searxng/searx/webapp.py

#!/usr/bin/env python
# SPDX-License-Identifier: AGPL-3.0-or-later
# lint: pylint
# pylint: disable=missing-function-docstring
"""WebbApp

"""
import hashlib
import hmac
import json
import os
import sys

from datetime import datetime, timedelta
from timeit import default_timer
from html import escape
from io import StringIO

import urllib
from urllib.parse import (
    urlencode,
    urlparse,
)

import httpx

from pygments import highlight
from pygments.lexers import get_lexer_by_name
from pygments.formatters import HtmlFormatter  # pylint: disable=no-name-in-module

from werkzeug.middleware.proxy_fix import ProxyFix
from werkzeug.serving import WSGIRequestHandler

import flask

from flask import (
    Flask,
    request,
    render_template,
    url_for,
    Response,
    make_response,
    redirect,
    send_from_directory,
)
from flask.ctx import has_request_context
from flask.json import jsonify

from babel.support import Translations
import flask_babel
from flask_babel import (
    Babel,
    gettext,
    format_date,
    format_decimal,
)

from searx import logger
from searx import brand
from searx import (
    settings,
    searx_debug,
)
from searx.settings_defaults import OUTPUT_FORMATS
from searx.exceptions import SearxParameterException
from searx.engines import (
    categories,
    engines,
    engine_shortcuts,
)
from searx.webutils import (
    UnicodeWriter,
    highlight_content,
    get_static_files,
    get_result_templates,
    get_themes,
    prettify_url,
    new_hmac,
    is_flask_run_cmdline,
)
from searx.webadapter import (
    get_search_query_from_webapp,
    get_selected_categories,
)
from searx.utils import (
    html_to_text,
    gen_useragent,
    dict_subset,
    match_language,
)
from searx.version import VERSION_STRING
from searx.query import RawTextQuery
from searx.plugins import plugins
from searx.plugins.oa_doi_rewrite import get_doi_resolver
from searx.preferences import (
    Preferences,
    ValidationException,
    LANGUAGE_CODES,
)
from searx.answerers import answerers
from searx.answerers import ask
from searx.metrics import (
    get_engines_stats,
    get_engine_errors,
    get_reliabilities,
    histogram,
    counter,
)

# renaming names from searx imports ...

from searx.autocomplete import search_autocomplete, backends as autocomplete_backends
from searx.languages import language_codes as languages
from searx.search import SearchWithPlugins, initialize as search_initialize
from searx.network import stream as http_stream
from searx.search.checker import get_result as checker_get_result
from searx.settings_loader import get_default_settings_path

# set Unix thread name
try:
    import setproctitle
except ImportError:
    pass
else:
    import threading
    old_thread_init = threading.Thread.__init__

    def new_thread_init(self, *args, **kwargs):
        # pylint: disable=protected-access, disable=c-extension-no-member
        old_thread_init(self, *args, **kwargs)
        setproctitle.setthreadtitle(self._name)
    threading.Thread.__init__ = new_thread_init

if sys.version_info[0] < 3:
    print('\033[1;31m Python2 is no longer supported\033[0m')
    sys.exit(1)

logger = logger.getChild('webapp')

# serve pages with HTTP/1.1
WSGIRequestHandler.protocol_version = "HTTP/{}".format(settings['server']['http_protocol_version'])

# check secret_key
if not searx_debug and settings['server']['secret_key'] == 'ultrasecretkey':
    logger.error('server.secret_key is not changed. Please use something else instead of ultrasecretkey.')
    sys.exit(1)

# about static
logger.debug('static directory is %s', settings['ui']['static_path'])
static_files = get_static_files(settings['ui']['static_path'])

# about templates
logger.debug('templates directory is %s', settings['ui']['templates_path'])
default_theme = settings['ui']['default_theme']
templates_path = settings['ui']['templates_path']
themes = get_themes(templates_path)
result_templates = get_result_templates(templates_path)
global_favicons = []
for indice, theme in enumerate(themes):
    global_favicons.append([])
    theme_img_path = os.path.join(settings['ui']['static_path'], 'themes', theme, 'img', 'icons')
    for (dirpath, dirnames, filenames) in os.walk(theme_img_path):
        global_favicons[indice].extend(filenames)

STATS_SORT_PARAMETERS = {
    'name': (False, 'name', ''),
    'score': (True, 'score', 0),
    'result_count': (True, 'result_count', 0),
    'time': (False, 'total', 0),
    'reliability': (False, 'reliability', 100),
}

# Flask app
app = Flask(
    __name__,
    static_folder=settings['ui']['static_path'],
    template_folder=templates_path
)

app.jinja_env.trim_blocks = True
app.jinja_env.lstrip_blocks = True
app.jinja_env.add_extension('jinja2.ext.loopcontrols')  # pylint: disable=no-member
app.secret_key = settings['server']['secret_key']

# see https://flask.palletsprojects.com/en/1.1.x/cli/
# True if "FLASK_APP=searx/webapp.py FLASK_ENV=development flask run"
flask_run_development = \
    os.environ.get("FLASK_APP") is not None\
    and os.environ.get("FLASK_ENV") == 'development'\
    and is_flask_run_cmdline()

# True if reload feature is activated of werkzeug, False otherwise (including uwsgi, etc..)
#  __name__ != "__main__" if searx.webapp is imported (make test, make docs, uwsgi...)
# see run() at the end of this file : searx_debug activates the reload feature.
werkzeug_reloader = flask_run_development or (searx_debug and __name__ == "__main__")

