# Health Tracker App - Development Blueprint

## Project Overview
A privacy-first Flutter health tracking app for Android (with future iOS support) that allows users to record weight, blood pressure, and mood data with local storage and optional encrypted cloud backups.

## High-Level Architecture

### Core Components
1. **Data Layer**: Local SQLite database with encryption support
2. **Business Logic**: BLoC pattern for state management
3. **UI Layer**: Material Design with dark mode support
4. **Security Layer**: RSA/AES encryption for premium features
5. **Backup System**: Encrypted cloud storage (premium)

### Key Technologies
- Flutter 3.x with Dart
- SQLite with sqflite package
- BLoC pattern for state management
- Local authentication (biometrics/password)
- Cryptography packages for encryption
- Charts for data visualization

## Development Phases

### Phase 1: Foundation & Core Infrastructure (Steps 1-4)
- Project setup and basic structure
- Database schema and models
- Basic navigation and theming
- Core data storage functionality

### Phase 2: MVP Data Recording (Steps 5-8)
- Weight tracking functionality
- Blood pressure recording
- Mood tracking with emoji selection
- Basic input validation

### Phase 3: Data Visualization (Steps 9-10)
- Weight graphs
- Blood pressure charts
- Data filtering and date ranges

### Phase 4: Settings & Export (Steps 11-12)
- Settings page with preferences
- Manual data export functionality
- Data backup/restore from local files

### Phase 5: Security Foundation (Steps 13-14)
- RSA key pair generation
- Local key storage with biometric protection
- Basic encryption setup

### Phase 6: Premium Features (Steps 15-16)
- In-app purchase integration
- Encrypted cloud backup system
- Premium feature gating

### Phase 7: Polish & Testing (Steps 17-18)
- UI polish and accessibility
- Comprehensive testing
- Performance optimization

---

## Detailed Implementation Steps with LLM Prompts

### Step 1: Project Setup and Basic Structure

```
Create a new Flutter project for a health tracking app with the following requirements:

1. Set up a new Flutter project named "health_tracker"
2. Configure the project structure with these directories:
   - lib/
     - models/
     - screens/
     - widgets/
     - services/
     - utils/
     - bloc/
   - assets/
   - test/

3. Update pubspec.yaml with essential dependencies:
   - sqflite (for local database)
   - flutter_bloc (for state management)
   - equatable (for value equality)
   - intl (for date formatting)
   - shared_preferences (for app settings)

4. Create a basic main.dart file that:
   - Sets up MaterialApp with dark theme support
   - Includes a basic home screen placeholder
   - Configures proper theme colors for health tracking

5. Add basic app constants in lib/utils/constants.dart for:
   - App name and version
   - Database configuration
   - Theme colors
   - Default values for health metrics

Ensure the project compiles and runs successfully on Android with a basic "Health Tracker" title and empty home screen.
```

### Step 2: Database Schema and Models

```
Building on the previous Flutter project setup, create the database foundation:

1. Create data models in lib/models/:
   - health_data.dart: Base class for all health entries with id, timestamp, notes
   - weight_entry.dart: Extends health_data, includes weight in kg, original unit
   - blood_pressure_entry.dart: Extends health_data, includes systolic/diastolic values
   - mood_entry.dart: Extends health_data, includes mood enum and emoji

2. Create mood_type.dart enum with:
   - Energized (⚡)
   - Calm (🌿) 
   - Neutral (😐)
   - Tired (😴)
   - Stressed (😰)
   - Sad (😢)
   - Irritable (😠)

3. Create database service in lib/services/database_service.dart:
   - SQLite database initialization
   - Tables for weight_entries, blood_pressure_entries, mood_entries
   - CRUD operations for each data type
   - Proper foreign key relationships
   - Database migration support

4. Add unit conversion utilities in lib/utils/unit_converter.dart:
   - Convert between kg, pounds, and stones for weight
   - Validate blood pressure ranges (systolic ≤ 300, diastolic ≤ 200)
   - Date/time formatting helpers

5. Create a simple database initialization test to verify tables are created correctly.

All models should include proper JSON serialization and validation methods.
```

