// Copyright (c) 2019 .NET Foundation and Contributors. All rights reserved.

// Licensed to the .NET Foundation under one or more agreements.

// The .NET Foundation licenses this file to you under the MIT license.

// See the LICENSE file in the project root for full license information.

using System;

using System.Collections.Generic;

using System.Collections.Specialized;

using System.Diagnostics.CodeAnalysis;

using System.Linq;

using Android.Views;

using AndroidX.ViewPager.Widget;

using DynamicData;

using DynamicData.Binding;

using Splat;

using Object = Java.Lang.Object;

namespace ReactiveUI.AndroidX

{

/// <summary>

/// ReactivePagerAdapter is a PagerAdapter that will interface with a

/// Observable change set, in a similar fashion to ReactiveTableViewSource.

/// </summary>

/// <typeparam name="TViewModel">The view model type.</typeparam>

[SuppressMessage("StyleCop.CSharp.MaintainabilityRules", "SA1402:FileMayOnlyContainASingleType", Justification = "Classes with the same class names within.")]

public class ReactivePagerAdapter<TViewModel> : PagerAdapter, IEnableLogger

where TViewModel : class

{

private readonly SourceList<TViewModel> _list;

private readonly Func<TViewModel, ViewGroup, View> _viewCreator;

private readonly Action<TViewModel, View> _viewInitializer;

private readonly IDisposable _inner;

/// <summary>

/// Initializes a new instance of the <see cref="ReactivePagerAdapter{TViewModel}"/> class.

/// </summary>

/// <param name="changeSet">The change set to page.</param>

/// <param name="viewCreator">A function which will create the view.</param>

/// <param name="viewInitializer">A action which will initialize a view.</param>

public ReactivePagerAdapter(

IObservable<IChangeSet<TViewModel>> changeSet,

Func<TViewModel, ViewGroup, View> viewCreator,

Action<TViewModel, View> viewInitializer = null)

{

_list = new SourceList<TViewModel>(changeSet);

_viewCreator = viewCreator;

_viewInitializer = viewInitializer;

_inner = _list.Connect().Subscribe(_ => NotifyDataSetChanged());

}

/// <inheritdoc/>

public override int Count => _list.Count;

/// <inheritdoc/>

public override bool IsViewFromObject(View view, Object @object)

{

return (View)@object == view;

}

/// <inheritdoc/>

public override Object InstantiateItem(ViewGroup container, int position)

{

var data = _list.Items.ElementAt(position);

// NB: PagerAdapter does not recycle itself.

var theView = _viewCreator(data, container);

var ivf = theView.GetViewHost() as IViewFor<TViewModel>;

if (ivf != null)

{

ivf.ViewModel = data;

}

_viewInitializer?.Invoke(data, theView);

container.AddView(theView, 0);

return theView;

}

/// <inheritdoc/>

public override void DestroyItem(ViewGroup container, int position, Object item)

{

if (container == null)

{

throw new ArgumentNullException(nameof(container));

}

if (item == null)

{

throw new ArgumentNullException(nameof(item));

}

if (!(item is View view))

{

throw new ArgumentException("Item must be of type View", nameof(item));

}

container.RemoveView(view);

}

/// <inheritdoc/>

protected override void Dispose(bool disposing)

{

if (disposing)

{

_inner?.Dispose();

_list?.Dispose();

}

base.Dispose(disposing);

}

}

/// <summary>

/// ReactivePagerAdapter is a PagerAdapter that will interface with a

/// Observable change set, in a similar fashion to ReactiveTableViewSource.

/// </summary>

/// <typeparam name="TViewModel">The view model type.</typeparam>

/// <typeparam name="TCollection">The type of collection.</typeparam>

[SuppressMessage("StyleCop.CSharp.MaintainabilityRules", "SA1402:FileMayOnlyContainASingleType", Justification = "Classes with the same class names within.")]

public class ReactivePagerAdapter<TViewModel, TCollection> : ReactivePagerAdapter<TViewModel>

where TViewModel : class

where TCollection : INotifyCollectionChanged, IEnumerable<TViewModel>

{

/// <summary>

/// Initializes a new instance of the <see cref="ReactivePagerAdapter{TViewModel, TCollection}"/> class.

/// </summary>

/// <param name="collection">The collection to page.</param>

/// <param name="viewCreator">The function which will create the view.</param>

/// <param name="viewInitializer">A action which will initialize the view.</param>

public ReactivePagerAdapter(

TCollection collection,

Func<TViewModel, ViewGroup, View> viewCreator,

Action<TViewModel, View> viewInitializer = null)

: base(collection.ToObservableChangeSet<TCollection, TViewModel>(), viewCreator, viewInitializer)

{

}

}

#pragma warning restore SA1600 // Elements should be documented

}