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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Reflection;
using Xamarin.Forms.Internals;
using System.Runtime.CompilerServices;
namespace Xamarin.Forms
{
internal class BindingExpression
{
internal const string PropertyNotFoundErrorMessage = "'{0}' property not found on '{1}', target property: '{2}.{3}'";
readonly List<BindingExpressionPart> _parts = new List<BindingExpressionPart>();
BindableProperty _targetProperty;
WeakReference<object> _weakSource;
WeakReference<BindableObject> _weakTarget;
internal BindingExpression(BindingBase binding, string path)
{
if (binding == null)
throw new ArgumentNullException(nameof(binding));
if (path == null)
throw new ArgumentNullException(nameof(path));
Binding = binding;
Path = path;
ParsePath();
}
internal BindingBase Binding { get; }
internal string Path { get; }
/// <summary>
/// Applies the binding expression to a previously set source and target.
/// </summary>
internal void Apply(bool fromTarget = false)
{
if (_weakSource == null || _weakTarget == null)
return;
BindableObject target;
if (!_weakTarget.TryGetTarget(out target))
{
Unapply();
return;
}
object source;
if (_weakSource.TryGetTarget(out source) && _targetProperty != null)
ApplyCore(source, target, _targetProperty, fromTarget);
}
/// <summary>
/// Applies the binding expression to a new source or target.
/// </summary>
internal void Apply(object sourceObject, BindableObject target, BindableProperty property)
{
_targetProperty = property;
BindableObject prevTarget;
if (_weakTarget != null && _weakTarget.TryGetTarget(out prevTarget) && !ReferenceEquals(prevTarget, target))
throw new InvalidOperationException("Binding instances can not be reused");
object previousSource;
if (_weakSource != null && _weakSource.TryGetTarget(out previousSource) && !ReferenceEquals(previousSource, sourceObject))
throw new InvalidOperationException("Binding instances can not be reused");
_weakSource = new WeakReference<object>(sourceObject);
_weakTarget = new WeakReference<BindableObject>(target);
ApplyCore(sourceObject, target, property);
}
internal void Unapply()
{
object sourceObject;
if (_weakSource != null && _weakSource.TryGetTarget(out sourceObject))
{
for (var i = 0; i < _parts.Count - 1; i++)
{
BindingExpressionPart part = _parts[i];
if (!part.IsSelf)
{
part.TryGetValue(sourceObject, out sourceObject);
}
part.Unsubscribe();
}
}
_weakSource = null;
_weakTarget = null;
}
/// <summary>
/// Applies the binding expression to a previously set source or target.
/// </summary>
void ApplyCore(object sourceObject, BindableObject target, BindableProperty property, bool fromTarget = false)
{
BindingMode mode = Binding.GetRealizedMode(_targetProperty);
if ((mode == BindingMode.OneWay || mode == BindingMode.OneTime) && fromTarget)
return;
bool needsGetter = (mode == BindingMode.TwoWay && !fromTarget) || mode == BindingMode.OneWay || mode == BindingMode.OneTime;
bool needsSetter = !needsGetter && ((mode == BindingMode.TwoWay && fromTarget) || mode == BindingMode.OneWayToSource);
object current = sourceObject;
object previous = null;
BindingExpressionPart part = null;
for (var i = 0; i < _parts.Count; i++)
{
part = _parts[i];
bool isLast = i + 1 == _parts.Count;
if (!part.IsSelf && current != null)
{
// Allow the object instance itself to provide its own TypeInfo
var reflectable = current as IReflectableType;
TypeInfo currentType = reflectable != null ? reflectable.GetTypeInfo() : current.GetType().GetTypeInfo();
if (part.LastGetter == null || !part.LastGetter.DeclaringType.GetTypeInfo().IsAssignableFrom(currentType))
SetupPart(currentType, part);
if (!isLast)
part.TryGetValue(current, out current);
}
if (!part.IsSelf && current != null)
{
if ((needsGetter && part.LastGetter == null) || (needsSetter && part.NextPart == null && part.LastSetter == null))
{
Log.Warning("Binding", PropertyNotFoundErrorMessage, part.Content, current, target.GetType(), property.PropertyName);
break;
}
}
if (mode == BindingMode.OneWay || mode == BindingMode.TwoWay)
{
var inpc = current as INotifyPropertyChanged;
