Connected.Components/Components/ItemsControlBase.cs

using Connected.Annotations;
using Microsoft.AspNetCore.Components;

namespace Connected.Components;

public abstract class ItemsControlBase<TChildComponent> : UIComponent
		 where TChildComponent : UIComponent

{
	/// <summary>
	/// Collection of T
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.General.Data)]
	public RenderFragment ChildContent { get; set; }

	/// <summary>
	/// Items - will be ignored when ItemsSource is not null
	/// </summary>
	public List<TChildComponent> Items { get; } = new List<TChildComponent>();

	private int _selectedIndexField = -1;
	/// <summary>
	/// Selected Item's index
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.General.Behavior)]
	public int SelectedIndex
	{
		get => _selectedIndexField;
		set
		{
			if (SelectedIndex == value)
				return;

			LastContainer = _selectedIndexField >= 0 ? SelectedContainer : null;
			_selectedIndexField = value;
			SelectionChanged();
			StateHasChanged();
			SelectedIndexChanged.InvokeAsync(value);
		}
	}

	[Parameter]
	public EventCallback<int> SelectedIndexChanged { get; set; }

	/// <summary>
	/// Gets the Selected TChildComponent
	/// </summary>
	public TChildComponent LastContainer { get; private set; } = null;

	/// <summary>
	/// Gets the Selected TChildComponent
	/// </summary>
	public TChildComponent SelectedContainer
	{
		get => SelectedIndex >= 0 && Items.Count > SelectedIndex ? Items[SelectedIndex] : null;
	}

	protected override Task OnAfterRenderAsync(bool firstRender)
	{
		if (firstRender)
		{
			if (Items.Count > 0 && SelectedIndex < 0)
				MoveTo(0);

		}
		return base.OnAfterRenderAsync(firstRender);
	}

	internal bool _moveNext = true;

	/// <summary>
	/// Move to Previous Item
	/// </summary>
	public void Previous()
	{
		_moveNext = false;

		if (SelectedIndex > 0)
			SelectedIndex--;
		else
			SelectedIndex = Items.Count - 1;
	}

	/// <summary>
	/// Move to Next Item
	/// </summary>
	public void Next()
	{
		_moveNext = true;

		if (SelectedIndex < (Items.Count - 1))
			SelectedIndex++;
		else
			SelectedIndex = 0;
	}

	/// <summary>
	/// Move to Item at desired index
	/// </summary>
	public void MoveTo(int index)
	{
		if (SelectedIndex != index)
		{
			_moveNext = index >= SelectedIndex;
			SelectedIndex = index;
		}
	}

	protected virtual void SelectionChanged() { }

	public virtual void AddItem(TChildComponent item) { }
}