Add shellgen core and backends modules

app/shellgen/backends/base.py

@@ -0,0 +1,52 @@
+"""Abstract base class for LLM backends."""
+
+from abc import ABC, abstractmethod
+from typing import Optional
+
+
+class LLMBackend(ABC):
+    """Abstract base class for LLM backends."""
+
+    @abstractmethod
+    def generate(self, prompt: str) -> str:
+        """Generate a response from the LLM.
+
+        Args:
+            prompt: The prompt to send to the LLM.
+
+        Returns:
+            The generated response text.
+        """
+        pass
+
+    @abstractmethod
+    def is_available(self) -> bool:
+        """Check if the backend is available.
+
+        Returns:
+            True if the backend can be used.
+        """
+        pass
+
+    @abstractmethod
+    def get_model_name(self) -> str:
+        """Get the name of the currently loaded model.
+
+        Returns:
+            Model name string.
+        """
+        pass
+
+    @abstractmethod
+    def set_model(self, model: str) -> None:
+        """Set the model to use.
+
+        Args:
+            model: Name of the model to load.
+        """
+        pass
+
+    @abstractmethod
+    def close(self) -> None:
+        """Clean up resources."""
+        pass