feat(dsi): add a paginated channel directory

List configured channels in a native menu with browsing and posting links.

hatenadir/ds/v2-xx/channels.ugo.py

@@ -0,0 +1,20 @@
+from twisted.web import resource
+
+from DB import Database
+from reximemo import dsi_url, make_menu, page_number, pagination_buttons
+
+
+class PyResource(resource.Resource):
+    isLeaf = True
+
+    def render_GET(self, request):
+        channels = Database.list_channels()
+        page = page_number(request, len(channels), 25)
+        buttons = [{"label": channel["title"], "url": dsi_url(request, f"ch/{channel['id']}.uls"), "icon": 101}
+                   for channel in channels[(page - 1) * 25:page * 25]]
+        pager = pagination_buttons(request, "channels.uls", page, len(channels), 25)
+        before = [button for button in pager if button["label"].startswith("Previous")]
+        after = [button for button in pager if button["label"].startswith("Next")]
+        request.setHeader(b"content-type", b"text/plain")
+        return make_menu(layout=(2, 1), title="Channels", subtitle_bottom="Choose a channel to browse or post.",
+                         left="Channels", right=str(len(channels)), buttons=before + buttons + after)