Feature/bitfield change detector factory

Modspec.Model/Generation/ModspecModelGenerator.cs

@@ -77,7 +77,8 @@ namespace {schema.Name};
                 List<string> bufferInitialisers = [];
                 List<string> fieldInitialisers = [];
                 List<ConstructorParameter> constructorParams = [];
-                WriteGroups(schema.Groups, mainWriter, appendixWriter, bufferInitialisers, fieldInitialisers, constructorParams);
+                List<string> bitfieldPointsWithLevels = [];
+                WriteGroups(schema.Groups, mainWriter, appendixWriter, bufferInitialisers, fieldInitialisers, constructorParams, bitfieldPointsWithLevels: bitfieldPointsWithLevels);
 
                 foreach (RepeatingGroup repeatingGroup in schema.RepeatingGroups)
                 {
@@ -137,6 +138,11 @@ namespace {schema.Name};
                 mainWriter.WriteLine("}");
                 mainWriter.WriteLine();
 
+                if (schema.GenerateChangeDetectionFactory && bitfieldPointsWithLevels.Count > 0)
+                {
+                    WriteChangeDetectionFactory(schema.Name, bitfieldPointsWithLevels, appendixWriter);
+                }
+
                 result = mainWriter.ToString() + appendixWriter.ToString();
                 return true;
             }
@@ -168,7 +174,7 @@ private static void WriteFieldsAndConstructor(string name, StringWriter mainWrit
             mainWriter.WriteLine($"{indent}\t}}");
         }
 
-        private static void WriteGroups(IReadOnlyCollection<Group> groups, StringWriter mainWriter, StringWriter appendixWriter, List<string> bufferInitialisers, List<string> fieldInitialisers, List<ConstructorParameter> constructorParams, string indent = "", string readOffsetField = "")
+        private static void WriteGroups(IReadOnlyCollection<Group> groups, StringWriter mainWriter, StringWriter appendixWriter, List<string> bufferInitialisers, List<string> fieldInitialisers, List<ConstructorParameter> constructorParams, string indent = "", string readOffsetField = "", List<string>? bitfieldPointsWithLevels = null)
         {
             foreach (Group group in groups)
             {
@@ -185,7 +191,7 @@ private static void WriteGroups(IReadOnlyCollection<Group> groups, StringWriter
                         // supplied count of elements, rather than max size of array)
                         throw new InvalidOperationException($"An array must be the last (or only) element in a group.");
                     }
-                    WritePoint(point, bufferName, group.Table, mainWriter, appendixWriter, fieldInitialisers, constructorParams, ref maxOffset, ref bufferSize, indent);
+                    WritePoint(point, bufferName, group.Table, mainWriter, appendixWriter, fieldInitialisers, constructorParams, ref maxOffset, ref bufferSize, indent, bitfieldPointsWithLevels);
                 }
                 if (String.IsNullOrEmpty(bufferSize))
                 {
@@ -209,7 +215,7 @@ private static void WriteGroups(IReadOnlyCollection<Group> groups, StringWriter
             }
         }
 
-        private static void WritePoint(Point point, string bufferName, Table table, StringWriter mainWriter, StringWriter appendixWriter, List<string> fieldInitialisers, List<ConstructorParameter> constructorParams, ref int maxOffset, ref string bufferSize, string indent = "")
+        private static void WritePoint(Point point, string bufferName, Table table, StringWriter mainWriter, StringWriter appendixWriter, List<string> fieldInitialisers, List<ConstructorParameter> constructorParams, ref int maxOffset, ref string bufferSize, string indent = "", List<string>? bitfieldPointsWithLevels = null)
         {
             string type;
             string readMethod;
@@ -337,6 +343,7 @@ private static void WritePoint(Point point, string bufferName, Table table, Stri
                 appendixWriter.WriteLine();
                 if (isFlags && masksByLevel.Count > 0)
                 {
+                    bitfieldPointsWithLevels?.Add(point.Name);
                     appendixWriter.WriteLine($"public static class {point.Name}Extensions");
                     appendixWriter.WriteLine("{");
                     appendixWriter.WriteLine($"\tpublic static Level GetLevel(this {point.Name} self)");
@@ -421,6 +428,24 @@ private static void WritePoint(Point point, string bufferName, Table table, Stri
             maxOffset += point.SizeInBytes * (point.Count?.MaxValue ?? 1);
         }
 
+        private static void WriteChangeDetectionFactory(string schemaName, List<string> points, StringWriter writer)
+        {
+            string clientName = $"{schemaName}Client";
+            writer.WriteLine($"public static class {schemaName}ChangeDetection");
+            writer.WriteLine("{");
+            writer.WriteLine($"\tpublic static BitfieldChangeDetector<{clientName}> CreateDetector()");
+            writer.WriteLine("\t{");
+            writer.WriteLine($"\t\treturn new BitfieldChangeDetector<{clientName}>()");
+            for (int i = 0; i < points.Count; i++)
+            {
+                string terminator = i < points.Count - 1 ? "" : ";";
+                writer.WriteLine($"\t\t\t.Track(c => c.{points[i]}, v => v.GetLevel()){terminator}");
+            }
+            writer.WriteLine("\t}");
+            writer.WriteLine("}");
+            writer.WriteLine();
+        }
+
         private static string ToFieldName(string name)
         {
             Span<char> result = stackalloc char[name.Length + 1];

Modspec.Model/Schema.cs

@@ -48,6 +48,19 @@ public class Schema
     /// </summary>
     public List<RepeatingGroup> RepeatingGroups { get; set; } = [];
 
+    /// <summary>
+    /// If true, the generator will emit a static factory class for creating a
+    /// <c>BitfieldChangeDetector</c> that tracks all bitfield points with level annotations.
+    /// The consuming project must provide a <c>BitfieldChangeDetector&lt;TClient&gt;</c> class
+    /// in the <c>Modspec.Model</c> namespace with the following method:
+    /// <code>
+    /// BitfieldChangeDetector&lt;TClient&gt; Track&lt;T&gt;(Func&lt;TClient, T&gt; getter, Func&lt;T, Level&gt; getLevel)
+    ///     where T : struct, Enum
+    /// </code>
+    /// The <c>Track</c> method must return the detector instance to support fluent chaining.
+    /// </summary>
+    public bool GenerateChangeDetectionFactory { get; set; }
+
     public void Serialise(Stream stream)
     {
         JsonSerializer.Serialize(stream, this, Options);