# initialize the engines except on the first run of the werkzeug server.
if not werkzeug_reloader\
   or (werkzeug_reloader and os.environ.get("WERKZEUG_RUN_MAIN") == "true"):
    search_initialize(enable_checker=True)

babel = Babel(app)

rtl_locales = ['ar', 'arc', 'bcc', 'bqi', 'ckb', 'dv', 'fa', 'fa_IR', 'glk', 'he',
               'ku', 'mzn', 'pnb', 'ps', 'sd', 'ug', 'ur', 'yi']
ui_locale_codes = [l.replace('_', '-') for l in settings['locales'].keys()]

# used when translating category names
_category_names = (gettext('files'),
                   gettext('general'),
                   gettext('music'),
                   gettext('social media'),
                   gettext('images'),
                   gettext('videos'),
                   gettext('it'),
                   gettext('news'),
                   gettext('map'),
                   gettext('onions'),
                   gettext('science'))

#
timeout_text = gettext('timeout')
parsing_error_text = gettext('parsing error')
http_protocol_error_text = gettext('HTTP protocol error')
network_error_text = gettext('network error')
exception_classname_to_text = {
    None: gettext('unexpected crash'),
    'timeout': timeout_text,
    'asyncio.TimeoutError': timeout_text,
    'httpx.TimeoutException': timeout_text,
    'httpx.ConnectTimeout': timeout_text,
    'httpx.ReadTimeout': timeout_text,
    'httpx.WriteTimeout': timeout_text,
    'httpx.HTTPStatusError': gettext('HTTP error'),
    'httpx.ConnectError': gettext("HTTP connection error"),
    'httpx.RemoteProtocolError': http_protocol_error_text,
    'httpx.LocalProtocolError': http_protocol_error_text,
    'httpx.ProtocolError': http_protocol_error_text,
    'httpx.ReadError': network_error_text,
    'httpx.WriteError': network_error_text,
    'httpx.ProxyError': gettext("proxy error"),
    'searx.exceptions.SearxEngineCaptchaException': gettext("CAPTCHA"),
    'searx.exceptions.SearxEngineTooManyRequestsException': gettext("too many requests"),
    'searx.exceptions.SearxEngineAccessDeniedException': gettext("access denied"),
    'searx.exceptions.SearxEngineAPIException': gettext("server API error"),
    'searx.exceptions.SearxEngineXPathException': parsing_error_text,
    'KeyError': parsing_error_text,
    'json.decoder.JSONDecodeError': parsing_error_text,
    'lxml.etree.ParserError': parsing_error_text,
}

_flask_babel_get_translations = flask_babel.get_translations


# monkey patch for flask_babel.get_translations
def _get_translations():
    if has_request_context() and request.form.get('use-translation') == 'oc':
        babel_ext = flask_babel.current_app.extensions['babel']
        return Translations.load(next(babel_ext.translation_directories), 'oc')

    return _flask_babel_get_translations()


flask_babel.get_translations = _get_translations


def _get_browser_or_settings_language(req, lang_list):
    for lang in req.headers.get("Accept-Language", "en").split(","):
        if ';' in lang:
            lang = lang.split(';')[0]
        if '-' in lang:
            lang_parts = lang.split('-')
            lang = "{}-{}".format(lang_parts[0], lang_parts[-1].upper())
        locale = match_language(lang, lang_list, fallback=None)
        if locale is not None:
            return locale
    return settings['search']['default_lang'] or 'en'


@babel.localeselector
def get_locale():
    if 'locale' in request.form\
       and request.form['locale'] in settings['locales']:
        # use locale from the form
        locale = request.form['locale']
        locale_source = 'form'
    elif request.preferences.get_value('locale') != '':
        # use locale from the preferences
        locale = request.preferences.get_value('locale')
        locale_source = 'preferences'
    else:
        # use local from the browser
        locale = _get_browser_or_settings_language(request, ui_locale_codes)
        locale = locale.replace('-', '_')
        locale_source = 'browser'

    # see _get_translations function
    # and https://github.com/searx/searx/pull/1863
    if locale == 'oc':
        request.form['use-translation'] = 'oc'
        locale = 'fr_FR'

    logger.debug(
        "%s uses locale `%s` from %s", urllib.parse.quote(request.url), locale, locale_source
    )

    return locale


# code-highlighter
@app.template_filter('code_highlighter')
def code_highlighter(codelines, language=None):
    if not language:
        language = 'text'

    try:
        # find lexer by programing language
        lexer = get_lexer_by_name(language, stripall=True)

    except Exception as e:  # pylint: disable=broad-except
        logger.exception(e, exc_info=True)
        # if lexer is not found, using default one
        lexer = get_lexer_by_name('text', stripall=True)

    html_code = ''
    tmp_code = ''
    last_line = None

    # parse lines
    for line, code in codelines:
        if not last_line:
            line_code_start = line

        # new codeblock is detected
        if last_line is not None and\
           last_line + 1 != line:

            # highlight last codepart
            formatter = HtmlFormatter(linenos='inline',
                                      linenostart=line_code_start,
                                      cssclass="code-highlight")
            html_code = html_code + highlight(tmp_code, lexer, formatter)

            # reset conditions for next codepart
            tmp_code = ''
            line_code_start = line

        # add codepart
        tmp_code += code + '\n'

        # update line
        last_line = line

    # highlight last codepart
    formatter = HtmlFormatter(linenos='inline', linenostart=line_code_start, cssclass="code-highlight")
    html_code = html_code + highlight(tmp_code, lexer, formatter)

    return html_code


# Extract domain from url
@app.template_filter('extract_domain')
def extract_domain(url):
    return urlparse(url)[1]


def get_base_url():
    return url_for('index', _external=True)


def get_current_theme_name(override=None):
    """Returns theme name.

