d933cca451
Follow-up to the planner WS reconnect-loop incident. Proposes compactly encoding the computed route in the Yjs session doc (single-source geometry + delta/varint polyline + run-length-encoded road metadata, dual-format backward-compatible reads) to cut a ~305 KB / 77 km route to ~40–60 KB — WITHOUT changing the routing-host "compute once, share via Yjs" model or GPX export output. Artifacts: proposal, design, specs (new planner-route-encoding capability), tasks. Validates --strict. Ready for /opsx:apply. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
36 lines
3 KiB
Markdown
36 lines
3 KiB
Markdown
## Why
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The planner's Yjs session doc stores the computed route very inefficiently: a 4-waypoint / 77 km route already serializes to **~305 KB**. Three sources of bloat in `routeData` (`apps/planner/app/lib/route-data.ts`, `writeComputedRoute`):
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1. **Geometry is stored twice** — `geojson` (a GeoJSON LineString of every coordinate) *and* `coordinates` (the same coordinates as a plain array), both `JSON.stringify`d.
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2. **Coordinates are stringified JSON floats** — `[13.4051234,52.5204567]` ≈ 22 bytes/point.
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3. **Seven per-coordinate road-metadata arrays** (`surfaces`, `highways`, `maxspeeds`, `smoothnesses`, `tracktypes`, `cycleways`, `bikeroutes`) stored as JSON `string[]` — in practice long runs of the same value.
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This grows linearly with route length toward the 5 MB doc cap, bloats every reconnect's full-state sync, and was the underlying cause of the WS reconnect-loop outage (mitigated, not removed, by raising the frame cap in #587). It is pure encoding waste: the data is *derived*, and the routing-host model already computes it exactly once.
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## What Changes
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Encode the computed route compactly in `routeData`, **without changing the routing-host "compute once, share via Yjs" model** — one elected client still computes via BRouter and writes the result into the doc for everyone to read; clients never recompute.
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- Store geometry **once** (single source of truth; derive the other representation at read time).
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- Encode the polyline compactly (delta + varint / encoded-polyline) instead of stringified JSON floats.
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- **Run-length-encode** the road-metadata arrays.
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- Centralize encode/decode in `route-data.ts` so all readers are transparently unaffected.
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- **Backward compatible**: the read path transparently handles both the existing JSON format (already persisted in `planner.sessions.yjs_state`) and the new encoding — no flag day, no migration downtime.
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Target: **~5× smaller** (≈305 KB → ≈40–60 KB for that route). `MAX_DOC_BYTES = 5 MB` stays the guard; GPX export output stays byte-compatible.
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## Capabilities
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### New Capabilities
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- `planner-route-encoding`: how the planner's computed route (geometry + road metadata) is compactly and backward-compatibly encoded in the Yjs session document, independent of how it is computed or shared.
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### Modified Capabilities
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<!-- None: the routing-host compute/share behavior and route-coloring semantics are unchanged; only the on-doc encoding changes. -->
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## Impact
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- `apps/planner/app/lib/route-data.ts` — `writeComputedRoute` / read helpers (`readComputedRoute`, `readRoadMetadata`, etc.): new encode on write, dual-format decode on read.
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- Readers via those helpers, unchanged at the call site: `SessionView` map rendering, elevation profile, GPX export, save-to-journal, road-type/surface coloring.
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- New encoding module + tests in `@trails-cool/planner` (or `@trails-cool/gpx`/`map-core` if the codec is reusable).
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- No schema change (`yjs_state` is opaque bytea); no API change; no change to routing-host election or BRouter usage.
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