[fix] engine - yahoo: rewrite and fix issues

Languages are supported by mapping the language to a domain.  If domain is not
found in :py:obj:`lang2domain` URL ``<lang>.search.yahoo.com`` is used.

BTW: fix issue reported at https://github.com/searx/searx/issues/3020

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

3 files changed, 110 insertions, 101 deletions

diff --git a/docs/src/searx.engines.yahoo.rst b/docs/src/searx.engines.yahoo.rst
new file mode 100644
index 000000000..df08550ca
--- /dev/null
+++ b/docs/src/searx.engines.yahoo.rst
@@ -0,0 +1,8 @@
+.. _yahoo engine:
+
+============
+Yahoo Engine
+============
+
+.. automodule:: searx.engines.yahoo
+  :members:
diff --git a/searx/data/engines_languages.json b/searx/data/engines_languages.json
index a4b0a8a5d..2e57a8f9e 100644
--- a/searx/data/engines_languages.json
+++ b/searx/data/engines_languages.json
@@ -28418,7 +28418,7 @@
     "sv",
     "th",
     "tr",
-    "zh-CHS",
-    "zh-CHT"
+    "zh_chs",
+    "zh_cht"
   ]
 }
\ No newline at end of file
diff --git a/searx/engines/yahoo.py b/searx/engines/yahoo.py
index b02af518d..09d06aff0 100644
--- a/searx/engines/yahoo.py
+++ b/searx/engines/yahoo.py
@@ -1,12 +1,24 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 # lint: pylint
-"""Yahoo (Web)
+"""Yahoo Search (Web)
+
+Languages are supported by mapping the language to a domain.  If domain is not
+found in :py:obj:`lang2domain` URL ``<lang>.search.yahoo.com`` is used.
 
 """
 
-from urllib.parse import unquote, urlencode
+from urllib.parse import (
+    unquote,
+    urlencode,
+)
 from lxml import html
-from searx.utils import extract_text, extract_url, match_language, eval_xpath
+
+from searx.utils import (
+    eval_xpath_getindex,
+    eval_xpath_list,
+    extract_text,
+    match_language,
+)
 
 # about
 about = {
@@ -22,35 +34,78 @@ about = {
 categories = ['general']
 paging = True
 time_range_support = True
-
-# search-url
-base_url = 'https://search.yahoo.com/'
-search_url = 'search?{query}&b={offset}&fl=1&vl=lang_{lang}'
-search_url_with_time = 'search?{query}&b={offset}&fl=1&vl=lang_{lang}&age={age}&btf={btf}&fr2=time'
-
-supported_languages_url = 'https://search.yahoo.com/web/advanced'
-
-# specific xpath variables
-results_xpath = "//div[contains(concat(' ', normalize-space(@class), ' '), ' Sr ')]"
-url_xpath = './/h3/a/@href'
-title_xpath = './/h3/a'
-content_xpath = './/div[contains(@class, "compText")]'
-suggestion_xpath = "//div[contains(concat(' ', normalize-space(@class), ' '), ' AlsoTry ')]//a"
+supported_languages_url = 'https://search.yahoo.com/preferences/languages'
+"""Supported languages are read from Yahoo preference page."""
 
 time_range_dict = {
-    'day': ['1d', 'd'],
-    'week': ['1w', 'w'],
-    'month': ['1m', 'm']
+    'day': ('1d', 'd'),
+    'week': ('1w', 'w'),
+    'month': ('1m', 'm'),
 }
 
 language_aliases = {
-    'zh-CN': 'zh-CHS',
-    'zh-TW': 'zh-CHT',
-    'zh-HK': 'zh-CHT'
+    'zh-HK': 'zh_chs',
+    'zh-CN': 'zh_chs',  # dead since 2015 / routed to hk.search.yahoo.com
+    'zh-TW': 'zh_cht',
 }
 
