feat(utils): add getIncomers function closes #461

README.md

@@ -581,6 +581,12 @@ Returns all direct child nodes of the passed node.
 
 `getOutgoers = (node: Node, elements: Elements): Node[]`
 
+### getIncomers
+
+Returns all direct incoming nodes of the passed node.
+
+`getOutgoers = (node: Node, elements: Elements): Node[]`
+
 ### getConnectedEdges
 
 Returns all edges that are connected to the passed nodes.

cypress/integration/flow/graph-utils.spec.js

@@ -1,4 +1,4 @@
-import { isNode, isEdge, getOutgoers, removeElements, addEdge } from '../../../src/utils/graph.ts';
+import { isNode, isEdge, getOutgoers, getIncomers, removeElements, addEdge } from '../../../src/utils/graph.ts';
 
 const nodes = [
   { id: '1', type: 'input', data: { label: 'Node 1' }, position: { x: 250, y: 5 } },
@@ -10,6 +10,7 @@ const nodes = [
 const edges = [
   { id: 'e1-2', source: '1', target: '2', animated: true },
   { id: 'e1-3', source: '1', target: '3' },
+  { id: 'e2-3', source: '2', target: '3' },
 ];
 
 const elements = [...nodes, ...edges];
@@ -29,10 +30,18 @@ describe('Graph Utils Testing', () => {
     const outgoers = getOutgoers(nodes[0], elements);
     expect(outgoers.length).to.be.equal(2);
 
-    const noOutgoers = getOutgoers(nodes[1], elements);
+    const noOutgoers = getOutgoers(nodes[2], elements);
     expect(noOutgoers.length).to.be.equal(0);
   });
 
+  it('tests getIncomers function', () => {
+    const incomers = getIncomers(nodes[2], elements);
+    expect(incomers.length).to.be.equal(2);
+
+    const noIncomers = getIncomers(nodes[0], elements);
+    expect(noIncomers.length).to.be.equal(0);
+  });
+
   describe('tests addEdge function', () => {
     it('adds edge', () => {
       const newEdge = { source: '2', target: '3' };

src/utils/graph.ts

@@ -1,6 +1,7 @@
+import { Store } from 'easy-peasy';
+
 import store, { StoreModel } from '../store';
 import { ElementId, Node, Edge, Elements, Transform, XYPosition, Rect, FitViewParams, Box, Connection } from '../types';
-import { Store } from 'easy-peasy';
 
 export const isEdge = (element: Node | Connection | Edge): element is Edge =>
   'id' in element && 'source' in element && 'target' in element;
@@ -17,6 +18,15 @@ export const getOutgoers = (node: Node, elements: Elements): Node[] => {
   return elements.filter((e) => outgoerIds.includes(e.id)) as Node[];
 };
 
+export const getIncomers = (node: Node, elements: Elements): Node[] => {
+  if (!isNode(node)) {
+    return [];
+  }
+
+  const incomersIds = elements.filter((e) => isEdge(e) && e.target === node.id).map((e) => (e as Edge).source);
+  return elements.filter((e) => incomersIds.includes(e.id)) as Node[];
+};
+
 export const removeElements = (elementsToRemove: Elements, elements: Elements): Elements => {
   const nodeIdsToRemove = elementsToRemove.map((n) => n.id);