    Checks in this order:
    1. override
    2. cookies
    3. settings"""

    if override and (override in themes or override == '__common__'):
        return override
    theme_name = request.args.get('theme', request.preferences.get_value('theme'))
    if theme_name not in themes:
        theme_name = default_theme
    return theme_name


def get_result_template(theme_name, template_name):
    themed_path = theme_name + '/result_templates/' + template_name
    if themed_path in result_templates:
        return themed_path
    return 'result_templates/' + template_name


def url_for_theme(endpoint, override_theme=None, **values):
    if endpoint == 'static' and values.get('filename'):
        theme_name = get_current_theme_name(override=override_theme)
        filename_with_theme = "themes/{}/{}".format(theme_name, values['filename'])
        if filename_with_theme in static_files:
            values['filename'] = filename_with_theme
    url = url_for(endpoint, **values)
    return url


def proxify(url):
    if url.startswith('//'):
        url = 'https:' + url

    if not settings.get('result_proxy'):
        return url

    url_params = dict(mortyurl=url.encode())

    if settings['result_proxy'].get('key'):
        url_params['mortyhash'] = hmac.new(settings['result_proxy']['key'],
                                           url.encode(),
                                           hashlib.sha256).hexdigest()

    return '{0}?{1}'.format(settings['result_proxy']['url'],
                            urlencode(url_params))


def image_proxify(url):

    if url.startswith('//'):
        url = 'https:' + url

    if not request.preferences.get_value('image_proxy'):
        return url

    if url.startswith('data:image/'):
        # 50 is an arbitrary number to get only the beginning of the image.
        partial_base64 = url[len('data:image/'):50].split(';')
        if len(partial_base64) == 2 \
           and partial_base64[0] in ['gif', 'png', 'jpeg', 'pjpeg', 'webp', 'tiff', 'bmp']\
           and partial_base64[1].startswith('base64,'):
            return url
        return None

    if settings.get('result_proxy'):
        return proxify(url)

    h = new_hmac(settings['server']['secret_key'], url.encode())

    return '{0}?{1}'.format(url_for('image_proxy'),
                            urlencode(dict(url=url.encode(), h=h)))


def get_translations():
    return {
        # when there is autocompletion
        'no_item_found': gettext('No item found')
    }


def render(template_name, override_theme=None, **kwargs):
    disabled_engines = request.preferences.engines.get_disabled()

    enabled_categories = set(category for engine_name in engines
                             for category in engines[engine_name].categories
                             if (engine_name, category) not in disabled_engines)

    if 'categories' not in kwargs:
        kwargs['categories'] = [x for x in
                                _get_ordered_categories()
                                if x in enabled_categories]

    if 'autocomplete' not in kwargs:
        kwargs['autocomplete'] = request.preferences.get_value('autocomplete')

    locale = request.preferences.get_value('locale')

    if locale in rtl_locales and 'rtl' not in kwargs:
        kwargs['rtl'] = True

    kwargs['searx_version'] = VERSION_STRING

    kwargs['method'] = request.preferences.get_value('method')

    kwargs['safesearch'] = str(request.preferences.get_value('safesearch'))

    kwargs['language_codes'] = languages
    if 'current_language' not in kwargs:
        kwargs['current_language'] = match_language(request.preferences.get_value('language'),
                                                    LANGUAGE_CODES)

    # override url_for function in templates
    kwargs['url_for'] = url_for_theme

    kwargs['image_proxify'] = image_proxify

    kwargs['proxify'] = proxify if settings.get('result_proxy', {}).get('url') else None
    kwargs['proxify_results'] = settings.get('result_proxy', {}).get('proxify_results', True)

    kwargs['opensearch_url'] = url_for('opensearch') + '?' \
        + urlencode({'method': kwargs['method'], 'autocomplete': kwargs['autocomplete']})

    kwargs['get_result_template'] = get_result_template

    kwargs['theme'] = get_current_theme_name(override=override_theme)

    kwargs['template_name'] = template_name

    kwargs['cookies'] = request.cookies

    kwargs['errors'] = request.errors

    kwargs['instance_name'] = settings['general']['instance_name']

    kwargs['results_on_new_tab'] = request.preferences.get_value('results_on_new_tab')

    kwargs['preferences'] = request.preferences

    kwargs['search_formats'] = [
        x for x in settings['search']['formats']
        if x != 'html']

    kwargs['brand'] = brand

    kwargs['translations'] = json.dumps(get_translations(), separators=(',', ':'))

    kwargs['scripts'] = set()
    kwargs['endpoint'] = 'results' if 'q' in kwargs else request.endpoint
    for plugin in request.user_plugins:
        for script in plugin.js_dependencies:
            kwargs['scripts'].add(script)

    kwargs['styles'] = set()
    for plugin in request.user_plugins:
        for css in plugin.css_dependencies:
            kwargs['styles'].add(css)

    start_time = default_timer()
    result = render_template(
        '{}/{}'.format(kwargs['theme'], template_name), **kwargs)
    request.render_time += default_timer() - start_time  # pylint: disable=assigning-non-slot

    return result


def _get_ordered_categories():
    ordered_categories = list(settings['ui']['categories_order'])
    ordered_categories.extend(x for x in sorted(categories.keys()) if x not in ordered_categories)
    return ordered_categories


@app.before_request
def pre_request():
    request.start_time = default_timer()  # pylint: disable=assigning-non-slot
    request.render_time = 0  # pylint: disable=assigning-non-slot
    request.timings = []  # pylint: disable=assigning-non-slot
    request.errors = []  # pylint: disable=assigning-non-slot

    preferences = Preferences(themes, list(categories.keys()), engines, plugins)  # pylint: disable=redefined-outer-name
    user_agent = request.headers.get('User-Agent', '').lower()
    if 'webkit' in user_agent and 'android' in user_agent:
        preferences.key_value_settings['method'].value = 'GET'
    request.preferences = preferences  # pylint: disable=assigning-non-slot

    try:
        preferences.parse_dict(request.cookies)

    except Exception as e:  # pylint: disable=broad-except
        logger.exception(e, exc_info=True)
        request.errors.append(gettext('Invalid settings, please edit your preferences'))