### Step 3: Basic Navigation and Theme Setup

```
Extend the Flutter health tracker project with navigation and theming:

1. Create a bottom navigation bar in lib/widgets/bottom_nav_bar.dart with tabs:
   - Home (dashboard/recent entries)
   - Add Data (data input forms)
   - Charts (visualization)
   - Settings

2. Update main.dart to include:
   - Comprehensive dark and light themes with health-focused colors
   - Theme switching capability
   - Bottom navigation integration
   - Proper state management setup with BLoC

3. Create basic screen placeholders in lib/screens/:
   - home_screen.dart: Dashboard showing recent entries
   - add_data_screen.dart: Tabbed view for adding different data types
   - charts_screen.dart: Data visualization screen
   - settings_screen.dart: App settings and preferences

4. Add navigation logic that:
   - Maintains selected tab state
   - Handles deep linking between tabs
   - Includes proper back button behavior

5. Create a shared app bar widget in lib/widgets/shared_app_bar.dart with:
   - Consistent styling across screens
   - Theme toggle button
   - Title that reflects current screen

The app should now have full navigation working with placeholder content in each screen.
```

### Step 4: Core Data Storage Service

```
Implement the core data persistence layer for the health tracker:

1. Complete the database service implementation in lib/services/database_service.dart:
   - Full CRUD operations for all health data types
   - Batch operations for data import/export
   - Query methods with date filtering
   - Data aggregation methods (averages, trends)
   - Duplicate detection and merging logic

2. Create BLoC classes in lib/bloc/:
   - health_data_bloc.dart: Manages all health data operations
   - health_data_event.dart: Events for add, update, delete, load operations
   - health_data_state.dart: States for loading, loaded, error conditions

3. Add data validation service in lib/services/validation_service.dart:
   - Weight validation (positive numbers, reasonable ranges)
   - Blood pressure validation (positive integers, max values)
   - Date validation (not future dates)
   - Duplicate entry prevention

4. Create error handling utilities in lib/utils/error_handler.dart:
   - Database error handling
   - User-friendly error messages
   - Logging capabilities for debugging

5. Update the home screen to:
   - Display recent entries from database
   - Show basic statistics (latest readings)
   - Handle loading and error states
   - Include pull-to-refresh functionality

Test that data can be successfully stored and retrieved from the SQLite database.
```

### Step 5: Weight Tracking Implementation

```
Implement comprehensive weight tracking functionality:

1. Create a detailed weight input form in lib/screens/add_weight_screen.dart:
   - Number input with decimal support
   - Unit selection (kg, pounds, stones) with radio buttons
   - Date/time picker (defaults to now)
   - Optional notes text field
   - Form validation with clear error messages

2. Add weight-specific widgets in lib/widgets/:
   - weight_input_widget.dart: Reusable weight input component
   - weight_list_item.dart: Display widget for weight entries
   - unit_selector_widget.dart: Unit conversion selector

3. Update the weight entry model to include:
   - Display weight in user's preferred unit
   - Conversion methods between units
   - Proper validation for weight ranges (20-500 kg equivalent)

4. Enhance the home screen to display:
   - Latest weight entry with trend indicator
   - Weight change from previous entry
   - Quick stats (weekly/monthly averages)

5. Add weight management to health_data_bloc:
   - AddWeightEvent and corresponding state handling
   - Update and delete weight entries
   - Load weight history with pagination

6. Create unit tests for:
   - Weight conversions
   - Form validation
   - Database operations

The weight tracking should be fully functional with proper validation and unit conversion.
```

### Step 6: Blood Pressure Recording

```
Implement blood pressure tracking with proper validation:

1. Create blood pressure input form in lib/screens/add_blood_pressure_screen.dart:
   - Two separate number inputs for systolic and diastolic
   - Input validation (positive integers only)
   - Range validation (systolic ≤ 300, diastolic ≤ 200)
   - Date/time picker
   - Optional notes field
   - Visual indicators for blood pressure categories (normal, elevated, etc.)

2. Add blood pressure widgets in lib/widgets/:
   - bp_input_widget.dart: Dual number input component
   - bp_list_item.dart: Display component with color coding
   - bp_category_indicator.dart: Shows BP category (normal/high/etc.)

3. Create blood pressure utility in lib/utils/blood_pressure_utils.dart:
   - BP category classification (normal, elevated, high stage 1/2)
   - Color coding for different categories
   - Validation helpers

4. Update home screen to show:
   - Latest BP reading with category indicator
   - Trend arrow (increasing/decreasing)
   - Quick access to add new BP reading

5. Add BP events to health_data_bloc:
   - AddBloodPressureEvent
   - Update/delete operations
   - Load BP history with filtering

6. Implement proper error handling for:
   - Invalid BP values
   - Database constraints
   - Form submission errors

Blood pressure tracking should include visual feedback and proper medical range validation.
```

