# SPDX-License-Identifier: AGPL-3.0-or-later
"""Load and initialize the ``engines``, see :py:func:`load_engines` and register
:py:obj:`engine_shortcuts`.

usage::

    load_engines( settings['engines'] )

"""

from __future__ import annotations

import sys
import copy
from os.path import realpath, dirname

from typing import Dict
import types
import inspect

from searx import logger, settings
from searx.enginelib import Engine
from searx.utils import load_module

logger = logger.getChild('engines')
ENGINE_DIR = dirname(realpath(__file__))
ENGINE_DEFAULT_ARGS = {
    # Common options in the engine module
    "engine_type": "online",
    "paging": False,
    "time_range_support": False,
    "safesearch": False,
    # settings.yml
    "categories": ["general"],
    "enable_http": False,
    "shortcut": "-",
    "timeout": settings["outgoing"]["request_timeout"],
    "display_error_messages": True,
    "disabled": False,
    "inactive": False,
    "about": {},
    "using_tor_proxy": False,
    "send_accept_language_header": False,
    "tokens": [],
    "max_page": 0,
}
# set automatically when an engine does not have any tab category
DEFAULT_CATEGORY = 'other'


# Defaults for the namespace of an engine module, see :py:func:`load_engine`

categories = {'general': []}
engines: Dict[str, Engine | types.ModuleType] = {}
engine_shortcuts = {}
"""Simple map of registered *shortcuts* to name of the engine (or ``None``).

::

    engine_shortcuts[engine.shortcut] = engine.name

:meta hide-value:
"""


def check_engine_module(module: types.ModuleType):
    # probe unintentional name collisions / for example name collisions caused
    # by import statements in the engine module ..

    # network: https://github.com/searxng/searxng/issues/762#issuecomment-1605323861
    obj = getattr(module, 'network', None)
    if obj and inspect.ismodule(obj):
        msg = f'type of {module.__name__}.network is a module ({obj.__name__}), expected a string'
        # logger.error(msg)
        raise TypeError(msg)


def load_engine(engine_data: dict) -> Engine | types.ModuleType | None:
    """Load engine from ``engine_data``.

    :param dict engine_data:  Attributes from YAML ``settings:engines/<engine>``
    :return: initialized namespace of the ``<engine>``.

    1. create a namespace and load module of the ``<engine>``
    2. update namespace with the defaults from :py:obj:`ENGINE_DEFAULT_ARGS`
    3. update namespace with values from ``engine_data``

    If engine *is active*, return namespace of the engine, otherwise return
    ``None``.

    This function also returns ``None`` if initialization of the namespace fails
    for one of the following reasons:

    - engine name contains underscore
    - engine name is not lowercase
    - required attribute is not set :py:func:`is_missing_required_attributes`

    """
    # pylint: disable=too-many-return-statements

    engine_name = engine_data.get('name')
    if engine_name is None:
        logger.error('An engine does not have a "name" field')
        return None
    if '_' in engine_name:
        logger.error('Engine name contains underscore: "{}"'.format(engine_name))
        return None

    if engine_name.lower() != engine_name:
        logger.warning('Engine name is not lowercase: "{}", converting to lowercase'.format(engine_name))
        engine_name = engine_name.lower()
        engine_data['name'] = engine_name

    # load_module
    module_name = engine_data.get('engine')
    if module_name is None:
        logger.error('The "engine" field is missing for the engine named "{}"'.format(engine_name))
        return None
    try:
        engine = load_module(module_name + '.py', ENGINE_DIR)
    except (SyntaxError, KeyboardInterrupt, SystemExit, SystemError, ImportError, RuntimeError):
        logger.exception('Fatal exception in engine "{}"'.format(module_name))
        sys.exit(1)
    except BaseException:
        logger.exception('Cannot load engine "{}"'.format(module_name))
        return None

    check_engine_module(engine)
    update_engine_attributes(engine, engine_data)
    update_attributes_for_tor(engine)

