using System.Collections.Generic;
using System.Linq;
using System.Threading;
using Cysharp.Threading.Tasks;
using RebootKit.Engine.Foundation;
using UnityEngine;
using UnityEngine.AddressableAssets;
using UnityEngine.Assertions;
using UnityEngine.ResourceManagement.AsyncOperations;
using UnityEngine.ResourceManagement.ResourceProviders;
using UnityEngine.SceneManagement;
using Logger = RebootKit.Engine.Foundation.Logger;

namespace RebootKit.Engine.Services.Simulation {
    public interface IWorldContext {
    }
    
    public class WorldService : IService {
        static readonly Logger s_Logger = new Logger(nameof(WorldService));
        
        enum WorldState {
            Unloaded,
            Loading,
            Loaded
        }

        WorldState m_WorldState = WorldState.Unloaded;
        WorldConfig m_Config;
        AsyncOperationHandle<SceneInstance> m_SceneInstance;

        public IWorldContext Context { get; private set; }
        
        readonly List<Actor> m_Actors = new List<Actor>();

        public void Dispose() {
            Unload();
        }
        
        public async UniTask LoadAsync(WorldConfig worldConfig, CancellationToken cancellationToken) {
            await UniTask.WaitWhile(() => m_WorldState == WorldState.Loading, cancellationToken: cancellationToken);

            Unload();

            m_WorldState = WorldState.Loading;
            m_Config = worldConfig;

            m_SceneInstance = worldConfig.mainScene.LoadSceneAsync(LoadSceneMode.Additive, false);
            await m_SceneInstance.ToUniTask(cancellationToken: cancellationToken);
            
            await m_SceneInstance.Result.ActivateAsync();
            SceneManager.SetActiveScene(m_SceneInstance.Result.Scene);

            foreach (GameObject root in m_SceneInstance.Result.Scene.GetRootGameObjects()) {
                if (root.TryGetComponent(out IWorldContext worldContext)) {
                    Assert.IsNull(Context, "WorldContext is already set. There should be only one WorldContext in the scene.");
                    Context = worldContext;
                }

                foreach (Actor actor in root.GetComponentsInChildren<Actor>()) {
                    RegisterActor(actor);
                }
            }

            m_WorldState = WorldState.Loaded;
        }
        
        public async UniTask<TRequiredActor> LoadAsync<TRequiredActor>(WorldConfig worldConfig, CancellationToken cancellationToken) where TRequiredActor : Actor {
            await LoadAsync(worldConfig, cancellationToken);
            
            TRequiredActor actor = m_Actors.FirstOrDefault(t => t is TRequiredActor) as TRequiredActor;
            if (actor is null) {
                s_Logger.Error($"Actor of type {typeof(TRequiredActor)} not found in the scene");
                return null;
            }
            
            return actor;
        }

        public void Unload() {
            KillAllActors();

            if (m_SceneInstance.IsValid()) {
                m_SceneInstance.Release();
                m_SceneInstance = default;
            }

            m_WorldState = WorldState.Unloaded;
            Context = null;
        }

        public async UniTask<TActor> SpawnActor<TActor>(AssetReferenceT<GameObject> asset, CancellationToken cancellationToken) where TActor : Actor {
            GameObject gameObject = await Addressables.InstantiateAsync(asset);
            if (cancellationToken.IsCancellationRequested) {
                asset.ReleaseInstance(gameObject);
                return null;
            }

            if (gameObject.TryGetComponent(out TActor actor)) {
                return actor;
            }

            asset.ReleaseInstance(gameObject);
            return null;
        }

        public void RegisterActor(Actor actor) {
            m_Actors.Add(actor);
        }

        public void KillActor(Actor actor) {
            Addressables.ReleaseInstance(actor.gameObject);
        }

        public void KillAllActors() {
            foreach (Actor actor in m_Actors) {
                Addressables.ReleaseInstance(actor.gameObject);
            }

            m_Actors.Clear();
        }
    }
}