implement automatic updater

updater/sources.py

@@ -0,0 +1,38 @@
+from xml.dom import minidom, pulldom
+
+import requests_cache
+
+requests_session = requests_cache.CachedSession('updater', backend='memory')
+
+
+class ApkRelease:
+    version_name: str
+    version_code: int
+    download_url: str
+
+    def __init__(self, version_name: str, version_code: int, download_url: str):
+        self.version_name = version_name
+        self.version_code = version_code
+        self.download_url = download_url
+
+
+def _child_el_content(el: minidom.Element, tag_name: str):
+    return el.getElementsByTagName(tag_name).item(0).firstChild.data
+
+
+def fdroid_recommended_release(repo: str, application_id: str):
+    with requests_session.get('{}/index.xml'.format(repo)) as r:
+        doc = pulldom.parseString(r.text)
+        for event, node in doc:
+            if event == pulldom.START_ELEMENT and node.tagName == 'application':
+                if node.getAttribute('id') == application_id:
+                    doc.expandNode(node)
+                    marketvercode = _child_el_content(node, 'marketvercode')
+                    for p in node.getElementsByTagName('package'):
+                        if _child_el_content(p, 'versioncode') == marketvercode:
+                            return ApkRelease(
+                                _child_el_content(p, 'version'),
+                                int(marketvercode),
+                                '{}/{}'.format(repo, _child_el_content(p, 'apkname'))
+                            )
+        raise Exception('Did not find {} in repo {}'.format(application_id, repo))