diff --git a/src/Blazor.SourceGenerators/Extensions/KeyValuePairExtensions.cs b/src/Blazor.SourceGenerators/Extensions/KeyValuePairExtensions.cs
new file mode 100644
index 0000000..1b49d7f
--- /dev/null
+++ b/src/Blazor.SourceGenerators/Extensions/KeyValuePairExtensions.cs
@@ -0,0 +1,20 @@
+// Copyright (c) David Pine. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Blazor.SourceGenerators.Extensions;
+
+internal static class KeyValuePairExtensions
+{
+    /// <summary>
+    /// Extends the <see cref="KeyValuePair{TKey, TValue}"/> type,
+    /// by exposing the <c>Deconstruct</c> functionality. Meaning that
+    /// we can now do the following:
+    /// <c>foreach (var (key, value) in Dictionary) { ... }</c>
+    /// </summary>
+    /// <typeparam name="TKey">The key <c>TKey</c> type.</typeparam>
+    /// <typeparam name="TValue">The value <c>TValue</c> type.</typeparam>
+    internal static void Deconstruct<TKey, TValue>(
+        this KeyValuePair<TKey, TValue> kvp,
+        out TKey key,
+        out TValue value) => (key, value) = (kvp.Key, kvp.Value);
+}
diff --git a/src/Blazor.SourceGenerators/TypeScript/ITypeScriptAbstractSyntaxTree.cs b/src/Blazor.SourceGenerators/TypeScript/ITypeScriptAbstractSyntaxTree.cs
index 8e68da9..f1b0730 100644
--- a/src/Blazor.SourceGenerators/TypeScript/ITypeScriptAbstractSyntaxTree.cs
+++ b/src/Blazor.SourceGenerators/TypeScript/ITypeScriptAbstractSyntaxTree.cs
@@ -7,9 +7,18 @@ namespace Blazor.SourceGenerators.TypeScript;
 
 public interface ITypeScriptAbstractSyntaxTree
 {
-    string RawSourceText { get; set; }
+    /// <summary>
+    /// Gets the raw source text used to parse the abstract syntax tree.
+    /// </summary>
+    string RawSourceText { get; }
 
-    RootNodeSourceFile RootNode { get; set; }
+    /// <summary>
+    /// Gets the root node (<see cref="RootNodeSourceFile"/>) of the abstract syntax tree.
+    /// </summary>
+    RootNodeSourceFile RootNode { get; }
 
-    void ParseAsAst(string source, string fileName = "app.ts");
+    /// <summary>
+    /// Gets the script target (<see cref="ScriptTarget"/>) of the abstract syntax tree."/>
+    /// </summary>
+    ScriptTarget Target { get; }
 }
diff --git a/src/Blazor.SourceGenerators/TypeScript/TypeScriptAbstractSyntaxTree.cs b/src/Blazor.SourceGenerators/TypeScript/TypeScriptAbstractSyntaxTree.cs
index e926874..4699110 100644
--- a/src/Blazor.SourceGenerators/TypeScript/TypeScriptAbstractSyntaxTree.cs
+++ b/src/Blazor.SourceGenerators/TypeScript/TypeScriptAbstractSyntaxTree.cs
@@ -9,34 +9,53 @@ namespace Blazor.SourceGenerators.TypeScript;
 
 internal sealed class TypeScriptAbstractSyntaxTree : ITypeScriptAbstractSyntaxTree
 {
-    private readonly ScriptTarget _languageVersion;
+    public ScriptTarget Target { get; }
 
-    public string RawSourceText { get; set; }
-    public RootNodeSourceFile RootNode { get; set; }
+    public string RawSourceText { get; }
 
-    public TypeScriptAbstractSyntaxTree(
-        string source = null,
+    public RootNodeSourceFile RootNode { get; }
+
+    private TypeScriptAbstractSyntaxTree(
+        string sourceText = null,
         string fileName = "app.ts",
-        ScriptTarget languageVersion = ScriptTarget.Latest)
+        ScriptTarget target = ScriptTarget.Latest)
     {
-        _languageVersion = languageVersion;
-        if (source is not null)
+        Target = target;
+
+        if (string.IsNullOrWhiteSpace(sourceText))
         {
-            ParseAsAst(source, fileName);
+            throw new ArgumentNullException(nameof(sourceText));
         }
-    }
 
