Pure math, no React, no scene access. Three primitives plus a facade:
- `snapScalar(value, step)` / `snapPointToGrid(point, step)` /
`snapVec3ToGrid(point, step)` — regular grid snapping. Default
step 0.25m matches the editor's wall tool.
- `snapPointToAngle(from, cursor, angleStep, gridStep?)` — locks a
cursor to the nearest angle multiple from a fixed point, preserves
distance, optionally re-grids the projected point. Default angle
step π/12 (15°).
- `snapAngleToList(angle, list, tolerance)` — snaps a free angle to
the nearest entry in a fixed list (e.g. 0/45/90/135) within a
tolerance; returns the original angle otherwise. Handles wrap.
- `snapServices` facade — `grid.*` + `angle.*` namespaces. Stable
contract that `DragAction.snap` callbacks receive. Phase 3 ports
the existing `snapWallDraftPoint` family from
`editor/.../wall-drafting.ts` under a `wall.*` namespace.
17 unit tests cover the math + the facade pass-through. No existing
callers re-wired yet — Phase 2 column/shelf tools are the first
consumers.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
First service in `core/src/services/`: pure, no React or R3F, takes
SceneApi + node data, returns results.
Exports:
- `canAttach(childId, hostId, scene)` — validates host attachment.
Rejects self-host, cycles (host's ancestor chain contains child),
chains past MAX_HOST_DEPTH (6), and host kinds outside the child
def's `capabilities.hostable.parents` allowlist. Returns a typed
AttachError discriminated union so callers can render specific
messages.
- `getSurface(host)` / `getTopSurfaceHeight(host)` — reads
`def.capabilities.surfaces` from the registry; resolves
function-valued heights with the node.
- `clampYToHostTop(host, y)` — convenience for placement code.
- `pickHost({ point, candidates, placedKind, hitTest? })` — given
spatially pre-filtered candidates, returns the first hostable.
The runtime is responsible for spatial filtering; this function
stays pure.
MAX_HOST_DEPTH = 6: the explore earlier found today's editor has no
cap on item-on-item nesting. Cap is bounded by hostable depth, not
total tree depth (sites/buildings/levels don't count).
17 tests cover all rejection paths + happy paths + function-valued
surface heights.
Re-exported from `@pascal-app/core` via a new `services/` barrel.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
