using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;

public class FollowPlayer : MonoBehaviour
{
    bool isRotating;
    //位置偏移（摄像机与人）
    private Vector3 offsetPosition;
    private bool dragPanMoveActive;
    private float dragPanSpeed = 1f;
    private Vector2 lastMousePosition;
    private float distance = 0;
    [Tooltip("最远视野距离 ")]
    public float farDistance = 50;
    [Tooltip("拉近视野速度")]
    public float scrollspeed = 2;//拉近视野速度
    public float rotateSpeed = 1.0f;//摄像机旋转的速度。
    //[Tooltip("摄像机的最小高度 ")]
    //public float camMinHeight = 0.1f;
    //[Tooltip("摄像机的最大高度 ")]
    //public float camMaxHeight = 20f;
    public float moveSpeed = 30f;
    public Transform player;
    [Tooltip("控制垂直旋转的物体")]
    public Transform verticalRotateObj;
    public bool OnUI = false;
    [SerializeField] private bool useDragPan = true;
    [SerializeField] private bool LowerY = true;

    void Update()
    {
        //处理视野的旋转
        RotateView();
        //处理视野的拉近和拉远的效果
        if(LowerY)
            ScrollView();
        //处理视野平移
        if(useDragPan)
            MovementView();

        if (EventSystem.current.IsPointerOverGameObject())
        {
            //print("在UI上");
            OnUI = true;

        }
        else
        {
            //print("不在UI上");
            OnUI = false;
        }
        if (OnUI == true)
        {
            useDragPan = false;
            LowerY = false;
        }
        else
        {
            useDragPan = true;
            LowerY = true;
        }
    }

    void RotateView()
    {
        float rotateDir = 0f;
        float rotateDirY = 0f;

        if (Input.GetMouseButtonDown(1))
        {
            isRotating = true;
            lastMousePosition = Input.mousePosition;
        }
        if (Input.GetMouseButtonUp(1))//1代表鼠标右键
        {
            isRotating = false;

        }

        if (isRotating)
        {
            float mouseMovementDelta = Input.mousePosition.x - lastMousePosition.x;
            rotateDir = mouseMovementDelta * rotateSpeed;

            float mouseMovementDeltaY = Input.mousePosition.y - lastMousePosition.y;
            rotateDirY = mouseMovementDeltaY * rotateSpeed;

            //向右滑动时正值，向左滑动是负值。
            //transform.RotateAround(player.position, player.up, rotateSpeed * Input.GetAxis("Mouse X"));

            //Vector3 originalPos = transform.position;
            //Quaternion originalRotation = transform.rotation;

            //transform.RotateAround(player.position, transform.right, -rotateSpeed * Input.GetAxis("Mouse Y"));//影响的属性有两个，position，rotation；

            //限制摄像机垂直滑动的距离；
            //float x = transform.eulerAngles.x;
            //if (x < 0 || x > 80)//当超出范围之后，我们将属性归位原来的，就是让旋转无效；
            //{
            //    transform.position = originalPos;
            //    transform.rotation = originalRotation;
            //}

            player.eulerAngles += new Vector3(0, rotateDir * Time.deltaTime, 0);

            Vector3 tempV3 = verticalRotateObj.eulerAngles - new Vector3(rotateDirY * Time.deltaTime, 0, 0);

            if (tempV3.x > 0 && tempV3.x < 90)//超出范围之外的旋转无效；
            {
                verticalRotateObj.eulerAngles = tempV3;
            }

        }


        //每次更新一下。
        offsetPosition = transform.position - player.position;
    }

    private void ScrollView()
    {
        //print(Input.GetAxis("Mouse ScrollWheel"));//向后 返回负值（拉近视野），向前滑动 返回正值（拉远视野）
        distance = offsetPosition.magnitude;//获得距离。
        distance -= Input.GetAxis("Mouse ScrollWheel") * scrollspeed;//拉近视野
        if (distance > 5 && distance < farDistance)
        {
            offsetPosition = offsetPosition.normalized * distance;//方向不变，将长度变为distance
            transform.position = offsetPosition + player.position;
        }
    }

    void MovementView()
    {
        Vector3 inputDir = new Vector3(0, 0, 0);

        if (Input.GetMouseButtonDown(0))
        {
            dragPanMoveActive = true;
            lastMousePosition = Input.mousePosition;
        }
        if (Input.GetMouseButtonUp(0))
        {
            dragPanMoveActive = false;
        }

        if (dragPanMoveActive)
        {
            Vector2 mouseMovementDelta = (Vector2)Input.mousePosition - lastMousePosition;

            // float dragPanSpeed = 1f;
            inputDir.x = mouseMovementDelta.x * dragPanSpeed;
            inputDir.z = mouseMovementDelta.y * dragPanSpeed;

            lastMousePosition = Input.mousePosition;

            Vector3 moveDir = player.forward * -inputDir.z + player.right * -inputDir.x;

            player.position += moveDir * moveSpeed * Time.deltaTime;
        }
        
    }

    //void OnDragMove(DragGesture gesture)
    //{//拖拽移动
    //    if (gesture.Phase == ContinuousGesturePhase.Started)
    //        if (gesture.Phase != ContinuousGesturePhase.Updated) return;
    //    Vector.x = -gesture.DeltaMove.x * moveRatio;
    //    Vector.y = 0;
    //    Vector.z = -gesture.DeltaMove.y * moveRatio;
    //    Vector3 temp2 = transform.TransformPoint(Vector);
    //    Quaternion quaTemp = Quaternion.AngleAxis(-transform.eulerAngles.x, transform.right);
    //    temp2 = quaTemp * (temp2 - transform.position) + transform.position;
    //    transform.position = temp2;
    //}

}