From 22c0bace5fb332d5f3b791612352e3d45c080231 Mon Sep 17 00:00:00 2001
From: Sandy Cash <lhcash@us.ibm.com>
Date: Thu, 23 Mar 2023 10:07:22 -0400
Subject: [PATCH] Graph.Add() returns pointer to new Vertex and error

---
 graph/graph.go     |  2 +-
 graph/list.go      |  4 +++-
 graph/list_test.go | 21 +++++++++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/graph/graph.go b/graph/graph.go
index f243c2c..58fd459 100644
--- a/graph/graph.go
+++ b/graph/graph.go
@@ -63,5 +63,5 @@ type Graph interface {
 	Path(int, int) ([]*Vertex, error)
 	// Add adds the specified Vertex to the graph.  Add does not do any uniqueness checks - it is up to the
 	// user to keep track of which vertices have already been added.
-	Add(Vertex)
+	Add(Vertex) (*Vertex, error)
 }
diff --git a/graph/list.go b/graph/list.go
index d534946..6432ae4 100644
--- a/graph/list.go
+++ b/graph/list.go
@@ -192,9 +192,11 @@ func New(vertices []Vertex) (Graph, error) {
 
 var addMutex sync.Mutex
 
-func (a AdjacencyList) Add(v Vertex) {
+func (a AdjacencyList) Add(v Vertex) (*Vertex, error) {
 	addMutex.Lock()
 	v.index = len(a)
 	a = append(a, &v)
 	addMutex.Unlock()
+
+	return a.AtIndex(v.index)
 }
diff --git a/graph/list_test.go b/graph/list_test.go
index cc88f04..b15b9e2 100644
--- a/graph/list_test.go
+++ b/graph/list_test.go
@@ -162,4 +162,25 @@ var _ = Describe("List", func() {
 			})
 		})
 	})
+
+	Describe("Add", func() {
+		var (
+			newVertex graph.Vertex
+		)
+
+		BeforeEach(func() {
+			newVertex = graph.Vertex{
+				Attributes: graph.Attributes{
+					"foo": "peter",
+				},
+			}
+		})
+
+		It("Adds the new Vertex", func() {
+			nvp, err := g.Add(newVertex)
+			Expect(nvp).NotTo(BeNil())
+			Expect(err).NotTo(HaveOccurred())
+			Expect(nvp.Get("foo").(string)).To(Equal("peter"))
+		})
+	})
 })