using System.Threading;
using KitsuneCafe.Sys;
using R3;
using UnityEngine;

namespace KitsuneCafe.Entities
{
  public class ParentToPlatform : MonoBehaviour
  {
    [SerializeField]
    private Raycaster raycaster;

    [SerializeField]
    private Transform self;

    [SerializeField]
    private Transform parent;

    private Transform empty;

    public Transform Parent => empty.parent;

    private CancellationTokenSource disableCancellationTokenSource;
    private CancellationToken disableCancellationToken => disableCancellationTokenSource.Token;

    private void Reset()
    {
      self = transform;
      parent = self.parent;
    }

    private void Awake()
    {
      empty = new GameObject($"Empty {self.name} Parent").transform;

      var r = parent == null ? self : parent;
      empty.SetParent(r.parent);
      r.SetParent(empty);
    }

    private void OnEnable()
    {
      disableCancellationTokenSource = new();

      Observable.ObservePropertyChanged(raycaster, rc => rc.Collisions)
        .Subscribe(_ =>
        {
          if (GetParent(out var newParent))
          {
            empty.SetParent(newParent, true);
          }
          else
          {
            empty.SetParent(parent, true);
          }
        })
        .RegisterTo(disableCancellationToken);
    }

    private bool GetParent(out Transform parent)
    {
      if (raycaster.IsColliding
        && raycaster.TryGetClosestHit(out var hit)
        && hit.transform != null
        && !hit.transform.gameObject.isStatic)
      {
        parent = hit.transform;
        return true;
      }

      parent = default;
      return false;
    }

    private void OnDisable()
    {
      disableCancellationTokenSource.Cancel();
    }
  }
}