[mod] client/simple: client plugins (#5406)

* [mod] client/simple: client plugins

Defines a new interface for client side *"plugins"* that coexist with server
side plugin system. Each plugin (e.g., `InfiniteScroll`) extends the base
`ts Plugin`. Client side plugins are independent and lazy‑loaded via `router.ts`
when their `load()` conditions are met. On each navigation request, all
applicable plugins are instanced.

Since these are client side plugins, we can only invoke them once DOM is fully
loaded. E.g. `Calculator` will not render a new `answer` block until fully
loaded and executed.

For some plugins, we might want to handle its availability in `settings.yml`
and toggle in UI, like we do for server side plugins. In that case, we extend
`py Plugin` instancing only the information and then checking client side if
[`settings.plugins`](https://github.com/inetol/searxng/blob/1ad832b1dc33f3f388da361ff2459b05dc86a164/client/simple/src/js/toolkit.ts#L134)
array has the plugin id.

* [mod] client/simple: rebuild static

1 files changed, 9 insertions, 214 deletions

diff --git a/searx/plugins/calculator.py b/searx/plugins/calculator.py
index 4e318a1e6..e815a6ebf 100644
--- a/searx/plugins/calculator.py
+++ b/searx/plugins/calculator.py
@@ -1,31 +1,19 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Calculate mathematical expressions using :py:obj:`ast.parse` (mode="eval")."""
+# pylint: disable=missing-module-docstring
 
-import typing
+import typing as t
 
-import ast
-import math
-import re
-import operator
-import multiprocessing
+from flask_babel import gettext  # pyright: ignore[reportUnknownVariableType]
 
-import babel
-import babel.numbers
-from flask_babel import gettext
-
-from searx.result_types import EngineResults
 from searx.plugins import Plugin, PluginInfo
 
-if typing.TYPE_CHECKING:
-    from searx.search import SearchWithPlugins
-    from searx.extended_types import SXNG_Request
+if t.TYPE_CHECKING:
     from searx.plugins import PluginCfg
 
 
+@t.final
 class SXNGPlugin(Plugin):
-    """Plugin converts strings to different hash digests.  The results are
-    displayed in area for the "answers".
-    """
+    """Parses and solves mathematical expressions."""
 
     id = "calculator"
 
@@ -34,200 +22,7 @@ class SXNGPlugin(Plugin):
 
