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feat(map-core): compact route codec (polyline + RLE) for planner doc

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Task group 1 of planner-route-encoding. Framework-free `route-codec.ts`:
- encodePolyline/decodePolyline — fixed-precision (1e5) delta + zig-zag
  varint + base64; lossless to ~1 m, version-tagged ("p1:").
- encodeRuns/decodeRuns — run-length codec for the per-coordinate
  road-metadata channels, tagged ("r1:").
- isEncodedPolyline/isEncodedRuns — so the read path (group 3) tells the
  new encoding apart from legacy JSON.

Not yet wired into route-data.ts (groups 2–3). Verified: map-core
typecheck + lint clean, 52/52 tests (round-trip within 1 m, empty/single,
RLE collapse, >3x smaller than JSON).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ullrich Schäfer 2026-07-15 16:55:34 +02:00
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openspec/changes/planner-route-encoding/tasks.md
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@ -1,8 +1,8 @@
## 1. Codec primitives
- [ ] 1.1 Add a framework-free codec in `@trails-cool/map-core` (e.g. `route-codec.ts`): `encodePolyline(coords: [lon,lat][]) -> string` / `decodePolyline(str) -> [lon,lat][]` using fixed-precision (1e5) delta + zig-zag varint + base64, with a version tag
- [ ] 1.2 Add `encodeRuns(values: string[]) -> string` / `decodeRuns(str, length?) -> string[]` run-length codec for the road-metadata channels
- [ ] 1.3 Unit tests: polyline round-trip within ~1 m over random + real fixtures; empty/single-point; RLE round-trip incl. all-same, all-distinct, and a realistic run pattern
- [x] 1.1 Add a framework-free codec in `@trails-cool/map-core` (e.g. `route-codec.ts`): `encodePolyline(coords: [lon,lat][]) -> string` / `decodePolyline(str) -> [lon,lat][]` using fixed-precision (1e5) delta + zig-zag varint + base64, with a version tag
- [x] 1.2 Add `encodeRuns(values: string[]) -> string` / `decodeRuns(str, length?) -> string[]` run-length codec for the road-metadata channels
- [x] 1.3 Unit tests: polyline round-trip within ~1 m over random + real fixtures; empty/single-point; RLE round-trip incl. all-same, all-distinct, and a realistic run pattern
## 2. Write path (new encoding)