fully migrate all search backends to new plugin system

archivebox/plugantic/base_searchbackend.py

@@ -0,0 +1,39 @@
+__package__ = 'archivebox.plugantic'
+
+from typing import Iterable, List
+from benedict import benedict
+from pydantic import Field
+
+
+from .base_hook import BaseHook, HookType
+
+
+
+class BaseSearchBackend(BaseHook):
+    hook_type: HookType = 'SEARCHBACKEND'
+
+    name: str = Field()       # e.g. 'singlefile'
+
+    @staticmethod
+    def index(snapshot_id: str, texts: List[str]):
+        return
+
+    @staticmethod
+    def flush(snapshot_ids: Iterable[str]):
+        return
+
+    @staticmethod
+    def search(text: str) -> List[str]:
+        raise NotImplementedError("search method must be implemented by subclass")
+    
+    
+    def register(self, settings, parent_plugin=None):
+        # self._plugin = parent_plugin                                      # for debugging only, never rely on this!
+
+        # Install queue into settings.SEARCH_BACKENDS
+        settings.SEARCH_BACKENDS = getattr(settings, "SEARCH_BACKENDS", None) or benedict({})
+        settings.SEARCH_BACKENDS[self.id] = self
+
+        # Record installed hook into settings.HOOKS
+        super().register(settings, parent_plugin=parent_plugin)
+