-    public void ParseAsAst(string source, string fileName = "app.ts")
-    {
-        RawSourceText = source;
+        RawSourceText = sourceText;
         var parser = new Parser();
         RootNode = parser.ParseSourceFile(
             fileName,
-            source,
-            _languageVersion,
+            sourceText,
+            Target,
             true,
             ScriptKind.Ts);
         RootNode.AbstractSyntaxTree = this;
         RootNode.ParseChildren(this);
     }
+
+    /// <summary>
+    /// Gets a representation of the TypeScript abstract syntax tree from the given
+    /// <paramref name="sourceText"/> and <paramref name="fileName"/>.
+    /// </summary>
+    /// <param name="sourceText">
+    /// The source text to parse the abstract syntax tree from.
+    /// </param>
+    /// <param name="fileName">
+    /// The name of the file to parse the abstract syntax tree from.
+    /// </param>
+    /// <param name="target">
+    /// The target script version to parse the abstract syntax tree from.
+    /// </param>
+    /// <returns>An instance of <see cref="ITypeScriptAbstractSyntaxTree"/> instance.</returns>
+    public static ITypeScriptAbstractSyntaxTree FromSourceText(
+        string sourceText,
+        string fileName = "lib.dom.d.ts",
+        ScriptTarget target = ScriptTarget.Latest) =>
+        new TypeScriptAbstractSyntaxTree(sourceText, fileName, target);
 }
diff --git a/src/Blazor.SourceGenerators/TypeScript/Types/INode.cs b/src/Blazor.SourceGenerators/TypeScript/Types/INode.cs
index 4c410d2..3431126 100644
--- a/src/Blazor.SourceGenerators/TypeScript/Types/INode.cs
+++ b/src/Blazor.SourceGenerators/TypeScript/Types/INode.cs
@@ -34,8 +34,8 @@ public interface INode : ITextRange
     TypeScriptType ContextualType { get; set; }
     TypeMapper ContextualMapper { get; set; }
     int TagInt { get; set; }
-    string GetText(string source = null);
-    string GetTextWithComments(string source = null);
+    ReadOnlySpan<char> GetText(string source = null);
+    ReadOnlySpan<char> GetTextWithComments(string source = null);
     string GetTreeString(bool withPos = true);
     string ToString(bool withPos);
     Node First { get; }
diff --git a/src/Blazor.SourceGenerators/TypeScript/Types/Node.cs b/src/Blazor.SourceGenerators/TypeScript/Types/Node.cs
index c0a4ece..8c364fe 100644
--- a/src/Blazor.SourceGenerators/TypeScript/Types/Node.cs
+++ b/src/Blazor.SourceGenerators/TypeScript/Types/Node.cs
@@ -2,14 +2,12 @@
 // Licensed under the MIT License.
 
 #nullable disable
+using System.Diagnostics;
 using Blazor.SourceGenerators.TypeScript.Compiler;
 
-// Copyright (c) David Pine. All rights reserved.
-// Licensed under the MIT License.
-
-#nullable disable
 namespace Blazor.SourceGenerators.TypeScript.Types;
 
+[DebuggerDisplay("{SourceText}")]
 public class Node : TextRange, INode
 {
     public List<Node> Children { get; set; } = new();
@@ -17,9 +15,14 @@ public class Node : TextRange, INode
 
     public string RawSourceText => AbstractSyntaxTree.RawSourceText;
 
+    public string SourceText => GetText().ToString();
+
     public string Identifier => Kind is TypeScriptSyntaxKind.Identifier
-        ? GetText()
-        : Children.FirstOrDefault(v => v.Kind is TypeScriptSyntaxKind.Identifier)?.GetText().Trim();
+        ? GetText().ToString()
+        : Children.FirstOrDefault(v => v.Kind is TypeScriptSyntaxKind.Identifier)
+            ?.GetText()
+            .Trim()
+            .ToString();
 
     public int ParentId { get; set; }
     public int Depth { get; set; }
@@ -63,23 +66,27 @@ public void ParseChildren(ITypeScriptAbstractSyntaxTree abstractSyntaxTree) =>
             return null;
         });
 
-    public string GetText(string source = null)
+    public ReadOnlySpan<char> GetText(string source = null)
     {
         source ??= RawSourceText;
 
-        return NodeStart is -1
-            ? Pos.HasValue && End.HasValue
-                ? source.SubString(Pos.Value, End.Value)
-                : null
-            : End.HasValue ? source.SubString(NodeStart, End.Value) : null;
+        var (start, end) = (Pos ?? NodeStart, End.Value);
+
+        return start is 0 || end is 0
+            ? null
+            : source.AsSpan(start, end - start);
     }
 
