Basic value preprocessor implementation

plist-cil/ValuePreprocessor.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Collections.Generic;
+
+namespace Claunia.PropertyList
+{
+    /// <summary>
+    ///     Allows you to override the default value class initialization for the values found
+    ///     in the parsed plists by registering your own preprocessing implementations.
+    /// </summary>
+    public static class ValuePreprocessor
+    {
+        public enum Types
+        {
+            BOOL, INTEGER, FLOATING_POINT, UNDEFINED_NUMBER,
+            STRING, DATA, DATE
+        };
+        
+        private record struct TypeIdentifier(Types ValueType, Type ProcessingType);
+        private static T NullPreprocessor<T>(T value) => value;
+
+        private static readonly Dictionary<TypeIdentifier, Delegate> _preprocessors = new()
+        {
+            { new(Types.BOOL, typeof(bool)), NullPreprocessor<bool> },
+            { new(Types.BOOL, typeof(string)), NullPreprocessor<string> },
+            { new(Types.INTEGER, typeof(string)), NullPreprocessor<string> },
+            { new(Types.FLOATING_POINT, typeof(string)), NullPreprocessor<string> },
+            { new(Types.UNDEFINED_NUMBER, typeof(string)), NullPreprocessor<string> },
+            { new(Types.STRING, typeof(string)), NullPreprocessor<string> },
+            { new(Types.DATA, typeof(string)), NullPreprocessor<string> },
+            { new(Types.DATA, typeof(byte[])), NullPreprocessor<byte[]> },
+            { new(Types.DATE, typeof(string)), NullPreprocessor<string> },
+            { new(Types.DATE, typeof(double)), NullPreprocessor<double> },
+        };
+
+        public static void Register<T>(Func<T, T> preprocessor, Types type) => 
+            _preprocessors[new(type, typeof(T))] = preprocessor;
+
+        public static T Preprocess<T>(T value, Types type) => 
+            TryGetPreprocessor(type, out Func<T, T> preprocess)
+                ? preprocess(value)
+                : throw new ArgumentException($"Failed to find a preprocessor for value '{value}'.");
+
+        private static bool TryGetPreprocessor<T>(Types type, out Func<T, T> preprocess)
+        {
+            if(_preprocessors.TryGetValue(new TypeIdentifier(type, typeof(T)), out Delegate preprocessor))
+            {
+                preprocess = (Func<T, T>) preprocessor;
+                return true;
+            }
+
+            preprocess = default;
+            return false;
+        }
+    }
+
+}