    # merge GET, POST vars
    # request.form
    request.form = dict(request.form.items())  # pylint: disable=assigning-non-slot
    for k, v in request.args.items():
        if k not in request.form:
            request.form[k] = v

    if request.form.get('preferences'):
        preferences.parse_encoded_data(request.form['preferences'])
    else:
        try:
            preferences.parse_dict(request.form)
        except Exception as e:  # pylint: disable=broad-except
            logger.exception(e, exc_info=True)
            request.errors.append(gettext('Invalid settings'))

    # init search language and locale
    if not preferences.get_value("language"):
        preferences.parse_dict({"language": _get_browser_or_settings_language(request, LANGUAGE_CODES)})
    if not preferences.get_value("locale"):
        preferences.parse_dict({"locale": get_locale()})

    # request.user_plugins
    request.user_plugins = []  # pylint: disable=assigning-non-slot
    allowed_plugins = preferences.plugins.get_enabled()
    disabled_plugins = preferences.plugins.get_disabled()
    for plugin in plugins:
        if ((plugin.default_on and plugin.id not in disabled_plugins)
                or plugin.id in allowed_plugins):
            request.user_plugins.append(plugin)


@app.after_request
def add_default_headers(response):
    # set default http headers
    for header, value in settings['server']['default_http_headers'].items():
        if header in response.headers:
            continue
        response.headers[header] = value
    return response


@app.after_request
def post_request(response):
    total_time = default_timer() - request.start_time
    timings_all = ['total;dur=' + str(round(total_time * 1000, 3)),
                   'render;dur=' + str(round(request.render_time * 1000, 3))]
    if len(request.timings) > 0:
        timings = sorted(request.timings, key=lambda v: v['total'])
        timings_total = ['total_' + str(i) + '_' + v['engine'] +
                         ';dur=' + str(round(v['total'] * 1000, 3)) for i, v in enumerate(timings)]
        timings_load = ['load_' + str(i) + '_' + v['engine'] +
                        ';dur=' + str(round(v['load'] * 1000, 3)) for i, v in enumerate(timings) if v.get('load')]
        timings_all = timings_all + timings_total + timings_load
    response.headers.add('Server-Timing', ', '.join(timings_all))
    return response


def index_error(output_format, error_message):
    if output_format == 'json':
        return Response(json.dumps({'error': error_message}),
                        mimetype='application/json')
    if output_format == 'csv':
        response = Response('', mimetype='application/csv')
        cont_disp = 'attachment;Filename=searx.csv'
        response.headers.add('Content-Disposition', cont_disp)
        return response

    if output_format == 'rss':
        response_rss = render(
            'opensearch_response_rss.xml',
            results=[],
            q=request.form['q'] if 'q' in request.form else '',
            number_of_results=0,
            base_url=get_base_url(),
            error_message=error_message,
            override_theme='__common__',
        )
        return Response(response_rss, mimetype='text/xml')

    # html
    request.errors.append(gettext('search error'))
    return render(
        'index.html',
        selected_categories=get_selected_categories(request.preferences, request.form),
    )


@app.route('/', methods=['GET', 'POST'])
def index():
    """Render index page."""

    # UI
    advanced_search = request.preferences.get_value('advanced_search')

    # redirect to search if there's a query in the request
    if request.form.get('q'):
        query = ('?' + request.query_string.decode()) if request.query_string else ''
        return redirect(url_for('search') + query, 308)

    return render(
        'index.html',
        selected_categories=get_selected_categories(request.preferences, request.form),
        advanced_search=advanced_search,
    )


@app.route('/search', methods=['GET', 'POST'])
def search():
    """Search query in q and return results.

    Supported outputs: html, json, csv, rss.
    """
    # pylint: disable=too-many-locals, too-many-return-statements, too-many-branches
    # pylint: disable=too-many-statements

    # output_format
    output_format = request.form.get('format', 'html')
    if output_format not in OUTPUT_FORMATS:
        output_format = 'html'

    if output_format not in settings['search']['formats']:
        flask.abort(403)

    # check if there is query (not None and not an empty string)
    if not request.form.get('q'):
        if output_format == 'html':
            return render(
                'index.html',
                advanced_search=request.preferences.get_value('advanced_search'),
                selected_categories=get_selected_categories(request.preferences, request.form),
            )
        return index_error(output_format, 'No query'), 400

    # search
    search_query = None
    raw_text_query = None
    result_container = None
    try:
        search_query, raw_text_query, _, _ = get_search_query_from_webapp(request.preferences, request.form)
        # search = Search(search_query) #  without plugins
        search = SearchWithPlugins(search_query, request.user_plugins, request)  # pylint: disable=redefined-outer-name

        result_container = search.search()

    except SearxParameterException as e:
        logger.exception('search error: SearxParameterException')
        return index_error(output_format, e.message), 400
    except Exception as e:  # pylint: disable=broad-except
        logger.exception(e, exc_info=True)
        return index_error(output_format, gettext('search error')), 500

    # results
    results = result_container.get_ordered_results()
    number_of_results = result_container.results_number()
    if number_of_results < result_container.results_length():
        number_of_results = 0

    # checkin for a external bang
    if result_container.redirect_url:
        return redirect(result_container.redirect_url)

