[mod] addition of various type hints / engine processors

Continuation of #5147 .. typification of the engine processors.

BTW:

- removed obsolete engine property https_support
- fixed & improved currency_convert
- engine instances can now implement a engine.setup method

[#5147] https://github.com/searxng/searxng/pull/5147

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

7 files changed, 644 insertions, 367 deletions

diff --git a/searx/search/processors/__init__.py b/searx/search/processors/__init__.py
index 760513253..5e896c711 100644
--- a/searx/search/processors/__init__.py
+++ b/searx/search/processors/__init__.py
@@ -2,83 +2,95 @@
 """Implement request processors used by engine-types."""
 
 __all__ = [
-    'EngineProcessor',
-    'OfflineProcessor',
-    'OnlineProcessor',
-    'OnlineDictionaryProcessor',
-    'OnlineCurrencyProcessor',
-    'OnlineUrlSearchProcessor',
-    'PROCESSORS',
+    "OfflineParamTypes",
+    "OnlineCurrenciesParams",
+    "OnlineDictParams",
+    "OnlineParamTypes",
+    "OnlineParams",
+    "OnlineUrlSearchParams",
+    "PROCESSORS",
+    "ParamTypes",
+    "RequestParams",
 ]
 
 import typing as t
 
-import threading
-
 from searx import logger
 from searx import engines
 
-from .online import OnlineProcessor
+from .abstract import EngineProcessor, RequestParams
 from .offline import OfflineProcessor
-from .online_dictionary import OnlineDictionaryProcessor
-from .online_currency import OnlineCurrencyProcessor
-from .online_url_search import OnlineUrlSearchProcessor
-from .abstract import EngineProcessor
+from .online import OnlineProcessor, OnlineParams
+from .online_dictionary import OnlineDictionaryProcessor, OnlineDictParams
+from .online_currency import OnlineCurrencyProcessor, OnlineCurrenciesParams
+from .online_url_search import OnlineUrlSearchProcessor, OnlineUrlSearchParams
 
-if t.TYPE_CHECKING:
-    from searx.enginelib import Engine
+logger = logger.getChild("search.processors")
 
-logger = logger.getChild('search.processors')
-PROCESSORS: dict[str, EngineProcessor] = {}
-"""Cache request processors, stored by *engine-name* (:py:func:`initialize`)
+OnlineParamTypes: t.TypeAlias = OnlineParams | OnlineDictParams | OnlineCurrenciesParams | OnlineUrlSearchParams
+OfflineParamTypes: t.TypeAlias = RequestParams
+ParamTypes: t.TypeAlias = OfflineParamTypes | OnlineParamTypes
 
-:meta hide-value:
-"""
 
+class ProcessorMap(dict[str, EngineProcessor]):
+    """Class to manage :py:obj:`EngineProcessor` instances in a key/value map
+    (instances stored by *engine-name*)."""
+
+    processor_types: dict[str, type[EngineProcessor]] = {
+        OnlineProcessor.engine_type: OnlineProcessor,
+        OfflineProcessor.engine_type: OfflineProcessor,
+        OnlineDictionaryProcessor.engine_type: OnlineDictionaryProcessor,
+        OnlineCurrencyProcessor.engine_type: OnlineCurrencyProcessor,
+        OnlineUrlSearchProcessor.engine_type: OnlineUrlSearchProcessor,
+    }
+
+    def init(self, engine_list: list[dict[str, t.Any]]):
+        """Initialize all engines and registers a processor for each engine."""
+
+        for eng_settings in engine_list:
+            eng_name: str = eng_settings["name"]
+
+            if eng_settings.get("inactive", False) is True:
+                logger.info("Engine of name '%s' is inactive.", eng_name)
+                continue
+
+            eng_obj = engines.engines.get(eng_name)
+            if eng_obj is None:
+                logger.warning("Engine of name '%s' does not exists.", eng_name)
+                continue
+
+            eng_type = getattr(eng_obj, "engine_type", "online")
+            proc_cls = self.processor_types.get(eng_type)
+            if proc_cls is None:
+                logger.error("Engine '%s' is of unknown engine_type: %s", eng_type)
+                continue
+
+            # initialize (and register) the engine
+            eng_proc = proc_cls(eng_obj)
+            eng_proc.initialize(self.register_processor)
 
-def get_processor_class(engine_type: str) -> type[EngineProcessor] | None:
-    """Return processor class according to the ``engine_type``"""
-    for c in [
-        OnlineProcessor,
-        OfflineProcessor,
-        OnlineDictionaryProcessor,
-        OnlineCurrencyProcessor,
-        OnlineUrlSearchProcessor,
-    ]:
-        if c.engine_type == engine_type:
-            return c
-    return None
-
-
-def get_processor(engine: "Engine | ModuleType", engine_name: str) -> EngineProcessor | None:
-    """Return processor instance that fits to ``engine.engine.type``"""
-    engine_type = getattr(engine, 'engine_type', 'online')
-    processor_class = get_processor_class(engine_type)
-    if processor_class is not None:
-        return processor_class(engine, engine_name)
-    return None
-
-
-def initialize_processor(processor: EngineProcessor):
-    """Initialize one processor
-
-    Call the init function of the engine
-    """
-    if processor.has_initialize_function:
-        _t = threading.Thread(target=processor.initialize, daemon=True)
-        _t.start()
-
-
-def initialize(engine_list: list[dict[str, t.Any]]):
-    """Initialize all engines and store a processor for each engine in
-    :py:obj:`PROCESSORS`."""
-    for engine_data in engine_list:
-        engine_name: str = engine_data['name']
-        engine = engines.engines.get(engine_name)
-        if engine:
-            processor = get_processor(engine, engine_name)
-            if processor is None:
-                engine.logger.error('Error get processor for engine %s', engine_name)
-            else:
-                initialize_processor(processor)
-                PROCESSORS[engine_name] = processor
+    def register_processor(self, eng_proc: EngineProcessor, eng_proc_ok: bool) -> bool:
+        """Register the :py:obj:`EngineProcessor`.
+
+        This method is usually passed as a callback to the initialization of the
+        :py:obj:`EngineProcessor`.
+
+        The value (true/false) passed in ``eng_proc_ok`` indicates whether the
+        initialization of the :py:obj:`EngineProcessor` was successful; if this
+        is not the case, the processor is not registered.
+        """
+
+        if eng_proc_ok:
+            self[eng_proc.engine.name] = eng_proc
+            # logger.debug("registered engine processor: %s", eng_proc.engine.name)
+        else:
+            logger.error("init method of engine %s failed (%s).", eng_proc.engine.name)
+
+        return eng_proc_ok
+
+
+PROCESSORS = ProcessorMap()
+"""Global :py:obj:`ProcessorMap`.
+
+:meta hide-value:
+"""
diff --git a/searx/search/processors/abstract.py b/searx/search/processors/abstract.py
index 2dd56855a..ec94ed3bf 100644
--- a/searx/search/processors/abstract.py
+++ b/searx/search/processors/abstract.py
@@ -1,7 +1,5 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Abstract base classes for engine request processors.
-
-"""
+"""Abstract base classes for all engine processors."""
 
