using System;
using System.Linq;

namespace Sandbox;

public static class SceneExtensions
{
	/// <param name="scene">The scene to search in.</param>
	extension( Scene scene )
	{
		/// <summary>
		/// Searches the scene for any enabled gameobjects with the DontDestroyOnLoad flag and destroys them.
		/// </summary>
		/// <param name="ignored">Component types to ignore deletion.</param>
		public void DestroyPersistentObjects( Type[] ignored = null )
		{
			var objects = scene.GetAllObjects( true )
				.Where( x => x.Flags == GameObjectFlags.DontDestroyOnLoad );
			
			if ( ignored is null || ignored.Length == 0 )
			{
				foreach ( var go in objects )
				{
					go.Destroy();
				}
				return;
			}
			
			var ignoredSet = ignored.ToHashSet();
			foreach ( var go in objects )
			{
				var hasIgnoredType = ignoredSet.Any( type => go.Components.Get( type ) is not null );
				if ( !hasIgnoredType )
				{
					go.Destroy();
				}
			}
		}
		
		/// <summary>
		/// Search the scene for a specific component instance.
		/// </summary>
		/// <typeparam name="T">Component to search for.</typeparam>
		/// <returns>Found component instance.</returns>
		/// <exception cref="InvalidOperationException">Thrown if no instance or multiple instances are found.</exception>
		public T GetInstance<T>() where T : Component
		{
			var components = scene.GetAllComponents<T>().ToList();
			return components.Count switch
			{
				0 => throw new InvalidOperationException( $"No instance of type {typeof(T).Name} found in scene." ),
				1 => components[0],
				_ => throw new InvalidOperationException( $"Multiple instances of type {typeof(T).Name} found in scene. Expected singleton." )
			};
		}
	}
}