refactor: extract drop indicator geometry

rust/spikes/leptos-tiptap-spike/src/editor_runtime/block_dnd.rs

@@ -3,7 +3,7 @@
 //! 本模块只承接拖拽命中所需的窄 helper，不处理 Leptos signal，
 //! 也不分发 editor command；调用方负责保留编辑器状态编排。
 
-use crate::editor_runtime::block_hover_state::DropPlacement;
+use crate::editor_runtime::block_hover_state::{DropIndicatorState, DropPlacement};
 use web_sys::{window, EventTarget};
 
 pub(crate) struct HandleCorridorGeometry {
@@ -57,6 +57,23 @@ pub(crate) fn drop_indicator_top(
     }
 }
 
+pub(crate) fn drop_indicator_from_geometry(
+    block_index: usize,
+    block_top: f64,
+    block_height: f64,
+    stage_top: f64,
+    client_y: i32,
+) -> DropIndicatorState {
+    let placement = drop_placement_from_block_point(client_y, block_top, block_height);
+    let block_bottom = block_top + block_height;
+    let top = drop_indicator_top(stage_top, block_top, block_bottom, placement);
+    DropIndicatorState {
+        index: block_index,
+        top,
+        placement,
+    }
+}
+
 pub(crate) fn event_target_from_point(client_x: i32, client_y: i32) -> Option<EventTarget> {
     window()
         .and_then(|win| win.document())
@@ -97,4 +114,24 @@ mod tests {
             DropPlacement::After
         );
     }
+
+    #[test]
+    fn drop_indicator_geometry_returns_stage_relative_top() {
+        assert_eq!(
+            drop_indicator_from_geometry(3, 140.0, 40.0, 100.0, 150),
+            DropIndicatorState {
+                index: 3,
+                top: 40.0,
+                placement: DropPlacement::Before,
+            }
+        );
+        assert_eq!(
+            drop_indicator_from_geometry(3, 140.0, 40.0, 100.0, 161),
+            DropIndicatorState {
+                index: 3,
+                top: 80.0,
+                placement: DropPlacement::After,
+            }
+        );
+    }
 }