 import typing as t
 
@@ -10,25 +8,75 @@ import threading
 from abc import abstractmethod, ABC
 from timeit import default_timer
 
-from searx import settings, logger
+from searx import get_setting
+from searx import logger
 from searx.engines import engines
 from searx.network import get_time_for_thread, get_network
 from searx.metrics import histogram_observe, counter_inc, count_exception, count_error
-from searx.exceptions import SearxEngineAccessDeniedException, SearxEngineResponseException
+from searx.exceptions import SearxEngineAccessDeniedException
 from searx.utils import get_engine_from_settings
 
 if t.TYPE_CHECKING:
+    import types
     from searx.enginelib import Engine
+    from searx.search.models import SearchQuery
+    from searx.results import ResultContainer
+    from searx.result_types import Result, LegacyResult  # pyright: ignore[reportPrivateLocalImportUsage]
+
+
+logger = logger.getChild("searx.search.processor")
+SUSPENDED_STATUS: dict[int | str, "SuspendedStatus"] = {}
+
+
+class RequestParams(t.TypedDict):
+    """Basic quantity of the Request parameters of all engine types."""
+
+    query: str
+    """Search term, stripped of search syntax arguments."""
+
+    category: str
+    """Current category, like ``general``.
+
+    .. hint::
+
+       This field is deprecated, don't use it in further implementations.
 
-logger = logger.getChild('searx.search.processor')
-SUSPENDED_STATUS: dict[int | str, 'SuspendedStatus'] = {}
+    This field is currently *arbitrarily* filled with the name of "one""
+    category (the name of the first category of the engine). In practice,
+    however, it is not clear what this "one" category should be; in principle,
+    multiple categories can also be activated in a search.
+    """
+
+    pageno: int
+    """Current page number, where the first page is ``1``."""
+
+    safesearch: t.Literal[0, 1, 2]
+    """Safe-Search filter (0:normal, 1:moderate, 2:strict)."""
+
+    time_range: t.Literal["day", "week", "month", "year"] | None
+    """Time-range filter."""
+
+    engine_data: dict[str, str]
+    """Allows the transfer of (engine specific) data to the next request of the
+    client.  In the case of the ``online`` engines, this data is delivered to
+    the client via the HTML ``<form>`` in response.
+
+    If the client then sends this form back to the server with the next request,
+    this data will be available.
+
+    This makes it possible to carry data from one request to the next without a
+    session context, but this feature (is fragile) and should only be used in
+    exceptional cases. See also :ref:`engine_data`."""
+
+    searxng_locale: str
+    """Language / locale filter from the search request, a string like 'all',
+    'en', 'en-US', 'zh-HK' .. and others, for more details see
+    :py:obj:`searx.locales`."""
 
 
 class SuspendedStatus:
     """Class to handle suspend state."""
 
-    __slots__ = 'suspend_end_time', 'suspend_reason', 'continuous_errors', 'lock'
-
     def __init__(self):
         self.lock: threading.Lock = threading.Lock()
         self.continuous_errors: int = 0
@@ -39,18 +87,18 @@ class SuspendedStatus:
     def is_suspended(self):
         return self.suspend_end_time >= default_timer()
 
-    def suspend(self, suspended_time: int, suspend_reason: str):
+    def suspend(self, suspended_time: int | None, suspend_reason: str):
         with self.lock:
             # update continuous_errors / suspend_end_time
             self.continuous_errors += 1
             if suspended_time is None:
-                suspended_time = min(
-                    settings['search']['max_ban_time_on_fail'],
-                    self.continuous_errors * settings['search']['ban_time_on_fail'],
-                )
+                max_ban: int = get_setting("search.max_ban_time_on_fail")
+                ban_fail: int = get_setting("search.ban_time_on_fail")
+                suspended_time = min(max_ban, ban_fail)
+
             self.suspend_end_time = default_timer() + suspended_time
             self.suspend_reason = suspend_reason
-            logger.debug('Suspend for %i seconds', suspended_time)
+            logger.debug("Suspend for %i seconds", suspended_time)
 
     def resume(self):
         with self.lock:
@@ -63,31 +111,63 @@ class SuspendedStatus:
 class EngineProcessor(ABC):
     """Base classes used for all types of request processors."""
 
-    __slots__ = 'engine', 'engine_name', 'suspended_status', 'logger'
+    engine_type: str
 
-    def __init__(self, engine: "Engine|ModuleType", engine_name: str):
-        self.engine: "Engine" = engine
-        self.engine_name: str = engine_name
-        self.logger: logging.Logger = engines[engine_name].logger
-        key = get_network(self.engine_name)
-        key = id(key) if key else self.engine_name
+    def __init__(self, engine: "Engine|types.ModuleType"):
+        self.engine: "Engine" = engine  # pyright: ignore[reportAttributeAccessIssue]
+        self.logger: logging.Logger = engines[engine.name].logger
+        key = get_network(self.engine.name)
+        key = id(key) if key else self.engine.name
         self.suspended_status: SuspendedStatus = SUSPENDED_STATUS.setdefault(key, SuspendedStatus())
 
-    def initialize(self):
-        try:
-            self.engine.init(get_engine_from_settings(self.engine_name))
-        except SearxEngineResponseException as exc:
-            self.logger.warning('Fail to initialize // %s', exc)
-        except Exception:  # pylint: disable=broad-except
-            self.logger.exception('Fail to initialize')
-        else:
-            self.logger.debug('Initialized')
+    def initialize(self, callback: t.Callable[["EngineProcessor", bool], bool]):
+        """Initialization of *this* :py:obj:`EngineProcessor`.
 
