Research-Stack/5-Applications/nodupe/wiki/Architecture/Aspect-Oriented-Design.md

Aspect-Oriented Design (AOD)

NoDupeLabs implements a minimal-core, plugin-first architecture based on Aspect-Oriented Design principles. This ensures that the core scanning engine remains lean and portable, while all specialized logic is externalized into swappable plugins.

Core Interfaces (Contracts)

The system defines formal contracts in nodupe/core/ that all implementations must follow.

Aspect	Interface	Standard Implementation
Hashing	HasherInterface	nodupe/plugins/hashing/
MIME Detection	MIMEDetectionInterface	nodupe/plugins/mime/
Archive Handling	ArchiveHandlerInterface	nodupe/plugins/archive/

Decoupling Strategy

Core components do not instantiate specific implementations. Instead, they request services from the ServiceContainer.

Example: FileWalker Decoupling

The FileWalker previously had a hard dependency on ArchiveHandler. It now uses Dependency Injection:

# Preferred approach
self._archive_handler = global_container.get_service('archive_handler_service')
if not self._archive_handler:
    self._archive_handler = DefaultFallback()

Benefits

1. Zero-Dependency Core: The core can run in restricted environments with only the Python standard library.
2. Hardware Acceleration: Plugins can provide specialized implementations (e.g., GPU-accelerated hashing) without changing core code.
3. Scalability: New file formats or protocols can be added by dropping in a new plugin directory.
4. Persistent Standards: All interactions across these aspects obey the system-wide Logging Policy.