-# remove yahoo-specific tracking-url
+lang2domain = {
+    'zh_chs' : 'hk.search.yahoo.com',
+    'zh_cht' : 'tw.search.yahoo.com',
+    'en'     : 'search.yahoo.com',
+
+    'bg'     : 'search.yahoo.com',
+    'cs'     : 'search.yahoo.com',
+    'da'     : 'search.yahoo.com',
+    'el'     : 'search.yahoo.com',
+    'et'     : 'search.yahoo.com',
+    'he'     : 'search.yahoo.com',
+    'hr'     : 'search.yahoo.com',
+    'ja'     : 'search.yahoo.com',
+    'ko'     : 'search.yahoo.com',
+    'sk'     : 'search.yahoo.com',
+    'sl'     : 'search.yahoo.com',
+
+}
+"""Map language to domain"""
+
+def _get_language(params):
+
+    lang = language_aliases.get(params['language'])
+    if lang is None:
+        lang = match_language(
+            params['language'], supported_languages, language_aliases
+        )
+    lang = lang.split('-')[0]
+    logger.debug("params['language']: %s --> %s" , params['language'], lang)
+    return lang
+
+def request(query, params):
+    """build request"""
+    offset = (params['pageno'] - 1) * 7 + 1
+    lang  =  _get_language(params)
+    age, btf = time_range_dict.get(
+        params['time_range'], ('', ''))
+
+    args = urlencode({
+        'p' : query,
+        'ei' : 'UTF-8',
+        'fl' : 1,
+        'vl' : 'lang_' + lang,
+        'btf' : btf,
+        'fr2' : 'time',
+        'age' : age,
+        'b' : offset,
+        'xargs' :0
+    })
+
+    domain = lang2domain.get(lang, '%s.search.yahoo.com' % lang)
+    params['url'] = 'https://%s/search?%s' % (domain, args)
+    return params
+
 def parse_url(url_string):
+    """remove yahoo-specific tracking-url"""
+
     endings = ['/RS', '/RK']
     endpositions = []
     start = url_string.find('http', url_string.find('/RU=') + 1)
@@ -66,73 +121,30 @@ def parse_url(url_string):
     end = min(endpositions)
     return unquote(url_string[start:end])
 
-def _get_url(query, offset, language, time_range):
-    if time_range in time_range_dict:
-        return base_url + search_url_with_time.format(
-            offset = offset,
-            query = urlencode({'p': query}),
-            lang = language,
-            age = time_range_dict[time_range][0],
-            btf = time_range_dict[time_range][1]
-        )
-    return base_url + search_url.format(
-        offset=offset,
-        query=urlencode({'p': query}),
-        lang=language
-    )
-
-def _get_language(params):
-    if params['language'] == 'all':
-        return 'en'
-
-    language = match_language(params['language'], supported_languages, language_aliases)
-    if language not in language_aliases.values():
-        language = language.split('-')[0]
-    language = language.replace('-', '_').lower()
-
-    return language
-
-
-# do search-request
-def request(query, params):
-    if params['time_range'] and params['time_range'] not in time_range_dict:
-        return params
-
-    offset = (params['pageno'] - 1) * 10 + 1
-    language = _get_language(params)
-
-    params['url'] = _get_url(query, offset, language, params['time_range'])
-
-    return params
-
-
-# get response from search-request
 def response(resp):
-    results = []
+    """parse response"""
 
+    results = []
     dom = html.fromstring(resp.text)
 
-    try:
-        results_num = int(
-            eval_xpath(
-                dom,
-                '//div[@class="compPagination"]/span[last()]/text()'
-            )[0].split()[0].replace(',', '')
-        )
-        results.append({'number_of_results': results_num})
-    except:  # pylint: disable=bare-except
-        pass
-
     # parse results
-    for result in eval_xpath(dom, results_xpath):
-        try:
-            url = parse_url(extract_url(eval_xpath(result, url_xpath), search_url))
-            title = extract_text(eval_xpath(result, title_xpath)[0])
+    for result in eval_xpath_list(dom, '//div[contains(@class,"algo-sr")]'):
+        url = eval_xpath_getindex(result, './/h3/a/@href', 0, default=None)
+        if url is None:
+            continue
+        url = parse_url(url)
 
-        except:  # pylint: disable=bare-except
+        title = eval_xpath_getindex(result, './/h3/a', 0, default=None)
+        if title is None:
             continue
+        offset = len(extract_text(title.xpath('span')))
+        title = extract_text(title)[offset:]
 
-        content = extract_text(eval_xpath(result, content_xpath)[0])
+        content = eval_xpath_getindex(
+            result, './/div[contains(@class, "compText")]', 0, default=''
+        )
+        if content:
+            content = extract_text(content)
 
         # append result
         results.append({
@@ -141,17 +153,10 @@ def response(resp):
             'content': content
         })
 
-    # if no suggestion found, return results
-    suggestions = eval_xpath(dom, suggestion_xpath)
-    if not suggestions:
-        return results
-
-    # parse suggestion
-    for suggestion in suggestions:
+    for suggestion in eval_xpath_list(dom, '//div[contains(@class, "AlsoTry")]'):
         # append suggestion
         results.append({'suggestion': extract_text(suggestion)})
 
-    # return results
     return results
 
 
@@ -159,13 +164,9 @@ def response(resp):
 def _fetch_supported_languages(resp):
     supported_languages = []
     dom = html.fromstring(resp.text)
-    options = eval_xpath(dom, '//div[@id="yschlang"]/span/label/input')
-    for option in options:
-        code_parts = eval_xpath(option, './@value')[0][5:].split('_')
-        if len(code_parts) == 2:
-            code = code_parts[0] + '-' + code_parts[1].upper()
-        else:
-            code = code_parts[0]
-        supported_languages.append(code)
+    offset = len('lang_')
+
+    for val in eval_xpath_list(dom, '//div[contains(@class, "lang-item")]/input/@value'):
+        supported_languages.append( val[offset:] )
 
     return supported_languages