# Solstice Countdown Widget & App Design

**Date:** 2026-03-23
**Project:** Solverv (Solstice Countdown)
**Status:** Design Approved

---

## Overview

Build an iOS app that displays a countdown to the next solstice or equinox, with season-specific imagery and detailed information. The app includes:
- **Widget Extension:** Compact countdown widget in small, medium, and large sizes
- **Main App:** Info screen showing expanded details including sunrise/sunset times and upcoming events

---

## Requirements

### Functional Requirements
1. Track all four annual solstices/equinoxes (Spring, Summer, Autumn, Winter)
2. Display countdown to next event in **days only**
3. Show season-specific images that change based on upcoming event
4. Calculate and display sunrise/sunset times for user's current location
5. Show expanded event details in main app (exact times, season descriptions, upcoming event previews)
6. Support multiple widget sizes (small, medium, large)

### Non-Functional Requirements
- All calculations happen locally (no external APIs)
- Works offline after initial setup
- Respects location privacy with explicit permission
- Single location permission prompt (shared via AppGroup)
- Data synced between app and widget via AppGroup container

---

## Architecture

### Data Models

**SolsticeEvent**
```
- name: String (e.g., "Summer Solstice", "Spring Equinox")
- date: Date (UTC)
- season: Season (enum: spring, summer, autumn, winter)
- seasonDescription: String (brief description of the season)
```

**SolsticeData**
```
- events: [SolsticeEvent] (hardcoded data, 2025-2030)
- nextEvent() -> SolsticeEvent (returns next upcoming event)
- allUpcoming(count: Int) -> [SolsticeEvent] (returns next N events)
- daysUntil(_ event: SolsticeEvent) -> Int
- progressToEvent(_ event: SolsticeEvent) -> (elapsed: Int, total: Int)
```

**SunTimes**
```
- latitude: Double
- longitude: Double
- date: Date
- sunrise() -> Date
- sunset() -> Date
```

### Data Sharing

**AppGroup Container:** Store user location and cached sunrise/sunset times using the container ID `group.com.ivarlovlie.solverv`

**AppGroup Data Schema:**
Stored in UserDefaults using the `group.com.ivarlovlie.solverv` container.
```json
{
  "userLocation.latitude": Double (e.g., 59.9139),
  "userLocation.longitude": Double (e.g., 10.7522),
  "userLocation.timestamp": String (ISO 8601, e.g., "2026-03-23T10:30:00Z"),
  "userLocation.isDefaultLocation": Boolean (true = Greenwich, false = user-granted location),

  "sunTimes.date": String (ISO 8601 date only, e.g., "2026-03-23"),
  "sunTimes.sunrise": String (ISO 8601 datetime in local timezone, e.g., "2026-03-23T06:42:00"),
  "sunTimes.sunset": String (ISO 8601 datetime in local timezone, e.g., "2026-03-23T18:15:00"),
  "sunTimes.timestamp": String (ISO 8601, when calculated, e.g., "2026-03-23T10:30:00Z")
}
```
All Date values stored as ISO 8601 strings for cross-process compatibility.

- **Widget Timeline:** Updates at midnight (local time) using `timelineReloadPolicy: .after(nextMidnight)`
- Both app and widget read from the same AppGroup container for consistency
- Cache invalidation: Sunrise/sunset cache is recalculated if stored date differs from today or location changes

---

## Widget Specification

### Small Widget (169×169)
- **Layout:** Vertical stack
  - Seasonal image (fills most of space)
  - Event name (small caption)
  - Countdown in days (large, bold text)
- **Refresh:** `timelineReloadPolicy: .after(nextMidnight)` where `nextMidnight` is calculated as:
  ```swift
  var calendar = Calendar.current
  var components = calendar.dateComponents([.year, .month, .day], from: Date())
  components.hour = 0
  components.minute = 0
  components.second = 0
  let todayMidnight = calendar.date(from: components)!
  let nextMidnight = calendar.date(byAdding: .day, value: 1, to: todayMidnight)!
  ```
  The widget refreshes daily at midnight local time, automatically accounting for DST transitions.
- **Purpose:** Quick glance at how many days remain

