#if ENABLE_INPUT_SYSTEM && ENABLE_INPUT_SYSTEM_PACKAGE
#define USE_INPUT_SYSTEM
 using UnityEngine.InputSystem;
 using UnityEngine.InputSystem.Controls;
#endif

using UnityEngine;

 public class SimpleCameraController : MonoBehaviour
 {
  #region 相機狀態(tài)
  /// <summary>
  /// 相機狀態(tài)
  /// </summary>
  class CameraState
  {
   public float yaw;
   public float pitch;
   public float roll;
   public float x;
   public float y;
   public float z;

   public void SetFromTransform(Transform t)
   {
    pitch = t.eulerAngles.x;
    yaw = t.eulerAngles.y;
    roll = t.eulerAngles.z;
    x = t.position.x;
    y = t.position.y;
    z = t.position.z;
   }

   public void Translate(Vector3 translation)
   {
    Vector3 rotatedTranslation = Quaternion.Euler(pitch, yaw, roll) * translation;

    x += rotatedTranslation.x;
    y += rotatedTranslation.y;
    z += rotatedTranslation.z;
   }

   public void LerpTowards(CameraState target, float positionLerpPct, float rotationLerpPct)
   {
    yaw = Mathf.Lerp(yaw, target.yaw, rotationLerpPct);
    pitch = Mathf.Lerp(pitch, target.pitch, rotationLerpPct);
    roll = Mathf.Lerp(roll, target.roll, rotationLerpPct);
    
    x = Mathf.Lerp(x, target.x, positionLerpPct);
    y = Mathf.Lerp(y, target.y, positionLerpPct);
    z = Mathf.Lerp(z, target.z, positionLerpPct);
   }

   public void UpdateTransform(Transform t)
   {
    t.eulerAngles = new Vector3(pitch, yaw, roll);
    t.position = new Vector3(x, y, z);
   }
  }
  #endregion

  CameraState m_TargetCameraState = new CameraState();
  CameraState m_InterpolatingCameraState = new CameraState();

  [Header("Movement Settings 移動設置")]
  [Tooltip("Exponential boost factor on translation, controllable by mouse wheel. 平移的指數(shù)增強因子，可通過鼠標滾輪控制。")]
  public float boost = 3.5f;

  [Tooltip("Time it takes to interpolate camera position 99% of the way to the target. 將相機位置插值到目標位置99%所需的時間。"), Range(0.001f, 1f)]
  public float positionLerpTime = 0.2f;

  [Header("Rotation Settings 旋轉設定")]
  [Tooltip("X = Change in mouse position. 改變鼠標位置。\nY = Multiplicative factor for camera rotation. 相機旋轉的乘性因子。")]
  public AnimationCurve mouseSensitivityCurve = new AnimationCurve(new Keyframe(0f, 0.5f, 0f, 5f), new Keyframe(1f, 2.5f, 0f, 0f));

  [Tooltip("Time it takes to interpolate camera rotation 99% of the way to the target. 插值相機旋轉99%到目標所需的時間。"), Range(0.001f, 1f)]
  public float rotationLerpTime = 0.01f;

  [Tooltip("Whether or not to invert our Y axis for mouse input to rotation. 是否將鼠標輸入的Y軸反轉為旋轉。")]
  public bool invertY = false;

  void OnEnable()
  {
   m_TargetCameraState.SetFromTransform(transform);
   m_InterpolatingCameraState.SetFromTransform(transform);
  }

  Vector3 GetInputTranslationDirection()
  {
   Vector3 direction = new Vector3();
   if (Input.GetKey(KeyCode.W))
   {
    direction += Vector3.forward;
   }
   if (Input.GetKey(KeyCode.S))
   {
    direction += Vector3.back;
   }
   if (Input.GetKey(KeyCode.A))
   {
    direction += Vector3.left;
   }
   if (Input.GetKey(KeyCode.D))
   {
    direction += Vector3.right;
   }
   if (Input.GetKey(KeyCode.Q))
   {
    direction += Vector3.down;
   }
   if (Input.GetKey(KeyCode.E))
   {
    direction += Vector3.up;
   }
   return direction;
  }
  
  void Update()
  {
   Vector3 translation = Vector3.zero;

#if ENABLE_LEGACY_INPUT_MANAGER

   // Exit Sample 按下Esc鍵退出游戲
   if (Input.GetKey(KeyCode.Escape))
   {
    Application.Quit();
 #if UNITY_EDITOR
 UnityEditor.EditorApplication.isPlaying = false; 
 #endif
   }
   // Hide and lock cursor when right mouse button pressed 按下鼠標右鍵時隱藏并鎖定光標
   if (Input.GetMouseButtonDown(1))
   {
    Cursor.lockState = CursorLockMode.Locked;
   }

   // Unlock and show cursor when right mouse button released 松開鼠標右鍵時解鎖并顯示光標
   if (Input.GetMouseButtonUp(1))
   {
    Cursor.visible = true;
    Cursor.lockState = CursorLockMode.None;
   }

   // Rotation 旋轉
   if (Input.GetMouseButton(1))
   {
    var mouseMovement = new Vector2(Input.GetAxis("Mouse X"), Input.GetAxis("Mouse Y") * (invertY ? 1 : -1));
    
    var mouseSensitivityFactor = mouseSensitivityCurve.Evaluate(mouseMovement.magnitude);

    m_TargetCameraState.yaw += mouseMovement.x * mouseSensitivityFactor;
    m_TargetCameraState.pitch += mouseMovement.y * mouseSensitivityFactor;
   }
   
   // Translation 移動
   translation = GetInputTranslationDirection() * Time.deltaTime;

   // Speed up movement when shift key held 按住shift鍵時加速移動
   if (Input.GetKey(KeyCode.LeftShift))
   {
    //原速度*10為按下Shift后的速度
    translation *= 10.0f;
   }

   // Modify movement by a boost factor (defined in Inspector and modified in play mode through the mouse scroll wheel) 通過增強因子修改移動（在檢查器中定義，通過鼠標滾輪在播放模式下修改）
   boost += Input.mouseScrollDelta.y * 0.2f;
   translation *= Mathf.Pow(2.0f, boost);

#elif USE_INPUT_SYSTEM 
   // TODO: make the new input system work 使新的輸入系統(tǒng)正常工作
#endif

   m_TargetCameraState.Translate(translation);

   // Framerate-independent interpolation 幀率無關插值
   // Calculate the lerp amount, such that we get 99% of the way to our target in the specified time 計算lerp的數(shù)量，這樣我們就可以在指定的時間內到達目標的99%
   var positionLerpPct = 1f - Mathf.Exp((Mathf.Log(1f - 0.99f) / positionLerpTime) * Time.deltaTime);
   var rotationLerpPct = 1f - Mathf.Exp((Mathf.Log(1f - 0.99f) / rotationLerpTime) * Time.deltaTime);
   m_InterpolatingCameraState.LerpTowards(m_TargetCameraState, positionLerpPct, rotationLerpPct);

   m_InterpolatingCameraState.UpdateTransform(transform);
  }
}