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

namespace SUISS.Cloud
{
    public class CloudRequestRunner
    {
        private class CoroutineWapper : CustomYieldInstruction
        {
            private bool _isRunning;

            private IEnumerator _innerRoutine;

            private CloudRequestRunner _scheduler;

            private MonoBehaviour _executor;

            public override bool keepWaiting => _isRunning;


            public CoroutineWapper(IEnumerator routine, CloudRequestRunner scheduler)
            {
                _scheduler = scheduler;
                _executor = _scheduler.Executor;
                _innerRoutine = routine;
                if (_executor != null)
                {
                    _isRunning = true;
                    _executor.StartCoroutine(Routine(routine));
                }
            }

            private IEnumerator Routine(IEnumerator routine)
            {
                while (routine.MoveNext())
                {
                    object yielded = routine.Current;
                    if (yielded != null && !_scheduler.IsSupportedYieldable(yielded))
                    {
                        UnityEngine.Debug.LogWarning(string.Format("The coroutine '{0}' yielded '{1}' which is not supported by '{2}'!", _innerRoutine, yielded ?? "null", _scheduler));
                    }
                    yield return yielded;
                }
                _scheduler.OnRoutineCompleted(_innerRoutine);
                _isRunning = false;
            }
        }

        private class CloudRequestRunnerMonoBehaviour : MonoBehaviour
        {
        }

        private HashSet<IEnumerator> _runningRoutines = new HashSet<IEnumerator>();

        private MonoBehaviour _executor;

        private string _executorName;

        private static CloudRequestRunner _instance;

        private MonoBehaviour Executor
        {
            get
            {
                if (_executor == null)
                {
                    UnityEngine.Debug.LogError($"{this} is going to create a second GameObject to run coroutines! (Is the app quitting?) Any coroutines running before this may not have been completed! I hope you never see this error! :(");
                    CreateScheduleExecutor();
                    _runningRoutines.Clear();
                }
                return _executor;
            }
        }

        private CloudRequestRunner()
        {
            _executorName = $"__CloudRequestRunner{UnityEngine.Random.Range(1000, 9999)}";
            CreateScheduleExecutor();
        }

        public static CustomYieldInstruction StartCoroutine(IEnumerator routine)
        {
            if (_instance == null)
            {
                _instance = new CloudRequestRunner();
            }
            return _instance.StartRoutine(routine);
        }

        private CustomYieldInstruction StartRoutine(IEnumerator routine)
        {
            if (_executor == null)
            {
                CreateScheduleExecutor();
            }
            if (_executor != null)
            {
                if (_runningRoutines.Contains(routine))
                {
                    throw new Exception($"You are calling StartRoutine on a routine '{routine}' that was already started.");
                }
                _runningRoutines.Add(routine);
                return new CoroutineWapper(routine, this);
            }
            UnityEngine.Debug.LogError($"The schedule executor backing this scheduler is null! Can't start {routine}");
            return null;
        }

        private bool IsSupportedYieldable(object yieldable)
        {
            return yieldable == null || yieldable is WWW || yieldable is YieldInstruction || yieldable is CustomYieldInstruction;
        }

        private void CreateScheduleExecutor()
        {
            if (_executor == null)
            {
                GameObject gameObject = GameObject.Find(_executorName);
                if (gameObject == null)
                {
                    gameObject = new GameObject();
                    gameObject.name = _executorName;
                    UnityEngine.Object.DontDestroyOnLoad(gameObject);
                }
                _executor = gameObject.GetComponent<MonoBehaviour>();
                if (_executor == null)
                {
                    _executor = gameObject.AddComponent<CloudRequestRunnerMonoBehaviour>();
                }
            }
        }

        private void OnRoutineCompleted(IEnumerator routine)
        {
            _runningRoutines.Remove(routine);
        }
    }
}