    # Server-Timing header
    request.timings = result_container.get_timings()  # pylint: disable=assigning-non-slot

    # output
    for result in results:
        if output_format == 'html':
            if 'content' in result and result['content']:
                result['content'] = highlight_content(escape(result['content'][:1024]), search_query.query)
            if 'title' in result and result['title']:
                result['title'] = highlight_content(escape(result['title'] or ''), search_query.query)
        else:
            if result.get('content'):
                result['content'] = html_to_text(result['content']).strip()
            # removing html content and whitespace duplications
            result['title'] = ' '.join(html_to_text(result['title']).strip().split())

        if 'url' in result:
            result['pretty_url'] = prettify_url(result['url'])

        # TODO, check if timezone is calculated right  # pylint: disable=fixme
        if result.get('publishedDate'):  # do not try to get a date from an empty string or a None type
            try:  # test if publishedDate >= 1900 (datetime module bug)
                result['pubdate'] = result['publishedDate'].strftime('%Y-%m-%d %H:%M:%S%z')
            except ValueError:
                result['publishedDate'] = None
            else:
                if result['publishedDate'].replace(tzinfo=None) >= datetime.now() - timedelta(days=1):
                    timedifference = datetime.now() - result['publishedDate'].replace(tzinfo=None)
                    minutes = int((timedifference.seconds / 60) % 60)
                    hours = int(timedifference.seconds / 60 / 60)
                    if hours == 0:
                        result['publishedDate'] = gettext('{minutes} minute(s) ago').format(minutes=minutes)
                    else:
                        result['publishedDate'] = gettext(
                            '{hours} hour(s), {minutes} minute(s) ago').format(
                                hours=hours, minutes=minutes
                            )
                else:
                    result['publishedDate'] = format_date(result['publishedDate'])

    if output_format == 'json':
        return Response(
            json.dumps(
                {
                    'query': search_query.query,
                    'number_of_results': number_of_results,
                    'results': results,
                    'answers': list(result_container.answers),
                    'corrections': list(result_container.corrections),
                    'infoboxes': result_container.infoboxes,
                    'suggestions': list(result_container.suggestions),
                    'unresponsive_engines': __get_translated_errors(result_container.unresponsive_engines)
                },
                default = lambda item: list(item) if isinstance(item, set) else item
            ),
            mimetype='application/json'
        )

    if output_format == 'csv':
        csv = UnicodeWriter(StringIO())
        keys = ('title', 'url', 'content', 'host', 'engine', 'score', 'type')
        csv.writerow(keys)
        for row in results:
            row['host'] = row['parsed_url'].netloc
            row['type'] = 'result'
            csv.writerow([row.get(key, '') for key in keys])
        for a in result_container.answers:
            row = {'title': a, 'type': 'answer'}
            csv.writerow([row.get(key, '') for key in keys])
        for a in result_container.suggestions:
            row = {'title': a, 'type': 'suggestion'}
            csv.writerow([row.get(key, '') for key in keys])
        for a in result_container.corrections:
            row = {'title': a, 'type': 'correction'}
            csv.writerow([row.get(key, '') for key in keys])
        csv.stream.seek(0)
        response = Response(csv.stream.read(), mimetype='application/csv')
        cont_disp = 'attachment;Filename=searx_-_{0}.csv'.format(search_query.query)
        response.headers.add('Content-Disposition', cont_disp)
        return response

    if output_format == 'rss':
        response_rss = render(
            'opensearch_response_rss.xml',
            results=results,
            answers=result_container.answers,
            corrections=result_container.corrections,
            suggestions=result_container.suggestions,
            q=request.form['q'],
            number_of_results=number_of_results,
            base_url=get_base_url(),
            override_theme='__common__',
        )
        return Response(response_rss, mimetype='text/xml')

    # HTML output format

    # suggestions: use RawTextQuery to get the suggestion URLs with the same bang
    suggestion_urls = list(map(lambda suggestion: {
                               'url': raw_text_query.changeQuery(suggestion).getFullQuery(),
                               'title': suggestion
                               },
                               result_container.suggestions))

    correction_urls = list(map(lambda correction: {
                               'url': raw_text_query.changeQuery(correction).getFullQuery(),
                               'title': correction
                               },
                               result_container.corrections))
    #
    return render(
        'results.html',
        results=results,
        q=request.form['q'],
        selected_categories=search_query.categories,
        pageno=search_query.pageno,
        time_range=search_query.time_range,
        number_of_results=format_decimal(number_of_results),
        suggestions=suggestion_urls,
        answers=result_container.answers,
        corrections=correction_urls,
        infoboxes=result_container.infoboxes,
        engine_data=result_container.engine_data,
        paging=result_container.paging,
        unresponsive_engines=__get_translated_errors(result_container.unresponsive_engines),
        current_language=match_language(search_query.lang,
                                        LANGUAGE_CODES,
                                        fallback=request.preferences.get_value("language")),
        base_url=get_base_url(),
        theme=get_current_theme_name(),
        favicons=global_favicons[themes.index(get_current_theme_name())],
        timeout_limit=request.form.get('timeout_limit', None)
    )


def __get_translated_errors(unresponsive_engines):
    translated_errors = []
    # make a copy unresponsive_engines to avoid "RuntimeError: Set changed size during iteration"
    # it happens when an engine modifies the ResultContainer after the search_multiple_requests method
    # has stopped waiting
    for unresponsive_engine in list(unresponsive_engines):
        error_user_text = exception_classname_to_text.get(unresponsive_engine[1])
        if not error_user_text:
            error_user_text = exception_classname_to_text[None]
        error_msg = gettext(error_user_text)
        if unresponsive_engine[2]:
            error_msg = "{} {}".format(error_msg, unresponsive_engine[2])
        if unresponsive_engine[3]:
            error_msg = gettext('Suspended') + ': ' + error_msg
        translated_errors.append((unresponsive_engine[0], error_msg))
    return sorted(translated_errors, key=lambda e: e[0])