-    @property
-    def has_initialize_function(self):
-        return hasattr(self.engine, 'init')
+        If processor's engine has an ``init`` method, it is called first.
+        Engine's ``init`` method is executed in a thread, meaning that the
+        *registration* (the ``callback``) may occur later and is not already
+        established by the return from this registration method.
+
+        Registration only takes place if the ``init`` method is not available or
+        is successfully run through.
+        """
+
+        if not hasattr(self.engine, "init"):
+            callback(self, True)
+            return
 
-    def handle_exception(self, result_container, exception_or_message, suspend=False):
+        if not callable(self.engine.init):
+            logger.error("Engine's init method isn't a callable (is of type: %s).", type(self.engine.init))
+            callback(self, False)
+            return
+
+        def __init_processor_thread():
+            eng_ok = self.init_engine()
+            callback(self, eng_ok)
+
+        # set up and start a thread
+        threading.Thread(target=__init_processor_thread, daemon=True).start()
+
+    def init_engine(self) -> bool:
+        eng_setting = get_engine_from_settings(self.engine.name)
+        init_ok: bool | None = False
+        try:
+            init_ok = self.engine.init(eng_setting)
+        except Exception:  # pylint: disable=broad-except
+            logger.exception("Init method of engine %s failed due to an exception.", self.engine.name)
+            init_ok = False
+        # In older engines, None is returned from the init method, which is
+        # equivalent to indicating that the initialization was successful.
+        if init_ok is None:
+            init_ok = True
+        return init_ok
+
+    def handle_exception(
+        self,
+        result_container: "ResultContainer",
+        exception_or_message: BaseException | str,
+        suspend: bool = False,
+    ):
         # update result_container
         if isinstance(exception_or_message, BaseException):
             exception_class = exception_or_message.__class__
@@ -96,13 +176,13 @@ class EngineProcessor(ABC):
             error_message = module_name + exception_class.__qualname__
         else:
             error_message = exception_or_message
-        result_container.add_unresponsive_engine(self.engine_name, error_message)
+        result_container.add_unresponsive_engine(self.engine.name, error_message)
         # metrics
-        counter_inc('engine', self.engine_name, 'search', 'count', 'error')
+        counter_inc('engine', self.engine.name, 'search', 'count', 'error')
         if isinstance(exception_or_message, BaseException):
-            count_exception(self.engine_name, exception_or_message)
+            count_exception(self.engine.name, exception_or_message)
         else:
-            count_error(self.engine_name, exception_or_message)
+            count_error(self.engine.name, exception_or_message)
         # suspend the engine ?
         if suspend:
             suspended_time = None
@@ -110,51 +190,63 @@ class EngineProcessor(ABC):
                 suspended_time = exception_or_message.suspended_time
             self.suspended_status.suspend(suspended_time, error_message)  # pylint: disable=no-member
 
-    def _extend_container_basic(self, result_container, start_time, search_results):
+    def _extend_container_basic(
+        self,
+        result_container: "ResultContainer",
+        start_time: float,
+        search_results: "list[Result | LegacyResult]",
+    ):
         # update result_container
-        result_container.extend(self.engine_name, search_results)
+        result_container.extend(self.engine.name, search_results)
         engine_time = default_timer() - start_time
         page_load_time = get_time_for_thread()
-        result_container.add_timing(self.engine_name, engine_time, page_load_time)
+        result_container.add_timing(self.engine.name, engine_time, page_load_time)
         # metrics
-        counter_inc('engine', self.engine_name, 'search', 'count', 'successful')
-        histogram_observe(engine_time, 'engine', self.engine_name, 'time', 'total')
+        counter_inc('engine', self.engine.name, 'search', 'count', 'successful')
+        histogram_observe(engine_time, 'engine', self.engine.name, 'time', 'total')
         if page_load_time is not None:
-            histogram_observe(page_load_time, 'engine', self.engine_name, 'time', 'http')
-
-    def extend_container(self, result_container, start_time, search_results):
+            histogram_observe(page_load_time, 'engine', self.engine.name, 'time', 'http')
+
+    def extend_container(
+        self,
+        result_container: "ResultContainer",
+        start_time: float,
+        search_results: "list[Result | LegacyResult]|None",
+    ):
         if getattr(threading.current_thread(), '_timeout', False):
             # the main thread is not waiting anymore
-            self.handle_exception(result_container, 'timeout', None)
+            self.handle_exception(result_container, 'timeout', False)
         else:
             # check if the engine accepted the request
             if search_results is not None:
                 self._extend_container_basic(result_container, start_time, search_results)
             self.suspended_status.resume()
 
-    def extend_container_if_suspended(self, result_container):
+    def extend_container_if_suspended(self, result_container: "ResultContainer") -> bool:
         if self.suspended_status.is_suspended:
             result_container.add_unresponsive_engine(
-                self.engine_name, self.suspended_status.suspend_reason, suspended=True
+                self.engine.name, self.suspended_status.suspend_reason, suspended=True
             )
             return True
         return False
 
-    def get_params(self, search_query, engine_category) -> dict[str, t.Any]:
-        """Returns a set of (see :ref:`request params <engine request arguments>`) or
-        ``None`` if request is not supported.
+    def get_params(self, search_query: "SearchQuery", engine_category: str) -> RequestParams | None:
+        """Returns a dictionary with the :ref:`request parameters <engine
+        request arguments>` (:py:obj:`RequestParams`), if the search condition
+        is not supported by the engine, ``None`` is returned:
 
-        Not supported conditions (``None`` is returned):
+        - *time range* filter in search conditions, but the engine does not have
+           a corresponding filter
+        - page number > 1 when engine does not support paging
+        - page number > ``max_page``
 
-        - A page-number > 1 when engine does not support paging.
-        - A time range when the engine does not support time range.
         """
         # if paging is not supported, skip
         if search_query.pageno > 1 and not self.engine.paging:
             return None
 
         # if max page is reached, skip
-        max_page = self.engine.max_page or settings['search']['max_page']
+        max_page = self.engine.max_page or get_setting("search.max_page")
         if max_page and max_page < search_query.pageno:
             return None
 
