using UnityEngine;
using UnityEngine.UI;
public class TargetToScreen : MonoBehaviour
{
    [Header("Assign below variables in the inspector:")]
    public Transform targetTransform;
    [SerializeField] Vector3 targetPositionOffset = new(0, 1, 0);
    [SerializeField] float screenBoundOffset = 0.1f;
    [SerializeField] RectTransform targetImage, targetImageArrow;
    [SerializeField] Text targetText;
    [Header("Below is for Debug use:")]
    [SerializeField] Vector3 screenPosition, screenBound;
    [SerializeField] Vector2 Arrowdirection;
    private void LateUpdate()
    {
        if(targetTransform)
            TargetToScreenPosition();
    }
    /// <summary>
    /// This function is to convert the world position of the target to the screen position, and then update the position of the target image and the arrow image.
    /// </summary>
    public void TargetToScreenPosition()
    {
        screenPosition = Camera.main.WorldToScreenPoint(targetTransform.position + targetPositionOffset);// simple way to get the screen position of the target
        (screenBound.x, screenBound.y) = (Screen.width, Screen.height);//get the screen size

        if (screenPosition.z < 0)//if the target is behind the camera, flip the screen position
        {
            screenPosition = -screenPosition;
            if (screenPosition.y > screenBound.y / 2)//this is to avoid small probablity that the target is behind the camera and the screen position is flipped, but the y position is still in the screen
            {
                screenPosition.y = screenBound.y;
            }
            else screenPosition.y = 0;
        }
        //clamp the screen position to the screen bound
        targetImage.transform.position = new Vector2(
                    Mathf.Clamp(screenPosition.x, screenBound.y * screenBoundOffset, screenBound.x - screenBound.y * screenBoundOffset),
                    Mathf.Clamp(screenPosition.y, screenBound.y * screenBoundOffset, screenBound.y - screenBound.y * screenBoundOffset)
                                );

        //optional, rotate the arrow to point to the target:
        Arrowdirection = targetImageArrow.transform.position - screenPosition;//get the direction of the arrow by subtracting the screen position of the target from the screen position of the arrow
        // Debug.Log(Arrowdirection.magnitude);
        if (Mathf.Abs(Arrowdirection.x + Arrowdirection.y) < 0.1 || !targetTransform.gameObject.activeSelf)
        {
            //disable the arrow when the target is too close to the center of the screen
            targetImageArrow.gameObject.SetActive(false);
            //TargetImageArrow.transform.up = Vector2.zero;
        }
        else
        {
            targetImageArrow.gameObject.SetActive(true);
            targetImageArrow.transform.up = Arrowdirection;
        }
        //optional, update the distance text
        targetText.text = Vector3.Distance(targetTransform.position, Camera.main.transform.position).ToString("F1") + "m";
    }
}