1 files changed, 169 insertions, 0 deletions
diff --git a/searx/answerers/_core.py b/searx/answerers/_core.py
new file mode 100644
index 000000000..9c50d026e
--- /dev/null
+++ b/searx/answerers/_core.py
@@ -0,0 +1,169 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+# pylint: disable=too-few-public-methods, missing-module-docstring
+
+from __future__ import annotations
+
+import abc
+import importlib
+import logging
+import pathlib
+import warnings
+
+from dataclasses import dataclass
+
+from searx.utils import load_module
+from searx.result_types.answer import BaseAnswer
+
+
+_default = pathlib.Path(__file__).parent
+log: logging.Logger = logging.getLogger("searx.answerers")
+
+
+@dataclass
+class AnswererInfo:
+    """Object that holds informations about an answerer, these infos are shown
+    to the user in the Preferences menu.
+
+    To be able to translate the information into other languages, the text must
+    be written in English and translated with :py:obj:`flask_babel.gettext`.
+    """
+
+    name: str
+    """Name of the *answerer*."""
+
+    description: str
+    """Short description of the *answerer*."""
+
+    examples: list[str]
+    """List of short examples of the usage / of query terms."""
+
+    keywords: list[str]
+    """See :py:obj:`Answerer.keywords`"""
+
+
+class Answerer(abc.ABC):
+    """Abstract base class of answerers."""
+
+    keywords: list[str]
+    """Keywords to which the answerer has *answers*."""
+
+    @abc.abstractmethod
+    def answer(self, query: str) -> list[BaseAnswer]:
+        """Function that returns a list of answers to the question/query."""
+
+    @abc.abstractmethod
+    def info(self) -> AnswererInfo:
+        """Informations about the *answerer*, see :py:obj:`AnswererInfo`."""
+
+
+class ModuleAnswerer(Answerer):
+    """A wrapper class for legacy *answerers* where the names (keywords, answer,
+    info) are implemented on the module level (not in a class).
+
+    .. note::
+
+       For internal use only!
+    """
+
+    def __init__(self, mod):
+
+        for name in ["keywords", "self_info", "answer"]:
+            if not getattr(mod, name, None):
+                raise SystemExit(2)
+        if not isinstance(mod.keywords, tuple):
+            raise SystemExit(2)
+
+        self.module = mod
+        self.keywords = mod.keywords  # type: ignore
+
+    def answer(self, query: str) -> list[BaseAnswer]:
+        return self.module.answer(query)
+
+    def info(self) -> AnswererInfo:
+        kwargs = self.module.self_info()
+        kwargs["keywords"] = self.keywords
+        return AnswererInfo(**kwargs)
+
+
+class AnswerStorage(dict):
+    """A storage for managing the *answerers* of SearXNG.  With the
+    :py:obj:`AnswerStorage.ask`” method, a caller can ask questions to all
+    *answerers* and receives a list of the results."""
+
+    answerer_list: set[Answerer]
+    """The list of :py:obj:`Answerer` in this storage."""
+
+    def __init__(self):
+        super().__init__()
+        self.answerer_list = set()
+
+    def load_builtins(self):
+        """Loads ``answerer.py`` modules from the python packages in
+        :origin:`searx/answerers`.  The python modules are wrapped by
+        :py:obj:`ModuleAnswerer`."""
+
+        for f in _default.iterdir():
+            if f.name.startswith("_"):
+                continue
+
+            if f.is_file() and f.suffix == ".py":
+                self.register_by_fqn(f"searx.answerers.{f.stem}.SXNGAnswerer")
+                continue
+
+            # for backward compatibility (if a fork has additional answerers)
+
+            if f.is_dir() and (f / "answerer.py").exists():
+                warnings.warn(
+                    f"answerer module {f} is deprecated / migrate to searx.answerers.Answerer", DeprecationWarning
+                )
+                mod = load_module("answerer.py", str(f))
+                self.register(ModuleAnswerer(mod))
+
+    def register_by_fqn(self, fqn: str):
+        """Register a :py:obj:`Answerer` via its fully qualified class namen(FQN)."""
+
+        mod_name, _, obj_name = fqn.rpartition('.')
+        mod = importlib.import_module(mod_name)
+        code_obj = getattr(mod, obj_name, None)
+
+        if code_obj is None:
+            msg = f"answerer {fqn} is not implemented"
+            log.critical(msg)
+            raise ValueError(msg)
+
+        self.register(code_obj())
+
+    def register(self, answerer: Answerer):
+        """Register a :py:obj:`Answerer`."""
+
+        self.answerer_list.add(answerer)
+        for _kw in answerer.keywords:
+            self[_kw] = self.get(_kw, [])
+            self[_kw].append(answerer)
+
+    def ask(self, query: str) -> list[BaseAnswer]:
+        """An answerer is identified via keywords, if there is a keyword at the
+        first position in the ``query`` for which there is one or more
+        answerers, then these are called, whereby the entire ``query`` is passed
+        as argument to the answerer function."""
+
+        results = []
+        keyword = None
+        for keyword in query.split():
+            if keyword:
+                break
+
+        if not keyword or keyword not in self:
+            return results
+
+        for answerer in self[keyword]:
+            for answer in answerer.answer(query):
+                # In case of *answers* prefix ``answerer:`` is set, see searx.result_types.Result
+                answer.engine = f"answerer: {keyword}"
+                results.append(answer)
+
+        return results
+
+    @property
+    def info(self) -> list[AnswererInfo]:
+        return [a.info() for a in self.answerer_list]