Added Validation logics

Toolkit.Foundation/Validation.cs

@@ -1,10 +1,89 @@
-namespace Toolkit.Foundation;
+using System.ComponentModel;
+using System.Linq.Expressions;
 
-public record Validation
+namespace Toolkit.Foundation;
+
+public class Validation(IValidatorCollection validators) :
+    IValidation
 {
-    public static ValidationEventArgs<TValue> As<TValue>(TValue value) =>
-        new(value);
+    public event PropertyChangedEventHandler? PropertyChanged;
 
-    public static ValidationEventArgs<TValue> As<TValue>() where TValue : new() =>
-        new(new TValue());
-}
+    public ValidationErrorCollection Errors { get; } = [];
+
+    public bool HasErrors => 
+        Errors.Count > 0;
+
+    internal IValidatorCollection Validators { get; } = validators;
+
+    public void Add<TProperty>(Expression<Func<TProperty>> property, 
+        ValidationRule[] rules,
+        ValidationTrigger trigger = ValidationTrigger.Deferred)
+    {
+        string? name = GetPropertyName(property);
+        Validators.Add(name, new Validator(name, rules));
+
+        if (trigger is ValidationTrigger.Immediate)
+        {
+            Validate(name);
+        }
+    }
+
+    public virtual void OnPropertyChanged(string propertyName,
+        object? before, object? after)
+    {
+        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+    }
+
+    public bool Validate(string name)
+    {
+        if (Errors.ContainsKey(name))
+        {
+            Errors.Remove(name);
+        }
+
+        if (Validators.TryGet(name, out Validator? validator))
+        {
+            if (validator is not null)
+            {
+                if (!validator.TryValidate(out string? message))
+                {
+                    Errors[name] = message ?? "";
+                }
+            }
+        }
+
+        OnPropertyChanged(nameof(Errors), null, null);
+        OnPropertyChanged(nameof(HasErrors), null, null);
+
+        return !HasErrors;
+    }
+
+    public bool Validate()
+    {
+        Errors.Clear();
+        foreach (Validator? validator in Validators)
+        {
+            if (validator.PropertyName is string name)
+            {
+                if (!validator.TryValidate(out string? message))
+                {
+                    Errors[name] = message ?? "";
+                }
+            }
+        }
+
+        OnPropertyChanged(nameof(Errors), null, null);
+        OnPropertyChanged(nameof(HasErrors), null, null);
+
+        return !HasErrors;
+    }
+
+    private string GetPropertyName<T>(Expression<Func<T>> predicate)
+    {
+        Expression? body = predicate.Body;
+        MemberExpression? memberExpression = body as MemberExpression ??
+            (MemberExpression)((UnaryExpression)body).Operand;
+
+        return memberExpression.Member.Name;
+    }
+}