@@ -162,39 +254,45 @@ class EngineProcessor(ABC):
         if search_query.time_range and not self.engine.time_range_support:
             return None
 
-        params = {}
-        params["query"] = search_query.query
-        params['category'] = engine_category
-        params['pageno'] = search_query.pageno
-        params['safesearch'] = search_query.safesearch
-        params['time_range'] = search_query.time_range
-        params['engine_data'] = search_query.engine_data.get(self.engine_name, {})
-        params['searxng_locale'] = search_query.lang
-
-        # deprecated / vintage --> use params['searxng_locale']
+        params: RequestParams = {
+            "query": search_query.query,
+            "category": engine_category,
+            "pageno": search_query.pageno,
+            "safesearch": search_query.safesearch,
+            "time_range": search_query.time_range,
+            "engine_data": search_query.engine_data.get(self.engine.name, {}),
+            "searxng_locale": search_query.lang,
+        }
+
+        # deprecated / vintage --> use params["searxng_locale"]
         #
         # Conditions related to engine's traits are implemented in engine.traits
-        # module. Don't do 'locale' decisions here in the abstract layer of the
+        # module. Don't do "locale" decisions here in the abstract layer of the
         # search processor, just pass the value from user's choice unchanged to
         # the engine request.
 
-        if hasattr(self.engine, 'language') and self.engine.language:
-            params['language'] = self.engine.language
+        if hasattr(self.engine, "language") and self.engine.language:
+            params["language"] = self.engine.language  # pyright: ignore[reportGeneralTypeIssues]
         else:
-            params['language'] = search_query.lang
+            params["language"] = search_query.lang  # pyright: ignore[reportGeneralTypeIssues]
 
         return params
 
     @abstractmethod
-    def search(self, query, params, result_container, start_time, timeout_limit):
+    def search(
+        self,
+        query: str,
+        params: RequestParams,
+        result_container: "ResultContainer",
+        start_time: float,
+        timeout_limit: float,
+    ):
         pass
 
     def get_tests(self):
-        tests = getattr(self.engine, 'tests', None)
-        if tests is None:
-            tests = getattr(self.engine, 'additional_tests', {})
-            tests.update(self.get_default_tests())
-        return tests
+        # deprecated!
+        return {}
 
     def get_default_tests(self):
+        # deprecated!
         return {}
diff --git a/searx/search/processors/offline.py b/searx/search/processors/offline.py
index 8835bfbf2..32e7164bf 100644
--- a/searx/search/processors/offline.py
+++ b/searx/search/processors/offline.py
@@ -1,26 +1,32 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Processors for engine-type: ``offline``
+"""Processors for engine-type: ``offline``"""
 
-"""
+import typing as t
+from .abstract import EngineProcessor, RequestParams
 
-from .abstract import EngineProcessor
+if t.TYPE_CHECKING:
+    from searx.results import ResultContainer
 
 
 class OfflineProcessor(EngineProcessor):
-    """Processor class used by ``offline`` engines"""
+    """Processor class used by ``offline`` engines."""
 
-    engine_type = 'offline'
+    engine_type: str = "offline"
 
-    def _search_basic(self, query, params):
-        return self.engine.search(query, params)
-
-    def search(self, query, params, result_container, start_time, timeout_limit):
+    def search(
+        self,
+        query: str,
+        params: RequestParams,
+        result_container: "ResultContainer",
+        start_time: float,
+        timeout_limit: float,
+    ):
         try:
-            search_results = self._search_basic(query, params)
+            search_results = self.engine.search(query, params)
             self.extend_container(result_container, start_time, search_results)
         except ValueError as e:
             # do not record the error
-            self.logger.exception('engine {0} : invalid input : {1}'.format(self.engine_name, e))
+            self.logger.exception('engine {0} : invalid input : {1}'.format(self.engine.name, e))
         except Exception as e:  # pylint: disable=broad-except
             self.handle_exception(result_container, e)
-            self.logger.exception('engine {0} : exception : {1}'.format(self.engine_name, e))
+            self.logger.exception('engine {0} : exception : {1}'.format(self.engine.name, e))
diff --git a/searx/search/processors/online.py b/searx/search/processors/online.py
index 778b4ac4d..23bb7fda0 100644
--- a/searx/search/processors/online.py
+++ b/searx/search/processors/online.py
@@ -1,8 +1,9 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Processors for engine-type: ``online``
+"""Processor used for ``online`` engines."""
 
-"""
-# pylint: disable=use-dict-literal
+__all__ = ["OnlineProcessor", "OnlineParams"]
+
+import typing as t
 
 from timeit import default_timer
 import asyncio
@@ -17,50 +18,132 @@ from searx.exceptions import (
     SearxEngineTooManyRequestsException,
 )
 from searx.metrics.error_recorder import count_error
-from .abstract import EngineProcessor
+from .abstract import EngineProcessor, RequestParams
+
+if t.TYPE_CHECKING:
+    from searx.search.models import SearchQuery
+    from searx.results import ResultContainer
+    from searx.result_types import EngineResults
+
+
+class HTTPParams(t.TypedDict):
+    """HTTP request parameters"""
+
+    method: t.Literal["GET", "POST"]
+    """HTTP request method."""
+
+    headers: dict[str, str]
+    """HTTP header information."""
+
+    data: dict[str, str]
+    """Sending `form encoded data`_.
+
+    .. _form encoded data:
+       https://www.python-httpx.org/quickstart/#sending-form-encoded-data
+    """
+
+    json: dict[str, t.Any]
+    """`Sending `JSON encoded data`_.
+
+    .. _JSON encoded data:
+       https://www.python-httpx.org/quickstart/#sending-json-encoded-data
+    """
+
+    content: bytes
+    """`Sending `binary request data`_.
+
+    .. _binary request data:
+       https://www.python-httpx.org/quickstart/#sending-json-encoded-data
+    """
+
+    url: str
+    """Requested url."""
+
+    cookies: dict[str, str]
+    """HTTP cookies."""
+
+    allow_redirects: bool
+    """Follow redirects"""
+
+    max_redirects: int
+    """Maximum redirects, hard limit."""
+
+    soft_max_redirects: int
+    """Maximum redirects, soft limit. Record an error but don't stop the engine."""
+
+    verify: None | t.Literal[False] | str  # not sure str really works
+    """If not ``None``, it overrides the verify value defined in the network.  Use
+    ``False`` to accept any server certificate and use a path to file to specify a
+    server certificate"""
+
+    auth: str | None
+    """An authentication to use when sending requests."""
+
+    raise_for_httperror: bool
+    """Raise an exception if the `HTTP response status code`_ is ``>= 300``.
+
+    .. _HTTP response status code:
+        https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status
+    """
+
 
+class OnlineParams(HTTPParams, RequestParams):
+    """Request parameters of a ``online`` engine."""
 
