using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class DropObject : MonoBehaviour, IDropHandler, IPointerEnterHandler, IPointerExitHandler
{
    public MeshRenderer receivingRenderer;
    public Color highlightColor = Color.yellow;

    private Material rendererMat;
    private Color normalColor;
    private Texture droppedTexture;

#if UNITY_EDITOR
    private void Reset()
    {
        receivingRenderer = GetComponentInChildren<MeshRenderer>();
    }
#endif

    public void OnEnable()
    {
        if (receivingRenderer != null)
        {
            rendererMat = receivingRenderer.material;
            normalColor = rendererMat.color;
            receivingRenderer.sharedMaterial = rendererMat;
        }
    }

    public void OnDrop(PointerEventData data)
    {
        if (rendererMat != null)
        {
            rendererMat.color = normalColor;

            var dropSprite = GetDropSprite(data);
            if (dropSprite != null)
            {
                rendererMat.mainTexture = droppedTexture = dropSprite.texture;
            }
        }
    }

    public void OnPointerEnter(PointerEventData data)
    {
        if (rendererMat != null)
        {
            var dropSprite = GetDropSprite(data);
            if (dropSprite != null)
            {
                rendererMat.color = highlightColor;
                rendererMat.mainTexture = null;
            }
        }
    }

    public void OnPointerExit(PointerEventData data)
    {
        if (rendererMat != null)
        {
            rendererMat.color = normalColor;
            rendererMat.mainTexture = droppedTexture;
        }
    }

    private Sprite GetDropSprite(PointerEventData data)
    {
        var originalObj = data.pointerDrag;
        if (originalObj == null) { return null; }

        var dragMe = originalObj.GetComponent<DragImage>();
        if (dragMe == null) { return null; }

        var srcImage = originalObj.GetComponent<Image>();
        if (srcImage == null) { return null; }

        return srcImage.sprite;
    }
}