refactor(interfaces): implement abstract interfaces and complete modular architecture migration

[ryanmccann1024]

Description:
This PR completes a major architectural refactoring of FUSION, introducing abstract interfaces for pluggable components and migrating the entire codebase to a modular architecture as outlined in the Architecture Plan v1 and v2. The changes establish a clean separation of concerns, improve testability, and enable future extensibility through well-defined interfaces.

🔧 Type of Change

Primary Change Type:

• 🐛 Bug Fix - Non-breaking change that fixes an issue
• ✨ New Feature - Non-breaking change that adds functionality
• 💥 Breaking Change - Change that would cause existing functionality to break
• 🔄 Refactor - Code change that neither fixes a bug nor adds a feature
• 📚 Documentation - Documentation only changes
• 🧪 Tests - Adding missing tests or correcting existing tests
• 🏗️ Build/CI - Changes to build process or CI configuration
• 🎨 Style - Code style changes (formatting, missing semicolons, etc.)
• ⚡ Performance - Performance improvements
• 🔒 Security - Security vulnerability fixes

Component(s) Affected:

• CLI Interface (fusion/cli/)
• Configuration System (fusion/configs/)
• Simulation Core (fusion/core/)
• ML/RL Modules (fusion/modules/rl/, fusion/modules/ml/)
• Routing Algorithms (fusion/modules/routing/)
• Spectrum Assignment (fusion/modules/spectrum/)
• SNR Calculations (fusion/modules/snr/)
• Visualization (fusion/visualization/)
• GUI Interface (fusion/gui/)
• Unity/HPC Integration (fusion/unity/)
• Testing Framework (tests/)
• Documentation
• GitHub Workflows (.github/)
• Build/Dependencies

🧪 Testing

Test Coverage:

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• Existing tests still pass
• Performance impact assessed

Test Details:

• Added comprehensive unit tests for new interface implementations (test_interface_basic.py, test_interface_integration.py, test_interfaces.py)
• Updated all existing tests to work with new package structure
• Added integration tests for the new IO module (test_io_exporter.py)
• Fixed import paths and dependencies throughout the test suite

Test Configuration Used:

[general_settings]
sim_type = CascadingFailure
request_type = 'generic'
# Configuration validated through new ConfigManager

Commands to Reproduce Testing:

# Run all tests
python -m pytest tests/

# Run interface-specific tests
python -m pytest tests/test_interface*.py -v

# Run simulation with new CLI
python -m fusion.cli.run_sim run_sim --config_path examples/configs/templates/default.ini --run_id test_refactor

Test Results:

• Operating System: macOS 13
• Python Version: 3.11.x
• Test Environment: local

📊 Impact Analysis

Performance Impact:

• No performance impact
• Performance improved
• Minor performance decrease (acceptable)
• Significant performance impact (needs discussion)

Memory Usage:

• No change in memory usage
• Memory usage optimized
• Minor increase in memory usage
• Significant memory impact

Backward Compatibility:

• Fully backward compatible
• Minor breaking changes with migration path
• Major breaking changes (requires version bump)

Dependencies:

• No new dependencies
• New dependencies added (list in Additional Notes)
• Dependencies removed/updated

🔄 Migration Guide

Breaking Changes:

1. All imports now use the fusion. package prefix
2. Top-level scripts moved into appropriate modules
3. Configuration management centralized through ConfigManager
4. CLI entry points restructured under fusion.cli

Migration Steps:

1. Update all imports to use new package structure:

   # Old: from engine import Engine
   # New: from fusion.core.simulation import Engine

2. Update CLI commands to use new entry points:

   # Old: python run_sim.py
   # New: python -m fusion.cli.run_sim run_sim

3. Update configuration paths to use new templates directory
4. Replace direct module imports with registry-based lookups

Before/After Examples:

# Before (old usage)
from routing import KShortestPath
router = KShortestPath(engine_props, sdn_props)

# After (new usage)  
from fusion.modules.routing.registry import RoutingRegistry
router = RoutingRegistry.get_algorithm('k_shortest_path', engine_props, sdn_props)

✅ Code Quality Checklist

Architecture & Design:

• Follows established architecture patterns
• Code is modular and follows separation of concerns
• Interfaces are well-defined and documented
• Error handling is comprehensive
• Logging is appropriate and informative

Code Standards:

• Code follows project style guidelines
• Variable and function names are descriptive
• Code is properly commented
• Complex logic is documented
• No dead code or unused imports

Configuration & CLI:

• CLI arguments follow established patterns
• Configuration validation updated (if needed)
• Schema updated for new config options
• Backward compatibility maintained for configs

Security:

• No sensitive information hardcoded
• Input validation performed where needed
• No security vulnerabilities introduced
• Dependencies scanned for vulnerabilities

📚 Documentation

Documentation Updates:

• Code comments added/updated
• API documentation updated
• User guide/tutorial updated
• Configuration reference updated
• CHANGELOG.md updated
• README updated (if needed)

Examples Added:

• Usage examples in docstrings
• Configuration examples
• CLI usage examples
• Integration examples

🚀 Deployment

Deployment Considerations:

• Safe to deploy to all environments
• Requires environment-specific configuration
• Needs database migration (if applicable)
• Requires manual steps (document below)

Manual Steps Required:

1. Update Python path to include the project root
2. Install package in development mode: pip install -e .
3. Update any deployment scripts to use new CLI entry points

🔍 Review Guidelines

For Reviewers:

• PR description is clear and complete
• Code changes align with described functionality
• Tests are comprehensive and pass
• Documentation is adequate
• No obvious security issues
• Performance impact is acceptable

Review Focus Areas:

• Interface design and extensibility
• Registry pattern implementation
• Configuration management system
• CLI argument parsing and validation
• Module import structure and dependencies

📝 Additional Notes

Open Questions:

• Should we provide more detailed migration scripts for existing users?
• Do we need to maintain any legacy compatibility layer?

Future Work:

• Complete implementation of concrete classes for all interfaces
• Add more comprehensive integration tests
• Implement remaining phases from Architecture Plan v2
• Add performance benchmarking suite

Related PRs:

• Refactor/scaffold #106 - refactor/scaffold
• Refactor/helpers #107 - refactor/helpers
• Refactor/sim-core #108 - refactor/sim-core
• Refactor/rl cli #109 - refactor/rl-cli
• Refactor/scaffold gui #110 - refactor/scaffold_gui

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🏁 Final Checklist

Before submitting this PR, confirm:

• I have followed the contributing guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

[ryanmccann1024]

Rough draft is good to go.