-    public string GetTextWithComments(string source = null)
+    public ReadOnlySpan<char> GetTextWithComments(string source = null)
     {
         source ??= RawSourceText;
-        return Pos != null && End != null
-            ? source.Substring((int)Pos, (int)End - (int)Pos)
-            : null;
+
+        var (start, end) =
+            (Pos.GetValueOrDefault(-1), End.GetValueOrDefault(-1));
+
+        return start is -1 || end is -1
+            ? null
+            : source.AsSpan(start, end - start);
     }
 
     public override string ToString() => ToString(true);
diff --git a/src/Blazor.SourceGenerators/Types/DependentTypeMapper.cs b/src/Blazor.SourceGenerators/Types/DependentTypeMapper.cs
new file mode 100644
index 0000000..ee55040
--- /dev/null
+++ b/src/Blazor.SourceGenerators/Types/DependentTypeMapper.cs
@@ -0,0 +1,124 @@
+// Copyright (c) David Pine. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Reflection.Metadata;
+using Blazor.SourceGenerators.TypeScript;
+using Blazor.SourceGenerators.TypeScript.Types;
+
+namespace Blazor.SourceGenerators.Types;
+
+internal static class DependentTypeMapper
+{
+    private static readonly Lazy<ITypeScriptAbstractSyntaxTree> s_lazyDefaultAst = new(() =>
+    {
+        var reader = TypeDeclarationReader.Default;
+        return TypeScriptAbstractSyntaxTree.FromSourceText(reader.RawSourceText);
+    });
+
+    /// <summary>
+    /// Gets a <see cref="Dictionary{TKey, TValue}"/> where the <c>TKey</c> is a
+    /// <see cref="string"/> and the <c>TValue</c> is a <see cref="Node"/>.
+    /// </summary>
+    /// <param name="interfaceName">The name of the <c>Name</c> in the TypeScript
+    /// _.d.ts_ file's <c>interface name { ... }</c> definition.</param>
+    /// <returns>A representation of all the dependent types as a
+    /// <see cref="Dictionary{TKey, TValue}"/> where the <c>TKey</c> is a
+    /// <see cref="string"/> and the <c>TValue</c> is a <see cref="Node"/>.
+    /// Returns empty when the underlying AST parser is null or has no
+    /// root node, or if there isn't an <c>interface</c> found.
+    /// </returns>
+    public static Dictionary<string, Node> GetDependentTypeMap(string interfaceName)
+    {
+        var ast = s_lazyDefaultAst.Value;
+        if (ast is null or { RootNode: null })
+        {
+            return new();
+        }
+
+        var rootNode = ast.RootNode;
+
+        var interfaceNode = rootNode.Children
+            .OfKind(TypeScriptSyntaxKind.InterfaceDeclaration)
+            .FirstOrDefault(type => type.Identifier == interfaceName);
+
+        if (interfaceNode is null)
+        {
+            return new Dictionary<string, Node>();
+        }
+
+        var dependentTypes = new Dictionary<string, Node>
+        {
+            [interfaceNode.Identifier] = interfaceNode
+        };
+
+        var queue = new Queue<Node>();
+        queue.Enqueue(interfaceNode);
+
+        while (queue.Count > 0)
+        {
+            var node = queue.Dequeue();
+
+            // Get methods
+            var methods =
+                node.OfKind(TypeScriptSyntaxKind.MethodSignature).Cast<MethodSignature>();
+
+            foreach (var method in methods)
+            {
+                // Get method parameters
+                var parameters =
+                    method.OfKind(TypeScriptSyntaxKind.Parameter).Cast<ParameterDeclaration>();
+
+                foreach (var parameter in parameters)
+                {
+                    // Get parameter type
+                    var typeReferences =
+                        parameter.OfKind(TypeScriptSyntaxKind.TypeReference)
+                            .Cast<TypeReferenceNode>();
+
+                    foreach (var typeReference in typeReferences)
+                    {
+                        dependentTypes[typeReference.Identifier] = typeReference;
+                        queue.Enqueue(typeReference);
+
+                        foreach ((var key, var @interface) in
+                            GetDependentTypeMap(interfaceName: typeReference.Identifier))
+                        {
+                            dependentTypes[@interface.Identifier] = @interface;
+                            queue.Enqueue(@interface);
+                        }
+                    }
+                }
+
+                // Get method return type
+                var returnTypeReferences =
+                    method.OfKind(TypeScriptSyntaxKind.TypeReference)
+                        .Cast<TypeReferenceNode>();
+
+                foreach (var typeReference in returnTypeReferences)
+                {
+                    dependentTypes[typeReference.Identifier] = typeReference;
+                    queue.Enqueue(typeReference);
+                }
+            }
+
+            // Get properties
+            var properties =
+                node.OfKind(TypeScriptSyntaxKind.PropertySignature)
+                    .Cast<PropertySignature>();
+
+            foreach (var property in properties)
+            {
+                dependentTypes[property.Identifier] = property;
+                queue.Enqueue(property);
+            }
+
+            foreach (var childNode in node.Children)
+            {
+                queue.Enqueue(childNode);
+            }
+        }
+
+        return dependentTypes;
+    }
+}
diff --git a/tests/Blazor.SourceGenerators.Tests/LibDomParserTests.cs b/tests/Blazor.SourceGenerators.Tests/LibDomParserTests.cs
index 8cf9933..4bdf6c4 100644
--- a/tests/Blazor.SourceGenerators.Tests/LibDomParserTests.cs
+++ b/tests/Blazor.SourceGenerators.Tests/LibDomParserTests.cs
@@ -16,7 +16,7 @@ public class LibDomParserTests
     public LibDomParserTests()
     {
         var reader = TypeDeclarationReader.Default;
-        _sut = new TypeScriptAbstractSyntaxTree(reader.RawSourceText);
+        _sut = TypeScriptAbstractSyntaxTree.FromSourceText(reader.RawSourceText);
     }
 
