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using System;
using System.Collections;
using System.Collections.Generic;
namespace Xamarin.Forms
{
public abstract class TriggerBase : BindableObject, IAttachedObject
{
bool _isSealed;
internal TriggerBase(Type targetType)
{
if (targetType == null)
throw new ArgumentNullException("targetType");
TargetType = targetType;
EnterActions = new SealedList<TriggerAction>();
ExitActions = new SealedList<TriggerAction>();
}
internal TriggerBase(Condition condition, Type targetType) : this(targetType)
{
Setters = new SealedList<Setter>();
Condition = condition;
Condition.ConditionChanged = OnConditionChanged;
}
public IList<TriggerAction> EnterActions { get; }
public IList<TriggerAction> ExitActions { get; }
public bool IsSealed
{
get { return _isSealed; }
private set
{
if (_isSealed == value)
return;
if (!value)
throw new InvalidOperationException("What is sealed can not be unsealed.");
_isSealed = value;
OnSeal();
}
}
public Type TargetType { get; }
internal Condition Condition { get; }
//Setters and Condition are used by Trigger, DataTrigger and MultiTrigger
internal IList<Setter> Setters { get; }
void IAttachedObject.AttachTo(BindableObject bindable)
{
IsSealed = true;
if (bindable == null)
throw new ArgumentNullException("bindable");
if (!TargetType.IsInstanceOfType(bindable))
throw new InvalidOperationException("bindable not an instance of AssociatedType");
OnAttachedTo(bindable);
}
void IAttachedObject.DetachFrom(BindableObject bindable)
{
if (bindable == null)
throw new ArgumentNullException("bindable");
OnDetachingFrom(bindable);
}
internal virtual void OnAttachedTo(BindableObject bindable)
{
if (Condition != null)
Condition.SetUp(bindable);
}
internal virtual void OnDetachingFrom(BindableObject bindable)
{
if (Condition != null)
Condition.TearDown(bindable);
}
internal virtual void OnSeal()
{
((SealedList<TriggerAction>)EnterActions).IsReadOnly = true;
((SealedList<TriggerAction>)ExitActions).IsReadOnly = true;
if (Setters != null)
((SealedList<Setter>)Setters).IsReadOnly = true;
if (Condition != null)
Condition.IsSealed = true;
}
void OnConditionChanged(BindableObject bindable, bool oldValue, bool newValue)
{
if (newValue)
{
foreach (TriggerAction action in EnterActions)
action.DoInvoke(bindable);
foreach (Setter setter in Setters)
setter.Apply(bindable);
}
else
{
foreach (Setter setter in Setters)
setter.UnApply(bindable);
foreach (TriggerAction action in ExitActions)
action.DoInvoke(bindable);
}
}
internal class SealedList<T> : IList<T>
{
readonly IList<T> _actual;
bool _isReadOnly;
public SealedList()
{
_actual = new List<T>();
}
public void Add(T item)
{
if (IsReadOnly)
throw new InvalidOperationException("This list is ReadOnly");
_actual.Add(item);
}
public void Clear()
{
if (IsReadOnly)
throw new InvalidOperationException("This list is ReadOnly");
_actual.Clear();
}
public bool Contains(T item)
{
return _actual.Contains(item);
}
public void CopyTo(T[] array, int arrayIndex)
{
_actual.CopyTo(array, arrayIndex);
}
public int Count
{
get { return _actual.Count; }
}
public bool IsReadOnly
{
get { return _isReadOnly; }
set
{
if (_isReadOnly == value)
return;
if (!value)
throw new InvalidOperationException("Can't change this back to non readonly");
_isReadOnly = value;
}
}
public bool Remove(T item)
{
if (IsReadOnly)
throw new InvalidOperationException("This list is ReadOnly");
return _actual.Remove(item);
}
IEnumerator IEnumerable.GetEnumerator()
{
return ((IEnumerable)_actual).GetEnumerator();
}
public IEnumerator<T> GetEnumerator()
{
return _actual.GetEnumerator();
}
public int IndexOf(T item)
{
return _actual.IndexOf(item);
}
public void Insert(int index, T item)
{
if (IsReadOnly)
throw new InvalidOperationException("This list is ReadOnly");
_actual.Insert(index, item);
}
public T this[int index]
{
get { return _actual[index]; }
set
{
if (IsReadOnly)
throw new InvalidOperationException("This list is ReadOnly");
_actual[index] = value;
}
}
public void RemoveAt(int index)
{
if (IsReadOnly)
throw new InvalidOperationException("This list is ReadOnly");
_actual.RemoveAt(index);
}
}
}
}
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