@app.route('/about', methods=['GET'])
def about():
    """Render about page"""
    return render(
        'about.html',
    )


@app.route('/autocompleter', methods=['GET', 'POST'])
def autocompleter():
    """Return autocompleter results"""

    # run autocompleter
    results = []

    # set blocked engines
    disabled_engines = request.preferences.engines.get_disabled()

    # parse query
    raw_text_query = RawTextQuery(request.form.get('q', ''), disabled_engines)
    sug_prefix = raw_text_query.getQuery()

    # normal autocompletion results only appear if no inner results returned
    # and there is a query part
    if len(raw_text_query.autocomplete_list) == 0 and len(sug_prefix) > 0:

        # get language from cookie
        language = request.preferences.get_value('language')
        if not language or language == 'all':
            language = 'en'
        else:
            language = language.split('-')[0]

        # run autocompletion
        raw_results = search_autocomplete(
            request.preferences.get_value('autocomplete'), sug_prefix, language
        )
        for result in raw_results:
            # attention: this loop will change raw_text_query object and this is
            # the reason why the sug_prefix was stored before (see above)
            results.append(raw_text_query.changeQuery(result).getFullQuery())

    if len(raw_text_query.autocomplete_list) > 0:
        for autocomplete_text in raw_text_query.autocomplete_list:
            results.append(raw_text_query.get_autocomplete_full_query(autocomplete_text))

    for answers in ask(raw_text_query):
        for answer in answers:
            results.append(str(answer['answer']))

    if request.headers.get('X-Requested-With') == 'XMLHttpRequest':
        # the suggestion request comes from the searx search form
        suggestions = json.dumps(results)
        mimetype = 'application/json'
    else:
        # the suggestion request comes from browser's URL bar
        suggestions = json.dumps([sug_prefix, results])
        mimetype = 'application/x-suggestions+json'

    return Response(suggestions, mimetype=mimetype)


@app.route('/preferences', methods=['GET', 'POST'])
def preferences():
    """Render preferences page && save user preferences"""

    # pylint: disable=too-many-locals, too-many-return-statements, too-many-branches
    # pylint: disable=too-many-statements

    # save preferences
    if request.method == 'POST':
        resp = make_response(redirect(url_for('index', _external=True)))
        try:
            request.preferences.parse_form(request.form)
        except ValidationException:
            request.errors.append(gettext('Invalid settings, please edit your preferences'))
            return resp
        return request.preferences.save(resp)

    # render preferences
    image_proxy = request.preferences.get_value('image_proxy')  # pylint: disable=redefined-outer-name
    disabled_engines = request.preferences.engines.get_disabled()
    allowed_plugins = request.preferences.plugins.get_enabled()

    # stats for preferences page
    filtered_engines = dict(filter(lambda kv: (kv[0], request.preferences.validate_token(kv[1])), engines.items()))

    engines_by_category = {}
    for c in categories:
        engines_by_category[c] = [e for e in categories[c] if e.name in filtered_engines]
        # sort the engines alphabetically since the order in settings.yml is meaningless.
        list.sort(engines_by_category[c], key=lambda e: e.name)

    # get first element [0], the engine time,
    # and then the second element [1] : the time (the first one is the label)
    stats = {}  # pylint: disable=redefined-outer-name
    max_rate95 = 0
    for _, e in filtered_engines.items():
        h = histogram('engine', e.name, 'time', 'total')
        median = round(h.percentage(50), 1) if h.count > 0 else None
        rate80 = round(h.percentage(80), 1) if h.count > 0 else None
        rate95 = round(h.percentage(95), 1) if h.count > 0 else None

        max_rate95 = max(max_rate95, rate95 or 0)

        result_count_sum = histogram('engine', e.name, 'result', 'count').sum
        successful_count = counter('engine', e.name, 'search', 'count', 'successful')
        result_count = int(result_count_sum / float(successful_count)) if successful_count else 0

        stats[e.name] = {
            'time': median,
            'rate80': rate80,
            'rate95': rate95,
            'warn_timeout': e.timeout > settings['outgoing']['request_timeout'],
            'supports_selected_language': _is_selected_language_supported(e, request.preferences),
            'result_count': result_count,
        }
    # end of stats

    # reliabilities
    reliabilities = {}
    engine_errors = get_engine_errors(filtered_engines)
    checker_results = checker_get_result()
    checker_results = checker_results['engines'] \
        if checker_results['status'] == 'ok' and 'engines' in checker_results else {}
    for _, e in filtered_engines.items():
        checker_result = checker_results.get(e.name, {})
        checker_success = checker_result.get('success', True)
        errors = engine_errors.get(e.name) or []
        if counter('engine', e.name, 'search', 'count', 'sent') == 0:
            # no request
            reliablity = None
        elif checker_success and not errors:
            reliablity = 100
        elif 'simple' in checker_result.get('errors', {}):
            # the basic (simple) test doesn't work: the engine is broken accoding to the checker
            # even if there is no exception
            reliablity = 0
        else:
            reliablity = 100 - sum([error['percentage'] for error in errors if not error.get('secondary')])

        reliabilities[e.name] = {
            'reliablity': reliablity,
            'errors': [],
            'checker': checker_results.get(e.name, {}).get('errors', {}).keys(),
        }
        # keep the order of the list checker_results[e.name]['errors'] and deduplicate.
        # the first element has the highest percentage rate.
        reliabilities_errors = []
        for error in errors:
            error_user_text = None
            if error.get('secondary') or 'exception_classname' not in error:
                continue
            error_user_text = exception_classname_to_text.get(error.get('exception_classname'))
            if not error:
                error_user_text = exception_classname_to_text[None]
            if error_user_text not in reliabilities_errors:
                reliabilities_errors.append(error_user_text)
        reliabilities[e.name]['errors'] = reliabilities_errors

