satellite-provider/plan.md

# Satellite Provider Service - Implementation Plan

## Executive Summary

This document outlines the detailed implementation plan for the Satellite Provider Service, which downloads satellite map tiles from Google Maps, stores them with metadata in PostgreSQL, and provides an API for requesting and retrieving map regions.

## Current Implementation Status (Updated 2025-11-01)

### ✅ Completed Features (Phases 1-7)
- **Database Layer**: PostgreSQL with Dapper ORM, DbUp migrations
- **Tile Management**: Download, cache, and store satellite tiles with year-based versioning
- **Region Processing**: Background queue processing with image stitching
- **API Endpoints**: Tile download, region request, and status endpoints
- **Docker Deployment**: Full containerization with docker-compose
- **Integration Tests**: Console-based test suite
- **Documentation**: Comprehensive README with API docs

### ⏳ In Progress (Phase 8)
- **Route Planning**: Split routes into overlapping regions with 200m spacing (NEW REQUIREMENT)

### Key Enhancements Implemented
1. **Year-Based Tile Versioning**: Automatic tile refresh each calendar year
2. **Image Stitching**: Combines tiles into seamless regional images with coordinate markers
3. **Comprehensive Error Handling**: Rate limiting, timeouts, network errors
4. **Rich Summary Reports**: Detailed statistics and metadata for each region

## 1. Code Analysis

### 1.1 Legacy Code Comparison

**Legacy Code (Azaion.Common/Services/SatelliteDownloader.cs):**
- Downloads tiles at 256x256 pixels (Google Maps standard)
- Composes tiles into one large image
- Splits and resizes to 512x512 TIFF files
- Uses MediatR for status updates
- Stores tiles in memory using ConcurrentDictionary
- Session-based authentication with Google Maps API

**Current Code (SatelliteProvider.Services/GoogleMapsDownloader.cs):**
- Downloads tiles at 256x256 pixels
- Saves tiles directly to disk as JPG files
- Simpler implementation without composing/splitting
- Session-based authentication with Google Maps API
- Uses concurrent queue for downloading

**Decision:** Use current code as base. It's simpler and more aligned with requirements (store tiles "as is"). The legacy code's image composition and resizing is unnecessary overhead for our use case.

### 1.2 Current Solution Structure

```
SatelliteProvider/
├── SatelliteProvider.Api          # Web API (ASP.NET 8.0)
├── SatelliteProvider.Common       # DTOs, interfaces, utilities
├── SatelliteProvider.Services     # Business logic (GoogleMapsDownloader)
└── SatelliteProvider.Tests        # Unit tests (XUnit)
```

### 1.3 Gap Analysis

**Missing Components:**
1. Database layer (Dapper + PostgreSQL)
2. Database migrations (DbUp)
3. Tile metadata storage/retrieval
4. Region request processing with background jobs
5. File system management for /tiles and /ready directories
6. API endpoints for region requests
7. Docker and docker-compose configuration
8. Integration tests as a separate console application

## 2. Architecture Design

### 2.1 Solution Structure (Updated)

```
SatelliteProvider/
├── SatelliteProvider.Api                  # Web API
├── SatelliteProvider.Common               # Shared DTOs, interfaces, utilities
├── SatelliteProvider.Services             # Business logic services
├── SatelliteProvider.DataAccess           # Database access layer (NEW)
├── SatelliteProvider.Tests                # Unit tests
├── SatelliteProvider.IntegrationTests     # Integration tests console app (NEW)
├── docker-compose.svc.yml                 # Service + dependencies (NEW)
└── docker-compose.tests.yml               # Tests + service + dependencies (NEW)
```

### 2.2 Data Model

**Tiles Table Schema:**
```sql
CREATE TABLE tiles (
    id UUID PRIMARY KEY,
    zoom_level INT NOT NULL,
    latitude DOUBLE PRECISION NOT NULL,
    longitude DOUBLE PRECISION NOT NULL,
    tile_size_meters DOUBLE PRECISION NOT NULL,
    tile_size_pixels INT NOT NULL,
    image_type VARCHAR(10) NOT NULL,
    maps_version VARCHAR(50),
    file_path VARCHAR(500) NOT NULL,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX idx_tiles_composite ON tiles(latitude, longitude, tile_size_meters);
CREATE INDEX idx_tiles_zoom ON tiles(zoom_level);
```

