[mod] Archlinux Wiki: improved request API & upgrade to data_type: traits_v1

re-implementation of the Archlinux Wiki:

- fetch_traits(): fetch languages, wiki URLs and title arguments
- add content field to the result list
- add documentation

Wikis from wiki.archlinux.fr, wiki.archlinux.ro, archtr.org/wiki do no longer
exists (has been merged in the main wiki).

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

4 files changed, 178 insertions, 110 deletions

diff --git a/docs/src/searx.engine.archlinux.rst b/docs/src/searx.engine.archlinux.rst
new file mode 100644
index 000000000..be48b1859
--- /dev/null
+++ b/docs/src/searx.engine.archlinux.rst
@@ -0,0 +1,9 @@
+.. _archlinux engine:
+
+==========
+Arch Linux
+==========
+
+.. automodule:: searx.engines.archlinux
+  :members:
+
diff --git a/searx/data/engine_traits.json b/searx/data/engine_traits.json
index f0e6ef045..8f416a636 100644
--- a/searx/data/engine_traits.json
+++ b/searx/data/engine_traits.json
@@ -1,4 +1,57 @@
 {
+  "arch linux wiki": {
+    "all_locale": null,
+    "custom": {
+      "title": {
+        "de": "Spezial:Suche",
+        "fa": "\u0648\u06cc\u0698\u0647:\u062c\u0633\u062a\u062c\u0648",
+        "ja": "\u7279\u5225:\u691c\u7d22",
+        "zh": "Special:\u641c\u7d22"
+      },
+      "wiki_netloc": {
+        "de": "wiki.archlinux.de",
+        "fa": "wiki.archusers.ir",
+        "ja": "wiki.archlinux.jp",
+        "zh": "wiki.archlinuxcn.org"
+      }
+    },
+    "data_type": "traits_v1",
+    "languages": {
+      "ar": "\u0627\u0644\u0639\u0631\u0628\u064a\u0629",
+      "bg": "\u0411\u044a\u043b\u0433\u0430\u0440\u0441\u043a\u0438",
+      "bs": "Bosanski",
+      "cs": "\u010ce\u0161tina",
+      "da": "Dansk",
+      "de": "Deutsch",
+      "el": "\u0395\u03bb\u03bb\u03b7\u03bd\u03b9\u03ba\u03ac",
+      "en": "English",
+      "es": "Espa\u00f1ol",
+      "fa": "\u0641\u0627\u0631\u0633\u06cc",
+      "fi": "Suomi",
+      "fr": "Fran\u00e7ais",
+      "he": "\u05e2\u05d1\u05e8\u05d9\u05ea",
+      "hr": "Hrvatski",
+      "hu": "Magyar",
+      "id": "Bahasa Indonesia",
+      "it": "Italiano",
+      "ja": "\u65e5\u672c\u8a9e",
+      "ko": "\ud55c\uad6d\uc5b4",
+      "lt": "Lietuvi\u0173",
+      "nl": "Nederlands",
+      "pl": "Polski",
+      "pt": "Portugu\u00eas",
+      "ru": "\u0420\u0443\u0441\u0441\u043a\u0438\u0439",
+      "sk": "Sloven\u010dina",
+      "sr": "\u0421\u0440\u043f\u0441\u043a\u0438 / srpski",
+      "sv": "Svenska",
+      "th": "\u0e44\u0e17\u0e22",
+      "tr": "T\u00fcrk\u00e7e",
+      "uk": "\u0423\u043a\u0440\u0430\u0457\u043d\u0441\u044c\u043a\u0430",
+      "zh": "\u4e2d\u6587\uff08\u7e41\u9ad4\uff09"
+    },
+    "regions": {},
+    "supported_languages": {}
+  },
   "bing": {
     "all_locale": null,
     "custom": {},
diff --git a/searx/engines/archlinux.py b/searx/engines/archlinux.py
index b5e426107..56c3b447f 100644
--- a/searx/engines/archlinux.py
+++ b/searx/engines/archlinux.py
@@ -1,15 +1,32 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
+# lint: pylint
 """
- Arch Linux Wiki
+Arch Linux Wiki
+~~~~~~~~~~~~~~~
+
+This implementation does not use a official API: Mediawiki provides API, but
+Arch Wiki blocks access to it.
 
