[enh] google scholar - python implementation of the engine

The old xpath configuration for google scholar did not work and is replaced by a
python implementation.

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

4 files changed, 300 insertions, 19 deletions

diff --git a/Makefile b/Makefile
index fbf5f94b8..4e451b7ca 100644
--- a/Makefile
+++ b/Makefile
@@ -195,7 +195,8 @@ PYLINT_FILES=\
 	searx/engines/google_videos.py \
 	searx/engines/google_images.py \
 	searx/engines/mediathekviewweb.py \
-	utils/fetch_external_bangs.py
+	utils/fetch_external_bangs.py \
+	searx/engines/google_scholar.py
 
 test.pylint: pyenvinstall
 	$(call cmd,pylint,$(PYLINT_FILES))
diff --git a/searx/data/engines_languages.json b/searx/data/engines_languages.json
index 324e4f3af..e6b41480c 100644
--- a/searx/data/engines_languages.json
+++ b/searx/data/engines_languages.json
@@ -25176,6 +25176,146 @@
       "name": "\u4e2d\u6587 (\u7e41\u9ad4)"
     }
   },
+  "google scholar": {
+    "af": {
+      "name": "Afrikaans"
+    },
+    "ar": {
+      "name": "\u0627\u0644\u0639\u0631\u0628\u064a\u0629"
+    },
+    "be": {
+      "name": "\u0431\u0435\u043b\u0430\u0440\u0443\u0441\u043a\u0430\u044f"
+    },
+    "bg": {
+      "name": "\u0431\u044a\u043b\u0433\u0430\u0440\u0441\u043a\u0438"
+    },
+    "ca": {
+      "name": "catal\u00e0"
+    },
+    "cs": {
+      "name": "\u010de\u0161tina"
+    },
+    "da": {
+      "name": "dansk"
+    },
+    "de": {
+      "name": "Deutsch"
+    },
+    "el": {
+      "name": "\u0395\u03bb\u03bb\u03b7\u03bd\u03b9\u03ba\u03ac"
+    },
+    "en": {
+      "name": "English"
+    },
+    "eo": {
+      "name": "esperanto"
+    },
+    "es": {
+      "name": "espa\u00f1ol"
+    },
+    "et": {
+      "name": "eesti"
+    },
+    "fa": {
+      "name": "\u0641\u0627\u0631\u0633\u06cc"
+    },
+    "fi": {
+      "name": "suomi"
+    },
+    "fr": {
+      "name": "fran\u00e7ais"
+    },
+    "hi": {
+      "name": "\u0939\u093f\u0928\u094d\u0926\u0940"
+    },
+    "hr": {
+      "name": "hrvatski"
+    },
+    "hu": {
+      "name": "magyar"
+    },
+    "hy": {
+      "name": "\u0570\u0561\u0575\u0565\u0580\u0565\u0576"
+    },
+    "id": {
+      "name": "Indonesia"
+    },
+    "is": {
+      "name": "\u00edslenska"
+    },
+    "it": {
+      "name": "italiano"
+    },
+    "iw": {
+      "name": "\u05e2\u05d1\u05e8\u05d9\u05ea"
+    },
+    "ja": {
+      "name": "\u65e5\u672c\u8a9e"
+    },
+    "ko": {
+      "name": "\ud55c\uad6d\uc5b4"
+    },
+    "lt": {
+      "name": "lietuvi\u0173"
+    },
+    "lv": {
+      "name": "latvie\u0161u"
+    },
+    "nl": {
+      "name": "Nederlands"
+    },
+    "no": {
+      "name": "norsk"
+    },
+    "pl": {
+      "name": "polski"
+    },
+    "pt": {
+      "name": "portugu\u00eas"
+    },
+    "ro": {
+      "name": "rom\u00e2n\u0103"
+    },
+    "ru": {
+      "name": "\u0440\u0443\u0441\u0441\u043a\u0438\u0439"
+    },
+    "sk": {
+      "name": "sloven\u010dina"
+    },
+    "sl": {
+      "name": "sloven\u0161\u010dina"
+    },
+    "sr": {
+      "name": "\u0441\u0440\u043f\u0441\u043a\u0438"
+    },
+    "sv": {
+      "name": "svenska"
+    },
+    "sw": {
+      "name": "Kiswahili"
+    },
+    "th": {
+      "name": "\u0e44\u0e17\u0e22"
+    },
+    "tl": {
+      "name": "Filipino"
+    },
+    "tr": {
+      "name": "T\u00fcrk\u00e7e"
+    },
+    "uk": {
+      "name": "\u0443\u043a\u0440\u0430\u0457\u043d\u0441\u044c\u043a\u0430"
+    },
+    "vi": {
+      "name": "Ti\u1ebfng Vi\u1ec7t"
+    },
+    "zh-CN": {
+      "name": "\u4e2d\u6587 (\u7b80\u4f53)"
+    },
+    "zh-TW": {
+      "name": "\u4e2d\u6587 (\u7e41\u9ad4)"
+    }
+  },
   "google videos": {
     "af": {
       "name": "Afrikaans"
diff --git a/searx/engines/google_scholar.py b/searx/engines/google_scholar.py
new file mode 100644
index 000000000..86bb01056
--- /dev/null
+++ b/searx/engines/google_scholar.py
@@ -0,0 +1,157 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""Google (Scholar)
+
+For detailed description of the *REST-full* API see: `Query Parameter
+Definitions`_.
+
+.. _Query Parameter Definitions:
+   https://developers.google.com/custom-search/docs/xml_results#WebSearch_Query_Parameter_Definitions
+"""
+
+# pylint: disable=invalid-name, missing-function-docstring
+
+from urllib.parse import urlencode
+from datetime import datetime
+from lxml import html
+from searx import logger
+
+from searx.utils import (
+    eval_xpath,
+    eval_xpath_list,
+    extract_text,
+)
+
+from searx.engines.google import (
+    get_lang_info,
+    time_range_dict,
+    detect_google_sorry,
+)
+
+# pylint: disable=unused-import
+from searx.engines.google import (
+    supported_languages_url,
