ss-tools/backend/src/core/plugin_loader.py

import importlib.util
import os
import sys # Added this line
from typing import Dict, Type, List, Optional
from .plugin_base import PluginBase, PluginConfig
from jsonschema import validate

# [DEF:PluginLoader:Class]
# @SEMANTICS: plugin, loader, dynamic, import
# @PURPOSE: Scans a specified directory for Python modules, dynamically loads them, and registers any classes that are valid implementations of the PluginBase interface.
# @LAYER: Core
# @RELATION: Depends on PluginBase. It is used by the main application to discover and manage available plugins.
class PluginLoader:
    """
    Scans a directory for Python modules, loads them, and identifies classes
    that inherit from PluginBase.
    """

    def __init__(self, plugin_dir: str):
        self.plugin_dir = plugin_dir
        self._plugins: Dict[str, PluginBase] = {}
        self._plugin_configs: Dict[str, PluginConfig] = {}
        self._load_plugins()

    def _load_plugins(self):
        """
        Scans the plugin directory, imports modules, and registers valid plugins.
        """
        if not os.path.exists(self.plugin_dir):
            os.makedirs(self.plugin_dir)

        # Add the plugin directory's parent to sys.path to enable relative imports within plugins
        # This assumes plugin_dir is something like 'backend/src/plugins'
        # and we want 'backend/src' to be on the path for 'from ..core...' imports
        plugin_parent_dir = os.path.abspath(os.path.join(self.plugin_dir, os.pardir))
        if plugin_parent_dir not in sys.path:
            sys.path.insert(0, plugin_parent_dir)

        for filename in os.listdir(self.plugin_dir):
            if filename.endswith(".py") and filename != "__init__.py":
                module_name = filename[:-3]
                file_path = os.path.join(self.plugin_dir, filename)
                self._load_module(module_name, file_path)

    def _load_module(self, module_name: str, file_path: str):
        """
        Loads a single Python module and extracts PluginBase subclasses.
        """
        # Try to determine the correct package prefix based on how the app is running
        if "backend.src" in __name__:
            package_prefix = "backend.src.plugins"
        else:
            package_prefix = "src.plugins"
            
        package_name = f"{package_prefix}.{module_name}"
        # print(f"DEBUG: Loading plugin {module_name} as {package_name}")
        spec = importlib.util.spec_from_file_location(package_name, file_path)
        if spec is None or spec.loader is None:
            print(f"Could not load module spec for {package_name}") # Replace with proper logging
            return

        module = importlib.util.module_from_spec(spec)
        try:
            spec.loader.exec_module(module)
        except Exception as e:
            print(f"Error loading plugin module {module_name}: {e}") # Replace with proper logging
            return

        for attribute_name in dir(module):
            attribute = getattr(module, attribute_name)
            if (
                isinstance(attribute, type)
                and issubclass(attribute, PluginBase)
                and attribute is not PluginBase
            ):
                try:
                    plugin_instance = attribute()
                    self._register_plugin(plugin_instance)
                except Exception as e:
                    print(f"Error instantiating plugin {attribute_name} in {module_name}: {e}") # Replace with proper logging

    def _register_plugin(self, plugin_instance: PluginBase):
        """
        Registers a valid plugin instance.
        """
        plugin_id = plugin_instance.id
        if plugin_id in self._plugins:
            print(f"Warning: Duplicate plugin ID '{plugin_id}' found. Skipping.") # Replace with proper logging
            return

        try:
            schema = plugin_instance.get_schema()
            # Basic validation to ensure it's a dictionary
            if not isinstance(schema, dict):
                raise TypeError("get_schema() must return a dictionary.")
                
            plugin_config = PluginConfig(
                id=plugin_instance.id,
                name=plugin_instance.name,
                description=plugin_instance.description,
                version=plugin_instance.version,
                schema=schema,
            )
            # The following line is commented out because it requires a schema to be passed to validate against.
            # The schema provided by the plugin is the one being validated, not the data.
            # validate(instance={}, schema=schema)
            self._plugins[plugin_id] = plugin_instance
            self._plugin_configs[plugin_id] = plugin_config
            print(f"Plugin '{plugin_instance.name}' (ID: {plugin_id}) loaded successfully.") # Replace with proper logging
        except Exception as e:
            print(f"Error validating plugin '{plugin_instance.name}' (ID: {plugin_id}): {e}") # Replace with proper logging


    def get_plugin(self, plugin_id: str) -> Optional[PluginBase]:
        """
        Returns a loaded plugin instance by its ID.
        """
        return self._plugins.get(plugin_id)

    def get_all_plugin_configs(self) -> List[PluginConfig]:
        """
        Returns a list of all loaded plugin configurations.
        """
        return list(self._plugin_configs.values())

    def has_plugin(self, plugin_id: str) -> bool:
        """
        Checks if a plugin with the given ID is loaded.
        """
        return plugin_id in self._plugins