using UnityEngine;
using UnityEngine.UI;

[RequireComponent(typeof(RectTransform))]
public class LineConnectorUI : MonoBehaviour
{
    public RectTransform start;
    public RectTransform end;
    public Image lineImage;
    public float thickness = 4f;
    public bool dynamicUpdate = true;

    private RectTransform rectTransform;

    private void Awake()
    {
        rectTransform = GetComponent<RectTransform>();
        if (lineImage == null)
        {
            lineImage = GetComponent<Image>();
        }
    }

    private void LateUpdate()
    {
        if (dynamicUpdate)
        {
            UpdateLine();
        }
    }

    public void SetEndpoints(RectTransform startPoint, RectTransform endPoint)
    {
        start = startPoint;
        end = endPoint;
        UpdateLine();
    }

    public void UpdateLine()
    {
        if (start == null || end == null)
        {
            return;
        }

        if (rectTransform == null)
        {
            rectTransform = GetComponent<RectTransform>();
        }

        RectTransform parent = rectTransform.parent as RectTransform;
        if (parent == null)
        {
            return;
        }

        Vector2 startPosition = GetCenterInParentSpace(parent, start);
        Vector2 endPosition = GetCenterInParentSpace(parent, end);
        Vector2 delta = endPosition - startPosition;

        rectTransform.anchorMin = new Vector2(0.5f, 0.5f);
        rectTransform.anchorMax = new Vector2(0.5f, 0.5f);
        rectTransform.pivot = new Vector2(0.5f, 0.5f);
        rectTransform.anchoredPosition = startPosition + delta * 0.5f;
        rectTransform.sizeDelta = new Vector2(delta.magnitude, Mathf.Max(1f, thickness));
        rectTransform.localRotation = Quaternion.Euler(0f, 0f, Mathf.Atan2(delta.y, delta.x) * Mathf.Rad2Deg);
    }

    private Vector2 GetCenterInParentSpace(RectTransform parent, RectTransform target)
    {
        Vector3 worldCenter = target.TransformPoint(target.rect.center);
        Vector3 localCenter = parent.InverseTransformPoint(worldCenter);
        return new Vector2(localCenter.x, localCenter.y);
    }
}