Refactor/sim-core

[ryanmccann1024]

📝 Description

This PR reorganizes core simulation and module logic into a cleaner and more maintainable directory structure under fusion/core/. Specifically:

• Moved simulation.py, routing.py, spectrum_assignment.py, request_generator.py, snr_measurements.py, and sdn_controller.py into fusion/core/ for semantic clarity and long-term scalability.
• Cleaned up unused or transitional code from the recently introduced batch_runner.py, which has now been removed.
• Ran linting on the fusion package to ensure consistent style across the refactored modules.

These structural changes reduce clutter in fusion/sim/ and establish fusion/core/ as the authoritative home for reusable simulation engine logic, allowing fusion/sim/ to focus exclusively on pipeline orchestration.

Fixes: # (issue number) ---

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🧐 Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (restructures core files and removes batch runner)
• 💅 UI/UX change (improves the user interface or experience)
• 📚 Documentation update
• ⚙️ Chore (refactoring, dependency cleanup, linting)

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💥 Impact of Breaking Change

This is a major structural breaking change:

• Any scripts or modules that previously imported simulation logic from fusion/sim/ must update their import paths to use fusion/core/.
• The batch_runner.py module was removed entirely. Any scripts depending on it must revert to using network_simulator.run() or refactor accordingly.

All internal CLI entrypoints (run_sim.py, run_train.py, etc.) have been updated to work with the new structure.

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🧪 How Has This Been Tested?

All changes were validated by:

• Running the full simulation CLI using:
  python -m fusion.cli.run_sim --config_path ini/run_ini/config.ini
• Verifying that all simulation outputs and logs are generated correctly
• Running the linter and confirming no style errors in fusion/
• Ensuring the CLI scripts reflect the new import paths and function normally

Test Configuration:

• Operating System: macOS Ventura 13.5
• Python version: 3.10.12
• Other Dependencies: Existing requirements.txt environment

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📸 Screenshots / Screen Recordings

N/A

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✅ Final Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my own 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.
• I have checked that my commit message follows the project's formatting guidelines.

[ryanmccann1024]

To be addressed in the next PR: Having one cli_workflow file instead of three entry points.