         self.info = PluginInfo(
             id=self.id,
-            name=gettext("Basic Calculator"),
-            description=gettext("Calculate mathematical expressions via the search bar"),
-            preference_section="general",
+            name=gettext("Calculator"),
+            description=gettext("Parses and solves mathematical expressions."),
+            preference_section="query",
         )
-
-    def timeout_func(self, timeout, func, *args, **kwargs):
-        que = mp_fork.Queue()
-        p = mp_fork.Process(target=handler, args=(que, func, args), kwargs=kwargs)
-        p.start()
-        p.join(timeout=timeout)
-        ret_val = None
-        # pylint: disable=used-before-assignment,undefined-variable
-        if not p.is_alive():
-            ret_val = que.get()
-        else:
-            self.log.debug("terminate function (%s: %s // %s) after timeout is exceeded", func.__name__, args, kwargs)
-            p.terminate()
-        p.join()
-        p.close()
-        return ret_val
-
-    def post_search(self, request: "SXNG_Request", search: "SearchWithPlugins") -> EngineResults:
-        results = EngineResults()
-
-        # only show the result of the expression on the first page
-        if search.search_query.pageno > 1:
-            return results
-
-        query = search.search_query.query
-        # in order to avoid DoS attacks with long expressions, ignore long expressions
-        if len(query) > 100:
-            return results
-
-        # replace commonly used math operators with their proper Python operator
-        query = query.replace("x", "*").replace(":", "/")
-
-        # Is this a term that can be calculated?
-        word, constants = "", set()
-        for x in query:
-            # Alphabetic characters are defined as "Letters" in the Unicode
-            # character database and are the constants in an equation.
-            if x.isalpha():
-                word += x.strip()
-            elif word:
-                constants.add(word)
-                word = ""
-
-        # In the term of an arithmetic operation there should be no other
-        # alphabetic characters besides the constants
-        if constants - set(math_constants):
-            return results
-
-        # use UI language
-        ui_locale = babel.Locale.parse(request.preferences.get_value("locale"), sep="-")
-
-        # parse the number system in a localized way
-        def _decimal(match: re.Match) -> str:
-            val = match.string[match.start() : match.end()]
-            val = babel.numbers.parse_decimal(val, ui_locale, numbering_system="latn")
-            return str(val)
-
-        decimal = ui_locale.number_symbols["latn"]["decimal"]
-        group = ui_locale.number_symbols["latn"]["group"]
-        query = re.sub(f"[0-9]+[{decimal}|{group}][0-9]+[{decimal}|{group}]?[0-9]?", _decimal, query)
-
-        # in python, powers are calculated via **
-        query_py_formatted = query.replace("^", "**")
-
-        # Prevent the runtime from being longer than 50 ms
-        res = self.timeout_func(0.05, _eval_expr, query_py_formatted)
-        if res is None or res[0] == "":
-            return results
-
-        res, is_boolean = res
-        if is_boolean:
-            res = "True" if res != 0 else "False"
-        else:
-            res = babel.numbers.format_decimal(res, locale=ui_locale)
-        results.add(results.types.Answer(answer=f"{search.search_query.query} = {res}"))
-
-        return results
-
-
-def _compare(ops: list[ast.cmpop], values: list[int | float]) -> int:
-    """
-    2 < 3 becomes ops=[ast.Lt] and values=[2,3]
-    2 < 3 <= 4 becomes ops=[ast.Lt, ast.LtE] and values=[2,3, 4]
-    """
-    for op, a, b in zip(ops, values, values[1:]):  # pylint: disable=invalid-name
-        if isinstance(op, ast.Eq) and a == b:
-            continue
-        if isinstance(op, ast.NotEq) and a != b:
-            continue
-        if isinstance(op, ast.Lt) and a < b:
-            continue
-        if isinstance(op, ast.LtE) and a <= b:
-            continue
-        if isinstance(op, ast.Gt) and a > b:
-            continue
-        if isinstance(op, ast.GtE) and a >= b:
-            continue
-
-        # Ignore impossible ops:
-        # * ast.Is
-        # * ast.IsNot
-        # * ast.In
-        # * ast.NotIn
-
-        # the result is False for a and b and operation op
-        return 0
-    # the results for all the ops are True
-    return 1
-
-
-operators: dict[type, typing.Callable] = {
-    ast.Add: operator.add,
-    ast.Sub: operator.sub,
-    ast.Mult: operator.mul,
-    ast.Div: operator.truediv,
-    ast.Pow: operator.pow,
-    ast.BitXor: operator.xor,
-    ast.BitOr: operator.or_,
-    ast.BitAnd: operator.and_,
-    ast.USub: operator.neg,
-    ast.RShift: operator.rshift,
-    ast.LShift: operator.lshift,
-    ast.Mod: operator.mod,
-    ast.Compare: _compare,
-}
-
-
-math_constants = {
-    'e': math.e,
-    'pi': math.pi,
-}
-
-
-# with multiprocessing.get_context("fork") we are ready for Py3.14 (by emulating
-# the old behavior "fork") but it will not solve the core problem of fork, nor
-# will it remove the deprecation warnings in py3.12 & py3.13.  Issue is
-# ddiscussed here: https://github.com/searxng/searxng/issues/4159
-mp_fork = multiprocessing.get_context("fork")
-
-
-def _eval_expr(expr):
-    """
-    Evaluates the given textual expression.
-
-    Returns a tuple of (numericResult, isBooleanResult).
-
-    >>> _eval_expr('2^6')
-    64, False
-    >>> _eval_expr('2**6')
-    64, False
-    >>> _eval_expr('1 + 2*3**(4^5) / (6 + -7)')
-    -5.0, False
-    >>> _eval_expr('1 < 3')
-    1, True
-    >>> _eval_expr('5 < 3')
-    0, True
-    >>> _eval_expr('17 == 11+1+5 == 7+5+5')
-    1, True
-    """
-    try:
-        root_expr = ast.parse(expr, mode='eval').body
-        return _eval(root_expr), isinstance(root_expr, ast.Compare)
-
-    except (SyntaxError, TypeError, ZeroDivisionError):
-        # Expression that can't be evaluated (i.e. not a math expression)
-        return "", False
-
-
-def _eval(node):
-    if isinstance(node, ast.Constant) and isinstance(node.value, (int, float)):
-        return node.value
-
-    if isinstance(node, ast.BinOp):
-        return operators[type(node.op)](_eval(node.left), _eval(node.right))
-
-    if isinstance(node, ast.UnaryOp):
-        return operators[type(node.op)](_eval(node.operand))
-
-    if isinstance(node, ast.Compare):
-        return _compare(node.ops, [_eval(node.left)] + [_eval(c) for c in node.comparators])
-
-    if isinstance(node, ast.Name) and node.id in math_constants:
-        return math_constants[node.id]
-
-    raise TypeError(node)
-
-
-def handler(q: multiprocessing.Queue, func, args, **kwargs):  # pylint:disable=invalid-name
-    try:
-        q.put(func(*args, **kwargs))
-    except:
-        q.put(None)
-        raise