     [Fact]
@@ -37,6 +37,7 @@ public void CanReplaceBruteForceParser()
         var cacheStorage =
             _sut.RootNode.OfKind(TypeScriptSyntaxKind.InterfaceDeclaration)
                 .Single(c => c is { Identifier: "CacheStorage" });
+
         Assert.NotNull(cacheStorage);
 
         var methods = cacheStorage.OfKind(TypeScriptSyntaxKind.MethodSignature).Cast<MethodSignature>();
diff --git a/tests/Blazor.SourceGenerators.Tests/TypeMapperTests.cs b/tests/Blazor.SourceGenerators.Tests/TypeMapperTests.cs
new file mode 100644
index 0000000..8ebff4f
--- /dev/null
+++ b/tests/Blazor.SourceGenerators.Tests/TypeMapperTests.cs
@@ -0,0 +1,51 @@
+// Copyright (c) David Pine. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Diagnostics;
+using Blazor.SourceGenerators.Types;
+using Blazor.SourceGenerators.TypeScript.Types;
+using Xunit;
+
+namespace Blazor.SourceGenerators.Tests;
+
+public class TypeMapperTests
+{
+    [Fact]
+    public void TypeMapperCorrectlyMapsKnownTypeMap()
+    {
+        static Dictionary<string, Node> GetTypeMapWithPotential(bool timePenalty)
+        {
+            var startingTimestamp = Stopwatch.GetTimestamp();
+            var sut = DependentTypeMapper.GetDependentTypeMap;
+
+            // The implementation: window.navigator.geolocation
+            var typeMap = sut("Geolocation");
+
+            Assert.NotEmpty(typeMap);
+            var elapsedTimestamp = Stopwatch.GetElapsedTime(startingTimestamp);
+
+            // This needs to take less than a second.
+            // But only fail the test if there is a time penalty.
+            Assert.True(
+                condition: timePenalty is false ||
+                elapsedTimestamp.TotalMilliseconds < 1_000, $"""
+                condition: timePenalty is {timePenalty is false}
+                or took longer than 1,000ms {elapsedTimestamp.TotalMilliseconds < 1_000}.
+                """);
+
+            return typeMap;
+        }
+
+        var typeMap = GetTypeMapWithPotential(timePenalty: false);
+
+        Assert.NotNull(typeMap["Geolocation"]);
+        Assert.NotNull(typeMap["PositionCallback"]);
+        Assert.NotNull(typeMap["PositionErrorCallback"]);
+        Assert.NotNull(typeMap["PositionOptions"]);
+
+        // TODO: these types should be present, but they're not...
+        // Assert.NotNull(typeMap["GeolocationPosition"]);
+        // Assert.NotNull(typeMap["GeolocationPositionError"]);
+        // Assert.NotNull(typeMap["GeolocationCoordinates"]);
+    }
+}