feat: Add comprehensive CLI options, export functionality, and TUI fi…

CHANGELOG.md

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+# Changelog
+
+All notable changes to the GPU Tracker project.
+
+## [1.1.0] - 2026-01-31
+
+### Added
+
+#### Command-Line Interface
+- **Sampling interval configuration** (`-interval` flag): Configure custom sampling rates from 1 second to any duration
+- **Database path customization** (`-db` flag): Specify custom location for SQLite database
+- **Version information** (`-version` flag): Display application version
+
+#### Operating Modes
+- **One-shot mode** (`-once` flag): Sample GPU state once and exit without starting TUI
+- **Continuous monitoring mode** (`-continuous` flag): Background sampling with automatic database saves
+- **User listing mode** (`-list-users` flag): Quick summary of GPU users and their memory consumption
+
+#### Export Functionality
+- **JSON export** (`-export json`): Export complete snapshot data in JSON format
+- **CSV export** (`-export csv`): Export data in CSV format for spreadsheet analysis
+- **Output file specification** (`-output` flag): Direct export output to file or stdout
+- Export includes full GPU metrics, process information, and timestamps
+
+#### Alert System
+- **Temperature threshold alerts** (`-max-temp` flag): Configurable temperature warnings (default: 90°C)
+- **Memory threshold alerts** (`-max-mem` flag): Configurable memory utilization warnings (default: 95%)
+- Visual alert indicators in TUI with red highlights
+- Alert messages in stderr for continuous and one-shot modes
+- Emoji indicators (⚠️) for better visibility
+
+#### TUI Enhancements
+- **User filtering** (key: `f`): Cycle through users to focus on specific user activity
+- **GPU filtering** (key: `g`): Filter view by specific GPU in multi-GPU systems
+- **Memory sorting** (key: `m`): Toggle sorting of processes by memory usage
+- **Clear filters** (key: `c`): Reset all active filters to full view
+- **Active filter indicators**: Visual display of currently applied filters in header
+- **Highlighted filtered items**: Active filters shown with arrow indicators (►)
+
+#### Configuration System
+- New `Config` struct for passing configuration to TUI
+- `NewWithConfig()` function for advanced TUI initialization
+- Backward compatible with existing `New()` function
+
+#### Documentation
+- **FEATURES.md**: Comprehensive feature documentation with examples
+- **QUICKSTART.md**: Quick reference guide for common operations
+- **CHANGELOG.md**: Version history and changes
+- Enhanced README.md with usage examples and integration guides
+- Advanced use case examples (monitoring, alerting, cron jobs)
+- Troubleshooting section expanded
+
+### Changed
+- Main function refactored to support multiple operating modes
+- TUI model enhanced with filtering and configuration support
+- View rendering updated to use filtered snapshots
+- Help text expanded with new keyboard shortcuts
+- Sample interval now configurable (was hardcoded to 5 seconds)
+- Export functions integrated directly in main package
+
+### Improved
+- Better separation of concerns (sampling, storage, display, export)
+- More flexible architecture for future extensions
+- Enhanced error handling in export functions
+- Clearer status messages in TUI
+- More informative help overlay
+- Better user experience with filtering indicators
+
+### Technical Details
+- Added `encoding/json` and `encoding/csv` imports
+- Added `flag` package for CLI argument parsing
+- Enhanced model struct with filter fields
+- New helper functions: `getUniqueUsers()`, `getFilteredSnapshot()`
+- Alert checking logic separated into `checkAlerts()` function
+- Export logic in `exportToJSON()` and `exportToCSV()` functions
+
+### Backward Compatibility
+- All existing features work unchanged
+- Database format unchanged - existing databases fully compatible
+- Default behavior preserved when no flags specified
+- Existing keyboard shortcuts unchanged
+- API compatible with version 1.0.x
+
+## [1.0.0] - Initial Release
+
+### Features
+- Live GPU monitoring via nvidia-smi
+- Per-user GPU memory tracking
+- Historical snapshot storage in SQLite
+- Interactive Terminal UI (TUI) using Bubble Tea
+- Auto-recording with 5-second intervals
+- Manual snapshot saving
+- History browsing by date and snapshot
+- GPU utilization and temperature display
+- Process tracking with PID to user mapping
+- Beautiful lipgloss-styled interface
+- Help overlay with keyboard shortcuts
+
+### Core Components
+- `/cmd/gpu-tracker/main.go`: Application entry point
+- `/internal/sampler/nvidia.go`: NVIDIA GPU sampling logic
+- `/internal/store/store.go`: SQLite database operations
+- `/internal/tui/`: Terminal UI components
+- `/internal/types/types.go`: Data structures
+- `/internal/util/proc_unix.go`: Process to user mapping
+
+### Initial Keyboard Shortcuts
+- `a`: Toggle auto-recording
+- `r`: Refresh snapshot
+- `s`: Save snapshot
+- `h`: Toggle history mode
+- `←/→`: Navigate snapshots
+- `↑/↓`: Navigate days
+- `t`: Jump to today
+- `q`: Quit
+- `?`: Toggle help
+
+### System Requirements
+- Go 1.21+
+- Linux OS
+- NVIDIA GPU with drivers
+- nvidia-smi utility
+- gcc for CGO (SQLite)
+
+---
+
+## Version Numbering
+
+This project follows [Semantic Versioning](https://semver.org/):
+- MAJOR version for incompatible API changes
+- MINOR version for added functionality (backward compatible)
+- PATCH version for backward compatible bug fixes
+
+## Upgrade Path
+
+### From 1.0.x to 1.1.0
+No special steps required:
+1. Replace binary with new version
+2. All existing data preserved
+3. New features available via flags and key shortcuts
+4. No configuration changes needed
+
+## Future Plans
+
+### Planned for 1.2.0
+- AMD GPU support (ROCm)
+- Web dashboard option
+- Prometheus exporter
+- Email notification system
+- Historical data analysis tools
+- Multi-host aggregation
+
+### Under Consideration
+- Intel GPU support
+- Remote monitoring
+- REST API server mode
+- Grafana dashboard templates
+- Docker container deployment
+- Configuration file support