    # supports
    supports = {}
    for _, e in filtered_engines.items():
        supports_selected_language = _is_selected_language_supported(e, request.preferences)
        safesearch = e.safesearch
        time_range_support = e.time_range_support
        for checker_test_name in checker_results.get(e.name, {}).get('errors', {}):
            if supports_selected_language and checker_test_name.startswith('lang_'):
                supports_selected_language = '?'
            elif safesearch and checker_test_name == 'safesearch':
                safesearch = '?'
            elif time_range_support and checker_test_name == 'time_range':
                time_range_support = '?'
        supports[e.name] = {
            'supports_selected_language': supports_selected_language,
            'safesearch': safesearch,
            'time_range_support': time_range_support,
        }

    #
    return render('preferences.html',
                  selected_categories=get_selected_categories(request.preferences, request.form),
                  all_categories=_get_ordered_categories(),
                  locales=settings['locales'],
                  current_locale=request.preferences.get_value("locale"),
                  image_proxy=image_proxy,
                  engines_by_category=engines_by_category,
                  stats=stats,
                  max_rate95=max_rate95,
                  reliabilities=reliabilities,
                  supports=supports,
                  answerers=[{'info': a.self_info(), 'keywords': a.keywords} for a in answerers],
                  disabled_engines=disabled_engines,
                  autocomplete_backends=autocomplete_backends,
                  shortcuts={y: x for x, y in engine_shortcuts.items()},
                  themes=themes,
                  plugins=plugins,
                  doi_resolvers=settings['doi_resolvers'],
                  current_doi_resolver=get_doi_resolver(request.args, request.preferences.get_value('doi_resolver')),
                  allowed_plugins=allowed_plugins,
                  theme=get_current_theme_name(),
                  preferences_url_params=request.preferences.get_as_url_params(),
                  base_url=get_base_url(),
                  locked_preferences=settings['preferences']['lock'],
                  preferences=True)


def _is_selected_language_supported(engine, preferences):  # pylint: disable=redefined-outer-name
    language = preferences.get_value('language')
    return (language == 'all'
            or match_language(language,
                              getattr(engine, 'supported_languages', []),
                              getattr(engine, 'language_aliases', {}), None))


@app.route('/image_proxy', methods=['GET'])
def image_proxy():
    # pylint: disable=too-many-return-statements

    url = request.args.get('url')

    if not url:
        return '', 400

    h = new_hmac(settings['server']['secret_key'], url.encode())

    if h != request.args.get('h'):
        return '', 400

    maximum_size = 5 * 1024 * 1024

    try:
        headers = dict_subset(request.headers, {'If-Modified-Since', 'If-None-Match'})
        headers['User-Agent'] = gen_useragent()
        stream = http_stream(
            method='GET',
            url=url,
            headers=headers,
            timeout=settings['outgoing']['request_timeout'],
            allow_redirects=True,
            max_redirects=20)

        resp = next(stream)
        content_length = resp.headers.get('Content-Length')
        if content_length and content_length.isdigit() and int(content_length) > maximum_size:
            return 'Max size', 400

        if resp.status_code == 304:
            return '', resp.status_code

        if resp.status_code != 200:
            logger.debug('image-proxy: wrong response code: {0}'.format(resp.status_code))
            if resp.status_code >= 400:
                return '', resp.status_code
            return '', 400

        if not resp.headers.get('content-type', '').startswith('image/'):
            logger.debug('image-proxy: wrong content-type: {0}'.format(resp.headers.get('content-type')))
            return '', 400

        headers = dict_subset(resp.headers, {'Content-Length', 'Length', 'Date', 'Last-Modified', 'Expires', 'Etag'})

        total_length = 0

        def forward_chunk():
            nonlocal total_length
            for chunk in stream:
                total_length += len(chunk)
                if total_length > maximum_size:
                    break
                yield chunk

        return Response(forward_chunk(), mimetype=resp.headers['Content-Type'], headers=headers)
    except httpx.HTTPError:
        return '', 400


@app.route('/stats', methods=['GET'])
def stats():
    """Render engine statistics page."""
    sort_order = request.args.get('sort', default='name', type=str)
    selected_engine_name = request.args.get('engine', default=None, type=str)

    filtered_engines = dict(filter(lambda kv: (kv[0], request.preferences.validate_token(kv[1])), engines.items()))
    if selected_engine_name:
        if selected_engine_name not in filtered_engines:
            selected_engine_name = None
        else:
            filtered_engines = [selected_engine_name]

    checker_results = checker_get_result()
    checker_results = checker_results['engines'] \
        if checker_results['status'] == 'ok' and 'engines' in checker_results else {}

    engine_stats = get_engines_stats(filtered_engines)
    engine_reliabilities = get_reliabilities(filtered_engines, checker_results)

    if sort_order not in STATS_SORT_PARAMETERS:
        sort_order = 'name'

    reverse, key_name, default_value = STATS_SORT_PARAMETERS[sort_order]

    def get_key(engine_stat):
        reliability = engine_reliabilities.get(engine_stat['name']).get('reliablity', 0)
        reliability_order = 0 if reliability else 1
        if key_name == 'reliability':
            key = reliability
            reliability_order = 0
        else:
            key = engine_stat.get(key_name) or default_value
            if reverse:
                reliability_order = 1 - reliability_order
        return (reliability_order, key, engine_stat['name'])

    engine_stats['time'] = sorted(engine_stats['time'], reverse=reverse, key=get_key)
    return render(
        'stats.html',
        sort_order=sort_order,
        engine_stats=engine_stats,
        engine_reliabilities=engine_reliabilities,
        selected_engine_name=selected_engine_name,
    )


