using UnityEngine;
using UnityEngine.Events;
using Obi;

[RequireComponent(typeof(ObiSolver))]
public class TangledRopesGameController : MonoBehaviour
{
	public TangledPegSlot[] pegSlots;
    public float pegHoverHeight = 1;
    public float maxPegDistanceFromSlot = 1.5f;
    public int framesWithoutContactsToWin = 30;
    public UnityEvent onFinish = new UnityEvent();

    private TangledPeg selectedPeg;
    private Plane floor = new Plane(Vector3.up, 0);
    private int framesSinceLastContact = 0;

    void OnEnable()
	{
        GetComponent<ObiSolver>().OnParticleCollision += Solver_OnParticleCollision;
	}

	private void OnDisable()
	{
        GetComponent<ObiSolver>().OnParticleCollision -= Solver_OnParticleCollision;
	}

    private TangledPegSlot FindCandidateSlot(TangledPeg peg)
    {
        // Go over all slots, find the closest one to the peg that's closer than
        // maxPegDistanceFromSlot:

        TangledPegSlot closest = null;
        float closestDistance = float.MaxValue;

        foreach (TangledPegSlot slot in pegSlots)
        {
            // reset slot color, to make sure it looks normal if it's not a candidate for our peg.
            slot.ResetColor();

            // ignore occupied slots:
            if (slot.currentPeg != null)
                continue;

            Vector3 slotOnFloor = floor.ClosestPointOnPlane(slot.transform.position);
            Vector3 pegOnFloor = floor.ClosestPointOnPlane(peg.transform.position);

            float distance = Vector3.Distance(slotOnFloor, pegOnFloor);
            if (distance < closestDistance && distance < maxPegDistanceFromSlot)
            {
                closest = slot;
                closestDistance = distance;
            }
        }

        return closest;
    }

	private void Update()
	{
        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);

        // User clicks, cast a ray towards the floor, see if it hits any peg.
        if (Input.GetMouseButtonDown(0))
        {
            if (Physics.Raycast(ray, out RaycastHit hit))
            {
                // if the ray hit a peg, store it as the selected peg and lift it off from its current slot.
                if (hit.transform.TryGetComponent(out TangledPeg peg) && peg.currentSlot != null)
                {
                    selectedPeg = peg;
                    selectedPeg.UndockFromCurrentSlot();
                }
            }
        }

        if (selectedPeg != null)
        {
            // Make selected peg follow the mouse cursor:
            if (floor.Raycast(ray, out float enter))
                selectedPeg.MoveTowards(ray.GetPoint(enter) + Vector3.up * pegHoverHeight);

            // Try to find a suitable slot to drop the peg:
            TangledPegSlot closest = FindCandidateSlot(selectedPeg);

            // If we found a candidate slot, tint it to give the player some visual feedback:
            if (closest != null)
                closest.Tint();

            // Drop selected peg:
            if (Input.GetMouseButtonUp(0))
            {
                // If we could find a free slot nearby, connect to it:
                if (closest != null)
                {
                    selectedPeg.currentSlot = null;
                    selectedPeg.DockInSlot(closest);
                    closest.ResetColor();
                }
                else  // If we couldn't find one or if it's too far, return to current slot.
                {
                    selectedPeg.DockInSlot(selectedPeg.currentSlot);
                }

                selectedPeg = null;
            }
        }

        // If all ropes have been contact-free for a certain amount of frames, trigger finish event.
        if (framesSinceLastContact >= framesWithoutContactsToWin && onFinish != null)
            onFinish.Invoke();
                
    }

    private void Solver_OnParticleCollision(ObiSolver s, ObiNativeContactList e)
	{
        // Count contacts between different ropes (that is, exclude self-contacts):
        int contactsBetweenRopes = 0;

        for (int i = 0; i < e.count; ++i)
        {
            var ropeA = s.particleToActor[s.simplices[e[i].bodyA]].actor;
            var ropeB = s.particleToActor[s.simplices[e[i].bodyB]].actor;

            if (ropeA != ropeB)
                contactsBetweenRopes++;
        }

        // If there's no contacts, bump the amount of frames we've been contact-free.
        // Otherwise reset the amount of frames to zero.
        if (contactsBetweenRopes == 0)
            framesSinceLastContact++;
        else
            framesSinceLastContact = 0;
    }
}