`, `scene.set_finish(ref, kind,
color="")`. GUI: Paint button (QColorDialog) + Material & Finish dropdowns in the
inspector; works on selection/group. CLI/voice: `wood-material`, `wood-finish`/
`wood-paint`; voice color words → hex via a small name table.

**Tests:** resolver priority; sanded lightening; tint determinism; finish/material
persist + migrate; group ops.

---

## Phase 2 — Finish costs in the estimate

**Goal:** finish/paint cost folds into the project estimate by **finish kind ×
surface area**.

**Design:** `EstimateRates` gains per-kind $/sq ft (`sanded` = abrasives only,
`clear`, `stain`, `paint`). `project_estimate` adds a finish line per part using
its `finish` + finished surface area. Labor already has a sanding/finishing line;
extend its time to vary by finish kind (paint/stain take longer) — editable.

**Tests:** paint vs clear vs raw produce expected finish $; editable rates flow
through; zero for raw.

---

## Phase 3 — Manufacturing allowance in the CutPlan (rough vs final)

**Goal:** the cut plan distinguishes the size you **cut** from the **final** size,
so sanded/finished parts are cut slightly oversize where applicable.

**Design:**
- `CutItem` gains `final_length_in`, `final_width_in`; existing `length_in`/
  `width_in` become the **rough cut** size.
- For a part whose `finish != raw`: `rough_length = final + sanding_allowance`;
  `rough_width = final + sanding_allowance` **only** for sheet goods / ripped
  widths. **[v2]** Dimensional lumber at full nominal width: rough_width = stock
  width (no add); fixed section thickness unchanged.
- `ShopSettings.sanding_allowance_in` (already exists) default `1/32"`, editable.
- Cut list shows both: `Cut 24 1/16" × 3 9/16"  →  final 24" × 3 1/2"`.
- Nesting/packing uses the **rough** size (that's what you cut from stock).

**Tests:** finished part's rough length = final + allowance; lumber width not
padded; raw parts unchanged; cut list shows rough→final; packing uses rough.

**Open Q (deferred):** compensating joinery fit for material lost to sanding
(e.g. tenon thickness). v1 keeps final dims as the fit truth. Note as future.

---

## Phase 4 — Batch builds (quantity N)

**Goal:** estimate N identical units, nesting all units together so offcuts carry
across units → real per-unit cost.

**Design:**
- `build_cut_plan(..., quantity=1)` **[v2 confirmed]**: replicate **CutItems**,
  not Parts — `ci_p3` → `ci_p3_u1, ci_p3_u2, …`. Label placements with unit #
  ("Unit 2 – left leg") in the layout.
- `project_estimate(..., quantity=N)`: materials from the N-unit plan;
  **setup labor once per batch**, per-operation time and consumables ×N. Report
  **total + per-unit** (total / N).
- UI: a quantity spinner in the BOM header; every tab reflects it.

**Tests:** qty=2 uses ≤ 2× sticks (often fewer via shared offcuts); per-unit =
total/2; consumables/labor scale; setup once.

---

## Phase 5 — Inventory ledger model (event-sourced)

**Goal:** the source of truth for shop stock/offcuts/builds.

**Design [v2]:** append-only event log; derive current state (cache totals for
speed). Lean event set:
- `purchase {stock, qty, unit, price?, date}`
- `consume {stock, qty, build_id}`
- `create_offcut {offcut, build_id}`
- `discard {offcut_id, fate: burned|trashed}`
- `adjustment {…, reason}`  (manual correction)
- `build_recorded {project, units, cost_snapshot, date}`

**`AvailableStock` interface [v2]:** standard stock and offcuts share one shape —
`{stock, material, length_in, width_in, is_sheet, source, bin?, usable,
reserved/consumed}`. The planner consumes both through this interface.

**Tests:** fold events → correct on-hand & offcut bin; cache matches fold;
adjustments apply; derived stats (units built, $ spent, waste split) correct.

---

## Phase 6 — Inventory workflows (the UX that matters)

**Workflow-first [v2], not spreadsheet-first:**
1. **Mark Purchased** — Shopping tab → "Add these to shop inventory?" → `purchase`
   events. Optionally record price paid.
2. **Record Build** — confirmation FIRST: shows *Consumed* (e.g. 2 × 2x4 8') and
   *Offcuts created* (18", 26", 12×24 ply); each offcut → **Keep / Trash / Burn /
   Ignore**. On confirm: emit consume/create_offcut/discard/build_recorded.
3. **Use Shop Inventory** toggle in BOM — "Use available offcuts first" →
   planner seeds from `AvailableStock` (reuses seeded-packing).

**Tests:** purchase adds on-hand; record-build deducts + creates offcuts + logs;
dispositions recorded; planner-with-offcuts uses ≤ as many new sticks.

---

## Phase 7 — Inventory window + stats (management view)

A top-level **Inventory** window (menu: *Shop → Inventory*) as a management/review
view, not the primary workflow. Tabs: On-hand, Offcut bin, Build history, Stats
(units built per project, $ spent, material used, waste % kept/burned/trashed).
Shop-wide.

---

## Locked sequence
1. Material + finish fields + color resolver
2. Finish costs in the estimate
3. Manufacturing allowance in CutPlan (rough vs final) — with the lumber-section caveat
4. Batch quantity in CutPlan
5. Inventory ledger model (event-sourced)
6. Purchase / Record-build / Use-offcuts workflows
7. Inventory window + stats

Each phase committed separately; phases 5–7 are the big block, built model-first.

## Settled decisions (formerly open questions)
- **Sanding:** rough-vs-final allowance on cut dims only; design dims stay final;
  lumber section not padded. (Rob + Codex.)
- **Finish:** single `finish` enum + color now; sheen later.
- **Pricing:** stock-based in v1; price key designed to extend to (stock,
  material, grade).
- **Batch labor:** setup once per batch, per-op ×N.
- **Inventory:** event-sourced source of truth; workflow-first UX; window second.
- **Still genuinely open:** auto-update price book from recorded purchase prices
  (opt-in?); offcut reuse default-on vs opt-in (leaning opt-in toggle).