[feat] engines: add repology.org engine for linux packages (#5103)

Repology_ monitors a huge number of package repositories and other sources
comparing packages versions across them and gathering other information.

Repology_ shows you in which repositories a given project is packaged, which
version is the latest and which needs updating, who maintains the package, and
other related information.

.. _Repology: https://repology.org/docs/about

Co-authored-by: Markus Heiser <markus.heiser@darmarit.de>
Format: reST

3 files changed, 109 insertions, 0 deletions

diff --git a/docs/dev/engines/online/repology.rst b/docs/dev/engines/online/repology.rst
new file mode 100644
index 000000000..485a5bcac
--- /dev/null
+++ b/docs/dev/engines/online/repology.rst
@@ -0,0 +1,8 @@
+.. _repology engine:
+
+========
+Repology
+========
+
+.. automodule:: searx.engines.repology
+   :members:
diff --git a/searx/engines/repology.py b/searx/engines/repology.py
new file mode 100644
index 000000000..022f23190
--- /dev/null
+++ b/searx/engines/repology.py
@@ -0,0 +1,95 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""Repology_ monitors a huge number of package repositories and other sources
+comparing packages versions across them and gathering other information.
+
+Repology_ shows you in which repositories a given project is packaged, which
+version is the latest and which needs updating, who maintains the package, and
+other related information.
+
+.. _Repology: https://repology.org/docs/about
+
+Configuration
+=============
+
+The engine is inactive by default, meaning it is not available in the service.
+If you want to offer the engine, the ``inactive`` flag must be set to ``false``.
+
+.. code:: yaml
+
+  - name: repology
+    inactive: false
+
+"""
+
+import typing as t
+
+from urllib.parse import urlencode
+from searx.result_types import EngineResults
+
+if t.TYPE_CHECKING:
+    from searx.extended_types import SXNG_Response
+
+about = {
+    'website': 'https://repology.org',
+    'wikidata_id': 'Q107409859',
+    'use_official_api': True,
+    'official_api_documentation': 'https://repology.org/api/v1',
+    'require_api_key': False,
+    'results': 'JSON',
+}
+categories: list[str] = ['packages', 'it']
+base_url: str = 'https://repology.org'
+
+
+def request(query: str, params: dict[str, t.Any]) -> None:
+    args = {
+        'search': query,
+    }
+    params['url'] = f"{base_url}/api/v1/projects/?{urlencode(args)}"
+
+
+def _get_most_common(items: list[str | None]) -> str | None:
+    counts: dict[str | None, int] = {}
+    for item in items:
+        if item:
+            counts[item] = counts.get(item, 0) + 1
+
+    if len(counts) == 0:
+        return None
+    return max(counts, key=counts.get)
+
+
+def _flatten(xss):
+    return [x for xs in xss for x in xs]
+
+
+def response(resp: 'SXNG_Response') -> EngineResults:
+    res = EngineResults()
+
+    resp_json = resp.json()
+    for pkgname, repositories in resp_json.items():
+
+        # either there's a package with status "newest" or we assume that the
+        # most commonly used version is the latest released (non-alpha) version
+        latest_version = None
+        for repo in repositories:
+            if repo.get("status") == "newest":
+                latest_version = repo["version"]
+                break
+        else:
+            latest_version = _get_most_common([repo.get("version") for repo in repositories])
+
+        res.add(
+            res.types.LegacyResult(
+                template='packages.html',
+                url=f"{base_url}/project/{pkgname}/versions",
+                title=pkgname,
+                content=_get_most_common([pkg.get("summary") for pkg in repositories]),
+                package_name=_get_most_common([pkg.get("visiblename") for pkg in repositories]),
+                version=latest_version,
+                license_name=_get_most_common(_flatten([pkg.get("licenses", []) for pkg in repositories])),
+                tags=list({pkg.get("repo") for pkg in repositories}),  # ensure that tags are unique
+            )
+        )
+
+    return res
diff --git a/searx/settings.yml b/searx/settings.yml
index 1957b1d29..94b2edd66 100644
--- a/searx/settings.yml
+++ b/searx/settings.yml
@@ -2525,6 +2525,12 @@ engines:
     categories: videos
     disabled: true
 
+  - name: repology
+    engine: repology
+    shortcut: rep
+    disabled: true
+    inactive: true
+
   - name: livespace
     engine: livespace
     shortcut: ls