-def default_request_params():
+
+def default_request_params() -> HTTPParams:
     """Default request parameters for ``online`` engines."""
     return {
-        # fmt: off
-        'method': 'GET',
-        'headers': {},
-        'data': {},
-        'url': '',
-        'cookies': {},
-        'auth': None
-        # fmt: on
+        "method": "GET",
+        "headers": {},
+        "data": {},
+        "json": {},
+        "content": b"",
+        "url": "",
+        "cookies": {},
+        "allow_redirects": False,
+        "max_redirects": 0,
+        "soft_max_redirects": 0,
+        "auth": None,
+        "verify": None,
+        "raise_for_httperror": True,
     }
 
 
 class OnlineProcessor(EngineProcessor):
     """Processor class for ``online`` engines."""
 
-    engine_type = 'online'
+    engine_type: str = "online"
+
+    def init_engine(self) -> bool:
+        """This method is called in a thread, and before the base method is
+        called, the network must be set up for the ``online`` engines."""
+        self.init_network_in_thread(start_time=default_timer(), timeout_limit=self.engine.timeout)
+        return super().init_engine()
 
-    def initialize(self):
+    def init_network_in_thread(self, start_time: float, timeout_limit: float):
         # set timeout for all HTTP requests
-        searx.network.set_timeout_for_thread(self.engine.timeout, start_time=default_timer())
+        searx.network.set_timeout_for_thread(timeout_limit, start_time=start_time)
         # reset the HTTP total time
         searx.network.reset_time_for_thread()
         # set the network
-        searx.network.set_context_network_name(self.engine_name)
-        super().initialize()
-
-    def get_params(self, search_query, engine_category):
-        """Returns a set of :ref:`request params <engine request online>` or ``None``
-        if request is not supported.
-        """
-        params = super().get_params(search_query, engine_category)
-        if params is None:
-            return None
+        searx.network.set_context_network_name(self.engine.name)
+
+    def get_params(self, search_query: "SearchQuery", engine_category: str) -> OnlineParams | None:
+        """Returns a dictionary with the :ref:`request params <engine request
+        online>` (:py:obj:`OnlineParams`), if the search condition is not
+        supported by the engine, ``None`` is returned."""
+
+        base_params: RequestParams | None = super().get_params(search_query, engine_category)
+        if base_params is None:
+            return base_params
 
-        # add default params
-        params.update(default_request_params())
+        params: OnlineParams = {**default_request_params(), **base_params}
+
+        headers = params["headers"]
 
         # add an user agent
-        params['headers']['User-Agent'] = gen_useragent()
+        headers["User-Agent"] = gen_useragent()
 
         # add Accept-Language header
         if self.engine.send_accept_language_header and search_query.locale:
@@ -71,73 +154,77 @@ class OnlineProcessor(EngineProcessor):
                     search_query.locale.territory,
                     search_query.locale.language,
                 )
-            params['headers']['Accept-Language'] = ac_lang
+            headers["Accept-Language"] = ac_lang
 
-        self.logger.debug('HTTP Accept-Language: %s', params['headers'].get('Accept-Language', ''))
+        self.logger.debug("HTTP Accept-Language: %s", headers.get("Accept-Language", ""))
         return params
 
-    def _send_http_request(self, params):
-        # create dictionary which contain all
-        # information about the request
-        request_args = dict(headers=params['headers'], cookies=params['cookies'], auth=params['auth'])
+    def _send_http_request(self, params: OnlineParams):
+
+        # create dictionary which contain all information about the request
+        request_args: dict[str, t.Any] = {
+            "headers": params["headers"],
+            "cookies": params["cookies"],
+            "auth": params["auth"],
+        }
 
-        # verify
-        # if not None, it overrides the verify value defined in the network.
-        # use False to accept any server certificate
-        # use a path to file to specify a server certificate
-        verify = params.get('verify')
+        verify = params.get("verify")
         if verify is not None:
-            request_args['verify'] = params['verify']
+            request_args["verify"] = verify
 
         # max_redirects
-        max_redirects = params.get('max_redirects')
+        max_redirects = params.get("max_redirects")
         if max_redirects:
-            request_args['max_redirects'] = max_redirects
+            request_args["max_redirects"] = max_redirects
 
         # allow_redirects
-        if 'allow_redirects' in params:
-            request_args['allow_redirects'] = params['allow_redirects']
+        if "allow_redirects" in params:
+            request_args["allow_redirects"] = params["allow_redirects"]
 
         # soft_max_redirects
-        soft_max_redirects = params.get('soft_max_redirects', max_redirects or 0)
+        soft_max_redirects: int = params.get("soft_max_redirects", max_redirects or 0)
 
         # raise_for_status
-        request_args['raise_for_httperror'] = params.get('raise_for_httperror', True)
+        request_args["raise_for_httperror"] = params.get("raise_for_httperror", True)
 
         # specific type of request (GET or POST)
-        if params['method'] == 'GET':
+        if params["method"] == "GET":
             req = searx.network.get
         else:
             req = searx.network.post
-
-        request_args['data'] = params['data']
+            if params["data"]:
+                request_args["data"] = params["data"]
+            if params["json"]:
+                request_args["json"] = params["json"]
+            if params["content"]:
+                request_args["content"] = params["content"]
 
         # send the request
-        response = req(params['url'], **request_args)
+        response = req(params["url"], **request_args)
 
