using System;
using System.Collections;
using Mountools.Tools;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.SceneManagement;

namespace Mountools.LoadingScreen
{
    [DisallowMultipleComponent]
#if MT_L_CHINESE
    [AddComponentMenu("Mountools/加载画面/异步加载画面")]
#endif
#if MT_L_ENGLISH
    [AddComponentMenu("Mountools/Loading Screen/Async Loading Screen")]
#endif
    public class LoadingScreen : MonoBehaviour
    {
        public static LoadingScreen GetLoadingScreen()
        {
            return FindObjectOfType<LoadingScreen>();
        }

        public float loadingStartWaitSeconds = 2;
        public float loadingDoneWaitSeconds = 2;
        
        public float fakeLoadingRate = 0.1f;

        private Coroutine _loadSceneCoroutine;
        public float progress;
        public bool isLoading;
        public string loadingSceneName;

        public UnityEvent<string> onLoad;
        public UnityEvent<float> onLoading;
        public UnityEvent onLoaded;
        
        public static void LoadScene(int sceneIndex, LoadSceneMode mode = LoadSceneMode.Single, bool fakeLoad = false)
        {
            LoadScene(SceneManager.GetSceneAt(sceneIndex).name, mode, fakeLoad);
        }
        
        public static void LoadScene(string sceneName, LoadSceneMode mode = LoadSceneMode.Single, bool fakeLoad = false)
        {
            var loadingScreen = GetLoadingScreen();

            if (loadingScreen == null)
            {
                Debug.LogWarning(
                    MountoolsLanguage.Lang(
                        "场景内没有加载画面！", 
                        "There are no Loading Screen in the scene!"
                    ));
                
                SceneManager.LoadScene(sceneName, mode);
            }
            else
            {
                loadingScreen.Load(sceneName, mode, fakeLoad);
            }
        }

        private void Load(string sceneName, LoadSceneMode mode = LoadSceneMode.Single, bool fakeLoad = false)
        {
            loadingSceneName = sceneName;
            
            if (_loadSceneCoroutine == null)
            {
                _loadSceneCoroutine = StartCoroutine(LoadSceneAsync(sceneName, mode, fakeLoad));
            }
            else
            {
                Debug.LogWarning(
                    MountoolsLanguage.Lang("请勿重复加载场景！", "Do not load the scene repeatedly!")
                    );
            }
        }

        private IEnumerator LoadSceneAsync(string sceneName, LoadSceneMode mode, bool fakeLoad)
        {
            // 设置状态，调用事件
            isLoading = true;
            onLoad.Invoke(sceneName); 
            
            // 等待动画播放
            yield return new WaitForSecondsRealtime(loadingStartWaitSeconds);
            
            // 开始加载
            var loadAsync = SceneManager.LoadSceneAsync(sceneName, mode);
            loadAsync.allowSceneActivation = false;
            
            progress = 0;

            if (fakeLoad)
            {
                // 假加载 (测试用)
                while (progress < 0.9f)
                {
                    progress += 0.1f;
                    onLoading.Invoke(progress);
                    yield return new WaitForSecondsRealtime(fakeLoadingRate);
                }
            }
            else
            {
                // 真加载
                while (progress < 0.86f)
                {
                    progress = (float) Math.Round(Mathf.Lerp(progress, loadAsync.progress, 0.2f), 3);
                    onLoading.Invoke(progress);
                    yield return new WaitForEndOfFrame();
                }
                
                // 等待完全加载
                while (loadAsync.progress < 0.9f)
                {
                    yield return new WaitForEndOfFrame();
                }
                
                // 完全加载后，进入新场景
                loadAsync.allowSceneActivation = true;
                
                // 继续播放剩余 10% 的动画
                while (progress < 0.99f)
                {
                    progress = (float) Math.Round(Mathf.Lerp(progress, 1f, 0.2f), 3);
                    onLoading.Invoke(progress);
                    yield return new WaitForEndOfFrame();
                }
            }

            // 进度条设置为 100%
            progress = 1;
            
            // 执行加载后事件
            onLoaded.Invoke();
            
            // 等待退出动画的播放
            yield return new WaitForSecondsRealtime(loadingDoneWaitSeconds);
            
            // 设置加载完成
            isLoading = false;
        }

        private void Start()
        {
            DontDestroyOnLoad(gameObject);
            
            onLoaded.AddListener(() =>
            {
                _loadSceneCoroutine = null;
            });
        }
    }
}