if (inpc != null && !ReferenceEquals(current, previous))
part.Subscribe(inpc);
}
previous = current;
}
Debug.Assert(part != null, "There should always be at least the self part in the expression.");
if (needsGetter)
{
object value = property.DefaultValue;
if (part.TryGetValue(current, out value) || part.IsSelf)
{
value = Binding.GetSourceValue(value, property.ReturnType);
}
else
value = Binding.FallbackValue ?? property.DefaultValue;
if (!TryConvert(part, ref value, property.ReturnType, true))
{
Log.Warning("Binding", "{0} can not be converted to type '{1}'", value, property.ReturnType);
return;
}
target.SetValueCore(property, value, SetValueFlags.ClearDynamicResource, BindableObject.SetValuePrivateFlags.Default | BindableObject.SetValuePrivateFlags.Converted);
}
else if (needsSetter && part.LastSetter != null && current != null)
{
object value = Binding.GetTargetValue(target.GetValue(property), part.SetterType);
if (!TryConvert(part, ref value, part.SetterType, false))
{
Log.Warning("Binding", "{0} can not be converted to type '{1}'", value, part.SetterType);
return;
}
object[] args;
if (part.IsIndexer)
{
args = new object[part.Arguments.Length + 1];
part.Arguments.CopyTo(args, 0);
args[args.Length - 1] = value;
}
else if (part.IsBindablePropertySetter)
{
args = new[] { part.BindablePropertyField, value };
}
else
{
args = new[] { value };
}
part.LastSetter.Invoke(current, args);
}
}
IEnumerable<BindingExpressionPart> GetPart(string part)
{
part = part.Trim();
if (part == string.Empty)
throw new FormatException("Path contains an empty part");
BindingExpressionPart indexer = null;
int lbIndex = part.IndexOf('[');
if (lbIndex != -1)
{
int rbIndex = part.LastIndexOf(']');
if (rbIndex == -1)
throw new FormatException("Indexer did not contain closing bracket");
int argLength = rbIndex - lbIndex - 1;
if (argLength == 0)
throw new FormatException("Indexer did not contain arguments");
string argString = part.Substring(lbIndex + 1, argLength);
indexer = new BindingExpressionPart(this, argString, true);
part = part.Substring(0, lbIndex);
part = part.Trim();
}
if (part.Length > 0)
yield return new BindingExpressionPart(this, part);
if (indexer != null)
yield return indexer;
}
void ParsePath()
{
string p = Path.Trim();
var last = new BindingExpressionPart(this, ".");
_parts.Add(last);
if (p[0] == '.')
{
if (p.Length == 1)
return;
p = p.Substring(1);
}
string[] pathParts = p.Split('.');
for (var i = 0; i < pathParts.Length; i++)
{
foreach (BindingExpressionPart part in GetPart(pathParts[i]))
{
last.NextPart = part;
_parts.Add(part);
last = part;
}
}
}
void SetupPart(TypeInfo sourceType, BindingExpressionPart part)
{
part.Arguments = null;
part.LastGetter = null;
part.LastSetter = null;
PropertyInfo property = null;
if (part.IsIndexer)
{
if (sourceType.IsArray)
{
int index;
if (!int.TryParse(part.Content, out index))
Log.Warning("Binding", "{0} could not be parsed as an index for a {1}", part.Content, sourceType);
else
part.Arguments = new object[] { index };
part.LastGetter = sourceType.GetDeclaredMethod("Get");
part.LastSetter = sourceType.GetDeclaredMethod("Set");
part.SetterType = sourceType.GetElementType();
}
DefaultMemberAttribute defaultMember = sourceType.GetCustomAttributes(typeof(DefaultMemberAttribute), true).OfType<DefaultMemberAttribute>().FirstOrDefault();
string indexerName = defaultMember != null ? defaultMember.MemberName : "Item";
part.IndexerName = indexerName;
#if NETSTANDARD2_0
try {
property = sourceType.GetDeclaredProperty(indexerName);
}
catch (AmbiguousMatchException) {
// Get most derived instance of property
foreach (var p in sourceType.GetProperties().Where(prop => prop.Name == indexerName)) {
if (property == null || property.DeclaringType.IsAssignableFrom(property.DeclaringType))
property = p;
}
}
#else
property = sourceType.GetDeclaredProperty(indexerName);
#endif
if (property == null) //is the indexer defined on the base class?
property = sourceType.BaseType.GetProperty(indexerName);
if (property == null) //is the indexer defined on implemented interface ?
