[fix] ahmia engine: requires rotating tokens to work

Ahmia recently implemented a 60 minute rotating token system when searching.

This fix uses the cache and updates the tokens on every request.

searx/engines/ahmia.py

@@ -3,9 +3,14 @@
 Ahmia (Onions)
 """
 
+import typing as t
+
 from urllib.parse import urlencode, urlparse, parse_qs
 from lxml.html import fromstring
+from searx.utils import gen_useragent, ElementType
 from searx.engines.xpath import extract_url, extract_text, eval_xpath_list, eval_xpath
+from searx.network import get
+from searx.enginelib import EngineCache
 
 # about
 about = {
@@ -23,6 +28,7 @@ paging = True
 page_size = 10
 
 # search url
+base_url = 'http://juhanurmihxlp77nkq76byazcldy2hlmovfu2epvl5ankdibsot4csyd.onion'
 search_url = 'http://juhanurmihxlp77nkq76byazcldy2hlmovfu2epvl5ankdibsot4csyd.onion/search/?{query}'
 time_range_support = True
 time_range_dict = {'day': 1, 'week': 7, 'month': 30}
@@ -34,10 +40,44 @@ title_xpath = './h4/a[1]'
 content_xpath = './/p[1]'
 correction_xpath = '//*[@id="didYouMean"]//a'
 number_of_results_xpath = '//*[@id="totalResults"]'
+name_token_xpath = '//form[@id="searchForm"]/input[@type="hidden"]/@name'
+value_token_xpath = '//form[@id="searchForm"]/input[@type="hidden"]/@value'
+
+CACHE: EngineCache
+"""Persistent (SQLite) key/value cache that deletes its values after ``expire``
+seconds."""
+
+
+def setup(engine_settings: dict[str, t.Any]) -> bool:
+    global CACHE  # pylint: disable=global-statement
+    CACHE = EngineCache(engine_settings["name"])
+    return True
+
+
+def _get_tokens(dom: ElementType | None = None) -> str:
+    """
+    The tokens are hidden in a hidden input field.
+    They update every minute, but allow up to 1 hour old tokens to be used.
+    To spend the least amount of requests, it is best to always get the newest
+    tokens from each request. In worst case if it has expired, it would
+    need to do a total of 2 requests (over tor, might be ridiculously slow).
+    """
+    if dom is None:
+        resp = get(base_url, headers={'User-Agent': gen_useragent()})
+        dom = fromstring(resp.text)
+    name_token = extract_text(dom.xpath(name_token_xpath))
+    value_token = extract_text(dom.xpath(value_token_xpath))
+    return f"{name_token}:{value_token}"
 
 
 def request(query, params):
-    params['url'] = search_url.format(query=urlencode({'q': query}))
+    token_str: str | None = CACHE.get('ahmia-tokens')
+    if not token_str:
+        token_str = _get_tokens()
+        CACHE.set('ahmia-tokens', token_str, expire=60 * 60)
+    name_token, value_token = token_str.split(":")
+
+    params['url'] = search_url.format(query=urlencode({'q': query, name_token: value_token}))
 
     if params['time_range'] in time_range_dict:
         params['url'] += '&' + urlencode({'d': time_range_dict[params['time_range']]})
@@ -77,4 +117,8 @@ def response(resp):
         except:  # pylint: disable=bare-except
             pass
 
+    # Update the tokens to the newest ones
+    token_str = _get_tokens(dom)
+    CACHE.set('ahmia-tokens', token_str, expire=60 * 60)
+
     return results