using UnityEngine;
 
/// <summary>
/// 虛擬搖桿管理器
/// </summary>
public class VirtualJoystickManager : MonoBehaviour
{
  private static VirtualJoystickManager _instance;
  public static VirtualJoystickManager Instance
  {
    get
    {
      if (_instance == null)
      {
        _instance = FindObjectOfType<VirtualJoystickManager>();
      }
      return _instance;
    }
  }
 
  [Header("是否始終可視")]
  public bool alwaysVisible;//是否始終可視
  [Header("是否限制虛擬搖桿位置")]
  public bool restrictVirtualJoystickPos;//是否限制虛擬搖桿位置
 
  [Header("虛擬搖桿物體")]
  [Header("==========")]
  public GameObject virtualJoystick;//虛擬搖桿父物體
  public GameObject inside;//內(nèi)環(huán)
  public GameObject outside;//外環(huán)
 
  [Header("最大拖拽距離")]
  [Header("==========")]
  public float maxDragLength;//最大拖拽距離
 
  private Vector3 virtualJoystickCenter;//虛擬軸中心
 
  private void Update()
  {
    //如果限制虛擬軸位置并且虛擬軸位置超出了限制范圍則不進(jìn)行任何操作
    if (restrictVirtualJoystickPos && JudgeIsValidRange() == false)
    {
      return;
    }
 
    //更新顯示
    UpdateShow();
 
    //更新虛擬搖桿位置
    if (Input.GetMouseButtonDown(0))
    {
      UpdateVirtualJoystickPos();
    }
    else if (Input.GetMouseButtonUp(0))
    {
      inside.transform.position = virtualJoystickCenter;
    }
 
    //更新內(nèi)環(huán)位置(限制拖拽范圍)
    if (Input.GetMouseButton(0))
    {
      UpdateInsidePos();
    }
  }
 
  /// <summary>
  /// 更新顯示
  /// </summary>
  private void UpdateShow()
  {
    if (alwaysVisible)
    {
      inside.SetActive(true);
      outside.SetActive(true);
    }
    else if (alwaysVisible == false)
    {
      if (Input.GetMouseButtonDown(0))
      {
        inside.SetActive(true);
        outside.SetActive(true);
      }
      if (Input.GetMouseButtonUp(0))
      {
        inside.SetActive(false);
        outside.SetActive(false);
      }
    }
  }
 
  /// <summary>
  /// 更新虛擬搖桿位置
  /// </summary>
  private void UpdateVirtualJoystickPos()
  {
    //得到虛擬軸的中心位置
    virtualJoystickCenter = ScreenToWorld(Input.mousePosition);
 
    //設(shè)置虛擬軸的位置
    virtualJoystick.transform.position = virtualJoystickCenter;
  }
 
  /// <summary>
  /// 更新內(nèi)環(huán)位置
  /// </summary>
  private void UpdateInsidePos()
  {
    inside.transform.position = ScreenToWorld(Input.mousePosition);
    if (Vector3.Distance(inside.transform.position, virtualJoystickCenter) > maxDragLength)
    {
      Vector3 normalizedPos = (inside.transform.position - virtualJoystickCenter).normalized;
      inside.transform.position = normalizedPos * maxDragLength + virtualJoystickCenter;
    }
  }
 
  /// <summary>
  /// 判斷是否為有效的范圍
  /// </summary>
  /// <returns>是否為有效的范圍</returns>
  private bool JudgeIsValidRange()
  {
    if (inside.activeInHierarchy)
    {
      return true;
    }
 
    Vector2 v = Input.mousePosition;
    if (v.x > Screen.width / 2 || v.x < 0)
    {
      return false;
    }
    else if (v.y > Screen.height / 2 || v.y < 0)
    {
      return false;
    }
    return true;
  }
 
  /// <summary>
  /// 屏幕坐標(biāo)轉(zhuǎn)世界坐標(biāo)
  /// </summary>
  /// <param name="screenPos">屏幕坐標(biāo)位置</param>
  /// <param name="camera">相機(jī)</param>
  /// <returns>轉(zhuǎn)換后的世界坐標(biāo)</returns>
  public static Vector3 ScreenToWorld(Vector3 screenPos, Camera camera = null)
  {
    if (camera == null)
    {
      camera = Camera.main;
    }
    Vector3 _screenPos = new Vector3(screenPos.x, screenPos.y, -camera.transform.position.z);
    Vector3 v = camera.ScreenToWorldPoint(_screenPos);
    return v;
  }
 
  /// <summary>
  /// 得到運(yùn)動(dòng)的方向和長(zhǎng)度
  /// </summary>
  /// <returns>方向和長(zhǎng)度</returns>
  public Vector3 GetDirAndLength()
  {
    return inside.transform.position - virtualJoystickCenter;
  }
}