step 2: add thread safe state commands and cache model

tests/test_commands.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+from dpg_map.commands import CommandKind, MapCommand, MapCommandQueue
+
+
+def test_overlay_updates_coalesce_by_overlay_tag() -> None:
+    queue = MapCommandQueue()
+
+    queue.put(MapCommand(CommandKind.UPDATE_OVERLAY, "map", {"tag": "vehicle", "lat": 1.0}))
+    queue.put(MapCommand(CommandKind.UPDATE_OVERLAY, "map", {"tag": "vehicle", "lat": 2.0}))
+    queue.put(MapCommand(CommandKind.UPDATE_OVERLAY, "map", {"tag": "other", "lat": 3.0}))
+
+    drained = queue.drain()
+
+    assert len(drained) == 2
+    assert drained[0].payload == {"tag": "vehicle", "lat": 2.0}
+    assert drained[1].payload == {"tag": "other", "lat": 3.0}
+
+
+def test_latest_view_update_wins_but_structural_commands_keep_order() -> None:
+    queue = MapCommandQueue()
+
+    queue.put(MapCommand(CommandKind.ADD_OVERLAY, "map", {"tag": "a"}))
+    queue.put(MapCommand(CommandKind.SET_VIEW, "map", {"zoom": 3}))
+    queue.put(MapCommand(CommandKind.SET_VIEW, "map", {"zoom": 4}))
+    queue.put(MapCommand(CommandKind.DELETE_OVERLAY, "map", {"tag": "a"}))
+
+    drained = queue.drain()
+
+    assert [command.kind for command in drained] == [
+        CommandKind.ADD_OVERLAY,
+        CommandKind.SET_VIEW,
+        CommandKind.DELETE_OVERLAY,
+    ]
+    assert drained[1].payload == {"zoom": 4}