using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;

using XericLibrary.Runtime.Type;

namespace XericLibrary
{
    /// <summary>
    /// 看向某物
    /// </summary>
    public class LookAtSomething : WeaklyMonoBase
	{
		#region 字段属性

		/// <summary>
		/// 看向目标的名称
		/// </summary>
		public string lookAtTargetName = "";

		/// <summary>
		/// 看向的目标
		/// </summary>
		[SerializeField]
		private Transform lookAtTarget = null;

		/// <summary>
		/// 设定看向的目标
		/// </summary>
		public Transform LookAtTarget
		{
			get => lookAtTarget;
			set
			{
				lookAtTarget = value;
				targetValid = lookAtTarget != null;
			}
		}

		/// <summary>
		/// 反转看向轴
		/// </summary>
		public bool ReversLookVector = false;

		/// <summary>
		/// 看向的轴
		/// </summary>
		public Vector3 LookAtVector = Vector3.forward;

		/// <summary>
		/// 启用旋转的轴
		/// </summary>
		public Vector3 UseableRotateVector = Vector3.one;

		/// <summary>
		/// 旋转角速度
		/// </summary>
		public float RotateSpeed = 1;

		/// <summary>
		/// 看向的目标有效
		/// </summary>
		private bool targetValid = true;


		#endregion

		#region 生命周期

		private void Awake()
		{
			if(lookAtTarget == null && lookAtTargetName != null && lookAtTargetName != "")
			{
				lookAtTarget = GameObject.Find(lookAtTargetName)?.transform;
			}
		}

		public void OnEnable()
		{
			targetValid = lookAtTarget != null;
		}

		public void Update()
		{
			if(!targetValid)
				return;

			var lookvec = ReversLookVector ? 
			transform.position - lookAtTarget.position:
			lookAtTarget.position - transform.position;

			Quaternion targetRotation = Quaternion.LookRotation(lookvec, LookAtVector);

			// 使用 slerp 插值平滑旋转
			float step = RotateSpeed * Time.deltaTime;
			transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, step);
		}

		#endregion
	}
}