93747: Fixed and improved ArrayMoveChangeAnalyzer

Author: Atmire-Kristof

src/app/core/data/array-move-change-analyzer.service.spec.ts

@@ -41,21 +41,28 @@ describe('ArrayMoveChangeAnalyzer', () => {
     ], new MoveTest(0, 3));
 
     testMove([
+      { op: 'move', from: '/2', path: '/3' },
       { op: 'move', from: '/0', path: '/3' },
-      { op: 'move', from: '/2', path: '/1' }
     ], new MoveTest(0, 3), new MoveTest(1, 2));
 
     testMove([
+      { op: 'move', from: '/3', path: '/4' },
       { op: 'move', from: '/0', path: '/1' },
-      { op: 'move', from: '/3', path: '/4' }
     ], new MoveTest(0, 1), new MoveTest(3, 4));
 
     testMove([], new MoveTest(0, 4), new MoveTest(4, 0));
 
     testMove([
+      { op: 'move', from: '/2', path: '/3' },
       { op: 'move', from: '/0', path: '/3' },
-      { op: 'move', from: '/2', path: '/1' }
     ], new MoveTest(0, 4), new MoveTest(1, 3), new MoveTest(2, 4));
+
+    testMove([
+      { op: 'move', from: '/3', path: '/4' },
+      { op: 'move', from: '/2', path: '/4' },
+      { op: 'move', from: '/1', path: '/3' },
+      { op: 'move', from: '/0', path: '/3' },
+    ], new MoveTest(4, 1), new MoveTest(4, 2), new MoveTest(0, 3));
   });
 
   describe('when some values are undefined (index 2 and 3)', () => {

src/app/core/data/array-move-change-analyzer.service.ts

@@ -16,22 +16,31 @@ export class ArrayMoveChangeAnalyzer<T> {
    * @param array2  The custom array to compare with the original
    */
   diff(array1: T[], array2: T[]): MoveOperation[] {
-    const result = [];
-    const moved = [...array1];
-    array1.forEach((value: T, index: number) => {
-      if (hasValue(value)) {
-        const otherIndex = array2.indexOf(value);
-        const movedIndex = moved.indexOf(value);
-        if (index !== otherIndex && movedIndex !== otherIndex) {
-          moveItemInArray(moved, movedIndex, otherIndex);
-          result.push(Object.assign({
-            op: 'move',
-            from: '/' + movedIndex,
-            path: '/' + otherIndex
-          }) as MoveOperation);
-        }
+    return this.getMoves(array1, array2).map((move) => Object.assign({
+      op: 'move',
+      from: '/' + move[0],
+      path: '/' + move[1],
+    }) as MoveOperation);
+  }
+
+  /**
+   * Determine a set of moves required to transform array1 into array2
+   * The moves are returned as an array of pairs of numbers where the first number is the original index and the second
+   * is the new index
+   * It is assumed the operations are executed in the order they're returned (and not simultaneously)
+   * @param array1
+   * @param array2
+   */
+  private getMoves(array1: any[], array2: any[]): number[][] {
+    const moved = [...array2];
+
+    return array1.reduce((moves, item, index) => {
+      if (hasValue(item) && item !== moved[index]) {
+        const last = moved.lastIndexOf(item);
+        moveItemInArray(moved, last, index);
+        moves.unshift([index, last]);
       }
-    });
-    return result;
+      return moves;
+    }, []);
   }
 }