{
foreach (var implementedInterface in sourceType.ImplementedInterfaces)
{
property = implementedInterface.GetProperty(indexerName);
if (property != null)
break;
}
}
if (property != null)
{
ParameterInfo parameter = property.GetIndexParameters().FirstOrDefault();
if (parameter != null)
{
try
{
object arg = Convert.ChangeType(part.Content, parameter.ParameterType, CultureInfo.InvariantCulture);
part.Arguments = new[] { arg };
}
catch (FormatException)
{
}
catch (InvalidCastException)
{
}
catch (OverflowException)
{
}
}
}
}
else {
TypeInfo type = sourceType;
while (type != null && property == null) {
property = type.GetDeclaredProperty(part.Content);
type = type.BaseType?.GetTypeInfo();
}
}
if (property != null)
{
if (property.CanRead && property.GetMethod.IsPublic && !property.GetMethod.IsStatic)
part.LastGetter = property.GetMethod;
if (property.CanWrite && property.SetMethod.IsPublic && !property.SetMethod.IsStatic)
{
part.LastSetter = property.SetMethod;
part.SetterType = part.LastSetter.GetParameters().Last().ParameterType;
if (Binding.AllowChaining)
{
FieldInfo bindablePropertyField = sourceType.GetDeclaredField(part.Content + "Property");
if (bindablePropertyField != null && bindablePropertyField.FieldType == typeof(BindableProperty) && sourceType.ImplementedInterfaces.Contains(typeof(IElementController)))
{
MethodInfo setValueMethod = null;
#if NETSTANDARD1_0
foreach (MethodInfo m in sourceType.AsType().GetRuntimeMethods())
{
if (m.Name.EndsWith("IElementController.SetValueFromRenderer"))
{
ParameterInfo[] parameters = m.GetParameters();
if (parameters.Length == 2 && parameters[0].ParameterType == typeof(BindableProperty))
{
setValueMethod = m;
break;
}
}
}
#else
setValueMethod = typeof(IElementController).GetMethod("SetValueFromRenderer", new[] { typeof(BindableProperty), typeof(object) });
#endif
if (setValueMethod != null)
{
part.LastSetter = setValueMethod;
part.IsBindablePropertySetter = true;
part.BindablePropertyField = bindablePropertyField.GetValue(null);
}
}
}
}
#if !NETSTANDARD1_0
TupleElementNamesAttribute tupleEltNames;
if ( property != null
&& part.NextPart != null
&& property.PropertyType.IsGenericType
&& ( property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<>)
|| property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<,>)
|| property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<,,>)
|| property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<,,,>)
|| property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<,,,,>)
|| property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<,,,,,>)
|| property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<,,,,,,>)
|| property.PropertyType.GetGenericTypeDefinition() == typeof(ValueTuple<,,,,,,,>))
&& (tupleEltNames = property.GetCustomAttribute(typeof(TupleElementNamesAttribute)) as TupleElementNamesAttribute) != null)
{
//modify the nextPart to access the tuple item via the ITuple indexer
var nextPart = part.NextPart;
var name = nextPart.Content;
var index = tupleEltNames.TransformNames.IndexOf(name);
if (index >= 0)
{
nextPart.IsIndexer = true;
nextPart.Content = index.ToString();
}
}
#endif
}
}
static Type[] DecimalTypes = new[] { typeof(float), typeof(decimal), typeof(double) };
bool TryConvert(BindingExpressionPart part, ref object value, Type convertTo, bool toTarget)
{
if (value == null)
return true;
if ((toTarget && _targetProperty.TryConvert(ref value)) || (!toTarget && convertTo.IsInstanceOfType(value)))
return true;
object original = value;
try
{
var stringValue = value as string ?? string.Empty;
// see: https://bugzilla.xamarin.com/show_bug.cgi?id=32871
// do not canonicalize "*.[.]"; "1." should not update bound BindableProperty
if (stringValue.EndsWith(".") && DecimalTypes.Contains(convertTo))
throw new FormatException();
// do not canonicalize "-0"; user will likely enter a period after "-0"
if (stringValue == "-0" && DecimalTypes.Contains(convertTo))
throw new FormatException();
value = Convert.ChangeType(value, convertTo, CultureInfo.InvariantCulture);
return true;
}
catch (InvalidCastException)
{
value = original;
return false;
}
catch (FormatException)
{
value = original;
