using UnityEngine;
using UnityEngine.UI;
 
public class LuckyTurntable : MonoBehaviour
{
 public enum State
 {
  None,  //待機狀態
  Start,  //加速階段
  Prepared, //等待數據階段
  End,  //減速階段
 }
 
 public delegate void OnFinishCallback();
 private event OnFinishCallback OnFinish;
 
 /// <summary>
 /// 設置完成時的回調
 /// </summary>
 /// <param name="onFinish"></param>
 public void SetOnFinishCallback(OnFinishCallback onFinish)
 {
  OnFinish += onFinish;
 }
 
 /// <summary>
 /// 最大速度
 /// </summary>
 public int velocity = 3000;
 
 public Transform node;
 public Button btnStart;
 public Button btnStop;
 public Button btnRandom;
 public InputField input;
 
 private State _state;
 /// <summary>
 /// 轉盤的狀態
 /// </summary>
 public State CurState
 {
  get
  {
   return _state;
  }
  private set
  {
   _state = value;
   switch (value)
   {
    //不同階段限制各按鈕的點擊狀態
    case State.None:
     btnStart.enabled = true;
     btnStop.enabled = false;
     btnRandom.enabled = false;
     break;
    case State.Start:
     btnStart.enabled = false;
     btnStop.enabled = true;
     btnRandom.enabled = true;
     break;
    case State.Prepared:
    case State.End:
     btnStart.enabled = false;
     btnStop.enabled = false;
     btnRandom.enabled = false;
     break;
   }
  }
 }
 
 private float _endAngle = 0f;
 /// <summary>
 /// 最終停止的角度[0, 360]
 /// </summary>
 public float EndAngle
 {
  get
  {
   return _endAngle;
  }
  set
  {
   _endAngle = Mathf.Abs(value);
   print("End Angle: " + value);
   _endAngle = _endAngle % 360; //將角度限定在[0, 360]這個區間
   _endAngle = -_endAngle - 360 * 2; //多N圈并取反，圈數能使減速階段變得更長，顯示更自然，逼真
  }
 }
 
 /// <summary>
 /// 加速持續時間
 /// </summary>
 private readonly float AcceleateTime = 1f;
 
 /// <summary>
 /// 減速前的最短持續時間
 /// </summary>
 private float _minTime = 3.0f;
 /// <summary>
 /// 角度緩存
 /// </summary>
 private float _tmpAngle = 0f;
 /// <summary>
 /// 時間統計
 /// </summary>
 private float _time;
 /// <summary>
 /// 速度變化因子
 /// </summary>
 private float _factor;
 
 private void Start()
 {
  CurState = State.None;
  btnStart.onClick.AddListener(OnStartClick);
  btnStop.onClick.AddListener(OnStopClick);
  btnRandom.onClick.AddListener(OnRandomClick);
 }
 
 private void Update()
 {
  if (CurState == State.None)
   return;
 
  _time += Time.deltaTime;
  if (CurState == State.End)
  {
   //通過差值運算實現精準地旋轉到指定角度（球型插值無法實現大于360°的計算）
   float k = 2f; //如果嫌減速太慢，可以加個系數修正一下
   _tmpAngle = Mathf.Lerp(_tmpAngle, EndAngle, Time.deltaTime * k);
 
   //這里只存在一個方向的旋轉，所以不存在歐拉角萬向節的問題，所以使用歐拉角和四元數直接賦值都是可以的
   node.rotation = Quaternion.Euler(0, 0, _tmpAngle);
   //node.eulerAngles = new Vector3(0, 0, _tmpAngle);
 
   if (1 >= Mathf.Abs(_tmpAngle - EndAngle))
   {
    CurState = State.None;
    if (null != OnFinish)
    {
     OnFinish();
     OnFinish = null;
    }
   }
  }
  else
  {
   //利用一個速度因子實現變加速的過程
   _factor = _time / AcceleateTime;
   _factor = _factor > 1 ? 1 : _factor;
   node.Rotate(Vector3.back, _factor * velocity * Time.deltaTime, Space.Self);
  }
 
  //當收到數據之后并且旋轉了一定時間后開始減速
  if (CurState == State.Prepared && _time > _minTime)
  {
   CurState = State.End;
   _tmpAngle = GetCurClockwiseAngle();
  }
 }
 
 /// <summary>
 /// 將當前指針的歐拉角轉換成順時針統計角度
 /// </summary>
 /// <returns></returns>
 private float GetCurClockwiseAngle()
 {
  //由于讀取到的值是[0, 180] U [-180, 0]，左邊由0至180遞增，右邊由180轉變成-180，然后遞增至0，所以需要轉相應的轉換
  return (-1) * (360 - node.eulerAngles.z) % 360;
 }
 
 private void OnStartClick()
 {
  CurState = State.Start;
  _time = 0;
 }
 
 /// <summary>
 /// 讀取輸入框中的角度并停止
 /// </summary>
 private void OnStopClick()
 {
  try
  {
   EndAngle = float.Parse(input.text);
  }
  catch
  {
   EndAngle = 0f;
  }
  CurState = State.Prepared;
 
 }
 
 /// <summary>
 /// 隨機一個角度并停止
 /// </summary>
 private void OnRandomClick()
 {
  EndAngle = UnityEngine.Random.Range(0f, 360f);
  CurState = State.Prepared;
 }
}