- API: Mediawiki provides API, but Arch Wiki blocks access to it
 """
 
-from urllib.parse import urlencode, urljoin
-from lxml import html
+from typing import TYPE_CHECKING
+from urllib.parse import urlencode, urljoin, urlparse
+import lxml
+import babel
+
+from searx import network
 from searx.utils import extract_text, eval_xpath_list, eval_xpath_getindex
+from searx.enginelib.traits import EngineTraits
+from searx.locales import language_tag
+
+if TYPE_CHECKING:
+    import logging
+
+    logger: logging.Logger
+
+traits: EngineTraits
+
 
-# about
 about = {
     "website": 'https://wiki.archlinux.org/',
     "wikidata_id": 'Q101445877',
@@ -22,125 +39,113 @@ about = {
 # engine dependent config
 categories = ['it', 'software wikis']
 paging = True
-base_url = 'https://wiki.archlinux.org'
-
-# xpath queries
-xpath_results = '//ul[@class="mw-search-results"]/li'
-xpath_link = './/div[@class="mw-search-result-heading"]/a'
-
-
-# cut 'en' from 'en-US', 'de' from 'de-CH', and so on
-def locale_to_lang_code(locale):
-    if locale.find('-') >= 0:
-        locale = locale.split('-')[0]
-    return locale
-
-
-# wikis for some languages were moved off from the main site, we need to make
-# requests to correct URLs to be able to get results in those languages
-lang_urls = {
-    # fmt: off
-    'all': {
-        'base': 'https://wiki.archlinux.org',
-        'search': '/index.php?title=Special:Search&offset={offset}&{query}'
-    },
-    'de': {
-        'base': 'https://wiki.archlinux.de',
-        'search': '/index.php?title=Spezial:Suche&offset={offset}&{query}'
-    },
-    'fr': {
-        'base': 'https://wiki.archlinux.fr',
-        'search': '/index.php?title=Spécial:Recherche&offset={offset}&{query}'
-    },
-    'ja': {
-        'base': 'https://wiki.archlinuxjp.org',
-        'search': '/index.php?title=特別:検索&offset={offset}&{query}'
-    },
-    'ro': {
-        'base': 'http://wiki.archlinux.ro',
-        'search': '/index.php?title=Special:Căutare&offset={offset}&{query}'
-    },
-    'tr': {
-        'base': 'http://archtr.org/wiki',
-        'search': '/index.php?title=Özel:Ara&offset={offset}&{query}'
-    }
-    # fmt: on
-}
-
-
-# get base & search URLs for selected language
-def get_lang_urls(language):
-    if language in lang_urls:
-        return lang_urls[language]
-    return lang_urls['all']
-
-
-# Language names to build search requests for
-# those languages which are hosted on the main site.
-main_langs = {
-    'ar': 'العربية',
-    'bg': 'Български',
-    'cs': 'Česky',
-    'da': 'Dansk',
-    'el': 'Ελληνικά',
-    'es': 'Español',
-    'he': 'עברית',
-    'hr': 'Hrvatski',
-    'hu': 'Magyar',
-    'it': 'Italiano',
-    'ko': '한국어',
-    'lt': 'Lietuviškai',
-    'nl': 'Nederlands',
-    'pl': 'Polski',
-    'pt': 'Português',
-    'ru': 'Русский',
-    'sl': 'Slovenský',
-    'th': 'ไทย',
-    'uk': 'Українська',
-    'zh': '简体中文',
-}
-supported_languages = dict(lang_urls, **main_langs)
+main_wiki = 'wiki.archlinux.org'
 
 
-# do search-request
 def request(query, params):
-    # translate the locale (e.g. 'en-US') to language code ('en')
-    language = locale_to_lang_code(params['language'])
-
-    # if our language is hosted on the main site, we need to add its name
-    # to the query in order to narrow the results to that language
-    if language in main_langs:
-        query += ' (' + main_langs[language] + ')'
 
-    # prepare the request parameters
-    query = urlencode({'search': query})
+    sxng_lang = params['searxng_locale'].split('-')[0]
+    netloc = traits.custom['wiki_netloc'].get(sxng_lang, main_wiki)
+    title = traits.custom['title'].get(sxng_lang, 'Special:Search')
+    base_url = 'https://' + netloc + '/index.php?'
     offset = (params['pageno'] - 1) * 20
 
-    # get request URLs for our language of choice
-    urls = get_lang_urls(language)
-    search_url = urls['base'] + urls['search']
-
-    params['url'] = search_url.format(query=query, offset=offset)
+    if netloc == main_wiki:
+        eng_lang: str = traits.get_language(sxng_lang, 'English')
+        query += ' (' + eng_lang + ')'
+    elif netloc == 'wiki.archlinuxcn.org':
+        base_url = 'https://' + netloc + '/wzh/index.php?'
+
+    args = {
+        'search': query,
+        'title': title,
+        'limit': 20,
+        'offset': offset,
+        'profile': 'default',
+    }
 
