Added plugin architecture (#322)

app/MindWork AI Studio/Tools/PluginSystem/ForbiddenPlugins.cs

@@ -0,0 +1,99 @@
+namespace AIStudio.Tools.PluginSystem;
+
+/// <summary>
+/// Checks if a plugin is forbidden.
+/// </summary>
+public static class ForbiddenPlugins
+{
+    private const string ID_PATTERN = "ID = \"";
+    private static readonly int ID_PATTERN_LEN = ID_PATTERN.Length;
+    
+    /// <summary>
+    /// Checks if the given code represents a forbidden plugin.
+    /// </summary>
+    /// <param name="code">The code to check.</param>
+    /// <returns>The result of the check.</returns>
+    public static PluginCheckResult Check(ReadOnlySpan<char> code)
+    {
+        var endIndex = 0;
+        var foundAnyId = false;
+        var id = ReadOnlySpan<char>.Empty;
+        while (true)
+        {
+            // Create a slice of the code starting at the end index.
+            // This way we can search for all IDs in the code:
+            code = code[endIndex..];
+            
+            // Read the next ID as a string:
+            if (!TryGetId(code, out id, out endIndex))
+            {
+                // When no ID was found at all, we block this plugin.
+                // When another ID was found previously, we allow this plugin.
+                if(foundAnyId)
+                    return new PluginCheckResult(false, null);
+                
+                return new PluginCheckResult(true, "No ID was found.");
+            }
+            
+            // Try to parse the ID as a GUID:
+            if (!Guid.TryParse(id, out var parsedGuid))
+            {
+                // Again, when no ID was found at all, we block this plugin.
+                if(foundAnyId)
+                    return new PluginCheckResult(false, null);
+                
+                return new PluginCheckResult(true, "The ID is not a valid GUID.");
+            }
+
+            // Check if the GUID is forbidden:
+            if (FORBIDDEN_PLUGINS.TryGetValue(parsedGuid, out var reason))
+                return new PluginCheckResult(true, reason);
+            
+            foundAnyId = true;
+        }
+    }
+    
+    private static bool TryGetId(ReadOnlySpan<char> code, out ReadOnlySpan<char> id, out int endIndex)
+    {
+        //
+        // Please note: the code variable is a slice of the original code.
+        // That means the indices are relative to the slice, not the original code.
+        //
+        
+        id = ReadOnlySpan<char>.Empty;
+        endIndex = 0;
+        
+        // Find the next ID:
+        var idStartIndex = code.IndexOf(ID_PATTERN);
+        if (idStartIndex < 0)
+            return false;
+        
+        // Find the start index of the value (Guid):
+        var valueStartIndex = idStartIndex + ID_PATTERN_LEN;
+        
+        // Find the end index of the value. In order to do that,
+        // we create a slice of the code starting at the value
+        // start index. That means that the end index is relative
+        // to the inner slice, not the original code nor the outer slice.
+        var valueEndIndex = code[valueStartIndex..].IndexOf('"');
+        if (valueEndIndex < 0)
+            return false;
+        
+        // From the perspective of the start index is the end index
+        // the length of the value:
+        endIndex = valueStartIndex + valueEndIndex;
+        id = code.Slice(valueStartIndex, valueEndIndex);
+        return true;
+    }
+    
+    /// <summary>
+    /// The forbidden plugins.
+    /// </summary>
+    /// <remarks>
+    /// A dictionary that maps the GUID of a plugin to the reason why it is forbidden.
+    /// </remarks>
+    // ReSharper disable once CollectionNeverUpdated.Local
+    private static readonly Dictionary<Guid, string> FORBIDDEN_PLUGINS =
+    [
+    ];
+}