**Regions Table Schema:**
```sql
CREATE TABLE regions (
    id UUID PRIMARY KEY,
    latitude DOUBLE PRECISION NOT NULL,
    longitude DOUBLE PRECISION NOT NULL,
    size_meters DOUBLE PRECISION NOT NULL,
    zoom_level INT NOT NULL,
    status VARCHAR(20) NOT NULL,
    csv_file_path VARCHAR(500),
    summary_file_path VARCHAR(500),
    tiles_downloaded INT DEFAULT 0,
    tiles_reused INT DEFAULT 0,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX idx_regions_status ON regions(status);
```

**Routes Table Schema (Phase 8 - New):**
```sql
CREATE TABLE routes (
    id UUID PRIMARY KEY,
    name VARCHAR(200),
    description TEXT,
    total_distance_meters DOUBLE PRECISION NOT NULL,
    total_points INT NOT NULL,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE route_points (
    id UUID PRIMARY KEY,
    route_id UUID NOT NULL REFERENCES routes(id) ON DELETE CASCADE,
    sequence_number INT NOT NULL,
    latitude DOUBLE PRECISION NOT NULL,
    longitude DOUBLE PRECISION NOT NULL,
    point_type VARCHAR(20) NOT NULL, -- 'start', 'end', 'intermediate'
    segment_index INT NOT NULL,
    distance_from_previous DOUBLE PRECISION,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    UNIQUE(route_id, sequence_number)
);

CREATE INDEX idx_route_points_route ON route_points(route_id, sequence_number);
CREATE INDEX idx_route_points_coords ON route_points(latitude, longitude);
```

### 2.3 Background Processing

**In-Memory Queue Implementation:**
- Use `System.Threading.Channels` for thread-safe, async-friendly queue
- Hosted service (IHostedService) to process queue items
- Status tracking in database (processing, completed, failed)
- Future migration path: Azure Storage Queue, AWS SQS, or RabbitMQ

### 2.4 Google Maps Tile Details

**Tile Size:** 
- Google Maps returns tiles at **256x256 pixels** (standard)
- We will store tiles as-is from Google Maps
- Store `tile_size_pixels = 256` in database

**Maps Version:**
- Google Maps doesn't expose explicit version via API
- Solution: Use download timestamp as version identifier
- Store as `maps_version = "downloaded_YYYY-MM-DD"`
- Consider ETags if available in HTTP response headers

**Image Format:**
- Google Maps returns JPEG for satellite tiles
- Store as JPG with `image_type = "jpg"`

## 3. Implementation Plan

### Phase 1: Database Layer (Priority: High) ✅ **COMPLETED**

**Task 1.1: Create DataAccess Project** ✅
- ✅ Created project `SatelliteProvider.DataAccess`
- ✅ Added Dapper NuGet package
- ✅ Added Npgsql NuGet package for PostgreSQL support
- ✅ Added DbUp NuGet package for migrations

**Task 1.2: Implement Database Migrations** ✅
- ✅ Created `Migrations` folder in DataAccess project
- ✅ Script 001: Create tiles table
- ✅ Script 002: Create regions table
- ✅ Script 003: Create indexes
- ✅ Script 004: Add version column for year-based versioning
- ✅ Implemented DbUp migration runner in Program.cs startup

**Task 1.3: Implement Repository Pattern** ✅
- ✅ Created `ITileRepository` interface
- ✅ Created `TileRepository` class implementing Dapper queries
- ✅ Created `IRegionRepository` interface
- ✅ Created `RegionRepository` class implementing Dapper queries
- ✅ Added connection string management in appsettings.json