### Step 7: Mood Tracking with Emoji Selection

```
Implement mood tracking functionality with emoji-based selection:

1. Create mood selection screen in lib/screens/add_mood_screen.dart:
   - Grid layout of mood emojis with labels
   - Single selection mode (radio button behavior)
   - Large, touchable emoji buttons
   - Date/time picker
   - Optional notes for mood context

2. Add mood-specific widgets in lib/widgets/:
   - mood_selector_grid.dart: Grid of selectable mood options
   - mood_emoji_button.dart: Individual mood selection button
   - mood_list_item.dart: Display component for mood entries

3. Enhance mood_type.dart enum with:
   - Mood descriptions and colors
   - Emoji representations
   - Helper methods for display
   - Mood intensity or energy levels

4. Update home screen to include:
   - Latest mood with emoji and timestamp
   - Mood pattern indicator (if sufficient data)
   - Quick mood logging shortcut

5. Add mood events to health_data_bloc:
   - AddMoodEvent with proper validation
   - Mood history loading and filtering
   - Update/delete mood entries

6. Create mood analytics in lib/services/mood_analytics.dart:
   - Mood frequency calculations
   - Pattern detection (time of day, day of week)
   - Mood stability indicators

7. Add haptic feedback for mood selection to enhance user experience.

The mood tracking should feel intuitive and engaging with clear visual feedback.
```

### Step 8: Data Validation and Error Handling

```
Implement comprehensive data validation and error handling across the app:

1. Create validation service in lib/services/validation_service.dart:
   - Centralized validation rules for all data types
   - Range checking for weight and BP values
   - Date validation (not future dates, reasonable past dates)
   - Duplicate entry detection with merge options

2. Add error handling utilities in lib/utils/error_handler.dart:
   - User-friendly error message mapping
   - Logging service for debugging
   - Error reporting capabilities
   - Network error handling (for future cloud features)

3. Create form validation widgets in lib/widgets/validation/:
   - validated_number_field.dart: Number input with validation
   - validated_date_picker.dart: Date picker with constraints
   - error_display_widget.dart: Consistent error message display

4. Update all input forms to include:
   - Real-time validation feedback
   - Clear error messages
   - Disabled submit buttons for invalid data
   - Loading states during data submission

5. Enhance BLoC error states:
   - Specific error types for different failure modes
   - Recovery suggestions for users
   - Retry mechanisms where appropriate

6. Add data integrity checks:
   - Database constraint validation
   - Orphaned record cleanup
   - Data consistency verification

7. Create validation tests covering:
   - Boundary value testing
   - Invalid input handling
   - Database constraint violations

All forms should provide immediate, clear feedback and gracefully handle all error conditions.
```

### Step 9: Weight Data Visualization

```
Implement comprehensive weight data visualization and charting:

1. Add charting dependencies to pubspec.yaml:
   - fl_chart for Flutter charts
   - collection for data manipulation

2. Create weight chart screen in lib/screens/weight_chart_screen.dart:
   - Line chart showing weight over time
   - Date range selector (1 week, 1 month, 3 months, all time)
   - Zoom and pan capabilities
   - Data point selection with details popup

3. Add chart widgets in lib/widgets/charts/:
   - weight_line_chart.dart: Main weight visualization component
   - chart_date_selector.dart: Time range selection buttons
   - chart_legend.dart: Chart legend and statistics
   - data_point_popup.dart: Detailed view of selected data points

4. Create chart data service in lib/services/chart_data_service.dart:
   - Weight data aggregation by time periods
   - Trend calculation (moving averages)
   - Data smoothing algorithms
   - Export data in chart-ready format

5. Add chart utilities in lib/utils/chart_utils.dart:
   - Date axis formatting
   - Y-axis scaling for weight units
   - Color schemes for different chart elements
   - Touch interaction handlers

6. Update charts screen to include:
   - Weight chart with proper axes labels
   - Statistics panel (average, min, max, trend)
   - Unit conversion for chart display
   - Export chart as image option

7. Add accessibility features:
   - Screen reader support for chart data
   - High contrast mode
   - Large text support

The weight chart should provide clear insights into weight trends over time.
```

