New binding mechanism: Expression tracking

2023-08-15 13:17:42 +02:00
parent 335433562a
commit b792639635
35 changed files with 971 additions and 311 deletions
--- a/src/Library/TerminalUI/ExpressionTrackers/ExpressionTrackerBase.cs
+++ b/src/Library/TerminalUI/ExpressionTrackers/ExpressionTrackerBase.cs
@@ -0,0 +1,82 @@
+using System.Collections.Specialized;
+using System.ComponentModel;
+
+namespace TerminalUI.ExpressionTrackers;
+
+public abstract class ExpressionTrackerBase : IExpressionTracker
+{
+    private object? _currentValue;
+    public List<string> TrackedPropertyNames { get; } = new();
+
+    protected bool SubscribeToValueChanges { get; set; } = true;
+
+    public event Action<string>? PropertyChanged;
+    public event Action<bool>? Update;
+    public object? GetValue() => _currentValue;
+    protected abstract object? ComputeValue();
+
+    protected void SubscribeToTracker(IExpressionTracker? expressionTracker)
+    {
+        if (expressionTracker is null) return;
+        expressionTracker.Update += UpdateValueAndChangeTrackers;
+    }
+
+    protected void UpdateValueAndChangeTrackers() => UpdateValueAndChangeTrackers(true);
+
+    private void UpdateValueAndChangeTrackers(bool couldCompute)
+    {
+        if (SubscribeToValueChanges)
+        {
+            if (_currentValue is INotifyPropertyChanged oldNotifyPropertyChanged)
+                oldNotifyPropertyChanged.PropertyChanged -= OnPropertyChanged;
+            if (_currentValue is INotifyCollectionChanged collectionChanged)
+                collectionChanged.CollectionChanged -= OnCollectionChanged;
+        }
+
+        var useNull = false;
+        try
+        {
+            if (couldCompute)
+            {
+                _currentValue = ComputeValue();
+
+                if (SubscribeToValueChanges)
+                {
+                    if (_currentValue is INotifyPropertyChanged notifyPropertyChanged)
+                        notifyPropertyChanged.PropertyChanged += OnPropertyChanged;
+                    if (_currentValue is INotifyCollectionChanged collectionChanged)
+                        collectionChanged.CollectionChanged += OnCollectionChanged;
+                }
+
+                Update?.Invoke(true);
+            }
+            else
+            {
+                useNull = true;
+            }
+        }
+        catch (Exception e)
+        {
+            useNull = true;
+        }
+
+        if (useNull)
+        {
+            _currentValue = null;
+            Update?.Invoke(false);
+        }
+    }
+
+    private void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e) 
+        => UpdateValueAndChangeTrackers();
+
+    private void OnPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName is null) return;
+
+        if (TrackedPropertyNames.Contains(e.PropertyName))
+        {
+            PropertyChanged?.Invoke(e.PropertyName);
+        }
+    }
+}