Add planner previews and streaming

tests/test_planner.py

@@ -0,0 +1,32 @@
+from server.config import ServerSettings
+from server.grid import GridManager
+from server.planner import GridPlanner
+from server.models import ActionType, GridInitRequest
+
+
+def test_planner_preferred_label(default_grid_request):
+    settings = ServerSettings()
+    manager = GridManager(settings)
+    request = GridInitRequest(**default_grid_request)
+    grid = manager.create_grid(request)
+    descriptor = grid.describe()
+    descriptor.cells[0].label = "target"
+
+    planner = GridPlanner()
+    payload = planner.build_payload(descriptor, preferred_label="target", action=ActionType.CLICK)
+
+    assert payload.target_cell == descriptor.cells[0].cell_id
+
+
+def test_planner_falls_back_to_center(default_grid_request):
+    settings = ServerSettings()
+    manager = GridManager(settings)
+    request = GridInitRequest(**default_grid_request)
+    grid = manager.create_grid(request)
+    descriptor = grid.describe()
+
+    planner = GridPlanner()
+    payload = planner.build_payload(descriptor, action=ActionType.CLICK)
+
+    assert payload.target_cell is not None
+    assert payload.grid_id == descriptor.grid_id