**Task 1.4: Configuration** ✅
- ✅ Added PostgreSQL connection string to appsettings.json
- ✅ Added PostgreSQL connection string to appsettings.Development.json
- ✅ Created configuration classes in Common project

### Phase 2: Enhanced Tile Downloading and Storage (Priority: High) ✅ **COMPLETED**

**Task 2.1: Update GoogleMapsDownloader** ✅
- ✅ Created GoogleMapsDownloaderV2 with enhanced functionality
- ✅ Returns list of downloaded tile metadata
- ✅ Calculates tile size in meters (based on zoom level)
- ✅ Stores maps version (download timestamp format)
- ✅ Implemented error handling and retry logic with exponential backoff
- ✅ Added rate limit exception handling

**Task 2.2: Implement Tile Service** ✅
- ✅ Created `ITileService` interface in Common
- ✅ Created `TileService` class in Services
- ✅ Implemented `DownloadAndStoreTilesAsync(lat, lon, size, zoom)`
- ✅ Checks database for existing tiles before downloading (with year-based versioning)
- ✅ Saves tile metadata to database after download
- ✅ Returns list of tile paths and metadata

**Task 2.3: File System Management** ✅
- ✅ Configured /tiles directory path from appsettings.json
- ✅ Directory creation on startup implemented
- ✅ Implemented tile naming convention: `tile_{zoom}_{x}_{y}_{timestamp}.jpg`
- ✅ File path storage in database

### Phase 3: Background Processing System (Priority: High) ✅ **COMPLETED**

**Task 3.1: Create Region Request Queue** ✅
- ✅ Created `IRegionRequestQueue` interface
- ✅ Implemented using System.Threading.Channels
- ✅ Thread-safe enqueue/dequeue operations
- ✅ Capacity limits and overflow handling

**Task 3.2: Create Background Worker** ✅
- ✅ Implemented `RegionProcessingService : IHostedService`
- ✅ Dequeues region requests
- ✅ Processes each region (download tiles, create CSV, create summary, stitch images)
- ✅ Updates region status in database (queued → processing → completed/failed)
- ✅ Error handling with specific exception types (RateLimitException, HttpRequestException)
- ✅ Timeout handling (5 minutes per region)

**Task 3.3: Implement Region Service** ✅
- ✅ Created `IRegionService` interface
- ✅ Created `RegionService` class
- ✅ Method: `RequestRegionAsync(id, lat, lon, size)` - adds to queue and database
- ✅ Method: `GetRegionStatusAsync(id)` - returns status and file paths
- ✅ Method: `ProcessRegionAsync(id)` - called by background worker

**Task 3.4: CSV and Summary File Generation** ✅
- ✅ Created /ready directory management
- ✅ Implemented CSV writer with tile coordinates and file paths
- ✅ Generates region_{id}_ready.csv with ordered tiles (top-left to bottom-right)
- ✅ Generates region_{id}_summary.txt with comprehensive statistics
- ✅ Generates region_{id}_stitched.jpg with combined satellite imagery
- ✅ Includes error summaries for failed regions

### Phase 4: API Endpoints (Priority: High) ✅ **COMPLETED**

**Task 4.1: Remove Old Endpoints** ⚠️ **PARTIALLY DONE**
- ⚠️ Some legacy endpoints still exist (GetSatelliteTilesByLatLon, GetSatelliteTilesByMgrs, UploadImage)
- ✅ Main functionality implemented with new endpoints

**Task 4.2: Implement Region Request Endpoint** ✅
- ✅ POST /api/satellite/request
- ✅ Request body: { id: UUID, latitude: double, longitude: double, sizeMeters: double, zoomLevel: int }
- ✅ Validation: size between 100-10000 meters
- ✅ Returns: { id: UUID, status: "queued", ... }
- ✅ Enqueues region processing

**Task 4.3: Implement Region Status Endpoint** ✅
- ✅ GET /api/satellite/region/{id}
- ✅ Returns: { id: UUID, status: string, csvPath: string?, summaryPath: string?, tilesDownloaded: int, tilesReused: int }
- ✅ Status values: "queued", "processing", "completed", "failed"

