using UnityEngine;
using TMPro;

public class RayCastSystem : MonoBehaviour
{
    [Header("Layer Settings")]
    public LayerMask interactableLayers;

    [Header("Highlight Settings")]
    public Color highlightColor = new Color(1f, 1f, 0f, 0.35f);
    public float padding = 1.02f; 

    private Camera mainCamera;
    private GameObject currentSelection;
    private GameObject outlineObject;
    private MeshFilter outlineFilter;
    private MeshRenderer outlineRenderer;
    private Rigidbody currentPickedRB = null;

    [Header("UI Elements")]
    public TMP_Text itemCountText;

    void Start()
    {
        mainCamera = Camera.main;
        CreateOutlineObject();
        if(itemCountText) itemCountText.gameObject.SetActive(false);
    }

    void CreateOutlineObject()
    {
        outlineObject = new GameObject("SelectionHighlight");
        outlineFilter = outlineObject.AddComponent<MeshFilter>();
        outlineRenderer = outlineObject.AddComponent<MeshRenderer>();

        Material ghostMat = new Material(Shader.Find("Standard"));
        
        // Optimize Material: Enable GPU Instancing
        ghostMat.enableInstancing = true; 
        ghostMat.SetFloat("_Mode", 3); // Transparent
        ghostMat.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
        ghostMat.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
        ghostMat.SetInt("_ZWrite", 0);
        ghostMat.DisableKeyword("_ALPHATEST_ON");
        ghostMat.EnableKeyword("_ALPHABLEND_ON");
        ghostMat.DisableKeyword("_ALPHAPREMULTIPLY_ON");
        ghostMat.renderQueue = 3000;

        ghostMat.color = highlightColor;
        ghostMat.EnableKeyword("_EMISSION");
        ghostMat.SetColor("_EmissionColor", highlightColor * 0.5f);

        outlineRenderer.material = ghostMat;
        outlineObject.SetActive(false);
        
        // OPTIMIZATION: Do not parent to the player. 
        // Keeping it in the root ensures Scale calculations are always 1:1 with the target.
        outlineObject.transform.SetParent(null); 
    }

    void Update()
    {
        RaycastHit hit;
        // Perform Raycast
        if (Physics.Raycast(mainCamera.transform.position, mainCamera.transform.forward, out hit, 100f, interactableLayers))
        {
            GameObject hitObject = hit.collider.gameObject;

            // Only run expensive logic if the selection ACTUALLY changed
            if (currentSelection != hitObject)
            {
                currentSelection = hitObject;
                UpdateOutline(currentSelection);
                UpdateUI(currentSelection); // Separated UI logic for cleanliness
            }

            // Keep outline snapped
            if (currentSelection != null && outlineObject.activeSelf)
            {
                FollowTarget(currentSelection);
            }
        }
        else
        {
            if (currentSelection != null) ClearSelection();
        }
    }

    void UpdateUI(GameObject target)
    {
        if (itemCountText == null) return;

        Shelf shelf = target.GetComponent<Shelf>();
        
        if (shelf != null)
        {
            // PERFORMANCE FIX: 
            // Instead of getting a whole dictionary, we just ask for the count directly.
            // You need to add 'public int ItemCount' or similar to your Shelf script.
            itemCountText.text = $"Items: {shelf.GetTotalItemCount()}"; 
            itemCountText.gameObject.SetActive(true);
        }
        else
        {
            itemCountText.gameObject.SetActive(false);
        }
    }

    void UpdateOutline(GameObject target)
    {
        if(currentPickedRB != null) {
            outlineObject.SetActive(false);
            return;
        }

        MeshFilter targetMeshFilter = target.GetComponent<MeshFilter>();
        if (targetMeshFilter == null) targetMeshFilter = target.GetComponentInChildren<MeshFilter>();

        if (targetMeshFilter == null) 
        {
            outlineObject.SetActive(false);
            return;
        }

        // Lightweight: Just swapping the reference, not creating new meshes
        outlineFilter.sharedMesh = targetMeshFilter.sharedMesh;
        
        FollowTarget(target);
        outlineObject.SetActive(true);
    }

    void FollowTarget(GameObject target)
    {
        outlineObject.transform.position = target.transform.position;
        outlineObject.transform.rotation = target.transform.rotation;
        // This math is safer now that outlineObject is not a child of the Player
        outlineObject.transform.localScale = target.transform.localScale * padding;
    }

    void ClearSelection()
    {
        currentSelection = null;
        outlineObject.SetActive(false);
        if (itemCountText) itemCountText.gameObject.SetActive(false);
    }

    public void SetCurrentPickedRB(Rigidbody rb)
    {
        currentPickedRB = rb;
        if (currentPickedRB != null) ClearSelection();
    }
}