using Sandbox;
using Sandbox.Audio;
using System.Threading;
using System.Threading.Tasks;

namespace Sandbox;

public sealed class DSPReverb : Component, Component.ITriggerListener
{
	[Property] public MixerHandle TargetMixer { get; set; }
	[Property] public DspPresetHandle Preset { get; set; }
	[Property] [Range(0f, 10f, 0.1f)]  public float FadeDuration { get; set; } = 1f;
	[Property] public BBox Bounds { get; set; } = new BBox(Vector3.One * -100f, Vector3.One * 100f);

	private DspProcessor _processor;
	private BoxCollider _triggerCollider;

	private CancellationTokenSource _cts;

	protected override void OnAwake()
	{
		base.OnAwake();

		_triggerCollider = Components.Create<BoxCollider>();
		_triggerCollider.IsTrigger = true;
		_triggerCollider.Static = true;
		_triggerCollider.Scale = Bounds.Size;
		_triggerCollider.Center = Bounds.Center;
	}

	public void OnTriggerEnter(Collider other)
	{
		_cts?.Cancel();
		_cts = new CancellationTokenSource();
		
		if(_processor != null) { TargetMixer.Get().RemoveProcessor(_processor);}
		
		_processor = new DspProcessor(Preset.Name);
		_processor.Mix = 0f;
		TargetMixer.Get().AddProcessor(_processor);
		
		_ = UpdateMixAsync(1f);
	}

	private async Task UpdateMixAsync(float targetMix)
	{
		float startMix = _processor.Mix;
		float elapsed = FadeDuration *  ((targetMix == 0f || startMix == 0f) ? 0f : Math.Min(startMix / targetMix, 1f));
		float lastTime = Time.Now;

		while (elapsed < FadeDuration && !_cts.IsCancellationRequested)
		{
			await Task.FixedUpdate();
			
			float delta = Time.Now - lastTime;
			elapsed += delta;
			
			float t = Math.Clamp(elapsed / FadeDuration, 0f, 1f);
			_processor.Mix = Math.Clamp(startMix + (targetMix - startMix) * t, 0f, 1f);
			
			lastTime = Time.Now;
		}
		
		if (!_cts.IsCancellationRequested)
		{
			_processor.Mix = targetMix;
		}
	}

	public void OnTriggerExit(Collider other)
	{
		_cts?.Cancel();
		_cts = new CancellationTokenSource();
		
		_ = UpdateMixAsync(0f).ContinueWith( (_) =>
		{
			if (_processor == null) return;
			
			TargetMixer.Get().RemoveProcessor(_processor);
			_processor = null;
		} );
	}

	protected override void DrawGizmos()
	{
		base.DrawGizmos();
		Gizmo.Draw.Color = Color.Green;
		Gizmo.Draw.LineBBox(Bounds);
	}
}