**Task 4.4: OpenAPI/Swagger Documentation** ✅
- ✅ Updated Swagger configuration
- ✅ Added endpoint descriptions
- ✅ Documented request/response models
- ✅ Custom operation filters for parameter descriptions

### Phase 5: Docker Configuration (Priority: Medium) ✅ **COMPLETED**

**Task 5.1: Create Dockerfiles** ✅
- ✅ Dockerfile for SatelliteProvider.Api
- ✅ Dockerfile for SatelliteProvider.IntegrationTests
- ✅ Multi-stage builds for optimization
- ✅ Base image: mcr.microsoft.com/dotnet/aspnet:8.0

**Task 5.2: Create docker-compose.yml** ✅
- ✅ Service: api (satellite-provider-api)
- ✅ Service: postgres (PostgreSQL 16)
- ✅ Volume: ./tiles mounted to host
- ✅ Volume: ./ready mounted to host
- ✅ Volume: ./logs mounted to host
- ✅ Network configuration
- ✅ Environment variables for configuration
- ✅ Health checks for dependencies

**Task 5.3: Create docker-compose.tests.yml** ✅
- ✅ Services: postgres, api, integration-tests
- ✅ Waits for API and database readiness
- ✅ Runs tests and exits with test results
- ✅ Separate test environment configuration

**Task 5.4: Environment Configuration** ✅
- ✅ Development configuration (appsettings.Development.json)
- ✅ Production configuration (appsettings.json)
- ✅ Environment-specific settings
- ✅ Secrets management via environment variables

### Phase 6: Integration Tests (Priority: Medium) ✅ **COMPLETED**

**Task 6.1: Create Integration Tests Project** ✅
- ✅ Created SatelliteProvider.IntegrationTests console app project
- ✅ Added necessary NuGet packages (XUnit, FluentAssertions, etc.)
- ✅ Configured to run as console application
- ✅ Setup for database and API access

**Task 6.2: Implement Test Scenarios** ✅
- ✅ TileTests: Test tile download and caching
- ✅ RegionTests: Test region request and processing
- ✅ Verify CSV creation and content
- ✅ Verify summary file creation
- ✅ Verify stitched image creation
- ✅ Test tile reuse functionality
- ✅ Test region status endpoint
- ✅ Test concurrent region requests

**Task 6.3: Test Data Management** ✅
- ✅ Database cleanup before tests
- ✅ Test data validation
- ✅ Isolated test environments via Docker

**Task 6.4: CI/CD Integration** ⏳
- ✅ Docker-based test execution configured
- ⏳ CI/CD pipeline integration (depends on CI/CD setup)
- ⏳ Code coverage analysis (optional enhancement)

### Phase 7: Additional Features and Improvements (Priority: Low) ✅ **COMPLETED**

**Task 7.1: Monitoring and Logging** ✅
- ✅ Structured logging with Serilog
- ✅ File and console logging
- ✅ Performance tracking in logs
- ✅ Error tracking with context

**Task 7.2: Caching Strategy** ✅
- ✅ Implemented year-based versioning for automatic tile refresh
- ✅ Tile reuse within the same year
- ✅ Historical tile preservation

**Task 7.3: API Rate Limiting** ⏳
- ⏳ Rate limiting for API endpoints (not implemented)
- ✅ Google Maps API error handling with retry logic
- ✅ Exponential backoff for failed requests

**Task 7.4: Documentation** ✅
- ✅ Comprehensive README.md with API documentation
- ✅ Configuration guide
- ✅ Docker deployment instructions
- ✅ Year-based versioning strategy documented

## 4. Technical Specifications

### 4.1 Technology Stack

- **Runtime:** .NET 8.0
- **Web Framework:** ASP.NET Core Web API
- **ORM:** Dapper 2.1.35
- **Database:** PostgreSQL (latest stable)
- **Migrations:** DbUp
- **Testing:** XUnit, Moq, FluentAssertions
- **Containerization:** Docker, Docker Compose
- **Image Processing:** SixLabors.ImageSharp 3.1.11
- **Logging:** Microsoft.Extensions.Logging

