hosts-go/memory-bank/activeContext.md

# Active Context: hosts-go

## Current Work Focus

**Status**: Phase 2 In Progress - Basic TUI prototype implemented
**Priority**: Expand Bubble Tea TUI with navigation and view features

## Recent Changes

### Phase 1: Core Functionality (COMPLETED) ✅
- ✅ **Hosts file parser**: Complete `internal/core/parser.go` implementation
- ✅ **Intelligent formatting**: Adaptive spacing and column alignment with GCD-based tab/space detection
- ✅ **Comment handling**: Disabled entries vs standalone comments with perfect preservation
- ✅ **File operations**: Safe backup system with timestamped backups in `~/.config/hosts-go/`
- ✅ **Error recovery**: Malformed line handling with non-fatal warnings
- ✅ **Format preservation**: Round-trip parsing maintains original formatting while improving alignment
- ✅ **Comprehensive testing**: 54 comprehensive tests covering all parser functionality (100% passing)
- ✅ **Demo application**: Full showcase of parser capabilities with real-world examples

### Parser Capabilities Achieved
- ✅ **Standard entries**: IPv4, IPv6, multiple aliases, inline comments
- ✅ **Disabled entries**: Commented lines with `# IP hostname` format detection
- ✅ **Standalone comments**: Header and section comments preserved separately
- ✅ **Style detection**: Automatic tab vs space detection with intelligent column widths
- ✅ **Search functionality**: Find entries by hostname or alias with O(1) performance
- ✅ **Validation layers**: IP address and hostname validation with clear error messages
- ✅ **Atomic operations**: Temporary files with rollback capability for safe writes

### Safety Features Implemented
- ✅ **Backup system**: Timestamped backups before any modification
- ✅ **Atomic writes**: Temp file → atomic move to prevent corruption
- ✅ **Warning system**: Non-fatal issues reported without stopping parsing
- ✅ **Format intelligence**: Detect and preserve original formatting style
- ✅ **Input validation**: Comprehensive IP and hostname validation

## Next Steps

### Immediate (Phase 2 - Current Priority)
1. **TUI Architecture Design** ✅
   - Main Bubble Tea model with list and detail panes
   - State tracks selection and window size

2. **Two-Pane Layout Implementation** ✅
   - Left pane: entry list using Bubbles list component
   - Right pane: detail view of selected entry
   - Responsive sizing handled in update

3. **Navigation System** 🟡
   - Basic keyboard navigation via list component
   - Need scroll handling and pane switching

4. **View Mode Implementation** 🟡
   - Read-only display of `/etc/hosts` entries
   - Status bar and active/inactive indicators in list implemented
   - Further styling improvements pending

### Medium-term (Phase 3)
1. **Edit Mode Implementation**
   - Explicit mode transition with visual indicators
   - Permission handling with sudo request
   - Entry modification forms with validation

2. **File Integration**
   - Connect TUI with existing parser functionality
   - Real-time display of actual `/etc/hosts` content
   - Live validation and formatting preview

3. **Advanced Features**
   - Entry toggle (activate/deactivate)
   - Add/edit/delete operations
   - Sorting and filtering capabilities

## Active Decisions and Considerations

### Architecture Decisions Finalized
- **Layered architecture**: TUI → Business Logic → System Interface (implemented and proven)
- **Parser-first approach**: Robust foundation before UI complexity (successfully completed)
- **Test-driven development**: 54 comprehensive tests proving approach effectiveness
- **Safety-first design**: Backup and atomic operations prevent data loss

### Parser Design Patterns Implemented
- **Intelligent formatting**: GCD-based spacing detection preserves original style
- **Warning system**: Non-fatal errors allow graceful degradation
- **Comment classification**: Distinguish between disabled entries and standalone comments
- **Round-trip consistency**: Parse → format → parse maintains structural integrity

### Technology Choices Validated
- **Go standard library**: Excellent for file operations and network validation
- **String manipulation**: Regex and string processing handle complex formatting
- **Testing ecosystem**: testify + table-driven tests provide excellent coverage
- **File safety**: Atomic operations with temp files prevent corruption

### TUI Design Decisions (Ready to Implement)
- **MVU pattern**: Bubble Tea's Model-View-Update for predictable state management
- **Component hierarchy**: Main model coordinates list, detail, and modal components
- **Keyboard-driven**: Primary interaction method with mouse support as enhancement
- **Mode-based interaction**: Clear view/edit mode distinction for safety

## Important Patterns and Preferences

### Code Organization
- Use `internal/` package for application-specific code
- Group related functionality in packages (`tui/`, `core/`, `utils/`)
- Keep main.go minimal - delegate to internal packages

### Testing Strategy
- Write tests before implementation (TDD)
- Mock external dependencies (file system, network)
- Use table-driven tests for multiple scenarios
- Test both success and error cases

### Error Handling
- Return errors explicitly, don't panic
- Provide clear error messages with context
- Implement graceful fallbacks where possible
- Log errors appropriately for debugging

### UI/UX Principles
- **Safety first**: Default to read-only mode
- **Clear feedback**: Show operation status and results
- **Keyboard-driven**: Efficient navigation without mouse dependency
- **Responsive**: Sub-16ms update cycles for smooth interaction

## Learnings and Project Insights

### Development Environment Proven
- **macOS compatibility**: All file operations work seamlessly on macOS
- **Go toolchain**: Excellent development experience with built-in testing
- **Terminal output**: Rich formatting possible with careful Unicode handling

### Parser Implementation Insights
- **Format detection**: GCD analysis effectively detects spacing patterns
- **Comment parsing**: Distinguishing disabled entries from comments requires careful regex work
- **Error handling**: Warning system allows processing to continue despite invalid lines
- **Performance**: String processing in Go handles large files efficiently

### User Experience Learnings
1. **Safety achieved**: Backup system and atomic writes prevent corruption
2. **Format preservation**: Users expect their formatting style to be maintained
3. **Clear feedback**: Parsing warnings help users understand file issues
4. **Predictable behavior**: Round-trip parsing gives confidence in modifications

### Technical Insights Gained
1. **File operations**: Atomic writes with temp files are essential for safety
2. **Parsing complexity**: Hosts files have many edge cases requiring careful handling
3. **Testing approach**: Table-driven tests excellent for covering format variations
4. **Code organization**: Clear separation between parsing and formatting logic
5. **Validation layers**: Multiple validation points catch issues early

### Ready for TUI Implementation
- **Solid foundation**: Parser handles all hosts file variations reliably
- **Proven patterns**: Test-driven development approach validated
- **Clear architecture**: Well-defined interfaces ready for TUI integration
- **Performance confidence**: Parser handles large files without issues

## Dependencies and Constraints

### External Dependencies
- **Bubble Tea ecosystem**: Core framework and components
- **System permissions**: sudo access for editing hosts file
- **File system**: Atomic write operations and backup capability

### Development Constraints
- **No breaking changes**: Must preserve existing hosts file format
- **Backward compatibility**: Work with various hosts file styles
- **Minimal dependencies**: Keep external dependencies focused and essential

## Communication Preferences

### Documentation Style
- **Concrete examples**: Show actual code snippets and command examples
- **Clear structure**: Use consistent heading hierarchy and formatting
- **Actionable items**: Specific next steps rather than vague suggestions

### Progress Tracking
- **Incremental development**: Small, testable changes
- **Regular updates**: Update memory bank after significant milestones
- **Clear status**: Always know what's working, what's not, and what's next