CrowdControl/Assets/Feel/MMTools/Tools/MMMovement/MMPreventPassingThrough2D.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Serialization;

namespace MoreMountains.Tools
{
	/// <summary>
	/// Prevents fast moving objects from going through colliders by casting a ray backwards after each movement
	/// </summary>
	[AddComponentMenu("More Mountains/Tools/Movement/MMPreventPassingThrough2D")]
	public class MMPreventPassingThrough2D : MonoBehaviour 
	{
		public enum Modes { Raycast, BoxCast }
		/// whether to cast a ray or a boxcast to look for targets
		public Modes Mode = Modes.Raycast;	
		/// the layer mask to search obstacles on
		public LayerMask ObstaclesLayerMask; 
		/// the bounds adjustment variable
		public float SkinWidth = 0.1f;
		/// whether or not to reposition the rb if hitting a trigger collider 
		public bool RepositionRigidbodyIfHitTrigger = true;
		/// whether or not to reposition the rb if hitting a non trigger collider
		[FormerlySerializedAs("RepositionRigidbody")] 
		public bool RepositionRigidbodyIfHitNonTrigger = true;

		[Header("Debug")]
		[MMReadOnly]
		public RaycastHit2D Hit;

		protected float _smallestBoundsWidth; 
		protected float _adjustedSmallestBoundsWidth; 
		protected float _squaredBoundsWidth; 
		protected Vector3 _positionLastFrame; 
		protected Rigidbody2D _rigidbody;
		protected Collider2D _collider;
		protected Vector2 _lastMovement;
		protected float _lastMovementSquared;
		protected RaycastHit2D _hitInfo;
		protected Vector2 _colliderSize;

		/// <summary>
		/// On Start we initialize our object
		/// </summary>
		protected virtual void Start() 
		{ 
			Initialization ();
		} 

		/// <summary>
		/// Grabs the rigidbody and computes the bounds width
		/// </summary>
		protected virtual void Initialization()
		{
			_rigidbody = GetComponent<Rigidbody2D>();
			_positionLastFrame = _rigidbody.position; 

			_collider = GetComponent<Collider2D>();
			if (_collider as BoxCollider2D != null)
			{
				_colliderSize = (_collider as BoxCollider2D).size;
			}
			
			_smallestBoundsWidth = Mathf.Min(Mathf.Min(_collider.bounds.extents.x, _collider.bounds.extents.y), _collider.bounds.extents.z); 
			_adjustedSmallestBoundsWidth = _smallestBoundsWidth * (1.0f - SkinWidth); 
			_squaredBoundsWidth = _smallestBoundsWidth * _smallestBoundsWidth; 
		}

		/// <summary>
		/// On Enable, we initialize our last frame position
		/// </summary>
		protected virtual void OnEnable()
		{
			_positionLastFrame = this.transform.position;
		}

		/// <summary>
		/// On fixedUpdate, checks the last movement and if needed casts a ray to detect obstacles
		/// </summary>
		protected virtual void Update() 
		{ 
			_lastMovement = this.transform.position - _positionLastFrame; 
			_lastMovementSquared = _lastMovement.sqrMagnitude;

			// if we've moved further than our bounds, we may have missed something
			if (_lastMovementSquared > _squaredBoundsWidth) 
			{ 
				float movementMagnitude = Mathf.Sqrt(_lastMovementSquared);

				// we cast a ray backwards to see if we should have hit something
				if (Mode == Modes.Raycast)
				{
					_hitInfo = MMDebug.RayCast(_positionLastFrame, _lastMovement.normalized, movementMagnitude, ObstaclesLayerMask, Color.blue, true);	
				}
				else
				{
					_hitInfo = Physics2D.BoxCast(origin: _positionLastFrame,
						size: _colliderSize,
						angle: 0,
						layerMask: ObstaclesLayerMask,
						direction: _lastMovement.normalized,
						distance: movementMagnitude);
				}

				if (_hitInfo.collider != null)
				{
					if (_hitInfo.collider.isTrigger) 
					{
						_hitInfo.collider.SendMessage("OnTriggerEnter2D", _collider, SendMessageOptions.DontRequireReceiver);
						if (RepositionRigidbodyIfHitTrigger)
						{
							this.transform.position = _hitInfo.point - (_lastMovement / movementMagnitude) * _adjustedSmallestBoundsWidth;
							_rigidbody.position = _hitInfo.point - (_lastMovement / movementMagnitude) * _adjustedSmallestBoundsWidth;
						}   
					}						

					if (!_hitInfo.collider.isTrigger)
					{
						Hit = _hitInfo;
						this.gameObject.SendMessage("PreventedCollision2D", Hit, SendMessageOptions.DontRequireReceiver);
						if (RepositionRigidbodyIfHitNonTrigger)
						{
							this.transform.position = _hitInfo.point - (_lastMovement / movementMagnitude) * _adjustedSmallestBoundsWidth;
							_rigidbody.position = _hitInfo.point - (_lastMovement / movementMagnitude) * _adjustedSmallestBoundsWidth;
						}                        
					}
				}
			} 
			_positionLastFrame = this.transform.position; 
		}
	}
}