    # avoid cyclic imports
    # pylint: disable=import-outside-toplevel
    from searx.enginelib.traits import EngineTraitsMap

    trait_map = EngineTraitsMap.from_data()
    trait_map.set_traits(engine)

    if not is_engine_active(engine):
        return None

    if is_missing_required_attributes(engine):
        return None

    set_loggers(engine, engine_name)

    if not any(cat in settings['categories_as_tabs'] for cat in engine.categories):
        engine.categories.append(DEFAULT_CATEGORY)

    return engine


def set_loggers(engine, engine_name):
    # set the logger for engine
    engine.logger = logger.getChild(engine_name)
    # the engine may have load some other engines
    # may sure the logger is initialized
    # use sys.modules.copy() to avoid "RuntimeError: dictionary changed size during iteration"
    # see https://github.com/python/cpython/issues/89516
    # and https://docs.python.org/3.10/library/sys.html#sys.modules
    modules = sys.modules.copy()
    for module_name, module in modules.items():
        if (
            module_name.startswith("searx.engines")
            and module_name != "searx.engines.__init__"
            and not hasattr(module, "logger")
        ):
            module_engine_name = module_name.split(".")[-1]
            module.logger = logger.getChild(module_engine_name)  # type: ignore


def update_engine_attributes(engine: Engine | types.ModuleType, engine_data):
    # set engine attributes from engine_data
    for param_name, param_value in engine_data.items():
        if param_name == 'categories':
            if isinstance(param_value, str):
                param_value = list(map(str.strip, param_value.split(',')))
            engine.categories = param_value  # type: ignore
        elif hasattr(engine, 'about') and param_name == 'about':
            engine.about = {**engine.about, **engine_data['about']}  # type: ignore
        else:
            setattr(engine, param_name, param_value)

    # set default attributes
    for arg_name, arg_value in ENGINE_DEFAULT_ARGS.items():
        if not hasattr(engine, arg_name):
            setattr(engine, arg_name, copy.deepcopy(arg_value))


def update_attributes_for_tor(engine: Engine | types.ModuleType):
    if using_tor_proxy(engine) and hasattr(engine, 'onion_url'):
        engine.search_url = engine.onion_url + getattr(engine, 'search_path', '')  # type: ignore
        engine.timeout += settings['outgoing'].get('extra_proxy_timeout', 0)  # type: ignore


def is_missing_required_attributes(engine):
    """An attribute is required when its name doesn't start with ``_`` (underline).
    Required attributes must not be ``None``.

    """
    missing = False
    for engine_attr in dir(engine):
        if not engine_attr.startswith('_') and getattr(engine, engine_attr) is None:
            logger.error('Missing engine config attribute: "{0}.{1}"'.format(engine.name, engine_attr))
            missing = True
    return missing


def using_tor_proxy(engine: Engine | types.ModuleType):
    """Return True if the engine configuration declares to use Tor."""
    return settings['outgoing'].get('using_tor_proxy') or getattr(engine, 'using_tor_proxy', False)


def is_engine_active(engine: Engine | types.ModuleType):
    # check if engine is inactive
    if engine.inactive is True:
        return False

    # exclude onion engines if not using tor
    if 'onions' in engine.categories and not using_tor_proxy(engine):
        return False

    return True


def register_engine(engine: Engine | types.ModuleType):
    if engine.name in engines:
        logger.error('Engine config error: ambiguous name: {0}'.format(engine.name))
        sys.exit(1)
    engines[engine.name] = engine

    if engine.shortcut in engine_shortcuts:
        logger.error('Engine config error: ambiguous shortcut: {0}'.format(engine.shortcut))
        sys.exit(1)
    engine_shortcuts[engine.shortcut] = engine.name

    for category_name in engine.categories:
        categories.setdefault(category_name, []).append(engine)


def load_engines(engine_list):
    """usage: ``engine_list = settings['engines']``"""
    engines.clear()
    engine_shortcuts.clear()
    categories.clear()
    categories['general'] = []
    for engine_data in engine_list:
        engine = load_engine(engine_data)
        if engine:
            register_engine(engine)
    return engines