         # check soft limit of the redirect count
         if len(response.history) > soft_max_redirects:
             # unexpected redirect : record an error
             # but the engine might still return valid results.
-            status_code = str(response.status_code or '')
-            reason = response.reason_phrase or ''
+            status_code = str(response.status_code or "")
+            reason = response.reason_phrase or ""
             hostname = response.url.host
             count_error(
-                self.engine_name,
-                '{} redirects, maximum: {}'.format(len(response.history), soft_max_redirects),
+                self.engine.name,
+                "{} redirects, maximum: {}".format(len(response.history), soft_max_redirects),
                 (status_code, reason, hostname),
                 secondary=True,
             )
 
         return response
 
-    def _search_basic(self, query, params):
+    def _search_basic(self, query: str, params: OnlineParams) -> "EngineResults|None":
         # update request parameters dependent on
         # search-engine (contained in engines folder)
         self.engine.request(query, params)
 
         # ignoring empty urls
-        if not params['url']:
+        if not params["url"]:
             return None
 
         # send request
@@ -147,13 +234,15 @@ class OnlineProcessor(EngineProcessor):
         response.search_params = params
         return self.engine.response(response)
 
-    def search(self, query, params, result_container, start_time, timeout_limit):
-        # set timeout for all HTTP requests
-        searx.network.set_timeout_for_thread(timeout_limit, start_time=start_time)
-        # reset the HTTP total time
-        searx.network.reset_time_for_thread()
-        # set the network
-        searx.network.set_context_network_name(self.engine_name)
+    def search(  # pyright: ignore[reportIncompatibleMethodOverride]
+        self,
+        query: str,
+        params: OnlineParams,
+        result_container: "ResultContainer",
+        start_time: float,
+        timeout_limit: float,
+    ):
+        self.init_network_in_thread(start_time, timeout_limit)
 
         try:
             # send requests and parse the results
@@ -162,7 +251,7 @@ class OnlineProcessor(EngineProcessor):
         except ssl.SSLError as e:
             # requests timeout (connect or read)
             self.handle_exception(result_container, e, suspend=True)
-            self.logger.error("SSLError {}, verify={}".format(e, searx.network.get_network(self.engine_name).verify))
+            self.logger.error("SSLError {}, verify={}".format(e, searx.network.get_network(self.engine.name).verify))
         except (httpx.TimeoutException, asyncio.TimeoutError) as e:
             # requests timeout (connect or read)
             self.handle_exception(result_container, e, suspend=True)
@@ -179,55 +268,13 @@ class OnlineProcessor(EngineProcessor):
                     default_timer() - start_time, timeout_limit, e
                 )
             )
-        except SearxEngineCaptchaException as e:
-            self.handle_exception(result_container, e, suspend=True)
-            self.logger.exception('CAPTCHA')
-        except SearxEngineTooManyRequestsException as e:
+        except (
+            SearxEngineCaptchaException,
+            SearxEngineTooManyRequestsException,
+            SearxEngineAccessDeniedException,
+        ) as e:
             self.handle_exception(result_container, e, suspend=True)
-            self.logger.exception('Too many requests')
-        except SearxEngineAccessDeniedException as e:
-            self.handle_exception(result_container, e, suspend=True)
-            self.logger.exception('SearXNG is blocked')
+            self.logger.exception(e.message)
         except Exception as e:  # pylint: disable=broad-except
             self.handle_exception(result_container, e)
-            self.logger.exception('exception : {0}'.format(e))
-
-    def get_default_tests(self):
-        tests = {}
-
-        tests['simple'] = {
-            'matrix': {'query': ('life', 'computer')},
-            'result_container': ['not_empty'],
-        }
-
-        if getattr(self.engine, 'paging', False):
-            tests['paging'] = {
-                'matrix': {'query': 'time', 'pageno': (1, 2, 3)},
-                'result_container': ['not_empty'],
-                'test': ['unique_results'],
-            }
-            if 'general' in self.engine.categories:
-                # avoid documentation about HTML tags (<time> and <input type="time">)
-                tests['paging']['matrix']['query'] = 'news'
-
-        if getattr(self.engine, 'time_range', False):
-            tests['time_range'] = {
-                'matrix': {'query': 'news', 'time_range': (None, 'day')},
-                'result_container': ['not_empty'],
-                'test': ['unique_results'],
-            }
-
-        if getattr(self.engine, 'traits', False):
-            tests['lang_fr'] = {
-                'matrix': {'query': 'paris', 'lang': 'fr'},
-                'result_container': ['not_empty', ('has_language', 'fr')],
-            }
-            tests['lang_en'] = {
-                'matrix': {'query': 'paris', 'lang': 'en'},
-                'result_container': ['not_empty', ('has_language', 'en')],
-            }
-
-        if getattr(self.engine, 'safesearch', False):
-            tests['safesearch'] = {'matrix': {'query': 'porn', 'safesearch': (0, 2)}, 'test': ['unique_results']}
-
-        return tests
+            self.logger.exception("exception : {0}".format(e))
diff --git a/searx/search/processors/online_currency.py b/searx/search/processors/online_currency.py
index 4a56fd05c..c79374f51 100644
--- a/searx/search/processors/online_currency.py
+++ b/searx/search/processors/online_currency.py
@@ -1,42 +1,71 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Processors for engine-type: ``online_currency``
+"""Processor used for ``online_currency`` engines."""
 
-"""
+import typing as t
 
 import unicodedata
 import re
 
+import flask_babel
+import babel
+
 from searx.data import CURRENCIES
-from .online import OnlineProcessor
+from .online import OnlineProcessor, OnlineParams
 
-parser_re = re.compile('.*?(\\d+(?:\\.\\d+)?) ([^.0-9]+) (?:in|to) ([^.0-9]+)', re.I)
+if t.TYPE_CHECKING:
+    from .abstract import EngineProcessor
+    from searx.search.models import SearchQuery
 
 
-def normalize_name(name: str):
-    name = name.strip()
-    name = name.lower().replace('-', ' ').rstrip('s')
-    name = re.sub(' +', ' ', name)
-    return unicodedata.normalize('NFKD', name).lower()
+search_syntax = re.compile(r".*?(\d+(?:\.\d+)?) ([^.0-9]+) (?:in|to) ([^.0-9]+)", re.I)
+"""Search syntax used for from/to currency (e.g. ``10 usd to eur``)"""
+
+
+class CurrenciesParams(t.TypedDict):
+    """Currencies request parameters."""
+
+    amount: float
+    """Currency amount to be converted"""
+
+    to_iso4217: str
+    """ISO_4217_ alpha code of the currency used as the basis for conversion.
+
+    .. _ISO_4217: https://en.wikipedia.org/wiki/ISO_4217
+    """
+
+    from_iso4217: str
+    """ISO_4217_ alpha code of the currency to be converted."""
+
+    from_name: str
+    """Name of the currency used as the basis for conversion."""
+
+    to_name: str
+    """Name of the currency of the currency to be converted."""
+
+
+class OnlineCurrenciesParams(CurrenciesParams, OnlineParams):  # pylint: disable=duplicate-bases
+    """Request parameters of a ``online_currency`` engine."""
 
 
 class OnlineCurrencyProcessor(OnlineProcessor):
     """Processor class used by ``online_currency`` engines."""
 