+    _fetch_supported_languages,
+)
+# pylint: enable=unused-import
+
+# about
+about = {
+    "website": 'https://scholar.google.com',
+    "wikidata_id": 'Q494817',
+    "official_api_documentation": 'https://developers.google.com/custom-search',
+    "use_official_api": False,
+    "require_api_key": False,
+    "results": 'HTML',
+}
+
+# engine dependent config
+categories = ['science']
+paging = True
+language_support = True
+use_locale_domain = True
+time_range_support = True
+safesearch = False
+
+logger = logger.getChild('google scholar')
+
+def time_range_url(params):
+    """Returns a URL query component for a google-Scholar time range based on
+    ``params['time_range']``.  Google-Scholar does only support ranges in years.
+    To have any effect, all the Searx ranges (*day*, *week*, *month*, *year*)
+    are mapped to *year*.  If no range is set, an empty string is returned.
+    Example::
+
+        &as_ylo=2019
+    """
+    # as_ylo=2016&as_yhi=2019
+    ret_val = ''
+    if params['time_range'] in time_range_dict:
+        ret_val= urlencode({'as_ylo': datetime.now().year -1 })
+    return '&' + ret_val
+
+
+def request(query, params):
+    """Google-Scholar search request"""
+
+    offset = (params['pageno'] - 1) * 10
+    lang_info = get_lang_info(
+        # pylint: disable=undefined-variable
+
+
+        # params, {}, language_aliases
+
+        params, supported_languages, language_aliases
+    )
+    # subdomain is: scholar.google.xy
+    lang_info['subdomain'] = lang_info['subdomain'].replace("www.", "scholar.")
+
+    query_url = 'https://'+ lang_info['subdomain'] + '/scholar' + "?" + urlencode({
+        'q':  query,
+        'hl': lang_info['hl'],
+        'lr': lang_info['lr'],
+        'ie': "utf8",
+        'oe':  "utf8",
+        'start' : offset,
+    })
+
+    query_url += time_range_url(params)
+
+    logger.debug("query_url --> %s", query_url)
+    params['url'] = query_url
+
+    logger.debug("HTTP header Accept-Language --> %s", lang_info['Accept-Language'])
+    params['headers']['Accept-Language'] = lang_info['Accept-Language']
+    params['headers']['Accept'] = (
+        'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8'
+    )
+
+    #params['google_subdomain'] = subdomain
+    return params
+
+def response(resp):
+    """Get response from google's search request"""
+    results = []
+
+    detect_google_sorry(resp)
+
+    # which subdomain ?
+    # subdomain = resp.search_params.get('google_subdomain')
+
+    # convert the text to dom
+    dom = html.fromstring(resp.text)
+
+    # parse results
+    for result in eval_xpath_list(dom, '//div[@class="gs_ri"]'):
+
+        title = extract_text(eval_xpath(result, './h3[1]//a'))
+
+        if not title:
+            # this is a [ZITATION] block
+            continue
+
+        url = eval_xpath(result, './h3[1]//a/@href')[0]
+        content = extract_text(eval_xpath(result, './div[@class="gs_rs"]')) or ''
+
+        pub_info = extract_text(eval_xpath(result, './div[@class="gs_a"]'))
+        if pub_info:
+            content += "[%s]" % pub_info
+
+        pub_type = extract_text(eval_xpath(result, './/span[@class="gs_ct1"]'))
+        if pub_type:
+            title = title + " " + pub_type
+
+        results.append({
+            'url':      url,
+            'title':    title,
+            'content':  content,
+        })
+
+    # parse suggestion
+    for suggestion in eval_xpath(dom, '//div[contains(@class, "gs_qsuggest_wrap")]//li//a'):
+        # append suggestion
+        results.append({'suggestion': extract_text(suggestion)})
+
+    for correction in eval_xpath(dom, '//div[@class="gs_r gs_pda"]/a'):
+        results.append({'correction': extract_text(correction)})
+
+    return results
diff --git a/searx/settings.yml b/searx/settings.yml
index 581f19348..e45afb59b 100644
--- a/searx/settings.yml
+++ b/searx/settings.yml
@@ -535,25 +535,8 @@ engines:
     #   android: *test_android
 
   - name : google scholar
-    engine : xpath
-    paging : True
-    search_url : https://scholar.google.com/scholar?start={pageno}&q={query}&hl=en&as_sdt=0,5&as_vis=1
-    results_xpath : //div[contains(@class, "gs_r")]/div[@class="gs_ri"]
-    url_xpath : .//h3/a/@href
-    title_xpath : .//h3/a
-    content_xpath : .//div[@class="gs_rs"]
-    suggestion_xpath : //div[@id="gs_res_ccl_top"]//a/b
-    page_size : 10
-    first_page_num : 0
-    categories : science
+    engine : google_scholar
     shortcut : gos
-    about:
-      website: https://scholar.google.com/
-      wikidata_id: Q494817
-      official_api_documentation:
-      use_official_api: false
-      require_api_key: false
-      results: HTML
 
   - name : google play apps
     engine : xpath