using System;
using Cysharp.Threading.Tasks;
using UnityEngine;
using Object = UnityEngine.Object;

namespace DanieleMarotta.RiversongCodeShowcase
{
    [RequiresWorldReadyForUpdate]
    [GameSystemGroup(typeof(LateGameSystemGroup))]
    public class TileHighlightSystem : GameSystem, IInitializable, IDisposable, IUpdatable, IOnWorldGenerationCompletedCallback
    {
        private static readonly int TileHighlightTextureID = Shader.PropertyToID("_Tile_Highlight_Texture");

        [InjectService]
        private GameConfig _config;

        [InjectService]
        private World _world;

        [InjectService]
        private WorldRenderingState _renderingState;

        [InjectService]
        private ISignalBus _signalBus;

        private GameObject _tileHighlightGameObject;

        public TileHighlightSystem(IServiceLocator serviceLocator) : base(serviceLocator)
        {
        }

        public UniTask InitializeAsync()
        {
            _signalBus.Subscribe<WorldGenerationCompletedSignal>(OnWorldGenerationCompleted);

            return UniTask.CompletedTask;
        }

        public void Dispose()
        {
            _signalBus.Unsubscribe<WorldGenerationCompletedSignal>(OnWorldGenerationCompleted);

            _renderingState.TileHighlight.Dispose();

            if (_tileHighlightGameObject)
            {
                Object.Destroy(_tileHighlightGameObject);
                _tileHighlightGameObject = null;
            }
        }

        private void OnWorldGenerationCompleted(WorldGenerationCompletedSignal signal)
        {
            signal.Callbacks.Add(this);
        }

        public async UniTask OnWorldGenerationCompletedAsync(World world)
        {
            _renderingState.TileHighlight.Create(_world.Size);
            Shader.SetGlobalTexture(TileHighlightTextureID, _renderingState.TileHighlight.Texture);

            var tileHighlightPrefab = await _config.UI.TileHighlight.Prefab.LoadAssetAsync<GameObject>();
            var tileHighlightGameObject = Object.Instantiate(tileHighlightPrefab);
            tileHighlightGameObject.transform.position = new Vector3(_world.Size.x * 0.5f, _config.GeneralSettings.BaseElevation + 0.002f, _world.Size.x * 0.5f);
            tileHighlightGameObject.transform.localScale = new Vector3(_world.Size.x, 1, _world.Size.y);
        }

        public void Update()
        {
            _renderingState.TileHighlight.Apply();
        }
    }
}