-    engine_type = 'online_currency'
+    engine_type: str = "online_currency"
 
-    def initialize(self):
+    def initialize(self, callback: t.Callable[["EngineProcessor", bool], bool]):
         CURRENCIES.init()
-        super().initialize()
+        super().initialize(callback)
 
-    def get_params(self, search_query, engine_category):
-        """Returns a set of :ref:`request params <engine request online_currency>`
-        or ``None`` if search query does not match to :py:obj:`parser_re`."""
+    def get_params(self, search_query: "SearchQuery", engine_category: str) -> OnlineCurrenciesParams | None:
+        """Returns a dictionary with the :ref:`request params <engine request
+        online_currency>` (:py:obj:`OnlineCurrenciesParams`).  ``None`` is
+        returned if the search query does not match :py:obj:`search_syntax`."""
 
-        params = super().get_params(search_query, engine_category)
-        if params is None:
-            return None
+        online_params: OnlineParams | None = super().get_params(search_query, engine_category)
 
-        m = parser_re.match(search_query.query)
+        if online_params is None:
+            return None
+        m = search_syntax.match(search_query.query)
         if not m:
             return None
 
@@ -46,22 +75,46 @@ class OnlineCurrencyProcessor(OnlineProcessor):
         except ValueError:
             return None
 
-        from_currency = CURRENCIES.name_to_iso4217(normalize_name(from_currency))
-        to_currency = CURRENCIES.name_to_iso4217(normalize_name(to_currency))
+        # most often $ stands for USD
+        if from_currency == "$":
+            from_currency = "$ us"
 
-        params['amount'] = amount
-        params['from'] = from_currency
-        params['to'] = to_currency
-        params['from_name'] = CURRENCIES.iso4217_to_name(from_currency, "en")
-        params['to_name'] = CURRENCIES.iso4217_to_name(to_currency, "en")
-        return params
+        if to_currency == "$":
+            to_currency = "$ us"
+
+        from_iso4217 = from_currency
+        if not CURRENCIES.is_iso4217(from_iso4217):
+            from_iso4217 = CURRENCIES.name_to_iso4217(_normalize_name(from_currency))
 
-    def get_default_tests(self):
-        tests = {}
+        to_iso4217 = to_currency
+        if not CURRENCIES.is_iso4217(to_iso4217):
+            to_iso4217 = CURRENCIES.name_to_iso4217(_normalize_name(to_currency))
 
-        tests['currency'] = {
-            'matrix': {'query': '1337 usd in rmb'},
-            'result_container': ['has_answer'],
+        if from_iso4217 is None or to_iso4217 is None:
+            return None
+
+        ui_locale = flask_babel.get_locale() or babel.Locale.parse("en")
+        from_name: str = CURRENCIES.iso4217_to_name(
+            from_iso4217, ui_locale.language
+        )  # pyright: ignore[reportAssignmentType]
+        to_name: str = CURRENCIES.iso4217_to_name(
+            to_iso4217, ui_locale.language
+        )  # pyright: ignore[reportAssignmentType]
+
+        params: OnlineCurrenciesParams = {
+            **online_params,
+            "amount": amount,
+            "from_iso4217": from_iso4217,
+            "to_iso4217": to_iso4217,
+            "from_name": from_name,
+            "to_name": to_name,
         }
 
-        return tests
+        return params
+
+
+def _normalize_name(name: str):
+    name = name.strip()
+    name = name.lower().replace("-", " ")
+    name = re.sub(" +", " ", name)
+    return unicodedata.normalize("NFKD", name).lower()
diff --git a/searx/search/processors/online_dictionary.py b/searx/search/processors/online_dictionary.py
index 968c180d0..5827296c6 100644
--- a/searx/search/processors/online_dictionary.py
+++ b/searx/search/processors/online_dictionary.py
@@ -1,60 +1,102 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Processors for engine-type: ``online_dictionary``
-
-"""
+"""Processor used for ``online_dictionary`` engines."""
 
+import typing as t
 import re
 
-from searx.utils import is_valid_lang
-from .online import OnlineProcessor
+from searx.sxng_locales import sxng_locales
+from .online import OnlineProcessor, OnlineParams
+
+if t.TYPE_CHECKING:
+    from searx.search.models import SearchQuery
+
+search_syntax = re.compile(r".*?([a-z]+)-([a-z]+) (.+)$", re.I)
+"""Search syntax used for from/to language (e.g. ``en-de``)"""
+
+FromToType: t.TypeAlias = tuple[bool, str, str]
+"""Type of a language descriptions in the context of a ``online_dictionary``."""
+
+
+class DictParams(t.TypedDict):
+    """Dictionary request parameters."""
+
+    from_lang: FromToType
+    """Language from which is to be translated."""
+
+    to_lang: FromToType
+    """Language to translate into."""
 
-parser_re = re.compile('.*?([a-z]+)-([a-z]+) (.+)$', re.I)
+    query: str
+    """Search term, cleaned of search syntax (*from-to* has been removed)."""
+
+
+class OnlineDictParams(DictParams, OnlineParams):  # pylint: disable=duplicate-bases
+    """Request parameters of a ``online_dictionary`` engine."""
 
 
 class OnlineDictionaryProcessor(OnlineProcessor):
-    """Processor class used by ``online_dictionary`` engines."""
+    """Processor class for ``online_dictionary`` engines."""
 
