using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Obi;

/**
 * Sample component that shows how to use Obi Rope to create a grappling hook for a 2.5D game.
 * 95% of the code is the grappling hook logic (user input, scene raycasting, launching, attaching the hook, etc) and parameter setup,
 * to show how to use Obi completely at runtime. This might not be practical for real-world scenarios,
 * but illustrates how to do it.
 *
 * Note that the choice of using actual rope simulation for grapple dynamics is debatable. Usually
 * a simple spring works better both in terms of performance and controllability. 
 * In my opinion a rope simulation should only be used as a post-process when the rope is too loose, to improve visuals.
 *
 * If complex interaction is required with the scene, a purely geometry-based eulerian approach (ala Worms ninja rope) can
 * be the right choice under certain circumstances.
 */
public class GrapplingHook : MonoBehaviour {

	public Collider character;
	public float hookExtendRetractSpeed = 2;
	public Material material;

	private ObiRope rope;
	private ObiCatmullRomCurve curve;
	private ObiSolver solver;
	private ObiRopeCursor cursor;

	private RaycastHit hookAttachment;
	private bool attached = false;

	void Awake () {

		// Create both the rope and the solver:	
		rope = gameObject.AddComponent<ObiRope>();
		curve = gameObject.AddComponent<ObiCatmullRomCurve>();
		solver = gameObject.AddComponent<ObiSolver>();

		// Provide a solver and a curve:
		rope.Solver = solver;
		rope.ropePath = curve;
		rope.GetComponent<MeshRenderer>().material = material;

		// Configure rope and solver parameters:
		rope.resolution = 0.1f;
		rope.BendingConstraints.stiffness = 0.2f;
		rope.UVScale = new Vector2(1,5);
		rope.NormalizeV = false;
		rope.UVAnchor = 1;

		solver.distanceConstraintParameters.iterations = 15;
		solver.pinConstraintParameters.iterations = 15;
		solver.bendingConstraintParameters.iterations = 1;

		// Add a cursor to change rope length:
		cursor = rope.gameObject.AddComponent<ObiRopeCursor>();	
		cursor.rope = rope;
		cursor.normalizedCoord = 0;
		cursor.direction = true;
	}
	
	/**
	 * Raycasts against the scene to see if we can attach the hook to something.
	 */
	private void LaunchHook(){
	
		// Get the mouse position in the scene, in the same XY plane as this object:
		Vector3 mouse = Input.mousePosition;
		mouse.z = transform.position.z - Camera.main.transform.position.z;
		Vector3 mouseInScene = Camera.main.ScreenToWorldPoint(mouse);

		// Get a ray from the character to the mouse:
		Ray ray = new Ray(transform.position,mouseInScene - transform.position);
		
		// Raycast to see what we hit:
		if (Physics.Raycast(ray,out hookAttachment)){

			// We actually hit something, so attach the hook!
			StartCoroutine(AttachHook());
		}

	}

	private IEnumerator AttachHook(){

		Vector3 localHit = curve.transform.InverseTransformPoint(hookAttachment.point);

		// Procedurally generate the initial rope shape (a simple straight line):
		curve.controlPoints.Clear();
		curve.controlPoints.Add(Vector3.zero);
		curve.controlPoints.Add(Vector3.zero);
		curve.controlPoints.Add(localHit);
		curve.controlPoints.Add(localHit);

		// Generate the particle representation of the rope (wait until it has finished):
		yield return rope.GeneratePhysicRepresentationForMesh();

		// Pin both ends of the rope (this enables two-way interaction between character and rope):
		/*ObiPinConstraintBatch pinConstraints = rope.PinConstraints.GetBatches()[0] as ObiPinConstraintBatch;
		pinConstraints.AddConstraint(0,character,transform.localPosition,0);
		pinConstraints.AddConstraint(rope.UsedParticles-1,hookAttachment.collider,hookAttachment.collider.transform.InverseTransformPoint(hookAttachment.point),0);*/

		// Add the rope to the solver to begin the simulation:
		rope.AddToSolver(null);
		rope.GetComponent<MeshRenderer>().enabled = true;

		attached = true;
	}

	private void DetachHook(){

		// Detach hook:
		rope.RemoveFromSolver(null);
		rope.GetComponent<MeshRenderer>().enabled = false;

		attached = false;

	}


	void Update () {

		if (Input.GetMouseButtonDown(0)){
			if (!attached)
				LaunchHook();
			else
				DetachHook();
		}

		if (Input.GetKey(KeyCode.W)){
			cursor.ChangeLength(rope.RestLength - hookExtendRetractSpeed * Time.deltaTime);
		}
		if (Input.GetKey(KeyCode.S)){
			cursor.ChangeLength(rope.RestLength + hookExtendRetractSpeed * Time.deltaTime);
		}
	}
}