[gnome-music/wip/mschraal/prioritypool-v3: 2/6] Add PriorityPool class for later use

[Marinus Schraal <mschraal src gnome org>]

commit 573a3967b25f8c4c810f13ec0426ea0dbd1d4a80
Author: Marinus Schraal <mschraal gnome org>
Date:   Tue Feb 1 13:24:53 2022 +0100

    Add PriorityPool class for later use

 gnomemusic/prioritypool.py | 66 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
---
diff --git a/gnomemusic/prioritypool.py b/gnomemusic/prioritypool.py
new file mode 100644
index 000000000..3ee43c33e
--- /dev/null
+++ b/gnomemusic/prioritypool.py
@@ -0,0 +1,66 @@
+# Copyright 2021 The GNOME Music developers
+#
+# GNOME Music is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# GNOME Music is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with GNOME Music; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+#
+# The GNOME Music authors hereby grant permission for non-GPL compatible
+# GStreamer plugins to be used and distributed together with GStreamer
+# and GNOME Music.  This permission is above and beyond the permissions
+# granted by the GPL license by which GNOME Music is covered.  If you
+# modify this code, you may extend this exception to your version of the
+# code, but you are not obligated to do so.  If you do not wish to do so,
+# delete this exception statement from your version.
+
+from __future__ import annotations
+from typing import List, Union
+import typing
+
+from gi.repository import GObject
+
+if typing.TYPE_CHECKING:
+    from gnomemusic.corealbum import CoreAlbum
+    from gnomemusic.coreartist import CoreArtist
+    from gnomemusic.coresong import CoreSong
+    CoreObject = Union[CoreAlbum, CoreArtist, CoreSong]
+
+
+class PriorityPool(GObject.GObject):
+    """Tracks async items that should be prioritized
+    """
+
+    _pool: List[int] = []
+
+    def __init__(self) -> None:
+        """
+        """
+        super().__init__()
+
+    def add(self, coreobjects: List[CoreObject], reset: bool = False) -> None:
+        ids = [id(coreobject) for coreobject in coreobjects]
+
+        if reset:
+            PriorityPool._pool = ids
+        else:
+            PriorityPool._pool += ids
+
+    def get_pool(self):
+        return PriorityPool._pool
+
+    @GObject.Property()
+    def pool(self) -> List[int]:
+        return PriorityPool._pool
+
+    @pool.setter  # type: ignore
+    def selected(self, value: List[CoreoObject]) -> None:
+        self.add(value, True)