New command playlistlength

Count the number of songs and their total playtime in the playlist.

src/command/AllCommands.cxx

@@ -148,6 +148,7 @@ static constexpr struct command commands[] = {
 	{ "playlistfind", PERMISSION_READ, 1, -1, handle_playlistfind },
 	{ "playlistid", PERMISSION_READ, 0, 1, handle_playlistid },
 	{ "playlistinfo", PERMISSION_READ, 0, 1, handle_playlistinfo },
+	{ "playlistlength", PERMISSION_READ, 1, 1, handle_playlistlength },
 	{ "playlistmove", PERMISSION_CONTROL, 3, 3, handle_playlistmove },
 	{ "playlistsearch", PERMISSION_READ, 1, -1, handle_playlistsearch },
 	{ "plchanges", PERMISSION_READ, 1, 2, handle_plchanges },

src/command/PlaylistCommands.cxx

@@ -17,6 +17,7 @@
 #include "SongLoader.hxx"
 #include "song/DetachedSong.hxx"
 #include "BulkEdit.hxx"
+#include "playlist/Length.hxx"
 #include "playlist/PlaylistQueue.hxx"
 #include "playlist/Print.hxx"
 #include "TimePrint.hxx"
@@ -149,6 +150,23 @@ handle_listplaylistinfo(Client &client, Request args, Response &r)
 	throw PlaylistError::NoSuchList();
 }
 
+CommandResult
+handle_playlistlength(Client &client, Request args, Response &r)
+{
+	const auto name = LocateUri(UriPluginKind::PLAYLIST, args.front(),
+				    &client
+#ifdef ENABLE_DATABASE
+					   , nullptr
+#endif
+					   );
+
+	if (playlist_file_length(r, client.GetPartition(), SongLoader(client),
+				name))
+		return CommandResult::OK;
+
+	throw PlaylistError::NoSuchList();
+}
+
 CommandResult
 handle_rm([[maybe_unused]] Client &client, Request args, [[maybe_unused]] Response &r)
 {

src/command/PlaylistCommands.hxx

@@ -26,6 +26,9 @@ handle_listplaylist(Client &client, Request request, Response &response);
 CommandResult
 handle_listplaylistinfo(Client &client, Request request, Response &response);
 
+CommandResult
+handle_playlistlength(Client &client, Request request, Response &response);
+
 CommandResult
 handle_rm(Client &client, Request request, Response &response);