# Tasks: enterprise-heightmap-tiles

**Change ID**: enterprise-heightmap-tiles
**Package**: `@suaveplan/heightmap-tiles`
**Target path**: `universal/geo/heightmap-tiles`
**Prerequisite packages on Verdaccio**: `@suaveplan/error`, `@suaveplan/types`, `@suaveplan/geo`, `@suaveplan/serialize`

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## 0. Pre-flight (non-negotiable)

- [ ] 0.1 Confirm clean working tree (`git status` reports nothing) and no in-flight worktrees with uncommitted work (`git worktree list` then `git status` in each)
- [ ] 0.2 If any worktrees exist under `.claude/worktrees/`, account for each one: still-active agent, work-pending-merge, or stale-and-prune. Stale worktrees MUST be removed (`git worktree remove`) before opening a new one — code that has been lost twice on main is the failure mode this guards against.
- [ ] 0.3 Confirm the package set in `MANIFEST.md` matches `find packages -maxdepth 3 -name package.json` count. Drift here means a prior change archived without regenerating the manifest.

## 1. Scaffold

- [ ] Create `universal/geo/heightmap-tiles/` with `src/`, `tests/`, `src/__benchmarks__/` and all feature subdirectories per the layout in `proposal.md`.
- [ ] Write `package.json` at version `0.1.0` with `"type": "module"`, `"sideEffects": false`, correct `exports` map, `dependencies`, and `devDependencies`.
- [ ] Write `tsconfig.json` extending `@suaveplan/typescript-config/library.json`.
- [ ] Write `vitest.config.ts` using `createTestConfig()` from `@suaveplan/testing/config`.
- [ ] Add `lint`, `typecheck`, `test`, `test:coverage`, `build`, `docs:check` scripts.

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## 2. Types + errors

- [ ] `src/types/common.ts` — `TileCoord`, `BitDepth`, `HeightmapTile`, `ElevationResult`, `EncodeOptions`, `PyramidBuilderOptions`, `BuildLevelOptions`, `HeightmapTileStore` (interface), `ContourLine`.
- [ ] `src/types/common.md` (≥200 words, both examples, API reference).
- [ ] `src/error-codes.ts` — `HeightmapErrorCode` (6 codes), metadata, register, eager call.
- [ ] `src/types/schemas.ts` + `schemas.md` — Zod schemas.

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## 3. Core modules

- [ ] **`src/coords/tile-coords/`** — `latLngToTileCoord`, `tileCoordToBoundingBox`, `tileCoordToLatLng`, `tilesInBoundingBox`, `tileParent`, `tileChildren`. Tests: known lat/lng → tile at zoom 10, bounding box round-trip, parent/children consistency at multiple zoom levels, `tilesInBoundingBox` returns correct count for small area.
- [ ] **`src/codec/delta-codec/`** — `deltaEncode(tile): HeightmapTile`: converts raw int16/int8 tile to delta-encoded (each cell = cell - previous); first cell = cell value. `deltaDecode(tile): HeightmapTile`: inverse. Both are lossless for int16/int8. Tests: encode/decode round-trip for flat tile (all zeros), random int16 array, verify delta values are smaller in magnitude for smooth terrain.
- [ ] **`src/codec/tile-codec/`** — `encodeTile(tile, options?): Uint8Array`: serialises header (coord, dimensions, bitDepth, min/maxElevation, encoding) then data via `@suaveplan/serialize` MessagePack profile. `decodeTile(data): HeightmapTile`. Tests: encode/decode round-trip for 256×256 uint16 tile, float32 tile, bit depth selection.
- [ ] **`src/store/memory-store/`** — `createMemoryTileStore(): HeightmapTileStore`: `get`/`put`/`delete`/`list` backed by a `Map<string, HeightmapTile>` (key = `z/x/y`). Tests: CRUD, list by zoom, list with bounding box filter.
- [ ] **`src/pyramid/pyramid-builder/`** — `TilePyramidBuilder(store, options)`: `addSourceTile(tile)`: stores at natural zoom; `buildLevel(zoom)`: for each tile at `zoom+1`, generates parent by bilinear down-sampling the 4 children (or nearest available); `buildAll(minZoom, maxZoom)`. Tests: single source tile at zoom 12 → can build zoom 11 and 10; bilinear average matches expected value for flat 4-cell grid.
- [ ] **`src/elevation/elevation-lookup/`** — `lookupElevation(store, lat, lng, zoom?)`: fetches tile at computed coord + 3 neighbours; bilinear interpolation from 4 nearest pixels. Returns `ElevationResult`. Tests: exact pixel hit → `confidence: 'exact'`, between pixels → `confidence: 'interpolated'`, no tile → `elevation: NaN`.
- [ ] **`src/elevation/contour-extractor/`** — `extractContours(tile, intervalMetres): ContourLine[]`: marching-squares algorithm over tile grid; groups adjacent edge crossings into polylines; closes loops. Tests: flat tile → no contours, slope tile → contours at expected elevations, closed contour for circular hill shape.

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## 4. OTel instrumentation

- [ ] Span `heightmap.pyramid_build` with attribute `heightmap.zoom`; counter `heightmap.tile_encode_total`; histogram `heightmap.encode_duration_ms`.

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## 5. Property-based tests (`tests/property.test.ts`)

- [ ] Delta encode/decode round-trip: for arbitrary `Int16Array` of length 256, `deltaDecode(deltaEncode(tile)).data` equals original.
- [ ] Tile coordinate arithmetic: `latLngToTileCoord(tileCoordToLatLng(coord), coord.z)` returns same coord for arbitrary valid coords.
- [ ] Contour bounds: all elevation values in `ContourLine[]` from `extractContours(tile, interval)` lie within `[tile.minElevation, tile.maxElevation]`.

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## 6. Benchmarks (`src/__benchmarks__/heightmap-tiles.bench.ts`)

- [ ] `encodeTile` for 256×256 float32 tile.
- [ ] `decodeTile` for same.
- [ ] `extractContours` for 256×256 tile with 10 m interval.

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## 7. Docs + verify

- [ ] One `.md` per implementation file (≥200 words, both examples, API reference). Root `README.md`.
- [ ] `bunx turbo lint typecheck test --filter=@suaveplan/heightmap-tiles` — green.
- [ ] `bunx turbo test:coverage --filter=@suaveplan/heightmap-tiles` — 100%.
- [ ] `bun scripts/publish.ts --package @suaveplan/heightmap-tiles`.
- [ ] Archive: `openspec/archive/2026-04-24-enterprise-heightmap-tiles/`.