using System.Security.Cryptography;
using DTLib.Extensions;
using Млаумчерб.Клиент.видимое;
using Млаумчерб.Клиент.классы;
using static Млаумчерб.Клиент.сеть.Сеть;

namespace Млаумчерб.Клиент.сеть.NetworkTaskFactories;

public class AssetsDownloadTaskFactory : INetworkTaskFactory
{
    private const string ASSET_SERVER_URL = "https://resources.download.minecraft.net/";
    private VersionDescriptor _descriptor;
    private SHA1 _hasher;
    private IOPath _indexFilePath;
    List<AssetDownloadProperties> _assetsToDownload = new();

    public AssetsDownloadTaskFactory(VersionDescriptor descriptor)
    {
        _descriptor = descriptor;
        _hasher = SHA1.Create();
        _indexFilePath = Пути.GetAssetIndexFilePath(_descriptor.assetIndex.id);
    }
    
    public async Task<NetworkTask?> CreateAsync(bool checkHashes)
    {
        if (!await CheckFilesAsync(checkHashes))
            return new NetworkTask(
                $"assets '{_descriptor.assetIndex.id}'",
                GetTotalSize(),
                Download
            );
        
        return null;
    }
    private async Task<bool> CheckFilesAsync(bool checkHashes)
    {
        if(!File.Exists(_indexFilePath))
        {
            Приложение.Логгер.LogInfo(nameof(Сеть), $"started downloading asset index to '{_indexFilePath}'");
            await DownloadFileHTTP(_descriptor.assetIndex.url, _indexFilePath);
            Приложение.Логгер.LogInfo(nameof(Сеть), "finished downloading asset index");
        }

        string indexFileText = File.ReadAllText(_indexFilePath);
        var assetIndex = JsonConvert.DeserializeObject<AssetIndex>(indexFileText) 
                     ?? throw new Exception($"can't deserialize asset index file '{_indexFilePath}'");
        
        _assetsToDownload.Clear();
        // removing duplicates for Dictionary (idk how can it be possible, but Newtonsoft.Json creates them)
        HashSet<string> assetHashes = new HashSet<string>();
        foreach (var pair in assetIndex.objects)
        {
            if (assetHashes.Add(pair.Value.hash))
            {
                var a = new AssetDownloadProperties(pair.Key, pair.Value);
                if (!File.Exists(a.filePath))
                {
                    _assetsToDownload.Add(a);
                }
                else if(checkHashes)
                {
                    await using var fs = File.OpenRead(a.filePath);
                    string hash = _hasher.ComputeHash(fs).HashToString();
                    if (hash != a.hash)
                        _assetsToDownload.Add(a);
                }
            }
        }
        
        return _assetsToDownload.Count == 0;
    }

    private long GetTotalSize()
    {
        long totalSize = 0;
        foreach (var a in _assetsToDownload) 
            totalSize += a.size;
        return totalSize;
    }

    private class AssetDownloadProperties
    {
        public string name;
        public string hash;
        public long size;
        public string url;
        public IOPath filePath;

        public AssetDownloadProperties(string key, AssetProperties p)
        {
            name = key;
            hash = p.hash;
            size = p.size;
            string hashStart = hash.Substring(0, 2);
            url = $"{ASSET_SERVER_URL}/{hashStart}/{hash}";
            filePath = Path.Concat(IOPath.ArrayCast(["assets", "objects", hashStart, hash], true));
        }
    }
    
    private async Task Download(NetworkProgressReporter pr, CancellationToken ct)
    {
        Приложение.Логгер.LogInfo(nameof(Сеть), "started downloading assets");
        ParallelOptions opt = new() { MaxDegreeOfParallelism = ParallelDownloadsN, CancellationToken = ct };
        await Parallel.ForEachAsync(_assetsToDownload, opt, 
            async (a, _ct) =>
            {
                Приложение.Логгер.LogDebug(nameof(Сеть), $"downloading asset '{a.name}' {a.hash}");
                await DownloadFileHTTP(a.url, a.filePath, _ct, pr.AddBytesCount);
            });
        Приложение.Логгер.LogInfo(nameof(Сеть), "finished downloading assets");
    }
}