@inherits DComponentBase
@implements IDisposable

@* One item of a DAccordion: a DCollapse (so collapse + neo-raised, keyboard and aria-expanded come from there) whose
   open state is the accordion's Active index. Opening it closes the others; clicking it while open closes it. *@
<DCollapse @attributes="AdditionalAttributes" IsOpen="@IsOpen" IsOpenChanged="OnIsOpenChanged" Icon="@Parent.Icon"
		   Disabled="@Disabled" HeaderClass="@HeaderClass" ContentClass="@ContentClass" Header="@Header"
		   Class="@Cx(Parent.Joined ? "join-item shadow-none!" : null, Class)">
	@ChildContent
</DCollapse>

@code {
	[CascadingParameter] DAccordion Parent { get; set; }
	[Parameter] public RenderFragment Header { get; set; }
	[Parameter] public RenderFragment ChildContent { get; set; }
	[Parameter] public bool Disabled { get; set; }
	[Parameter] public string HeaderClass { get; set; }
	[Parameter] public string ContentClass { get; set; }

	bool IsOpen => Parent.Active >= 0 && Parent.Active == Parent.IndexOf(this);

	protected override void OnInitialized()
	{
		if (Parent is null)
			throw new InvalidOperationException($"{nameof(DAccordionItem)} must be inside a {nameof(DAccordion)}.");
		Parent.Add(this);
	}

	Task OnIsOpenChanged(bool isOpen) => Parent.Select(isOpen ? Parent.IndexOf(this) : -1);

	public void Dispose() => Parent?.Remove(this);
}