### 4.2 NuGet Packages to Add

**SatelliteProvider.DataAccess:**
- Dapper (2.1.35)
- Npgsql (latest stable)
- DbUp (latest stable)
- Microsoft.Extensions.Configuration.Abstractions

**SatelliteProvider.Api:**
- Npgsql (for PostgreSQL connection)

**SatelliteProvider.IntegrationTests:**
- All existing test packages
- System.CommandLine (for console app)
- Testcontainers (optional, for Docker-based integration tests)

### 4.3 Configuration Structure

**appsettings.json:**
```json
{
  "ConnectionStrings": {
    "DefaultConnection": "Host=localhost;Database=satelliteprovider;Username=postgres;Password=postgres"
  },
  "MapConfig": {
    "Service": "GoogleMaps",
    "ApiKey": "YOUR_API_KEY_HERE"
  },
  "StorageConfig": {
    "TilesDirectory": "/tiles",
    "ReadyDirectory": "/ready"
  },
  "ProcessingConfig": {
    "MaxConcurrentDownloads": 4,
    "DefaultZoomLevel": 20,
    "QueueCapacity": 100
  }
}
```

### 4.4 API Endpoints Summary

| Method | Endpoint | Description | Status |
|--------|----------|-------------|--------|
| POST | /api/satellite/tiles/download | Download single tile at coordinates | ✅ Implemented |
| POST | /api/satellite/request | Request tiles for a region | ✅ Implemented |
| GET | /api/satellite/region/{id} | Get region status and file paths | ✅ Implemented |
| POST | /api/satellite/route | Plan route and split into regions | ⏳ To be implemented |
| GET | /api/satellite/route/{id} | Get route information with points | ⏳ To be implemented |

### 4.5 File Naming Conventions

**Tiles:**
```
/tiles/tile_{zoom}_{x}_{y}_{timestamp}.jpg
Example: /tiles/tile_20_12345_67890_20231015143022.jpg
```

**CSV Files:**
```
/ready/region_{id}_ready.csv
Example: /ready/region_550e8400-e29b-41d4-a716-446655440000_ready.csv
```

**Summary Files:**
```
/ready/region_{id}_summary.txt
Example: /ready/region_550e8400-e29b-41d4-a716-446655440000_summary.txt
```

### 4.6 CSV File Format

```csv
latitude,longitude,file_path
37.7749,-122.4194,/tiles/tile_20_12345_67890_20231015143022.jpg
37.7750,-122.4194,/tiles/tile_20_12346_67890_20231015143023.jpg
```

Rows ordered from top-left to bottom-right covering the requested region.

### 4.7 Summary File Format

```
Region Processing Summary
========================
Region ID: 550e8400-e29b-41d4-a716-446655440000
Center: 37.7749, -122.4194
Size: 500 meters
Zoom Level: 20

Processing Statistics:
- Tiles Downloaded: 45
- Tiles Reused from Cache: 12
- Total Tiles: 57
- Processing Time: 12.5 seconds
- Started: 2023-10-15 14:30:15
- Completed: 2023-10-15 14:30:28

Files Created:
- CSV: /ready/region_550e8400-e29b-41d4-a716-446655440000_ready.csv
- Summary: /ready/region_550e8400-e29b-41d4-a716-446655440000_summary.txt
```

## 5. Testing Strategy

### 5.1 Unit Tests
- Test GeoUtils calculations
- Test tile coordinate conversions
- Test repository methods (with mocked database)
- Test service business logic

### 5.2 Integration Tests
- End-to-end region request flow
- Database operations
- File system operations
- API endpoint testing
- Background processing

### 5.3 Test Coverage Goals
- Minimum 80% code coverage
- 100% coverage for critical paths (downloading, storage, region processing)

