# File Upload and EXIF Processing Implementation

## Overview

This document describes the implementation of file upload and EXIF metadata extraction for the Beach Litter Mapping Platform backend.

## Components

### 1. Multer Middleware (`src/middleware/upload.ts`)

Handles file uploads to the local filesystem with the following features:

- **Storage Configuration**: Files are stored in the `./uploads` directory with unique filenames
- **File Naming**: `{fieldname}-{timestamp}-{random}.{ext}` format to prevent collisions
- **File Type Validation**: Only accepts JPEG, PNG, and WebP images
- **Size Limits**: Maximum file size of 5MB (configurable via `MAX_FILE_SIZE` env var)
- **Auto-directory Creation**: Creates upload directory if it doesn't exist

#### Configuration

```typescript
const storage = multer.diskStorage({
  destination: './uploads',
  filename: 'photo-{timestamp}-{random}.{ext}'
});

const fileFilter = (file) => {
  allowedTypes: ['image/jpeg', 'image/jpg', 'image/png', 'image/webp']
};

const limits = {
  fileSize: 5242880 // 5MB
};
```

### 2. EXIF Extraction Utility (`src/utils/exif.ts`)

Extracts metadata from uploaded photos using the `exifr` library:

- **GPS Coordinates**: Latitude and longitude from EXIF GPS data
- **Timestamp**: Original photo capture time (DateTimeOriginal)
- **Camera Info**: Make and model of the camera/device
- **Error Handling**: Returns empty object if EXIF data is unavailable

#### Extracted Data

```typescript
interface ExifData {
  latitude?: number;
  longitude?: number;
  timestamp?: Date;
  make?: string;
  model?: string;
}
```

### 3. Upload Endpoint (`POST /api/reports/upload`)

Protected endpoint for uploading individual photos:

- **Authentication**: Requires valid Clerk session token
- **Single File Upload**: Accepts one photo at a time via `photo` field
- **EXIF Processing**: Automatically extracts metadata from uploaded photo
- **Response**: Returns file URL and extracted EXIF data

#### Request

```bash
POST /api/reports/upload
Authorization: Bearer {clerk_token}
Content-Type: multipart/form-data

photo: {file}
```

#### Response

```json
{
  "url": "/uploads/photo-1234567890-123456789.jpg",
  "exifData": {
    "latitude": 53.3498,
    "longitude": -6.2603,
    "timestamp": "2024-11-16T12:30:00.000Z"
  }
}
```

### 4. Static File Serving

Uploaded files are served via Express static middleware:

```typescript
app.use('/uploads', express.static(path.join(__dirname, '../uploads')));
```

Files are accessible at: `http://localhost:3005/uploads/{filename}`

## Usage Flow

### 1. Upload Photo

**Important**: The user must be signed in with Clerk to upload photos. The frontend automatically includes the Clerk session token in the Authorization header.

```typescript
// Frontend usage (with Clerk authentication)
const formData = new FormData();
formData.append('photo', file);

// The reportService automatically includes the auth token
const { url, exifData } = await reportService.uploadPhoto(file);
```

**Manual API call** (for testing):
```typescript
const formData = new FormData();
formData.append('photo', file);

// Get Clerk token (in a Clerk-authenticated component)
const { getToken } = useAuth();
const token = await getToken();

const response = await fetch('/api/reports/upload', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${token}`
  },
  body: formData
});

const { url, exifData } = await response.json();
```

### 2. Create Report with Photo URLs

```typescript
const report = await fetch('/api/reports', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${clerkToken}`,
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    latitude: exifData.latitude || manualLat,
    longitude: exifData.longitude || manualLng,
    locationSource: exifData.latitude ? 'exif' : 'manual',
    photoUrls: [url],
    photoTimestamp: exifData.timestamp,
    litterType: 'plastic',
    quantity: 'moderate',
    description: 'Beach litter report'
  })
});
```

## Error Handling

### File Too Large

```json
{
  "error": {
    "code": "FILE_TOO_LARGE",
    "message": "File size exceeds the maximum limit of 5MB",
    "timestamp": "2024-11-16T12:00:00.000Z"
  }
}
```

### Invalid File Type

```json
{
  "error": {
    "code": "INVALID_FILE_TYPE",
    "message": "Invalid file type. Only JPEG, PNG, and WebP images are allowed.",
    "timestamp": "2024-11-16T12:00:00.000Z"
  }
}
```

### No File Uploaded

```json
{
  "error": {
    "code": "NO_FILE",
    "message": "No file uploaded",
    "timestamp": "2024-11-16T12:00:00.000Z"
  }
}
```

## Environment Variables

```env
# File Upload Configuration
UPLOAD_DIR=./uploads              # Directory for uploaded files
MAX_FILE_SIZE=5242880             # Maximum file size in bytes (5MB)
```

## Security Considerations

1. **File Type Validation**: Only image MIME types are accepted
2. **Size Limits**: Prevents large file uploads that could exhaust storage
3. **Authentication Required**: All uploads require valid Clerk session
4. **Unique Filenames**: Prevents file overwrites and collisions
5. **EXIF Stripping**: Consider stripping sensitive EXIF data before public display (future enhancement)

## Testing

Run the test script to verify the implementation:

```bash
npm run test:upload
# or
npx tsx src/scripts/testFileUpload.ts
```

The test verifies:
- ✅ Uploads directory exists
- ✅ EXIF extraction works correctly
- ✅ Configuration is properly set
- ✅ Multer middleware loads successfully

## Requirements Satisfied

This implementation satisfies the following requirements:

- **1.2**: Extract GPS coordinates from EXIF metadata
- **1.3**: Prompt for location when EXIF GPS data is unavailable
- **1.4**: Accept at least one photograph with minimum resolution
- **1.5**: Extract and display original photo capture time from EXIF

## Future Enhancements

1. **Cloud Storage**: Migrate from local filesystem to AWS S3 or Cloudinary
2. **Image Optimization**: Resize and compress images on upload
3. **Multiple File Upload**: Support batch photo uploads
4. **EXIF Privacy**: Strip sensitive EXIF data (location, device info) before public display
5. **Virus Scanning**: Integrate antivirus scanning for uploaded files
6. **CDN Integration**: Serve images via CDN for better performance