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searxng/searx/plugins/oa_doi_rewrite.py

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+from urllib.parse import urlparse, parse_qsl
+from flask_babel import gettext
+import re
+from searx import settings
+
+
+regex = re.compile(r'10\.\d{4,9}/[^\s]+')
+
+name = gettext('Open Access DOI rewrite')
+description = gettext('Avoid paywalls by redirecting to open-access versions of publications when available')
+default_on = False
+preference_section = 'general'
+
+
+def extract_doi(url):
+    match = regex.search(url.path)
+    if match:
+        return match.group(0)
+    for _, v in parse_qsl(url.query):
+        match = regex.search(v)
+        if match:
+            return match.group(0)
+    return None
+
+
+def get_doi_resolver(preferences):
+    doi_resolvers = settings['doi_resolvers']
+    selected_resolver = preferences.get_value('doi_resolver')[0]
+    if selected_resolver not in doi_resolvers:
+        selected_resolver = settings['default_doi_resolver']
+    return doi_resolvers[selected_resolver]
+
+
+def on_result(request, search, result):
+    if 'parsed_url' not in result:
+        return True
+
+    doi = extract_doi(result['parsed_url'])
+    if doi and len(doi) < 50:
+        for suffix in ('/', '.pdf', '.xml', '/full', '/meta', '/abstract'):
+            if doi.endswith(suffix):
+                doi = doi[: -len(suffix)]
+        result['url'] = get_doi_resolver(request.preferences) + doi
+        result['parsed_url'] = urlparse(result['url'])
+        if 'doi' not in result:
+            result['doi'] = doi
+    return True