# Rollback Features Not Implemented

This document explains advanced rollback features that were considered but not implemented, and the reasons why.

## Why These Features Were Not Added

The goal was to create a **clean, simple, and maintainable** rollback system that handles 90% of real-world cases without over-engineering. These features were deemed too complex for the current scope.

## Advanced Features Considered

### 1. State Persistence

**What it would do:**
- Save rollback state to `/var/lib/apt-wrapper/rollback-state.json`
- Allow rollback even after the program restarts
- Include checksums and schema versioning

**Why not implemented:**
- Adds file I/O complexity
- Requires error handling for disk operations
- The current in-memory approach is sufficient for most use cases

### 2. Pre-Transaction Snapshots

**What it would do:**
- Use `apt-clone` or `dpkg --get-selections` to create system snapshots
- Store complete package state before transactions
- Enable more comprehensive rollbacks

**Why not implemented:**
- `apt-clone` may not be available on all systems
- Snapshot management adds significant complexity
- Current approach handles the most common scenarios

### 3. Enhanced Dependency Awareness

**What it would do:**
- Track reverse dependencies with `apt-cache rdepends`
- Distinguish between user-installed and auto-installed packages
- Handle meta-package dependencies

**Why not implemented:**
- APT already handles most dependency resolution
- Adds parsing complexity for dependency graphs
- Current simple approach works for most cases

### 4. Sophisticated Version Handling

**What it would do:**
- Find closest available version if exact version not found
- User-configurable fallback strategies (`--strict`, `--nearest`, `--remove`)
- Handle version conflicts gracefully

**Why not implemented:**
- Version resolution is complex and error-prone
- Current "remove if can't downgrade" approach is simple and safe
- Most users don't need fine-grained version control

### 5. Concurrency Safety

**What it would do:**
- Use APT locking mechanisms
- Handle concurrent package operations
- Prevent rollback conflicts

**Why not implemented:**
- APT already provides basic locking
- Concurrent operations are rare in practice
- Adds complexity without clear benefit

### 6. Critical Package Detection

**What it would do:**
- Identify essential packages using `dpkg -l`
- Prevent rollback of critical system packages
- Add safety checks for system stability

**Why not implemented:**
- Most users don't try to rollback critical packages
- APT already provides some protection
- Adds complexity for edge cases

### 7. Dry-Run Mode

**What it would do:**
- Show what would be rolled back without doing it
- Machine-readable JSON output
- Preview rollback operations

**Why not implemented:**
- Current `changed_packages()` method provides similar functionality
- Dry-run for rollback is less critical than for installation
- Adds output formatting complexity

### 8. Resume/Abort Operations

**What it would do:**
- Allow resuming interrupted rollbacks
- Provide `--abort` to cancel rollback operations
- Handle partial rollback states

**Why not implemented:**
- Rollbacks are typically fast operations
- Current fail-fast approach is simpler
- Resume logic adds significant complexity

### 9. Enhanced Error Handling

**What it would do:**
- Accumulate warnings instead of failing immediately
- Provide detailed error context
- Suggest recovery actions

**Why not implemented:**
- Current error handling is clear and actionable
- Warning accumulation can hide critical issues
- Simple approach is easier to debug

### 10. Configuration Management

**What it would do:**
- Track configuration file changes
- Restore previous configurations
- Handle package configuration conflicts

**Why not implemented:**
- Configuration management is extremely complex
- APT already handles most configuration issues
- Beyond the scope of a simple package manager wrapper

## Future Considerations

If the simple rollback system proves insufficient, these features could be added in future versions:

1. **State persistence** would be the first addition for production use
2. **Enhanced error handling** would improve user experience
3. **Dry-run mode** would be useful for automation
4. **Critical package detection** would add safety for system packages

## Design Philosophy

The current implementation follows these principles:

- **Simplicity over completeness**: Handle common cases well
- **Fail fast**: Clear error messages when things go wrong
- **Maintainability**: Easy to understand and modify
- **Reliability**: Works consistently in real-world scenarios

This approach ensures the rollback system is robust, understandable, and maintainable while handling the vast majority of actual use cases.