[RC] Implementation of news functionality from archlinux.org

.gitignore

@@ -3,3 +3,4 @@ __pycache__/
 Dockerfile
 locale/*.mo
 locale/pikaur.pot
+.idea/

pikaur/news.py

@@ -0,0 +1,151 @@
+import datetime
+import urllib.request
+import urllib.error
+import xml.etree.ElementTree
+import os
+from http.client import HTTPResponse
+from html.parser import HTMLParser
+
+from typing import TextIO
+
+from pikaur.config import CACHE_ROOT
+import pikaur.pprint
+from pikaur.pacman import
+
+
+# TODO internationalization
+# TODO get initial date (if dat-file not present) from last installed local package from the repo
+
+class News(object):
+    _last_seen_news: str
+    URL = 'https://www.archlinux.org'
+    DIR = '/feeds/news/'
+
+    def __init__(self) -> None:
+        self._last_seen_news = self._get_last_seen_news()
+
+    def check_news(self) -> None:
+        rss_feed = self._get_rss_feed()
+        if not rss_feed:  # could not get data
+            return
+        xml_feed: xml.etree.ElementTree.ElementTree = \
+            xml.etree.ElementTree.fromstring(rss_feed)
+        if self._is_new(self._last_online_news(xml_feed)):
+            self._print_news(xml_feed)
+
+    def _get_rss_feed(self) -> str:
+        try:
+            http_response: HTTPResponse = urllib.request.urlopen(
+                self.URL + self.DIR
+            )
+        except urllib.error.URLError:
+            pikaur.pprint.print_stdout('Could not fetch archlinux.org news')
+            return ''
+        str_response: str = ''
+        for line in http_response:
+            str_response += line.decode('UTF-8').strip()
+        return str_response
+
+    @staticmethod
+    def _last_online_news(xml_feed: xml.etree.ElementTree.ElementTree) -> str:
+        # we find the first 'pubDate' tag, which indicates
+        # the most recent entry
+        news_entry: xml.etree.ElementTree.Element
+        for news_entry in xml_feed.iter('item'):
+            child: xml.etree.ElementTree.Element
+            for child in news_entry:
+                if 'pubDate' in child.tag:
+                    return child.text
+        # if we get to here, then something went really wrong
+        # no valid news found
+        return ''
+
+
+    @staticmethod
+    def _get_last_seen_news() -> str:
+        filename: str = os.path.join(CACHE_ROOT, 'last_seen_news.dat')
+        last_seen_fd: TextIO
+        try:
+            with open(filename) as last_seen_fd:
+                return last_seen_fd.readline().strip()
+        except IOError:
+            # if file doesn't exist, this feature was run the first time
+            # then we want to see all news from this moment on
+            now: datetime.datetime = datetime.datetime.utcnow()
+            time_formatted: str = now.strftime('%a, %d %b %Y %H:%M:%S +0000')
+            try:
+                with open(filename, 'w') as last_seen_fd:
+                    last_seen_fd.write(time_formatted)
+            except IOError:
+                msg: str = 'Could not initialize {}'.format(filename)
+                pikaur.pprint.print_stdout(msg)
+            return time_formatted
+
+    def _is_new(self, last_online_news: str) -> bool:
+        last_seen_news_date = datetime.datetime.strptime(
+            self._last_seen_news, '%a, %d %b %Y %H:%M:%S %z'
+        )
+        if not last_online_news:
+            raise ValueError('The news feed could not be received or parsed.')
+        last_online_news_date: datetime = datetime.datetime.strptime(
+            last_online_news, '%a, %d %b %Y %H:%M:%S %z'
+        )
+        return last_online_news_date > last_seen_news_date
+
+    def _print_news(self, xml_feed: xml.etree.ElementTree.ElementTree):
+        news_entry: xml.etree.ElementTree.Element
+        for news_entry in xml_feed.iter('item'):
+            child: xml.etree.ElementTree.Element
+            for child in news_entry:
+                if 'pubDate' in child.tag:
+                    if self._is_new(child.text):
+                        self._print_one_entry(news_entry)
+                    else:
+                        # no more news
+                        return
+
+    # noinspection PyUnboundLocalVariable
+    @staticmethod
+    def _print_one_entry(news_entry: xml.etree.ElementTree.Element) -> None:
+        child: xml.etree.ElementTree.Element
+        for child in news_entry:
+            if 'title' in child.tag:
+                title: str = child.text
+            if 'pubDate' in child.tag:
+                pub_date: str = child.text
+            if 'description' in child.tag:
+                description: str = child.text
+        pikaur.pprint.print_stdout(
+            pikaur.pprint.color_line(title, 11) + ' (' + pub_date + ')'
+        )
+        pikaur.pprint.print_stdout(
+            pikaur.pprint.format_paragraph(strip_tags(description))
+        )
+
+
+class MLStripper(HTMLParser):
+    def error(self, message: object) -> None:
+        pass
+
+    def __init__(self) -> None:
+        super().__init__()
+        self.reset()
+        self.strict = False
+        self.convert_charrefs = True
+        self.fed = []
+
+    def handle_data(self, data: object) -> None:
+        self.fed.append(data)
+
+    def get_data(self) -> str:
+        return ''.join(self.fed)
+
+
+def strip_tags(html: object) -> str:
+    mlstripper = MLStripper()
+    mlstripper.feed(html)
+    return mlstripper.get_data()
+
+
+if __name__ == '__main__':
+    News().check_news()