Graph GetNodeByIdentifier and readme fix

README.md

@@ -62,22 +62,22 @@ graph.Add(myEdge);
 
 ```csharp
 // Subgraph identifier need to start with "cluster" to be identified as a cluster
-var mySubGraph = new DotSubGraph().WithIdentifier("cluster_0");
+var mySubgraph = new DotSubgraph().WithIdentifier("cluster_0");
 
 // Create a subgraph with attributes (only used for cluster)
-var mySubGraph = new DotSubGraph()
-    .WithIdentifier("cluster_0")
+var mySubgraph2 = new DotSubgraph()
+    .WithIdentifier("cluster_1")
     .WithColor(DotColor.Red)
     .WithStyle(DotSubGraphStyle.Dashed)
     .WithLabel("My subgraph!");
 
 // Add node, edge, subgraph
 subGraph.Add(myNode);
 subGraph.Add(myEdge);
-subGraph.Add(mySubGraph2);
+subGraph.Add(mySubgraph2);
 
 // Add subgraph to main graph
-graph.Add(mySubGraph);
+graph.Add(mySubgraph);
 ```
 
 ## Compile to DOT format

Sources/DotNetGraph.Tests/Core/DotGraphTests.cs

@@ -89,4 +89,36 @@ public async Task CompileDirectedGraphWithOneNode()
         var result = writer.GetStringBuilder().ToString();
         result.Should().Be("digraph Test {\n\tTestNode\n}\n");
     }
+
+    [TestMethod]
+    public void GetNodeByIdentifier()
+    {
+        var node = new DotNode()
+            .WithIdentifier("TestNode");
+
+        var graph = new DotGraph()
+            .WithIdentifier("Test")
+            .Directed()
+            .Add(node);
+
+        var nodeFromGraph = graph.GetNodeByIdentifier("TestNode");
+
+        nodeFromGraph.Should().Be(node);
+    }
+
+    [TestMethod]
+    public void GetNodeByIdentifier_MissingNode()
+    {
+        var node = new DotNode()
+            .WithIdentifier("TestNode");
+
+        var graph = new DotGraph()
+            .WithIdentifier("Test")
+            .Directed()
+            .Add(node);
+
+        var nodeFromGraph = graph.GetNodeByIdentifier("NotTestNode");
+
+        nodeFromGraph.Should().BeNull();
+    }
 }

Sources/DotNetGraph/Core/DotBaseGraph.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 using DotNetGraph.Attributes;
 using DotNetGraph.Compilation;
@@ -15,6 +16,14 @@ public DotRankDirAttribute RankDir
             set => SetAttribute("rankdir", value);
         }
 
+        public DotNode GetNodeByIdentifier(string identifier, bool isHtml = false)
+        {
+            return Elements
+                .Where(e => e is DotNode)
+                .Cast<DotNode>()
+                .FirstOrDefault(node => node.Identifier == new DotIdentifier(identifier, isHtml));
+        }
+
         public List<IDotElement> Elements { get; } = new List<IDotElement>();
 
         public abstract override Task CompileAsync(CompilationContext context);

Sources/DotNetGraph/Core/DotIdentifier.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
@@ -6,7 +7,7 @@
 
 namespace DotNetGraph.Core
 {
-    public class DotIdentifier : IDotElement
+    public class DotIdentifier : IDotElement, IEquatable<DotIdentifier>
     {
         private static readonly Regex NoQuotesRequiredRegex
             = new Regex("^([a-zA-Z\\200-\\377_][a-zA-Z\\200-\\3770-9_]*|[-]?(.[0-9]+|[0-9]+(.[0-9]+)?))$");
@@ -50,5 +51,42 @@ private static bool RequiresDoubleQuotes(string value)
         {
             return ReservedWords.Contains(value) || !NoQuotesRequiredRegex.IsMatch(value);
         }
+
+        public bool Equals(DotIdentifier other)
+        {
+            if (ReferenceEquals(null, other))
+                return false;
+            if (ReferenceEquals(this, other))
+                return true;
+            return Value == other.Value && IsHtml == other.IsHtml;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj))
+                return false;
+            if (ReferenceEquals(this, obj))
+                return true;
+            if (obj.GetType() != GetType())
+                return false;
+            return Equals((DotIdentifier) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return ((Value != null ? Value.GetHashCode() : 0) * 397) ^ IsHtml.GetHashCode();
+            }
+        }
+
+        public static bool operator ==(DotIdentifier identifier1, DotIdentifier identifier2)
+        {
+            if (identifier1 is null)
+                return identifier2 is null;
+            return identifier1.Equals(identifier2);
+        }
+
+        public static bool operator !=(DotIdentifier identifier1, DotIdentifier identifier2) => !(identifier1 == identifier2);
     }
 }