using System;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.Networking;
namespace VRMShaders
    {
    public class AssetBundleCache:IDisposable
    {
        private Dictionary<string,AssetBundle> bundleDict=new Dictionary<string, AssetBundle>();
        static AssetBundleCache instance;
        public static AssetBundleCache Instance=>instance??new AssetBundleCache();
        private Dictionary<string,Task<AssetBundle>>loadingDict=new Dictionary<string, Task<AssetBundle>>();
        public AssetBundleCache()
        {
            instance=this;
        }
        /// <summary>
        /// Set Folder Path that material bundle located
        /// </summary>
        /// <value></value>
        public string LoadFolderPath{get;set;}
        /// <summary>
        /// Toggle to remove bundle hash when loading
        /// </summary>
        /// <value></value>
        public bool IsLocal{get;set;}

        public void Dispose()
        {
            instance=null;
            foreach(var bundle in bundleDict.Values)
            {
                bundle.UnloadAsync(true);
            }
        }
        public async Task<T> GetBundleAssetAsync<T>(string bundleName,string assetName)where T:UnityEngine.Object
        {
            AssetBundle bundle=await GetBundleAsync(bundleName);
            return await bundle.GetAssetAsync<T>(assetName);
        }
        public async Task<AssetBundle> GetBundleAsync(string bundleName)
        {
            //Direct load bundle locally by using its name instead of name-hash pair
            if(IsLocal)
                bundleName=bundleName.Substring(0, bundleName.LastIndexOf('-'));
            if(bundleDict.ContainsKey(bundleName)&&bundleDict[bundleName]!=null)
            {
                return bundleDict[bundleName];
            }
            else
            {
                if(loadingDict.ContainsKey(bundleName))
                {
                    return await loadingDict[bundleName];
                }
                var path=Path.Combine(LoadFolderPath,bundleName);
                #if UNITY_WEBGL
                var request = UnityWebRequestAssetBundle.GetAssetBundle(path);
                loadingDict[bundleName]= WaitAssetBundleTask(request,request.SendWebRequest());
                #else
                var quest=AssetBundle.LoadFromFileAsync(path);
                loadingDict[bundleName]=WaitAssetBundleTask(quest);
                #endif
                bundleDict[bundleName]=await loadingDict[bundleName];
                return bundleDict[bundleName];
            }
        }
        private static async Task<AssetBundle> WaitAssetBundleTask(UnityWebRequest request,UnityWebRequestAsyncOperation operation)
        {
            while(!operation.isDone)
            {
                await Task.Yield();
            }
            return (request.downloadHandler as DownloadHandlerAssetBundle).assetBundle;
        }
        private static async Task<AssetBundle> WaitAssetBundleTask(AssetBundleCreateRequest request)
        {
            while(!request.isDone)
            {
                await Task.Yield();
            }
            return request.assetBundle;
        }
    }
    internal static class AssetBundleRequestExtension
    {
        internal static async Task<T> GetAssetAsync<T>(this AssetBundle bundle,string assetName) where T:UnityEngine.Object
        {
            var quest=bundle.LoadAssetAsync<T>(assetName);
            await WaitRequestTask(quest);
            return quest.asset as T;
        }
        private static async Task WaitRequestTask(AssetBundleRequest request)
        {
            while(!request.isDone)
            {
                await Task.Yield();
            }
        }
    }
    
}