feat: Build the positions of the Switch handle #1739 (#2018)

### What problem does this PR solve?

feat: Build the positions of the Switch handle #1739

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/flow/utils.ts

@@ -1,7 +1,7 @@
 import { DSLComponents } from '@/interfaces/database/flow';
 import { removeUselessFieldsFromValues } from '@/utils/form';
 import { humanId } from 'human-id';
-import { curry, sample } from 'lodash';
+import { curry, intersectionWith, isEqual, sample } from 'lodash';
 import pipe from 'lodash/fp/pipe';
 import isObject from 'lodash/isObject';
 import { Edge, Node, Position } from 'reactflow';
@@ -172,10 +172,24 @@ export const isEdgeEqual = (previous: Edge, current: Edge) =>
   previous.sourceHandle === current.sourceHandle;
 
 export const buildNewPositionMap = (
-  categoryDataKeys: string[],
-  indexesInUse: number[],
+  currentKeys: string[],
+  previousPositionMap: Record<string, IPosition>,
 ) => {
-  return categoryDataKeys.reduce<Record<string, IPosition>>((pre, cur) => {
+  // index in use
+  const indexesInUse = Object.values(previousPositionMap).map((x) => x.idx);
+  const previousKeys = Object.keys(previousPositionMap);
+  const intersectionKeys = intersectionWith(
+    previousKeys,
+    currentKeys,
+    (categoryDataKey, positionMapKey) => categoryDataKey === positionMapKey,
+  );
+  // difference set
+  const currentDifferenceKeys = currentKeys.filter(
+    (x) => !intersectionKeys.some((y) => y === x),
+  );
+  const newPositionMap = currentDifferenceKeys.reduce<
+    Record<string, IPosition>
+  >((pre, cur) => {
     // take a coordinate
     const effectiveIdxes = CategorizeAnchorPointPositions.map(
       (x, idx) => idx,
@@ -188,4 +202,10 @@ export const buildNewPositionMap = (
 
     return pre;
   }, {});
+
+  return { intersectionKeys, newPositionMap };
+};
+
+export const isKeysEqual = (currentKeys: string[], previousKeys: string[]) => {
+  return isEqual(currentKeys.sort(), previousKeys.sort());
 };