neon-sprawl/docs/plans/NEON-28-implementation-plan.md

# NEON-28 — Implementation plan

## Story reference

| Field | Value |
|--------|--------|
| **Key** | NEON-28 |
| **Title** | E1.M2: Camera integration hardening + dependent contract notes |
| **Jira** | [NEON-28](https://neon-sprawl.atlassian.net/browse/NEON-28) |
| **Parent** | [NEON-1 — Epic 1 — Core Player Runtime](https://neon-sprawl.atlassian.net/browse/NEON-1) |
| **Module** | [E1.M2 — IsometricCameraController](../decomposition/modules/E1_M2_IsometricCameraController.md); umbrella [NEON-10](https://neon-sprawl.atlassian.net/browse/NEON-10) |

**Jira source:** Description and acceptance criteria were pulled from Jira via Atlassian MCP (cloud `neon-sprawl`, issue **NEON-28**). This plan is the working implementation breakdown; if Jira edits after this date, re-sync the checklist.

**Board:** Transitioned **To Do → In Progress** on kickoff (Atlassian MCP `transitionJiraIssue`, transition id `2` / name `prog`).

## Goal, scope, and out-of-scope

**Goal (from Jira):** Close the **E1.M2 prototype slice** with stable contracts, documentation, and hooks so **E6.M2** (and other dependents) can rely on `CameraState` and presentation assumptions without spelunking implementation.

**In scope (from Jira)**

- **Finalize `CameraState`:** follow target, **yaw** (prototype `0`; document semantics if orbit is enabled mid-project), zoom band / effective framing, **policy flags as needed** (add fields only when the documented consumer contract requires them; otherwise state explicitly what is **not** in state and where to read it on the rig).
- **Implementation snapshot in module doc:** **Mid-project rotation policy** and **post-release freeze** from `E1_M2_IsometricCameraController.md` (prototype **fixed yaw for players**; optional `allow_yaw` / limits seam; world-anchored gameplay preferred; telegraph readability). **Cross-link [NEON-10](https://neon-sprawl.atlassian.net/browse/NEON-10)** / module backlog for traceability.
- **Client-local authority** and **fixed pitch/roll** for isometric presentation — align [client_server_authority.md](../decomposition/modules/client_server_authority.md) references in E1.M2 / E6.M2 notes.
- **Optional telemetry:** document hooks for throttled `camera_zoom_changed` and occlusion/perf counters **when E9.M1** schema exists (no requirement to implement telemetry in this story unless already trivial TODO cleanup).
- **Dependency register + alignment:** E1.M2 **Ready** (or agreed status) with pointers to scripts/scenes per acceptance criteria.

**Additional in-repo hardening (engineering, supports “stable contracts”)**

- **`IsometricFollowCamera` occluder lifecycle:** `_occluder_overrides` must not **leak or fault** when occluder bodies are **freed** or invalid; purge invalid keys and restore surviving `MeshInstance3D` overrides.

**Out of scope (from Jira)**

- New gameplay features; **E1.M3 / E1.M4** work.
- Committing to **yaw orbit in UX** without product sign-off (policy allows mid-project enablement only).

## Acceptance criteria checklist

Jira acceptance criteria (verbatim intent):

- [x] **Module dependency register / module doc:** E1.M2 **Ready** (or agreed status) with pointers to scripts/scenes.
- [x] **`CameraState` contract** summarized in one place and matches module doc (**includes yaw**).
- [x] **E6.M2 note:** what consumers may read vs undefined; how **yaw** affects camera-adjacent UX if non-zero later.
- [x] **Epic 1 Slice 2** acceptance satisfied: prototype keeps **yaw fixed for players**, zoom within bands, readable motion, occlusion policy active; aligns with updated module wording (not “camera has no yaw,” but **yaw not exposed / remains default in UX**).

**Supporting engineering checks (not a substitute for Jira AC):**

- [x] Occluder invalid-key purge covered by tests or documented manual steps (see [Tests](#tests)).
- [x] [epic_01_core_player_runtime.md](../decomposition/epics/epic_01_core_player_runtime.md) **Slice 2** bullets use the same **yaw / presentation** language as the module (replace over-simplified “no rotation” if it contradicts the rotation policy).

