From b80192ace6202c3d7d7d7cf7de3ec06d2d0888d6 Mon Sep 17 00:00:00 2001
From: Jon Brandenburg <jbrandenburg@yahoo.com>
Date: Sun, 16 Jul 2023 22:05:45 -0400
Subject: [PATCH] added Vertices() to Graph interface

---
 directed.go   | 4 ++++
 graph.go      | 4 ++++
 undirected.go | 4 ++++
 3 files changed, 12 insertions(+)

diff --git a/directed.go b/directed.go
index 95d67f52..8448066b 100644
--- a/directed.go
+++ b/directed.go
@@ -62,6 +62,10 @@ func (d *directed[K, T]) Vertex(hash K) (T, error) {
 	return vertex, err
 }
 
+func (d *directed[K, T]) Vertices() ([]K, error) {
+	return d.store.ListVertices()
+}
+
 func (d *directed[K, T]) VertexWithProperties(hash K) (T, VertexProperties, error) {
 	vertex, properties, err := d.store.Vertex(hash)
 	if err != nil {
diff --git a/graph.go b/graph.go
index 9376eb5f..f243b8be 100644
--- a/graph.go
+++ b/graph.go
@@ -88,6 +88,10 @@ type Graph[K comparable, T any] interface {
 	// doesn't exist.
 	Vertex(hash K) (T, error)
 
+	// Vertices returns a slice of all vertices in the graph. These vertices are of type
+	// Vertice[K] and hence will contain the vertex hashes, not the vertex values.
+	Vertices() ([]K, error)
+
 	// VertexWithProperties returns the vertex with the given hash along with
 	// its properties or ErrVertexNotFound if it doesn't exist.
 	VertexWithProperties(hash K) (T, VertexProperties, error)
diff --git a/undirected.go b/undirected.go
index 37d320c6..0586bf25 100644
--- a/undirected.go
+++ b/undirected.go
@@ -43,6 +43,10 @@ func (u *undirected[K, T]) Vertex(hash K) (T, error) {
 	return vertex, err
 }
 
+func (u *undirected[K, T]) Vertices() ([]K, error) {
+	return u.store.ListVertices()
+}
+
 func (u *undirected[K, T]) VertexWithProperties(hash K) (T, VertexProperties, error) {
 	vertex, prop, err := u.store.Vertex(hash)
 	if err != nil {