## 6. Deployment Strategy

### 6.1 Development Environment
```bash
docker-compose -f docker-compose.svc.yml up
```

### 6.2 Running Integration Tests
```bash
docker-compose -f docker-compose.tests.yml up --abort-on-container-exit
```

### 6.3 Production Deployment
- Use docker-compose.svc.yml as base
- Override with production-specific configuration
- Configure volumes for persistent storage
- Set up backup strategy for PostgreSQL
- Configure SSL/TLS for API
- Set up monitoring and alerting

## 7. Security Considerations

1. **API Key Management:** Store Google Maps API key in environment variables or secrets manager
2. **Database Security:** Use strong passwords, restrict network access
3. **Input Validation:** Validate all API inputs (coordinates, size limits)
4. **File System Security:** Restrict write access to /tiles and /ready directories
5. **Rate Limiting:** Implement to prevent abuse
6. **HTTPS:** Enforce HTTPS in production

## 8. Performance Considerations

1. **Concurrent Downloads:** Use 4 concurrent connections to Google Maps
2. **Database Indexing:** Composite index on (latitude, longitude, tile_size_meters)
3. **Caching:** Reuse existing tiles to minimize downloads
4. **Async Operations:** All I/O operations are async
5. **Background Processing:** Non-blocking region processing

## 9. Monitoring and Observability

1. **Logging:** Structured logging for all operations
2. **Metrics:** Track download counts, cache hit rates, processing times
3. **Health Checks:** API and database health endpoints
4. **Error Tracking:** Log errors with context for debugging

## 10. Future Enhancements

1. **Cloud Queue Integration:** Replace in-memory queue with Azure/AWS queue
2. **CDN Integration:** Serve tiles via CDN
3. **Tile Expiration:** Implement automatic tile refresh
4. **Multiple Map Providers:** Support for other satellite imagery providers
5. **WebSocket Support:** Real-time progress updates
6. **Admin Dashboard:** UI for monitoring and management
7. **Tile Stitching:** API to stitch tiles into single large image

### Phase 8: Route Planning Feature (Priority: High) ⏳ **NEW REQUIREMENT**

**Overview**: Implement route planning functionality that splits a route into overlapping regions with intermediate points spaced no more than 200 meters apart.

**Task 8.1: Database Schema for Routes**
- Create routes table to store route information
- Create route_points table to store route points (start, end, intermediate)
- Migration script 005: Create routes tables
- Add indexes for efficient route querying

**Task 8.2: Route Calculation Logic**
- Implement intermediate point calculation algorithm
- Calculate distance between two points using GeoUtils
- Generate intermediate points along the route with max 200m spacing
- Ensure equal spacing between points

**Task 8.3: Route Repository**
- Create `IRouteRepository` interface
- Create `RouteRepository` class
- CRUD operations for routes and route points
- Query methods for retrieving routes with points

**Task 8.4: Route Service**
- Create `IRouteService` interface
- Create `RouteService` class
- Method: `CreateRouteAsync(points)` - creates route with intermediate points
- Method: `GetRouteAsync(id)` - retrieves route with all points

**Task 8.5: Route API Endpoints**
- POST /api/satellite/route - create route from array of points
- GET /api/satellite/route/{id} - get route information with intermediate points
- Input validation (minimum 2 points, valid coordinates)
- Return route with calculated intermediate points

**Task 8.6: Integration with Region Processing**
- Each route point (including intermediate) represents a region center
- Option to automatically request regions for all route points
- Track processing status for route-based regions

**Task 8.7: Tests**
- Unit tests for intermediate point calculation
- Integration tests for route creation and retrieval
- Test various scenarios (short routes < 200m, long routes > 200m, multi-segment routes)

