Implement HDR command

lib/nntp/tiny/session.py

@@ -471,6 +471,38 @@ class Session():
     def _cmd_article(self, identifier: Optional[str]=None):
         return self._serve_message(MessagePart.WHOLE, identifier)
 
+    def _send_message_header(self, message: Message, name: str):
+        return self.print("%d %s" % (
+            message.id, message.headers.get(name, '')
+        ))
+
+    def _cmd_hdr(self, name: str, msg: Optional[str]=None):
+        if self.newsgroup is None:
+            return self.respond(ResponseCode.NNTP_NEWSGROUP_NOT_SELECTED)
+
+        if msg is None:
+            if self.article_id is None:
+                return self.respond(ResponseCode.NNTP_ARTICLE_INVALID_NUMBER)
+
+            message = self.db.get(Message, self.article_id)
+
+            self.respond(ResponseCode.NNTP_HEADERS_FOLLOW)
+            self._send_message_header(message, name)
+        else:
+            msgrange = MessageRange.parse(msg)
+
+            sql  = f"select * from {Message.name} where "
+            sql += " newsgroup_id = ? and " + msgrange.where()
+
+            cr = self.db.query_sql(Message, sql, (self.newsgroup.id,))
+
+            self.respond(ResponseCode.NNTP_HEADERS_FOLLOW)
+
+            for message in cr.each():
+                self._send_message_header(message, name)
+
+        return self.end()
+
     COMMANDS = {
         'CAPABILITIES': _cmd_capabilities,
         'GROUP':        _cmd_group,
@@ -480,7 +512,8 @@ class Session():
         'NEWGROUPS':    _cmd_newgroups,
         'HEAD':         _cmd_head,
         'BODY':         _cmd_body,
-        'ARTICLE':      _cmd_article
+        'ARTICLE':      _cmd_article,
+        'HDR':          _cmd_hdr,
     }
 
     def handle(self):