### Medium Widget (364×169)
- **Layout:** Horizontal split
  - Left: Seasonal image (square)
  - Right: Vertical stack with event name, countdown (large), progress bar
- **Refresh:** `timelineReloadPolicy: .after(nextMidnight)` — refreshes at midnight local time to update countdown
- **Purpose:** Balance of visual and numeric information

### Large Widget (364×364)
- **Layout:** Vertical stack
  - Top half: Seasonal image
  - Bottom half: Event name, countdown, progress bar, preview of next 3 upcoming events (mini list)
- **Refresh:** `timelineReloadPolicy: .after(nextMidnight)` — refreshes at midnight local time to update countdown
- **Purpose:** Comprehensive view with upcoming events preview

### Images
- One image per season (spring, summer, autumn, winter)
- Sourced from Assets.xcassets
- Same image shown for all events in that season

**Image Specifications:**
- **Asset Names:** `SeasonSpring`, `SeasonSummer`, `SeasonAutumn`, `SeasonWinter` (stored in Assets.xcassets)
- **Color Set Strategy:** Each season asset has two variants (light and dark mode) using Xcode's Color Set appearance settings
- **Aspect Ratio:** 1:1 (square)
- **Resolutions per variant:**
  - 1x: 1024×1024
  - 2x: 2048×2048
  - 3x: 3072×3072
- **Safe Area:** Ensure important visual content avoids outer 20-point margin (on a 1024×1024 base, keep content within 960×960 center area)
- **Format:** PNG with alpha channel
- **Fallback:** If image fails to load, display solid color matching the season (spring: #4CAF50, summer: #FFC107, autumn: #FF9800, winter: #2196F3)

---

## Main App Info Screen

### Top Section
- Seasonal image (landscape orientation friendly)
- Next event name (large)
- Countdown in days (very large, prominent)
- Progress bar showing days elapsed since the previous solstice/equinox divided by total days until next solstice/equinox
  - Calculation: `(today - lastSolsticeDate) / (nextSolsticeDate - lastSolsticeDate)`
  - Example: Winter Solstice was Dec 21, 2025 (passed). Spring Equinox is Mar 20, 2026 (89 days later). On Jan 21, 2026, progress is 31/89 days elapsed.
  - The progress bar **resets to 0%** the moment a new solstice/equinox occurs

### Middle Section
- **Today's Sun Times**
  - Sunrise time
  - Sunset time
  - Calculated from device location
- **Season Info**
  - Season name
  - Brief description (e.g., "Spring Equinox — Day and night are approximately equal length")

### Bottom Section
- **Upcoming Events List** (scrollable)
  - Shows next 8-12 events
  - Each row displays:
    - Event name (e.g., "Spring Equinox")
    - Date/Time in local timezone, 12-hour format with AM/PM (e.g., "Mar 20, 2026 2:46 PM")
    - Days remaining as integer (e.g., "45 days")
    - Season color indicator: 12pt circle matching the season's primary color (spring: green, summer: yellow, autumn: orange, winter: blue)

### Navigation
- Tab bar or simple navigation to this screen
- Refresh button to manually update sunrise/sunset (in case location changed)

---

## Time Zone & Location Handling

### Location
- Request permission on first app launch
- Store latitude/longitude in AppGroup container
- Fall back to Greenwich/UTC (0°, 0°) if permission denied
- User can manually update location in app settings

### Time Zones
- All solstice times stored in UTC (as they are now)
- Convert to user's local timezone for display
- Sunrise/sunset calculated for user's timezone and location