### Step 10: Blood Pressure and Mood Visualization

```
Complete the data visualization suite with blood pressure and mood charts:

1. Create blood pressure chart in lib/widgets/charts/bp_chart.dart:
   - Dual-line chart (systolic and diastolic)
   - Color-coded zones for BP categories
   - Reference lines for normal/high thresholds
   - Interactive data point selection

2. Add mood visualization in lib/widgets/charts/mood_chart.dart:
   - Bar chart or emoji timeline for mood entries
   - Color coding for different moods
   - Mood frequency analysis
   - Pattern detection visualization

3. Create comprehensive charts screen in lib/screens/charts_screen.dart:
   - Tabbed interface for different chart types
   - Unified date range controls
   - Chart switching with smooth transitions
   - Statistics summary for each data type

4. Add chart analytics in lib/services/analytics_service.dart:
   - Correlation analysis between metrics
   - Trend detection algorithms
   - Statistical summaries
   - Insight generation

5. Create chart configuration in lib/utils/chart_config.dart:
   - Consistent styling across all charts
   - Theme-aware color schemes
   - Responsive design for different screen sizes
   - Animation configurations

6. Update charts with advanced features:
   - Data smoothing options
   - Trend line overlays
   - Comparative analysis (month over month)
   - Data density visualization

7. Add chart interaction features:
   - Pinch to zoom
   - Drag to pan
   - Long press for details
   - Double tap to reset view

All charts should be visually appealing, informative, and accessible across different devices.
```

### Step 11: Settings and Preferences Management

```
Implement comprehensive settings and preferences management:

1. Create settings screen in lib/screens/settings_screen.dart:
   - Organized sections: Display, Data, Privacy, About
   - Theme selection (light/dark/system)
   - Unit preferences (weight units, date formats)
   - Data retention settings
   - Export/import options

2. Add settings widgets in lib/widgets/settings/:
   - setting_section.dart: Grouped settings with headers
   - setting_switch.dart: Toggle switches for boolean settings
   - setting_selector.dart: Multiple choice settings
   - setting_info_tile.dart: Read-only information displays

3. Create preferences service in lib/services/preferences_service.dart:
   - SharedPreferences wrapper with type safety
   - Default value management
   - Settings change notifications
   - Settings validation and migration

4. Add settings BLoC in lib/bloc/settings/:
   - settings_bloc.dart: Manages all app preferences
   - settings_event.dart: Events for updating preferences
   - settings_state.dart: Current settings state

5. Create settings models in lib/models/settings/:
   - app_settings.dart: Main settings model
   - theme_settings.dart: Theme-related preferences
   - unit_settings.dart: Unit conversion preferences
   - privacy_settings.dart: Privacy-related options

6. Update existing screens to respect settings:
   - Theme changes applied globally
   - Unit preferences used in all displays
   - Date format preferences applied consistently

7. Add settings features:
   - Data clearing with confirmation
   - App version and build information
   - Privacy policy and terms display
   - Contact information for support

Settings should be persistent, well-organized, and immediately applied throughout the app.
```

### Step 12: Data Export and Local Backup

```
Implement comprehensive data export and local backup functionality:

1. Create export service in lib/services/export_service.dart:
   - Export all data to JSON format
   - Export individual data types (weight only, BP only, etc.)
   - Export date range selections
   - File validation and integrity checks

2. Add import/restore service in lib/services/import_service.dart:
   - Import data from JSON backup files
   - Duplicate detection and merge logic (prefer existing data over backup)
   - Data validation during import
   - Progress tracking for large imports

3. Create backup management screen in lib/screens/backup_screen.dart:
   - Export data button with file picker
   - Import/restore data with file selection
   - Backup history and file management
   - Progress indicators for long operations

4. Add file handling utilities in lib/utils/file_utils.dart:
   - Safe file writing to downloads directory
   - File sharing capabilities
   - File validation and error handling
   - Temporary file cleanup

5. Create backup widgets in lib/widgets/backup/:
   - export_dialog.dart: Export options and confirmation
   - import_dialog.dart: Import file selection and options
   - backup_progress.dart: Progress indicator for operations
   - file_info_widget.dart: Display file details

6. Add backup data models in lib/models/backup/:
   - backup_metadata.dart: Backup file information
   - export_options.dart: User export preferences
   - import_result.dart: Import operation results

7. Implement data merge logic:
   - Timestamp-based duplicate detection
   - Conflict resolution (prefer app data over backup)
   - Data integrity validation after merge
   - Rollback capability if import fails

8. Add comprehensive error handling:
   - File permission errors
   - Storage space validation
   - Corrupted file handling
   - User-friendly error messages

Users should be able to easily backup and restore their health data with clear feedback and robust error handling.
```

