#if (UNITY_EDITOR || DEVELOPMENT_BUILD) && !UPDATE_MANAGER_DISABLE_PROFILER_MARKERS
#define ENABLE_PROFILER_MARKERS
#endif

using System;
using LanLib.UpdateManager.Internal;
using LanLib.UpdateManager.Jobs;
using UnityEngine;

namespace LanLib.UpdateManager
{
    /// <summary>
    /// Singleton MonoBehaviour that calls <see cref="IUpdatable.ManagedUpdate"/>, <see cref="ILateUpdatable.ManagedLateUpdate"/> or <see cref="IFixedUpdatable.ManagedFixedUpdate"/> to registered objects every frame.
    /// </summary>
    /// <remarks>
    /// Any C# object can be registered for updates, including MonoBehaviours, pure C# classes and structs, as long as they implement <see cref="IUpdatable"/>, <see cref="ILateUpdatable"/> or <see cref="IFixedUpdatable"/>.
    /// Managed methods are called inside a try/catch block, so that exceptions don't stop other objects from updating.
    /// <br/>
    /// This class doesn't implement any execution order mechanism, so don't rely on managed methods being executed in any order.
    /// In fact, the order of executed methods will most likely change during the lifetime of the UpdateManager.
    /// </remarks>
    [ExecuteAlways]
    public class UpdateManager : MonoBehaviour
    {
        /// <summary>Get or create the singleton instance</summary>
        public static UpdateManager Instance => (ApplicationUtils.IsQuitting || _instance != null)
            ? _instance
            : (_instance = CreateInstance());

        protected static UpdateManager _instance;

        private static UpdateManager CreateInstance()
        {
            var gameObject = new GameObject(nameof(UpdateManager))
            {
                hideFlags = HideFlags.DontSave,
            };
#if UNITY_EDITOR
            if (!Application.isPlaying)
            {
                gameObject.hideFlags = HideFlags.HideAndDontSave;
            }
            else
#endif
            {
                DontDestroyOnLoad(gameObject);
            }

            return gameObject.AddComponent<UpdateManager>();
        }

#if UNITY_EDITOR
        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
        private static void DestroyEditorUpdateManager()
        {
            if (_instance)
            {
                DestroyImmediate(_instance.gameObject);
            }
        }
#endif

        /// <summary>
        /// Returns whether there are any objects registered for managed updates.
        /// </summary>
        public bool HasRegisteredObjects => _updatableObjects.Count > 0
                                            || _lateUpdatableObjects.Count > 0
                                            || _fixedUpdatableObjects.Count > 0;

        private readonly FastRemoveList<IUpdatable> _updatableObjects = new FastRemoveList<IUpdatable>();
        private readonly FastRemoveList<ILateUpdatable> _lateUpdatableObjects = new FastRemoveList<ILateUpdatable>();
        private readonly FastRemoveList<IFixedUpdatable> _fixedUpdatableObjects = new FastRemoveList<IFixedUpdatable>();

        protected void Update()
        {
            UpdateJobTime.InstanceRef.Refresh();
            foreach (IUpdatable updatable in _updatableObjects)
            {
                try
                {
#if ENABLE_PROFILER_MARKERS
                    using (ProfilerMarkerMap.Get("ManagedUpdate", updatable))
#endif
                        updatable.ManagedUpdate();
                }
                catch (Exception ex)
                {
                    Debug.LogException(ex);
                }
            }
        }

        protected void LateUpdate()
        {
            foreach (ILateUpdatable lateUpdatable in _lateUpdatableObjects)
            {
                try
                {
#if ENABLE_PROFILER_MARKERS
                    using (ProfilerMarkerMap.Get("ManagedLateUpdate", lateUpdatable))
#endif
                        lateUpdatable.ManagedLateUpdate();
                }
                catch (Exception ex)
                {
                    Debug.LogException(ex);
                }
            }
        }

        protected void FixedUpdate()
        {
            foreach (IFixedUpdatable fixedUpdatable in _fixedUpdatableObjects)
            {
                try
                {
#if ENABLE_PROFILER_MARKERS
                    using (ProfilerMarkerMap.Get("ManagedFixedUpdate", fixedUpdatable))
#endif
                        fixedUpdatable.ManagedFixedUpdate();
                }
                catch (Exception ex)
                {
                    Debug.LogException(ex);
                }
            }
        }

        /// <summary>
        /// Register <paramref name="obj"/> to be updated every frame.
        /// </summary>
        /// <remarks>
        /// Registering updatable objects is O(1).
        /// Registering an object more than once is a no-op.
        /// </remarks>
        public void Register(IManagedObject obj)
        {
            if (obj is IUpdatable updatable)
            {
                _updatableObjects.Add(updatable);
            }

            if (obj is ILateUpdatable lateUpdatable)
            {
                _lateUpdatableObjects.Add(lateUpdatable);
            }

            if (obj is IFixedUpdatable fixedUpdatable)
            {
                _fixedUpdatableObjects.Add(fixedUpdatable);
            }

            enabled = HasRegisteredObjects;
        }

        /// <summary>
        /// Unregister <paramref name="updatable"/>, so it is not updated every frame anymore.
        /// </summary>
        /// <remarks>
        /// Unregistering updatable objects is O(1).
        /// Unregistering an object that wasn't registered is a no-op.
        /// </remarks>
        public void Unregister(IManagedObject obj)
        {
            if (obj is IUpdatable updatable)
            {
                _updatableObjects.Remove(updatable);
            }

            if (obj is ILateUpdatable lateUpdatable)
            {
                _lateUpdatableObjects.Remove(lateUpdatable);
            }

            if (obj is IFixedUpdatable fixedUpdatable)
            {
                _fixedUpdatableObjects.Remove(fixedUpdatable);
            }

            enabled = HasRegisteredObjects;
        }

        /// <summary>
        /// Unregisters all updatable objects at once.
        /// </summary>
        public void Clear()
        {
            _updatableObjects.Clear();
            _lateUpdatableObjects.Clear();
            _fixedUpdatableObjects.Clear();
            enabled = false;
        }
    }
}