using Godot;
using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;

/// <summary>
/// Provides defer-like behavior that's easier to work with in C#
/// </summary>
public partial class defer_manager : Node
{
	// Called when the node enters the scene tree for the first time.
	public override void _Ready()
	{
	}
	private readonly ConcurrentQueue<Action> ActionQueue = new();
	// Called every frame. 'delta' is the elapsed time since the previous frame.
	public override void _Process(double delta)
	{
		while (ActionQueue.TryDequeue(out Action a))
		{
			a?.Invoke();
		}
	}
	public void DeferForget(Action action)
	{
		ActionQueue.Enqueue(action);
	}
	public async Task DeferAsync(Action action)
	{
		using SemaphoreSlim slim = new(0);
		ActionQueue.Enqueue(() =>
			{
				action?.Invoke();
				slim.Release();
			}
		);
		await slim.WaitAsync();
	}
	public async Task<T> DeferAsync<T>(Func<T> func)
	{
		if (func is null)
			throw new Exception("Cannot defer null function");
		using SemaphoreSlim slim = new(0);
		T[] box = { default };
		ActionQueue.Enqueue(() =>
			{
				box[0] = func.Invoke();
				slim.Release();
			}
		);
		await slim.WaitAsync();
		return box[0];
	}
	public void Defer(Action action)
	{
		using SemaphoreSlim slim = new(0);
		ActionQueue.Enqueue(() =>
			{
				action?.Invoke();
				slim.Release();
			}
		);
		slim.WaitAsync();
	}
	public T Defer<T>(Func<T> func)
	{
		if (func is null)
			throw new Exception("Cannot defer null function");
		using SemaphoreSlim slim = new(0);
		T[] box = { default };
		ActionQueue.Enqueue(() =>
			{
				box[0] = func.Invoke();
				slim.Release();
			}
		);
		slim.WaitAsync();
		return box[0];
	}
}