## Technical approach

1. **Contract documentation (primary)**
   - **`camera_state.gd`:** Expand file header (and/or class-level comments) so it is a **concise, accurate** summary of fields: `yaw` = orbit delta vs presentation compass; `distance`; `zoom_band_index`; `focus_world`; `follow_target_path`; refresh **every `_process`** on the rig.
   - **`E1_M2_IsometricCameraController.md`:** Single **Consumer contract** subsection: table linking each `CameraState` field + rig exports (`allow_yaw`, `presentation_yaw_deg`, resources). Include **mid-project rotation** + **post-release freeze** pointers; link **NEON-10**, **NEON-25–NEON-27**, **NEON-30** as appropriate.
   - **`E6_M2_ConsentAndRiskUxSignals.md`:** **E1.M2 camera adjacency** — allowed reads (`CameraState` fields), **undefined** (what stays on rig only), **yaw non-zero later** (presentation / HUD implications in one short paragraph); link authority (server must not use camera pose for gameplay).
   - **`module_dependency_register.md`:** Set E1.M2 **Status** to **Ready** (or agreed label) and replace “NEON-28 remains” narrative with **shipped** wording + script/scene pointers.
   - **`documentation_and_implementation_alignment.md`:** E1.M2 row matches register + NEON-28 completion.
   - **`epic_01_core_player_runtime.md`:** Adjust **Slice 2** scope/acceptance lines so they reflect **fixed yaw in UX** and documented orbit seam, not flat “camera never rotates” if that misleads.

2. **`CameraState` “finalize”**
   - Reconcile code and docs. Add **policy flags** to `CameraState` only if the E6.M2 / E1.M2 contract text commits to them; otherwise explicitly document **“no policy flags in state yet; read rig exports.”**

3. **`isometric_follow_camera.gd` hardening**
   - At start of `_update_occlusion` (and/or restore passes): drop dictionary keys whose body is **`not is_instance_valid`**; restore materials where `MeshInstance3D` is still valid; then erase entries.

4. **Optional telemetry**
   - Keep or add **TODO(E9.M1)** pointers in rig / policy scripts; no new telemetry pipeline unless out of scope exception is agreed.

5. **Tests**
   - Static helper tests for **occluder key validity** / purge behavior where headless-safe; manual **queue_free** occluder check in editor for full confidence.

## Decisions

| Topic | Choice | Rationale |
|-------|--------|-----------|
| **`CameraState` policy flags** | **Doc-first** | Add fields only if Jira/E6.M2 contract text requires a snapshot; avoid speculative API. |
| **Invalid occluder keys** | **Purge + restore** | Prevents stuck materials and leaks when occluders despawn. |
| **Epic Slice 2 wording** | **Align with rotation policy** | Satisfies Jira AC on “yaw not exposed / default in UX” vs misleading “no rotation.” |

## Files to add

**None** unless occlusion tests are split out (optional `client/test/isometric_follow_camera_occlusion_hardening_test.gd`).

## Files to modify

| Path | Rationale |
|------|-----------|
| `client/scripts/camera_state.gd` | Finalize field documentation; optional policy flags if contract requires. |
| `client/scripts/isometric_follow_camera.gd` | Occluder invalid-key purge; keep TODO(E9.M1) aligned with Jira optional telemetry note. |
| `docs/decomposition/modules/E1_M2_IsometricCameraController.md` | Consumer contract, NEON-28 snapshot, NEON-10 / rotation policy cross-links. |
| `docs/decomposition/modules/E6_M2_ConsentAndRiskUxSignals.md` | E1.M2 adjacency + yaw UX note + authority. |
| `docs/decomposition/modules/module_dependency_register.md` | E1.M2 Ready + pointers; remove “hardening remains.” |
| `docs/decomposition/modules/documentation_and_implementation_alignment.md` | E1.M2 row updated. |
| `docs/decomposition/epics/epic_01_core_player_runtime.md` | Slice 2 wording vs yaw/presentation policy. |
| `client/test/isometric_follow_camera_test.gd` | Tests for new static guards / occluder key validity if added. |

## Tests

| File | Coverage |
|------|----------|
| `client/test/isometric_follow_camera_test.gd` | **Change.** Guards for occluder override dictionary key validity / purge helper if extracted. |
| `client/test/camera_state_test.gd` | **Change only if** new `CameraState` fields ship — round-trip defaults. |

**Manual verification:** Main scene — zoom bands, occlusion fade, fixed yaw UX; free an occluder while faded and confirm no errors / stuck materials; spot-check Slice 2 behaviors (readable motion, occlusion active).

## Open questions / risks

- **`CameraState` policy flags:** Product may later require explicit booleans for risk UX; if E6.M2 text stays non-committal, keep flags out and document **rig as source** until a follow-on story.
- None otherwise.

## Shipped (2026-04-10)

- `camera_state.gd` consumer contract header; `isometric_follow_camera.gd` invalid occluder purge + `occluder_override_key_is_valid`; tests in `isometric_follow_camera_test.gd`.
- Docs: `E1_M2_IsometricCameraController.md` (Ready, consumer contract, NEON-28 snapshot), `E6_M2_ConsentAndRiskUxSignals.md` (E1.M2 adjacency), `module_dependency_register.md`, `documentation_and_implementation_alignment.md`, `epic_01_core_player_runtime.md` Slice 2.