@app.route('/stats/errors', methods=['GET'])
def stats_errors():
    filtered_engines = dict(filter(lambda kv: (kv[0], request.preferences.validate_token(kv[1])), engines.items()))
    result = get_engine_errors(filtered_engines)
    return jsonify(result)


@app.route('/stats/checker', methods=['GET'])
def stats_checker():
    result = checker_get_result()
    return jsonify(result)


@app.route('/robots.txt', methods=['GET'])
def robots():
    return Response("""User-agent: *
Allow: /
Allow: /about
Disallow: /stats
Disallow: /preferences
Disallow: /*?*q=*
""", mimetype='text/plain')


@app.route('/opensearch.xml', methods=['GET'])
def opensearch():
    method = 'post'

    if request.preferences.get_value('method') == 'GET':
        method = 'get'

    # chrome/chromium only supports HTTP GET....
    if request.headers.get('User-Agent', '').lower().find('webkit') >= 0:
        method = 'get'

    ret = render(
        'opensearch.xml',
        opensearch_method=method,
        override_theme='__common__'
    )

    resp = Response(response=ret,
                    status=200,
                    mimetype="application/opensearchdescription+xml")
    return resp


@app.route('/favicon.ico')
def favicon():
    return send_from_directory(
        os.path.join(
            app.root_path,
            settings['ui']['static_path'],
            'themes',
            get_current_theme_name(),
            'img'),
        'favicon.png',
        mimetype = 'image/vnd.microsoft.icon'
    )

@app.route('/clear_cookies')
def clear_cookies():
    resp = make_response(redirect(url_for('index', _external=True)))
    for cookie_name in request.cookies:
        resp.delete_cookie(cookie_name)
    return resp


@app.route('/config')
def config():
    """Return configuration in JSON format."""
    _engines = []
    for name, engine in engines.items():
        if not request.preferences.validate_token(engine):
            continue

        supported_languages = engine.supported_languages
        if isinstance(engine.supported_languages, dict):
            supported_languages = list(engine.supported_languages.keys())

        _engines.append({
            'name': name,
            'categories': engine.categories,
            'shortcut': engine.shortcut,
            'enabled': not engine.disabled,
            'paging': engine.paging,
            'language_support': engine.language_support,
            'supported_languages': supported_languages,
            'safesearch': engine.safesearch,
            'time_range_support': engine.time_range_support,
            'timeout': engine.timeout
        })

    _plugins = []
    for _ in plugins:
        _plugins.append({'name': _.name, 'enabled': _.default_on})

    return jsonify({
        'categories': list(categories.keys()),
        'engines': _engines,
        'plugins': _plugins,
        'instance_name': settings['general']['instance_name'],
        'locales': settings['locales'],
        'default_locale': settings['ui']['default_locale'],
        'autocomplete': settings['search']['autocomplete'],
        'safe_search': settings['search']['safe_search'],
        'default_theme': settings['ui']['default_theme'],
        'version': VERSION_STRING,
        'brand': {
            'CONTACT_URL': brand.CONTACT_URL,
            'GIT_URL': brand.GIT_URL,
            'DOCS_URL': brand.DOCS_URL
        },
        'doi_resolvers': list(settings['doi_resolvers'].keys()),
        'default_doi_resolver': settings['default_doi_resolver'],
    })


@app.errorhandler(404)
def page_not_found(_e):
    return render('404.html'), 404


def run():
    logger.debug('starting webserver on %s:%s', settings['server']['bind_address'], settings['server']['port'])
    app.run(
        debug=searx_debug,
        use_debugger=searx_debug,
        port=settings['server']['port'],
        host=settings['server']['bind_address'],
        threaded=True,
        extra_files=[
            get_default_settings_path()
        ],
    )


class ReverseProxyPathFix:
    '''Wrap the application in this middleware and configure the
    front-end server to add these headers, to let you quietly bind
    this to a URL other than / and to an HTTP scheme that is
    different than what is used locally.

    http://flask.pocoo.org/snippets/35/

    In nginx:
    location /myprefix {
        proxy_pass http://127.0.0.1:8000;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Scheme $scheme;
        proxy_set_header X-Script-Name /myprefix;
        }

    :param wsgi_app: the WSGI application
    '''
    # pylint: disable=too-few-public-methods

    def __init__(self, wsgi_app):

        self.wsgi_app = wsgi_app
        self.script_name = None
        self.scheme = None
        self.server = None

        if settings['server']['base_url']:

            # If base_url is specified, then these values from are given
            # preference over any Flask's generics.

            base_url = urlparse(settings['server']['base_url'])
            self.script_name = base_url.path
            if self.script_name.endswith('/'):
                # remove trailing slash to avoid infinite redirect on the index
                # see https://github.com/searx/searx/issues/2729
                self.script_name = self.script_name[:-1]
            self.scheme = base_url.scheme
            self.server = base_url.netloc

    def __call__(self, environ, start_response):
        script_name = self.script_name or environ.get('HTTP_X_SCRIPT_NAME', '')
        if script_name:
            environ['SCRIPT_NAME'] = script_name
            path_info = environ['PATH_INFO']
            if path_info.startswith(script_name):
                environ['PATH_INFO'] = path_info[len(script_name):]

        scheme = self.scheme or environ.get('HTTP_X_SCHEME', '')
        if scheme:
            environ['wsgi.url_scheme'] = scheme

        server = self.server or environ.get('HTTP_X_FORWARDED_HOST', '')
        if server:
            environ['HTTP_HOST'] = server
        return self.wsgi_app(environ, start_response)


application = app
# patch app to handle non root url-s behind proxy & wsgi
app.wsgi_app = ReverseProxyPathFix(ProxyFix(application.wsgi_app))

if __name__ == "__main__":
    run()