**Estimated Time:** 2-3 days

## 11. Implementation Timeline

**Total Estimated Time:** 15-20 working days (Phases 1-7 completed, Phase 8 remaining)

| Phase | Duration | Dependencies | Status |
|-------|----------|--------------|--------|
| Phase 1: Database Layer | 2-3 days | None | ✅ **COMPLETED** |
| Phase 2: Enhanced Tile Downloading | 2-3 days | Phase 1 | ✅ **COMPLETED** |
| Phase 3: Background Processing | 3-4 days | Phase 1, Phase 2 | ✅ **COMPLETED** |
| Phase 4: API Endpoints | 1-2 days | Phase 3 | ✅ **COMPLETED** |
| Phase 5: Docker Configuration | 2-3 days | Phase 4 | ✅ **COMPLETED** |
| Phase 6: Integration Tests | 3-4 days | Phase 5 | ✅ **COMPLETED** |
| Phase 7: Additional Features | 2-3 days | Phase 6 | ✅ **COMPLETED** |
| **Phase 8: Route Planning** | **2-3 days** | **Phase 1, Phase 2** | **⏳ IN PROGRESS** |

**Critical Path:** ~~Phase 1 → Phase 2 → Phase 3 → Phase 4 → Phase 5 → Phase 6~~ → **Phase 8 (Route Planning)**

## 12. Risk Assessment

| Risk | Impact | Probability | Mitigation |
|------|--------|-------------|------------|
| Google Maps API changes | High | Low | Monitor API changes, version locking |
| API quota exceeded | High | Medium | Implement caching, rate limiting |
| Disk space exhaustion | Medium | Medium | Implement cleanup policy, monitoring |
| Database performance | Medium | Low | Proper indexing, connection pooling |
| Concurrent processing issues | Medium | Low | Thorough testing, proper locking |

## 13. Success Criteria

1. ✅ API successfully downloads and stores tiles - **COMPLETED**
2. ✅ Metadata stored correctly in PostgreSQL - **COMPLETED**
3. ✅ Region requests processed in background - **COMPLETED**
4. ✅ CSV and summary files generated correctly - **COMPLETED**
5. ✅ Tile caching works (reuses existing tiles) - **COMPLETED**
6. ✅ Docker containers run successfully - **COMPLETED**
7. ✅ Integration tests pass - **COMPLETED**
8. ✅ API documentation complete - **COMPLETED**
9. ✅ Performance meets requirements (< 30s for 1000m region) - **COMPLETED**
10. ✅ Image stitching implemented - **COMPLETED**
11. ⏳ Route planning feature - **IN PROGRESS** (see Phase 8)

## 14. Open Questions and Decisions Made

### Questions from Analysis:
1. **Legacy Code?** ✅ Analyzed - Use current code as base
2. **Background Processing?** ✅ In-memory queue with Channels
3. **Database Migrations?** ✅ DbUp
4. **Tile Size?** ✅ 256x256 pixels (Google Maps standard)
5. **Maps Version?** ✅ Use download timestamp + year-based versioning
6. **Composite Key?** ✅ Indexed composite key, UUID primary key
7. **Integration Tests?** ✅ Separate console app project
8. **Image Stitching?** ✅ Implemented with ImageSharp, generates region_{id}_stitched.jpg
9. **Tile Versioning?** ✅ Year-based versioning for automatic annual refresh

### New Questions for Phase 8 (Route Planning):

1. **Route Point Spacing?** 
   - Max 200m between consecutive points
   - Equal spacing along route segments
   
2. **Route Storage?**
   - Store routes table with route metadata
   - Store route_points table with individual points and sequence
   
3. **Automatic Region Processing?**
   - Decision needed: Should route creation automatically trigger region requests for all points?
   - Or: Manual trigger via separate endpoint?
   
4. **Route Point Metadata?**
   - Track point type: start, end, or intermediate
   - Store segment information (which route segment the point belongs to)
   
5. **Route-Based Region Tracking?**
   - Link regions to routes for progress tracking
   - Aggregate route completion status based on all region statuses

## 15. Next Steps

1. Review and approve this implementation plan
2. Set up development environment
3. Create feature branches for each phase
4. Begin Phase 1: Database Layer implementation
5. Daily stand-ups to track progress
6. Regular code reviews for each completed phase

---

**Document Version:** 2.0  
**Created:** 2025-10-26  
**Last Updated:** 2025-11-01  
**Author:** AI Assistant  
**Status:** Phases 1-7 Completed, Phase 8 (Route Planning) In Progress