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Prefab.Base/GenericAttributes.cs

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+using System.Collections.ObjectModel;
+
+namespace Prefab.Base;
+
+/// <summary>
+/// Provides a customizable attribute bag with change tracking for Prefab domain objects.
+/// </summary>
+public class GenericAttributes : ICanBeCustomized
+{
+    private readonly Dictionary<string, object> _attributes = new();
+    private readonly List<GenericAttributeChange> _changes = new();
+
+    /// <inheritdoc />
+    IReadOnlyDictionary<string, object> IHasGenericAttributes.GenericAttributes => new ReadOnlyDictionary<string, object>(_attributes);
+
+    /// <summary>
+    /// Gets the ordered list of attribute mutations recorded since the last call to <see cref="ClearChanges"/>.
+    /// </summary>
+    public IReadOnlyList<GenericAttributeChange> Changes => _changes.AsReadOnly();
+
+    /// <summary>
+    /// Provides an extension point for enforcing key/value requirements before persisting the attribute.
+    /// </summary>
+    /// <param name="key">The attribute key being modified.</param>
+    /// <param name="value">The proposed attribute value.</param>
+    protected virtual void ValidateAttribute(string key, object value)
+    {
+        // Default: no validation. Override in derived classes for custom logic.
+    }
+
+    /// <summary>
+    /// Sets or replaces an attribute value and records the mutation.
+    /// </summary>
+    /// <param name="key">The attribute key to set.</param>
+    /// <param name="value">The attribute value.</param>
+    public void SetAttribute(string key, object value)
+    {
+        _attributes.TryGetValue(key, out var oldValue);
+        ValidateAttribute(key, value);
+        _attributes[key] = value;
+        _changes.Add(new GenericAttributeChange(key, oldValue, value));
+    }
+
+    /// <summary>
+    /// Removes an attribute if present and records the removal.
+    /// </summary>
+    /// <param name="key">The attribute key to remove.</param>
+    /// <returns><c>true</c> when the key existed and was removed; otherwise <c>false</c>.</returns>
+    public bool RemoveAttribute(string key)
+    {
+        if (_attributes.TryGetValue(key, out var oldValue) && _attributes.Remove(key))
+        {
+            _changes.Add(new GenericAttributeChange(key, oldValue, null));
+            return true;
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Attempts to read an attribute value and cast it to the requested type.
+    /// </summary>
+    /// <param name="key">The attribute key to read.</param>
+    /// <param name="value">Receives the typed attribute value when successful.</param>
+    /// <typeparam name="T">The expected attribute type.</typeparam>
+    /// <returns><c>true</c> when the attribute exists and matches the requested type.</returns>
+    public bool TryGetAttribute<T>(string key, out T value)
+    {
+        if (_attributes.TryGetValue(key, out var obj) && obj is T t)
+        {
+            value = t;
+            return true;
+        }
+
+        value = default!;
+        return false;
+    }
+
+    /// <summary>
+    /// Creates an immutable snapshot copy of the current attributes.
+    /// </summary>
+    public IReadOnlyDictionary<string, object> Snapshot() => new ReadOnlyDictionary<string, object>(new Dictionary<string, object>(_attributes));
+
+    /// <summary>
+    /// Clears all recorded attribute changes while keeping the current attribute values intact.
+    /// </summary>
+    public void ClearChanges() => _changes.Clear();
+}