### Step 13: Security Foundation - Key Generation and Storage

```
Implement the security foundation for encryption features:

1. Add cryptography dependencies to pubspec.yaml:
   - crypto for hashing
   - encrypt for AES encryption
   - pointycastle for RSA operations
   - local_auth for biometric authentication

2. Create key management service in lib/services/key_management_service.dart:
   - RSA key pair generation (2048-bit minimum)
   - Secure key storage using flutter_secure_storage
   - Key derivation functions for symmetric keys
   - Key rotation capabilities

3. Add authentication service in lib/services/auth_service.dart:
   - Biometric authentication setup
   - Password fallback for non-biometric devices
   - Authentication state management
   - Secure session handling

4. Create security models in lib/models/security/:
   - key_pair.dart: RSA key pair representation
   - auth_method.dart: Enumeration of authentication methods
   - security_settings.dart: User security preferences

5. Implement secure storage service in lib/services/secure_storage_service.dart:
   - Encrypted local data storage
   - Key derivation from user authentication
   - Secure deletion of sensitive data
   - Storage integrity verification

6. Add security utilities in lib/utils/security_utils.dart:
   - Random number generation
   - Hash functions for data integrity
   - Secure comparison functions
   - Entropy validation

7. Create security initialization:
   - First-time setup wizard for security
   - Key generation progress indicator
   - Authentication method selection
   - Security test and validation

8. Add security BLoC in lib/bloc/security/:
   - security_bloc.dart: Manages authentication and encryption
   - security_event.dart: Events for auth and key operations
   - security_state.dart: Current security status

The security foundation should be robust, well-tested, and follow cryptographic best practices.
```

### Step 14: Local Data Encryption

```
Implement local data encryption using the security foundation:

1. Update database service to support encryption in lib/services/database_service.dart:
   - Encrypt sensitive data before storage
   - Decrypt data when retrieving
   - Maintain plaintext indices for searching
   - Handle encryption key changes

2. Create encryption service in lib/services/encryption_service.dart:
   - AES encryption/decryption for data
   - RSA encryption for key protection
   - Data integrity verification
   - Encryption performance optimization

3. Add encrypted data models in lib/models/encrypted/:
   - encrypted_health_data.dart: Encrypted wrapper for health data
   - encryption_metadata.dart: Encryption version and algorithm info
   - integrity_check.dart: Data integrity verification

4. Update existing data models to support encryption:
   - Optional encryption for all health data
   - Backwards compatibility with unencrypted data
   - Transparent encryption/decryption in data access

5. Create encryption utilities in lib/utils/encryption_utils.dart:
   - Data serialization for encryption
   - Padding and formatting helpers
   - Encryption strength validation
   - Performance monitoring

6. Add encryption settings in lib/screens/security_settings_screen.dart:
   - Enable/disable local encryption
   - Encryption strength selection
   - Re-encryption of existing data
   - Encryption status display

7. Implement encryption migration:
   - Migrate unencrypted data to encrypted format
   - Progress tracking for large datasets
   - Rollback capability if migration fails
   - Data verification after migration

8. Add comprehensive testing:
   - Encryption/decryption round-trip tests
   - Performance benchmarks
   - Key rotation testing
   - Data integrity verification

Local data should be securely encrypted with transparent access for the user and robust error handling.
```

