using UnityEngine;
using System.Collections.Generic;

public class PlacementValidator : MonoBehaviour, IValidator
{
    [SerializeField] private LayerMask collisionLayerMask;
    [SerializeField] private float toleranceSkin = 0.05f; // Shrinks the check box slightly

    public void SetLayerMask(LayerMask cLayerMask) => collisionLayerMask = cLayerMask;

    public bool IsValidPlacement(GameObject objToPlace)
    {
        Collider objCollider = objToPlace.GetComponent<Collider>();
        if (objCollider == null) return true;
        if (objCollider.isTrigger) return true;
        if (objCollider.gameObject.layer == LayerMask.NameToLayer("Gizmos")) return true;

        return CheckCollider(objCollider, objToPlace.transform.root);
    }

    private bool CheckCollider(Collider objCollider, Transform root)
    {
        Collider[] hits = new Collider[0];

        if (objCollider is BoxCollider box)
        {
            Vector3 center = objCollider.transform.TransformPoint(box.center);
            Vector3 lossyScale = objCollider.transform.lossyScale;
            Vector3 scale = new Vector3(Mathf.Abs(lossyScale.x), Mathf.Abs(lossyScale.y), Mathf.Abs(lossyScale.z));
            Vector3 size = Vector3.Scale(box.size, scale);
            
            // Apply tolerance (shrink on both sides of each axis), but never shrink below 80% of original size
            Vector3 overlapSize = new Vector3(
                Mathf.Max(size.x - toleranceSkin * 2f, size.x * 0.8f),
                Mathf.Max(size.y - toleranceSkin * 2f, size.y * 0.8f),
                Mathf.Max(size.z - toleranceSkin * 2f, size.z * 0.8f)
            );

            hits = Physics.OverlapBox(center, overlapSize * 0.5f, objCollider.transform.rotation, collisionLayerMask);
        }
        else if (objCollider is SphereCollider sphere)
        {
            Vector3 center = objCollider.transform.TransformPoint(sphere.center);
            Vector3 lossyScale = objCollider.transform.lossyScale;
            float maxScale = Mathf.Max(Mathf.Abs(lossyScale.x), Mathf.Max(Mathf.Abs(lossyScale.y), Mathf.Abs(lossyScale.z)));
            float radius = sphere.radius * maxScale;
            float overlapRadius = Mathf.Max(0f, radius - toleranceSkin);

            hits = Physics.OverlapSphere(center, overlapRadius, collisionLayerMask);
        }
        else if (objCollider is CapsuleCollider capsule)
        {
            Vector3 center = objCollider.transform.TransformPoint(capsule.center);
            Vector3 lossyScale = objCollider.transform.lossyScale;
            float scaleX = Mathf.Abs(lossyScale.x);
            float scaleY = Mathf.Abs(lossyScale.y);
            float scaleZ = Mathf.Abs(lossyScale.z);

            float radiusScale = Mathf.Max(scaleX, scaleZ);
            float heightScale = scaleY;
            Vector3 dir = objCollider.transform.up;

            if (capsule.direction == 0) // X-axis
            {
                radiusScale = Mathf.Max(scaleY, scaleZ);
                heightScale = scaleX;
                dir = objCollider.transform.right;
            }
            else if (capsule.direction == 2) // Z-axis
            {
                radiusScale = Mathf.Max(scaleX, scaleY);
                heightScale = scaleZ;
                dir = objCollider.transform.forward;
            }

            float radius = capsule.radius * radiusScale;
            float height = capsule.height * heightScale;

            float overlapRadius = Mathf.Max(0f, radius - toleranceSkin);
            float overlapHeight = Mathf.Max(0f, height - (toleranceSkin * 2f));
            
            float pointOffset = Mathf.Max(0f, (overlapHeight * 0.5f) - overlapRadius);

            Vector3 point0 = center + dir * pointOffset;
            Vector3 point1 = center - dir * pointOffset;

            hits = Physics.OverlapCapsule(point0, point1, overlapRadius, collisionLayerMask);
        }
        else if (objCollider is MeshCollider mc && mc.sharedMesh != null)
        {
            Bounds localBounds = mc.sharedMesh.bounds;
            Vector3 center = objCollider.transform.TransformPoint(localBounds.center);
            Vector3 lossyScale = objCollider.transform.lossyScale;
            Vector3 scale = new Vector3(Mathf.Abs(lossyScale.x), Mathf.Abs(lossyScale.y), Mathf.Abs(lossyScale.z));
            Vector3 size = Vector3.Scale(localBounds.size, scale);

            Vector3 overlapSize = new Vector3(
                Mathf.Max(size.x - toleranceSkin * 2f, size.x * 0.8f),
                Mathf.Max(size.y - toleranceSkin * 2f, size.y * 0.8f),
                Mathf.Max(size.z - toleranceSkin * 2f, size.z * 0.8f)
            );

            hits = Physics.OverlapBox(center, overlapSize * 0.5f, objCollider.transform.rotation, collisionLayerMask);
        }
        else
        {
            // Fallback: AABB check
            Vector3 center = objCollider.bounds.center;
            Vector3 size = objCollider.bounds.size;

            Vector3 overlapSize = new Vector3(
                Mathf.Max(size.x - toleranceSkin * 2f, size.x * 0.8f),
                Mathf.Max(size.y - toleranceSkin * 2f, size.y * 0.8f),
                Mathf.Max(size.z - toleranceSkin * 2f, size.z * 0.8f)
            );

            hits = Physics.OverlapBox(center, overlapSize * 0.5f, Quaternion.identity, collisionLayerMask);
        }

        foreach (Collider hit in hits)
        {
            if (hit.transform.root == root) continue;
            if (hit.isTrigger) continue;
            return false;
        }

        return true;
    }
}