trails/openspec/changes/multi-day-routes/tasks.md

1. Data Model & Computation

• 1.1 Add overnight property support to Yjs waypoint Y.Maps: helper functions setOvernight(yjs, index, value) and isOvernight(yMap) in a new apps/planner/app/lib/overnight.ts
• 1.2 Create computeDays() pure function in packages/gpx/src/compute-days.ts: takes Waypoint[] + TrackPoint[][], returns DayStage[] (day number, waypoint range, distance, ascent, descent). Export from package index.
• 1.3 Create useDays() hook in apps/planner/app/lib/use-days.ts: maps Yjs waypoints + EnrichedRoute into computeDays() input, returns reactive DayStage[]

2. Sidebar Day Breakdown

• 2.1 Create DayBreakdown component: renders collapsible day sections with per-day stats (distance, ascent, estimated time), Day 1 expanded by default
• 2.2 Add overnight toggle button (moon icon) to each waypoint row in WaypointSidebar — amber styling when active, calls setOvernight()
• 2.3 Integrate DayBreakdown into WaypointSidebar: show day-grouped view when any waypoint has overnight, flat list otherwise
• 2.4 Add route summary header to sidebar: total distance, ascent, number of days (e.g. "Berlin -> Erfurt 343 km ^868m 2 days")

3. Map Integration

• 3.1 Add overnight marker variant to PlannerMap: amber-brown circle (--stop token) for overnight waypoints, replacing default olive marker
• 3.2 Add day label DivIcon markers on route at day boundaries: white pill with "Day N . X km" text, positioned at overnight waypoint coordinates
• 3.3 Add right-click context menu on waypoint markers with "Mark as overnight stop" / "Remove overnight stop" option

4. Elevation Chart

• 4.1 Add day divider rendering to ElevationChart: dashed vertical lines at overnight waypoint distances with "Day N" labels at top
• 4.2 Show per-day distance ranges on x-axis labels (e.g. "120 km" at each day boundary)

5. GPX Roundtrip

• 5.1 Extend generateGpx in @trails-cool/gpx to emit <type>overnight</type> for waypoints with isDayBreak: true
• 5.2 Extend parseGpx in @trails-cool/gpx to recognize <type>overnight</type> and set isDayBreak: true on parsed waypoints
• 5.3 Add multi-track export option: split track into one <trk> per day, each named "Day N: Start - End"

6. Journal Integration

• 6.1 Update updateRoute in apps/journal/app/lib/routes.server.ts to extract dayBreaks indices from parsed GPX waypoints and write to dayBreaks column
• 6.2 Expose dayBreaks and per-day stats in route detail loader (routes.$id.tsx)
• 6.3 Add day breakdown section to route detail page: per-day distance, ascent, descent, start/end names — shown only when dayBreaks is non-empty
• 6.4 Color route map segments per day (alternating colors) on the route detail map when dayBreaks exist

7. i18n

• 7.1 Add Planner translation keys for en + de: day labels ("Day 1", "Tag 1"), overnight toggle ("Mark as overnight stop" / "Als Übernachtung markieren"), per-day stats, route summary
• 7.2 Add Journal translation keys for en + de: day breakdown header, per-day stats labels

8. Testing

• 8.1 Unit tests for computeDays(): single day (no overnight), two days, three days, empty route, single waypoint, overnight on first/last waypoint edge cases
• 8.2 Unit tests for overnight.ts helpers: set/clear/check overnight on Y.Map
• 8.3 Unit tests for GPX roundtrip: generate with isDayBreak, parse back, verify isDayBreak preserved
• 8.4 Unit tests for dayBreaks extraction in route update logic
• 8.5 E2E test: add waypoints, toggle overnight on one, verify sidebar shows day breakdown with correct stats
• 8.6 E2E test: export GPX with day breaks, verify downloaded file contains overnight metadata
• 8.7 E2E test: save multi-day route to Journal, verify day breakdown displays on route detail page