### Step 15: In-App Purchase Integration

```
Implement in-app purchase functionality for premium features:

1. Add in-app purchase dependencies to pubspec.yaml:
   - in_app_purchase for payment processing
   - Add necessary Android/iOS configuration files

2. Create purchase service in lib/services/purchase_service.dart:
   - Initialize purchase connection
   - Load available products (Pro subscription)
   - Handle purchase flow and verification
   - Restore previous purchases

3. Add premium feature gate in lib/services/premium_service.dart:
   - Check premium status throughout app
   - Feature access control
   - Premium feature demonstrations
   - Upgrade prompts and flows

4. Create purchase models in lib/models/purchase/:
   - premium_status.dart: User's premium subscription status
   - purchase_result.dart: Purchase operation results
   - product_info.dart: Available premium products

5. Add purchase UI in lib/screens/premium_screen.dart:
   - Premium features showcase
   - Pricing and subscription options
   - Purchase flow with progress indicators
   - Terms of service and privacy policy

6. Create purchase widgets in lib/widgets/purchase/:
   - premium_feature_card.dart: Showcase premium features
   - purchase_button.dart: Styled purchase action button
   - subscription_status.dart: Display current premium status
   - restore_purchase_button.dart: Restore previous purchases

7. Add premium BLoC in lib/bloc/purchase/:
   - purchase_bloc.dart: Manages purchase state and operations
   - purchase_event.dart: Events for purchase operations
   - purchase_state.dart: Purchase status and results

8. Implement feature gating throughout app:
   - Encrypted cloud backup (premium only)
   - Advanced chart features (premium only)
   - Export limitations for free users
   - Premium badges and indicators

9. Add purchase error handling:
   - Network connectivity issues
   - Payment processing errors
   - Account verification problems
   - User-friendly error messages

The premium purchase system should be seamless, secure, and clearly communicate value to users.
```

### Step 16: Encrypted Cloud Backup System

```
Implement encrypted cloud backup as a premium feature:

1. Add cloud storage dependencies to pubspec.yaml:
   - firebase_core and firebase_storage for cloud storage
   - http for direct API calls
   - Configure Firebase project and authentication

2. Create cloud backup service in lib/services/cloud_backup_service.dart:
   - Upload encrypted data to cloud storage
   - Download and decrypt backup data
   - Backup versioning and management
   - Sync conflict resolution

3. Add cloud encryption in lib/services/cloud_encryption_service.dart:
   - End-to-end encryption before upload
   - User-specific encryption keys
   - Key derivation for cloud storage
   - Backup integrity verification

4. Create backup sync models in lib/models/backup/:
   - cloud_backup.dart: Cloud backup metadata
   - sync_status.dart: Synchronization state
   - backup_version.dart: Backup versioning information
   - conflict_resolution.dart: Sync conflict handling

5. Add cloud backup UI in lib/screens/cloud_backup_screen.dart:
   - Enable/disable automatic backups
   - Manual backup and restore options
   - Backup history and management
   - Sync status and progress indicators

6. Create cloud backup widgets in lib/widgets/cloud_backup/:
   - backup_status_card.dart: Display backup status
   - sync_progress.dart: Backup/restore progress indicators
   - backup_schedule.dart: Automatic backup configuration
   - conflict_resolution_dialog.dart: Handle sync conflicts

7. Add cloud backup BLoC in lib/bloc/cloud_backup/:
   - cloud_backup_bloc.dart: Manages cloud operations
   - cloud_backup_event.dart: Events for backup operations
   - cloud_backup_state.dart: Backup status and progress

8. Implement automatic backup scheduling:
   - Background sync capability
   - Configurable backup frequency
   - Network-aware backup timing
   - Battery optimization considerations

9. Add comprehensive error handling:
   - Network connectivity issues
   - Cloud storage quota limits
   - Authentication failures
   - Data corruption detection

10. Create backup recovery features:
    - Multiple device support
    - Backup restoration to new devices
    - Partial data recovery options
    - Backup verification before restore

Cloud backup should be secure, reliable, and seamlessly integrated with the premium subscription model.
```