### Sunrise/Sunset Algorithm
- Implement a simplified solar position algorithm based on the NOAA algorithm (https://github.com/NOAA-OWP/sunpy)
- No external APIs; algorithm is self-contained
- **Algorithm Reference:** NOAA Solar Position Algorithm
  - Calculate solar declination using Spencer's formula
  - Calculate equation of time for date
  - Calculate hour angle at sunrise/sunset
  - Convert to local solar time then UTC
- **Inputs:** latitude (Double), longitude (Double), date (Date in user's timezone)
- **Outputs:** sunrise (Date), sunset (Date) in local timezone
- **Cache:** Store in AppGroup container; recalculate daily or when location changes
- **Accuracy:** Results valid to ±2 minutes

---

## Error Handling & Edge Cases

### Location Permission
- App requests permission on first launch
- If denied, use default location (Greenwich) and notify user
- User can grant permission later in system Settings

### Time Zone Edge Cases
- Solstice at midnight: Display correctly in both UTC and local time
- User crosses timezone: Times update automatically on app launch
- Widget timezone: Uses device timezone (set by system)

### Data Integrity
- Solstice dates are hardcoded and immutable
- Sunrise/sunset cached but recalculated daily
- Widget syncs with app via AppGroup on launch

---

## Testing Strategy

### Widget Testing
- Preview all three widget sizes with mock solstice data
- Verify countdown updates correctly across timezone boundaries
- Test image display in different iOS versions (iOS 17 fallback)

### App Testing
- Verify sunrise/sunset calculations against known values
- Test location permission flows (allowed, denied, not yet asked)
- Test data sync between app and widget
- Verify time zone conversions for various user locations

### Integration Testing
- Widget refreshes daily and displays current countdown
- App and widget show consistent "next event" data
- Location changes update sunrise/sunset in real time

---

## Implementation Notes

### Existing Code
- `SolvervDef` already contains solstice dates (2025-2030)
- Widget structure (`Solsnu_Widget.swift`) is scaffolded
- Main app has basic SwiftUI structure ready for info screen

### New Components to Build
- `SunTimes` calculation (sunrise/sunset)
- `SolsticeEvent` model
- Widget layout variants (small, medium, large)
- Info screen UI
- AppGroup data sharing

### Dependencies
- None (all calculations are built-in or custom)
- WidgetKit (already available)
- SwiftUI (already used)

---

## Additional Clarifications

### Solstice Date Coverage
- Hardcoded data spans 2025–2030
- After 2030, app continues functioning but upcoming events won't display beyond December 2030
- Plan for data expansion before 2030: extend to 2040+ in an app update

### Season Assignment
- The displayed season for an event is always the season being celebrated
- Example: Spring Equinox always displays spring imagery (green), even if shown during late winter on the calendar

### Offline Functionality
- **First Launch:**
  - App requests location permission
  - If granted: Fetch location and calculate sunrise/sunset for that location, cache in AppGroup container
  - If denied: Use default location (Greenwich, 0°/0°) and cache as `isDefaultLocation: true`
  - All subsequent uses work offline
- **Subsequent Use:**
  - App and widget work entirely offline; solstice dates and countdown calculations are all local
  - Sunrise/sunset times use cached values from AppGroup container
- **State Recovery on Permission Changes:**
  - If app is running when user changes location permission in Settings, recalculate sunrise/sunset on next app foreground event
  - If AppGroup container is missing or corrupted on launch, fall back to Greenwich location and log error
- **Widget Behavior When Location Unavailable:**
  - Widget always displays countdown (never fails)
  - Sunrise/sunset times display as "—" if location permission denied and no cached data exists

---

## Success Criteria

✅ Widget displays countdown in days
✅ Seasonal image changes based on next event
✅ All four solstices/equinoxes tracked
✅ Sunrise/sunset times calculated from location
✅ Info screen shows all requested details
✅ App and widget data stay in sync
✅ Works offline after initial setup
✅ All three widget sizes render correctly