# Trip Planner Refactoring Summary

## Overview
Refactored the trip planner system to use a single source of truth for all trip data, eliminating duplicate state management and improving data flow consistency.

## Key Changes

### 1. Created Unified TripContext (`src/contexts/TripContext.tsx`)

**Purpose**: Centralized state management for all trip-related data

**Core State**:
- `trip`: Main trip data including days, places, and metadata
- `loading`: Loading state for async operations
- `activeDayId`: Currently selected day

**Derived State** (computed automatically):
- `activeDay`: Current day object
- `activeDayPlaces`: Places for the active day
- `allMapMarkers`: All markers across all days
- `activeDayMapMarkers`: Markers for active day only
- `activeDayTimelineBlocks`: Timeline blocks grouped by time of day

**UI State**:
- `hoveredPlaceId`: Place being hovered
- `selectedPlaceId`: Place being selected
- `highlightedPlaceId`: Place being highlighted (animation)
- `newlyAddedPlaceId`: Newly added place (for scroll/highlight)

**Actions**:
- `loadTrip(tripId)`: Load trip from database
- `addPlaceToDay(placeId, dayId)`: Add place to a day
- `removePlaceFromDay(tripPlaceId)`: Remove place from day
- `reorderPlaces(dayId, places)`: Reorder places via drag & drop
- `updateTripData(updates)`: Update trip metadata
- `setActiveDayId(dayId)`: Change active day
- UI state setters for hover/select/highlight

### 2. Refactored TripPlanner.tsx

**Removed**:
- Local `trip` state
- Local `loading` state
- Local `activeDayId` state
- Duplicate `hoveredPlaceId`, `selectedPlaceId`, etc.
- Local `loadTrip()` function
- Computed `allPlaces` and `activeDayPlaces` (now from context)

**Now Uses Context**:
```typescript
const {
  trip,
  loading,
  activeDayId,
  setActiveDayId,
  activeDay,
  activeDayPlaces,
  allMapMarkers,
  activeDayMapMarkers,
  hoveredPlaceId,
  setHoveredPlaceId,
  // ... etc
  loadTrip,
  removePlaceFromDay,
  reorderPlaces,
} = useTrip();
```

**Benefits**:
- Single source of truth for trip data
- Automatic re-renders when data changes
- No manual state synchronization needed
- Cleaner component code
- Easier to test and debug

### 3. Updated API Layer

**Added to `src/db/api.ts`**:
- `tripPlacesApi.updateOrderIndex()`: Update single place order

### 4. Updated App.tsx

**Added TripProvider**:
```typescript
<AuthProvider>
  <CurrentTripProvider>
    <TripProvider>
      <Router>
        {/* ... */}
      </Router>
    </TripProvider>
  </CurrentTripProvider>
</AuthProvider>
```

## Data Flow

### Before Refactoring:
```
Database → TripPlanner (local state) → Props → Child Components
                ↓
         Manual sync between:
         - trip state
         - activeDayId
         - places arrays
         - map markers
         - timeline blocks
```

### After Refactoring:
```
Database → TripContext (single source) → useTrip() hook → All Components
                ↓
         Automatic derivation:
         - activeDay from activeDayId
         - activeDayPlaces from activeDay
         - allMapMarkers from trip.days
         - activeDayMapMarkers from activeDayId
         - activeDayTimelineBlocks from activeDayPlaces
```

## Benefits

### 1. Single Source of Truth
- All trip data lives in TripContext
- No duplicate state across components
- Consistent data everywhere

### 2. Automatic Derivation
- Derived values (markers, timeline blocks) computed automatically
- No manual synchronization needed
- Always consistent with source data

### 3. Simplified Components
- Components use `useTrip()` hook
- No prop drilling
- Cleaner, more maintainable code

### 4. Better Performance
- Memoized derived values
- Re-renders only when necessary
- Optimized data flow

### 5. Easier Testing
- Context can be mocked easily
- Isolated state management
- Clear data dependencies

## Migration Guide

### For Components Using Trip Data:

**Before**:
```typescript
function MyComponent({ trip, activeDayId, places, onUpdate }) {
  // Use props
}
```

**After**:
```typescript
function MyComponent() {
  const { trip, activeDayId, activeDayPlaces, updateTripData } = useTrip();
  // Use context directly
}
```

### For Components Updating Trip Data:

**Before**:
```typescript
await tripPlacesApi.remove(id);
await loadTrip(); // Manual reload
```

**After**:
```typescript
await removePlaceFromDay(id); // Automatic reload
```

## Future Improvements

1. **Add Optimistic Updates**: Update UI immediately, rollback on error
2. **Add Undo/Redo**: Track state history in context
3. **Add Caching**: Cache trip data to reduce API calls
4. **Add Real-time Sync**: Use Supabase Realtime for multi-user editing
5. **Split Context**: Separate UI state from data state if needed

## Testing Recommendations

1. Test TripContext in isolation
2. Mock TripContext for component tests
3. Test derived values computation
4. Test action side effects
5. Test error handling in actions

## Notes

- The Trip interface in TripContext includes all fields from the database schema
- Backward compatibility maintained with alias fields (start_date/startDate)
- Type casting used where necessary for component compatibility
- All lint errors resolved