### Step 17: UI Polish and Accessibility

```
Polish the user interface and implement comprehensive accessibility features:

1. Enhance visual design across all screens:
   - Consistent color schemes and typography
   - Improved spacing and layout proportions
   - Smooth animations and transitions
   - Loading states and micro-interactions

2. Add accessibility features in lib/utils/accessibility.dart:
   - Screen reader support (Semantics widgets)
   - High contrast mode support
   - Large text scaling support
   - Focus management and navigation

3. Create polished widgets in lib/widgets/polished/:
   - animated_card.dart: Smooth card animations
   - skeleton_loader.dart: Content loading placeholders
   - gradient_button.dart: Premium-feeling buttons
   - status_indicator.dart: Visual status communications

4. Implement advanced theming in lib/themes/:
   - theme_data.dart: Comprehensive theme definitions
   - color_schemes.dart: Light and dark color palettes
   - text_themes.dart: Typography scale and styles
   - component_themes.dart: Individual widget theming

5. Add responsive design support:
   - Adaptive layouts for different screen sizes
   - Tablet-optimized interfaces
   - Landscape orientation support
   - Dynamic font sizing

6. Create onboarding experience in lib/screens/onboarding/:
   - welcome_screen.dart: App introduction
   - tutorial_screens.dart: Feature walkthroughs
   - setup_wizard.dart: Initial configuration
   - privacy_explanation.dart: Privacy benefits explanation

7. Implement advanced UI patterns:
   - Pull-to-refresh with custom indicators
   - Swipe actions for list items
   - Long press context menus
   - Haptic feedback throughout

8. Add error state illustrations:
   - Empty state graphics and messages
   - Error illustrations with retry actions
   - Network connectivity indicators
   - Loading state improvements

9. Optimize performance:
   - Image optimization and caching
   - List view performance improvements
   - Memory usage optimization
   - Battery usage considerations

The app should feel professional, accessible, and delightful to use across all user scenarios.
```

### Step 18: Testing and Quality Assurance

```
Implement comprehensive testing and quality assurance:

1. Create unit tests in test/unit/:
   - models/ - Test all data models and serialization
   - services/ - Test business logic and data operations
   - utils/ - Test utility functions and converters
   - bloc/ - Test state management and business logic

2. Add integration tests in test/integration/:
   - database_test.dart: Full database operation testing
   - encryption_test.dart: End-to-end encryption testing
   - backup_restore_test.dart: Backup and restore workflows
   - purchase_flow_test.dart: Premium purchase testing

3. Create widget tests in test/widget/:
   - Test all custom widgets in isolation
   - Form validation testing
   - Chart rendering and interaction tests
   - Navigation and routing tests

4. Add end-to-end tests in integration_test/:
   - Complete user workflows
   - Data entry and visualization flows
   - Settings and preferences testing
   - Premium feature activation testing

5. Implement performance testing:
   - Database query performance
   - Chart rendering performance
   - Memory usage profiling
   - Battery usage analysis

6. Create accessibility testing:
   - Screen reader compatibility
   - High contrast mode testing
   - Large text scaling verification
   - Keyboard navigation testing

7. Add security testing:
   - Encryption/decryption validation
   - Key management security
   - Data integrity verification
   - Authentication flow testing

8. Implement test utilities in test/helpers/:
   - Test data factories
   - Mock services and repositories
   - Test database setup helpers
   - Common test assertion helpers

9. Add continuous integration setup:
   - Automated test running
   - Code coverage reporting
   - Performance regression detection
   - Security vulnerability scanning

10. Create test documentation:
    - Test strategy and approach
    - Test case specifications
    - Bug reporting templates
    - Testing checklist for releases

The app should have comprehensive test coverage ensuring reliability, security, and performance across all features and user scenarios.
```

---

## Implementation Notes

### Development Best Practices
1. **Incremental Development**: Each step builds directly on the previous step
2. **No Orphaned Code**: Every feature is immediately integrated and functional
3. **Test-Driven Approach**: Write tests alongside implementation
4. **Security First**: Implement security measures from the beginning
5. **Performance Awareness**: Consider performance implications throughout

### Key Integration Points
- Database changes should be immediately reflected in UI
- All forms should connect to the BLoC state management
- Charts should update automatically when data changes
- Settings should be applied immediately across the app
- Premium features should be properly gated and tested

### Quality Gates
Each step should be verified by:
1. Code compiles without errors
2. Basic functionality works as expected
3. No regression in previous features
4. Proper error handling is implemented
5. Code follows Flutter best practices

### Risk Mitigation
- Start with core functionality before advanced features
- Implement data validation early and thoroughly
- Test encryption and security features extensively
- Have rollback plans for database migrations
- Implement comprehensive error handling throughout

This blueprint provides a solid foundation for building a professional, secure, and user-friendly health tracking application using Flutter.
