feat: allow to pass a keyExtractor in order to have use a custom id for an Edge. Handy for vertices with n edges

Author: emyann

src/data-structures/Graph/GraphEdge.ts

@@ -1,13 +1,23 @@
 import { GraphVertex } from './GraphVertex';
+export type EdgeKeyExtractor<T> = (edge: T) => string | number;
 
 export class GraphEdge<TVertex, TEdge> {
-  constructor(public startVertex: GraphVertex<TVertex, TEdge>, public endVertex: GraphVertex<TVertex, TEdge>, public value: TEdge) {}
+  constructor(
+    public startVertex: GraphVertex<TVertex, TEdge>,
+    public endVertex: GraphVertex<TVertex, TEdge>,
+    public value: TEdge,
+    private keyExtractor?: EdgeKeyExtractor<GraphEdge<TVertex, TEdge>>
+  ) {}
 
   getKey() {
-    const startVertexKey = this.startVertex.getKey();
-    const endVertexKey = this.endVertex.getKey();
+    if (!this.keyExtractor) {
+      const startVertexKey = this.startVertex.getKey();
+      const endVertexKey = this.endVertex.getKey();
 
-    return `${startVertexKey}_${endVertexKey}`;
+      return `${startVertexKey}_${endVertexKey}`;
+    } else {
+      return this.keyExtractor(this);
+    }
   }
 
   reverse() {

src/examples/index.ts

@@ -1,4 +1,5 @@
 import { Graph, LinkedList, GraphEdge, GraphVertex, VertexKeyExtractor } from '../index';
+import { EdgeKeyExtractor } from '../data-structures';
 interface User {
   age: number;
 }
@@ -18,24 +19,29 @@ enum LinkKind {
   Parent = 'parent'
 }
 interface UserLink {
+  id: string;
   kind: LinkKind;
 }
 const keyExtractor: VertexKeyExtractor<User> = user => user.age;
+const edgeKeyExtractor: EdgeKeyExtractor<GraphEdge<User, UserLink>> = edge => edge.value.id;
+
 const graph = new Graph<User, UserLink>(true);
 const vertex1 = new GraphVertex<User, UserLink>({ age: 10 }, keyExtractor);
 const vertex2 = new GraphVertex<User, UserLink>({ age: 22 }, keyExtractor);
-const edge = new GraphEdge<User, UserLink>(vertex1, vertex2, { kind: LinkKind.Friend });
+const edge = new GraphEdge<User, UserLink>(vertex1, vertex2, { id: '1', kind: LinkKind.Friend }, edgeKeyExtractor);
 
 const vertex3 = new GraphVertex<User, UserLink>({ age: 30 }, keyExtractor);
 const vertex4 = new GraphVertex<User, UserLink>({ age: 35 }, keyExtractor);
-const edge2 = new GraphEdge<User, UserLink>(vertex3, vertex4, { kind: LinkKind.Parent });
+const edge2 = new GraphEdge<User, UserLink>(vertex3, vertex4, { id: '2', kind: LinkKind.Parent }, edgeKeyExtractor);
+const edge3 = new GraphEdge<User, UserLink>(vertex3, vertex4, { id: '3', kind: LinkKind.Parent }, edgeKeyExtractor);
 
 graph
   .addVertex(vertex1)
   .addVertex(vertex2)
   .addEdge(edge)
   .addVertex(vertex3)
   .addVertex(vertex4)
-  .addEdge(edge2);
+  .addEdge(edge2)
+  .addEdge(edge3);
 console.log('grah vertices =>', graph.getAllVertices());
 console.log('grah edges =>', graph.getAllEdges());