return false;
}
catch (OverflowException)
{
value = original;
return false;
}
}
class BindingPair
{
public BindingPair(BindingExpressionPart part, object source, bool isLast)
{
Part = part;
Source = source;
IsLast = isLast;
}
public bool IsLast { get; set; }
public BindingExpressionPart Part { get; private set; }
public object Source { get; private set; }
}
internal class WeakPropertyChangedProxy
{
readonly WeakReference<INotifyPropertyChanged> _source = new WeakReference<INotifyPropertyChanged>(null);
readonly WeakReference<PropertyChangedEventHandler> _listener = new WeakReference<PropertyChangedEventHandler>(null);
readonly PropertyChangedEventHandler _handler;
readonly EventHandler _bchandler;
internal WeakReference<INotifyPropertyChanged> Source => _source;
public WeakPropertyChangedProxy()
{
_handler = new PropertyChangedEventHandler(OnPropertyChanged);
_bchandler = new EventHandler(OnBCChanged);
}
public WeakPropertyChangedProxy(INotifyPropertyChanged source, PropertyChangedEventHandler listener) : this()
{
SubscribeTo(source, listener);
}
public void SubscribeTo(INotifyPropertyChanged source, PropertyChangedEventHandler listener)
{
source.PropertyChanged += _handler;
var bo = source as BindableObject;
if (bo != null)
bo.BindingContextChanged += _bchandler;
_source.SetTarget(source);
_listener.SetTarget(listener);
}
public void Unsubscribe()
{
INotifyPropertyChanged source;
if (_source.TryGetTarget(out source) && source != null)
source.PropertyChanged -= _handler;
var bo = source as BindableObject;
if (bo != null)
bo.BindingContextChanged -= _bchandler;
_source.SetTarget(null);
_listener.SetTarget(null);
}
void OnPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (_listener.TryGetTarget(out var handler) && handler != null)
handler(sender, e);
else
Unsubscribe();
}
void OnBCChanged(object sender, EventArgs e)
{
OnPropertyChanged(sender, new PropertyChangedEventArgs("BindingContext"));
}
}
class BindingExpressionPart
{
readonly BindingExpression _expression;
readonly PropertyChangedEventHandler _changeHandler;
WeakPropertyChangedProxy _listener;
public BindingExpressionPart(BindingExpression expression, string content, bool isIndexer = false)
{
_expression = expression;
IsSelf = content == Forms.Binding.SelfPath;
Content = content;
IsIndexer = isIndexer;
_changeHandler = PropertyChanged;
}
public void Subscribe(INotifyPropertyChanged handler)
{
INotifyPropertyChanged source;
if (_listener != null && _listener.Source.TryGetTarget(out source) && ReferenceEquals(handler, source))
// Already subscribed
return;
// Clear out the old subscription if necessary
Unsubscribe();
_listener = new WeakPropertyChangedProxy(handler, _changeHandler);
}
public void Unsubscribe()
{
var listener = _listener;
if (listener != null)
{
listener.Unsubscribe();
_listener = null;
}
}
public object[] Arguments { get; set; }
public object BindablePropertyField { get; set; }
public string Content { get; internal set; }
public string IndexerName { get; set; }
public bool IsBindablePropertySetter { get; set; }
public bool IsIndexer { get; internal set; }
public bool IsSelf { get; }
public MethodInfo LastGetter { get; set; }
public MethodInfo LastSetter { get; set; }
public BindingExpressionPart NextPart { get; set; }
public Type SetterType { get; set; }
public void PropertyChanged(object sender, PropertyChangedEventArgs args)
{
BindingExpressionPart part = NextPart ?? this;
string name = args.PropertyName;
if (!string.IsNullOrEmpty(name))
{
if (part.IsIndexer)
{
if (name.Contains("["))
{
if (name != string.Format("{0}[{1}]", part.IndexerName, part.Content))
return;
}
else if (name != part.IndexerName)
return;
}
else if (name != part.Content)
{
return;
}
}
Device.BeginInvokeOnMainThread(() => _expression.Apply());
}
public bool TryGetValue(object source, out object value)
{
value = source;
if (LastGetter != null && value != null)
{
if (IsIndexer)
{
try
{
value = LastGetter.Invoke(value, Arguments);
}
catch (TargetInvocationException ex)
{
if (!(ex.InnerException is KeyNotFoundException))
throw;
value = null;
}
return true;
}
value = LastGetter.Invoke(value, Arguments);
return true;
}
return false;
}
}
}
}