using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using UnityEngine;

namespace DDD
{
    public class TimeManager : Singleton<TimeManager>, IManager, IEventHandler<TimeScaleChangeEvent>
    {
        private readonly Dictionary<object, float> _timeScaleRequests = new();
        public float CurrentTimeScale { get; private set; } = 1f;
        
        private float _baseFixedDeltaTime;
        
        public void PreInit()
        {
            _baseFixedDeltaTime = Time.fixedDeltaTime;
            EventBus.Register(this);
        }

        public Task Init()
        {
            return Task.CompletedTask;
        }

        public void PostInit()
        {
            
        }

        private void OnDestroy()
        {
            EventBus.Unregister(this);
#if UNITY_EDITOR
            Time.fixedDeltaTime = _baseFixedDeltaTime; // 재실행 시 값 복원 (Editor용 안전장치)
#endif
        }
        
        protected override void OnApplicationQuit()
        {
            base.OnApplicationQuit();
            
            Time.fixedDeltaTime = _baseFixedDeltaTime;
        }

        private void UpdateTimeScale()
        {
            // 우선순위: 0이 하나라도 있으면 무조건 정지, 그 외엔 최소값 적용
            float newTimeScale = 1f;

            if (_timeScaleRequests.ContainsValue(0f))
            {
                newTimeScale = 0f;
            }
            else if (_timeScaleRequests.Count > 0)
            {
                newTimeScale = Mathf.Min(1f, Mathf.Min(float.MaxValue, GetMinTimeScale()));
            }

            if (Mathf.Approximately(newTimeScale, CurrentTimeScale)) return;

            CurrentTimeScale = newTimeScale;
            Time.timeScale = CurrentTimeScale;
            Time.fixedDeltaTime = _baseFixedDeltaTime * CurrentTimeScale;
        }

        private float GetMinTimeScale() => _timeScaleRequests.Values.Prepend(1f).Min();

        public bool IsPaused => Mathf.Approximately(CurrentTimeScale, 0f);
        
        public void Invoke(TimeScaleChangeEvent evt)
        {
            if (evt.NewTimeScale < 1f)
            {
                _timeScaleRequests[evt.Requester] = evt.NewTimeScale;
            }
            else
            {
                _timeScaleRequests.Remove(evt.Requester);
            }

            UpdateTimeScale();
        }
    }
}