+    params['url'] = base_url + urlencode(args)
     return params
 
 
-# get response from search-request
 def response(resp):
-    # get the base URL for the language in which request was made
-    language = locale_to_lang_code(resp.search_params['language'])
-    base_url = get_lang_urls(language)['base']
 
     results = []
+    dom = lxml.html.fromstring(resp.text)
 
-    dom = html.fromstring(resp.text)
+    # get the base URL for the language in which request was made
+    sxng_lang = resp.search_params['searxng_locale'].split('-')[0]
+    netloc = traits.custom['wiki_netloc'].get(sxng_lang, main_wiki)
+    base_url = 'https://' + netloc + '/index.php?'
+
+    for result in eval_xpath_list(dom, '//ul[@class="mw-search-results"]/li'):
+        link = eval_xpath_getindex(result, './/div[@class="mw-search-result-heading"]/a', 0)
+        content = extract_text(result.xpath('.//div[@class="searchresult"]'))
+        results.append(
+            {
+                'url': urljoin(base_url, link.get('href')),
+                'title': extract_text(link),
+                'content': content,
+            }
+        )
 
-    # parse results
-    for result in eval_xpath_list(dom, xpath_results):
-        link = eval_xpath_getindex(result, xpath_link, 0)
-        href = urljoin(base_url, link.attrib.get('href'))
-        title = extract_text(link)
+    return results
 
-        results.append({'url': href, 'title': title})
 
-    return results
+def fetch_traits(engine_traits: EngineTraits):
+    """Fetch languages from Archlinix-Wiki.  The location of the Wiki address of a
+    language is mapped in a :py:obj:`custom field
+    <searx.enginelib.traits.EngineTraits.custom>` (``wiki_netloc``).  Depending
+    on the location, the ``title`` argument in the request is translated.
+
+    .. code:: python
+
+       "custom": {
+         "wiki_netloc": {
+           "de": "wiki.archlinux.de",
+            # ...
+           "zh": "wiki.archlinuxcn.org"
+         }
+         "title": {
+           "de": "Spezial:Suche",
+            # ...
+           "zh": "Special:\u641c\u7d22"
+         },
+       },
+
+    """
+
+    engine_traits.custom['wiki_netloc'] = {}
+    engine_traits.custom['title'] = {}
+
+    title_map = {
+        'de': 'Spezial:Suche',
+        'fa': 'ویژه:جستجو',
+        'ja': '特別:検索',
+        'zh': 'Special:搜索',
+    }
+
+    resp = network.get('https://wiki.archlinux.org/')
+    if not resp.ok:
+        print("ERROR: response from wiki.archlinix.org is not OK.")
+
+    dom = lxml.html.fromstring(resp.text)
+    for a in eval_xpath_list(dom, "//a[@class='interlanguage-link-target']"):
+
+        sxng_tag = language_tag(babel.Locale.parse(a.get('lang'), sep='-'))
+        # zh_Hans --> zh
+        sxng_tag = sxng_tag.split('_')[0]
+
+        netloc = urlparse(a.get('href')).netloc
+        if netloc != 'wiki.archlinux.org':
+            title = title_map.get(sxng_tag)
+            if not title:
+                print("ERROR: title tag from %s (%s) is unknown" % (netloc, sxng_tag))
+                continue
+            engine_traits.custom['wiki_netloc'][sxng_tag] = netloc
+            engine_traits.custom['title'][sxng_tag] = title
+
+        eng_tag = extract_text(eval_xpath_list(a, ".//span"))
+        engine_traits.languages[sxng_tag] = eng_tag
+
+    engine_traits.languages['en'] = 'English'
diff --git a/searx/sxng_locales.py b/searx/sxng_locales.py
index b6ae85848..eedf664b0 100644
--- a/searx/sxng_locales.py
+++ b/searx/sxng_locales.py
@@ -81,6 +81,7 @@ sxng_locales = (
     ('ru-RU', 'Русский', 'Россия', 'Russian', '\U0001f1f7\U0001f1fa'),
     ('sk', 'Slovenčina', '', 'Slovak', '\U0001f310'),
     ('sl', 'Slovenščina', '', 'Slovenian', '\U0001f310'),
+    ('sr', 'Српски', '', 'Serbian', '\U0001f310'),
     ('sv', 'Svenska', '', 'Swedish', '\U0001f310'),
     ('sv-SE', 'Svenska', 'Sverige', 'Swedish', '\U0001f1f8\U0001f1ea'),
     ('th', 'ไทย', '', 'Thai', '\U0001f310'),