-    engine_type = 'online_dictionary'
+    engine_type: str = "online_dictionary"
 
-    def get_params(self, search_query, engine_category):
-        """Returns a set of :ref:`request params <engine request online_dictionary>` or
-        ``None`` if search query does not match to :py:obj:`parser_re`.
-        """
-        params = super().get_params(search_query, engine_category)
-        if params is None:
-            return None
+    def get_params(self, search_query: "SearchQuery", engine_category: str) -> OnlineDictParams | None:
+        """Returns a dictionary with the :ref:`request params <engine request
+        online_dictionary>` (:py:obj:`OnlineDictParams`).  ``None`` is returned
+        if the search query does not match :py:obj:`search_syntax`."""
 
-        m = parser_re.match(search_query.query)
+        online_params: OnlineParams | None = super().get_params(search_query, engine_category)
+        if online_params is None:
+            return None
+        m = search_syntax.match(search_query.query)
         if not m:
             return None
 
         from_lang, to_lang, query = m.groups()
-
-        from_lang = is_valid_lang(from_lang)
-        to_lang = is_valid_lang(to_lang)
-
+        from_lang = _get_lang_descr(from_lang)
+        to_lang = _get_lang_descr(to_lang)
         if not from_lang or not to_lang:
             return None
 
-        params['from_lang'] = from_lang
-        params['to_lang'] = to_lang
-        params['query'] = query
+        params: OnlineDictParams = {
+            **online_params,
+            "from_lang": from_lang,
+            "to_lang": to_lang,
+            "query": query,
+        }
 
         return params
 
-    def get_default_tests(self):
-        tests = {}
-
-        if getattr(self.engine, 'paging', False):
-            tests['translation_paging'] = {
-                'matrix': {'query': 'en-es house', 'pageno': (1, 2, 3)},
-                'result_container': ['not_empty', ('one_title_contains', 'house')],
-                'test': ['unique_results'],
-            }
-        else:
-            tests['translation'] = {
-                'matrix': {'query': 'en-es house'},
-                'result_container': ['not_empty', ('one_title_contains', 'house')],
-            }
-
-        return tests
+
+def _get_lang_descr(lang: str) -> FromToType | None:
+    """Returns language's code and language's english name if argument ``lang``
+    describes a language known by SearXNG, otherwise ``None``.
+
+    Examples:
+
+    .. code:: python
+
+        >>> _get_lang_descr("zz")
+        None
+        >>> _get_lang_descr("uk")
+        (True, "uk", "ukrainian")
+        >>> _get_lang_descr(b"uk")
+        (True, "uk", "ukrainian")
+        >>> _get_lang_descr("en")
+        (True, "en", "english")
+        >>> _get_lang_descr("Español")
+        (True, "es", "spanish")
+        >>> _get_lang_descr("Spanish")
+        (True, "es", "spanish")
+
+    """
+    lang = lang.lower()
+    is_abbr = len(lang) == 2
+    if is_abbr:
+        for l in sxng_locales:
+            if l[0][:2] == lang:
+                return (True, l[0][:2], l[3].lower())
+        return None
+    for l in sxng_locales:
+        if l[1].lower() == lang or l[3].lower() == lang:
+            return (True, l[0][:2], l[3].lower())
+    return None
diff --git a/searx/search/processors/online_url_search.py b/searx/search/processors/online_url_search.py
index 3db970df0..d4841a7f9 100644
--- a/searx/search/processors/online_url_search.py
+++ b/searx/search/processors/online_url_search.py
@@ -1,45 +1,64 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Processors for engine-type: ``online_url_search``
-
-"""
+"""Processor used for ``online_url_search`` engines."""
 
+import typing as t
 import re
-from .online import OnlineProcessor
 
-re_search_urls = {
-    'http': re.compile(r'https?:\/\/[^ ]*'),
-    'ftp': re.compile(r'ftps?:\/\/[^ ]*'),
-    'data:image': re.compile('data:image/[^; ]*;base64,[^ ]*'),
+from .online import OnlineProcessor, OnlineParams
+
+if t.TYPE_CHECKING:
+    from .abstract import EngineProcessor
+    from searx.search.models import SearchQuery
+
+
+search_syntax = {
+    "http": re.compile(r"https?:\/\/[^ ]*"),
+    "ftp": re.compile(r"ftps?:\/\/[^ ]*"),
+    "data:image": re.compile("data:image/[^; ]*;base64,[^ ]*"),
 }
+"""Search syntax used for a URL search."""
+
+
+class UrlParams(t.TypedDict):
+    """URL request parameters."""
+
+    search_urls: dict[str, str | None]
+
+
+class OnlineUrlSearchParams(UrlParams, OnlineParams):  # pylint: disable=duplicate-bases
+    """Request parameters of a ``online_url_search`` engine."""
 
 
 class OnlineUrlSearchProcessor(OnlineProcessor):
     """Processor class used by ``online_url_search`` engines."""
 
-    engine_type = 'online_url_search'
+    engine_type: str = "online_url_search"
 
-    def get_params(self, search_query, engine_category):
-        """Returns a set of :ref:`request params <engine request online>` or ``None`` if
-        search query does not match to :py:obj:`re_search_urls`.
-        """
+    def get_params(self, search_query: "SearchQuery", engine_category: str) -> OnlineUrlSearchParams | None:
+        """Returns a dictionary with the :ref:`request params <engine request
+        online_currency>` (:py:obj:`OnlineUrlSearchParams`).  ``None`` is
+        returned if the search query does not match :py:obj:`search_syntax`."""
 
-        params = super().get_params(search_query, engine_category)
-        if params is None:
+        online_params: OnlineParams | None = super().get_params(search_query, engine_category)
+        if online_params is None:
             return None
 
-        url_match = False
-        search_urls = {}
+        search_urls: dict[str, str | None] = {}
+        has_match: bool = False
 
-        for k, v in re_search_urls.items():
-            m = v.search(search_query.query)
-            v = None
+        for url_schema, url_re in search_syntax.items():
+            search_urls[url_schema] = None
+            m = url_re.search(search_query.query)
             if m:
-                url_match = True
-                v = m[0]
-            search_urls[k] = v
+                has_match = True
+                search_urls[url_schema] = m[0]
 
-        if not url_match:
+        if not has_match:
             return None
 
-        params['search_urls'] = search_urls
+        params: OnlineUrlSearchParams = {
+            **online_params,
+            "search_urls": search_urls,
+        }
+
         return params