using System.Buffers;
using System.Net.Http;
using Млаумчерб.Клиент.видимое;
using Млаумчерб.Клиент.классы;

namespace Млаумчерб.Клиент.сеть;

public static class Сеть
{
    public static int ParallelDownloadsN = 32;
    public static HttpClient http = new();

    public static async Task DownloadFileHTTP(string url, IOPath outPath, CancellationToken ct = default,
        Action<ArraySegment<byte>>? transformFunc = null)
    {
        await using var src = await http.GetStreamAsync(url, ct);
        await using var dst = File.OpenWrite(outPath);

        await src.CopyTransformAsync(dst, transformFunc, ct).ConfigureAwait(false);
    }

    public static async Task CopyTransformAsync(this Stream src, Stream dst,
        Action<ArraySegment<byte>>? transformFunc = null, CancellationToken ct = default)
    {
        // default dotnet runtime buffer size
        int bufferSize = 81920;
        byte[] readBuffer = ArrayPool<byte>.Shared.Rent(bufferSize);
        byte[] writeBuffer = ArrayPool<byte>.Shared.Rent(bufferSize);
        try
        {
            var readTask = src.ReadAsync(readBuffer, 0, bufferSize, ct).ConfigureAwait(false);
            while (true)
            {
                int readCount = await readTask;
                if (readCount == 0)
                    break;
                (readBuffer, writeBuffer) = (writeBuffer, readBuffer);
                readTask = src.ReadAsync(readBuffer, 0, bufferSize, ct).ConfigureAwait(false);
                transformFunc?.Invoke(new ArraySegment<byte>(writeBuffer, 0, readCount));
                dst.Write(writeBuffer, 0, readCount);
            }
        }
        catch (OperationCanceledException)
        {
        }
        finally
        {
            ArrayPool<byte>.Shared.Return(readBuffer);
            ArrayPool<byte>.Shared.Return(writeBuffer);
        }
    }
    
    private static readonly string[] VERSION_MANIFEST_URLS =
    {
        "https://piston-meta.mojang.com/mc/game/version_manifest_v2.json"
    };

    private static async Task<List<RemoteVersionDescriptorProps>> GetRemoteVersionDescriptorsAsync()
    {
        List<RemoteVersionDescriptorProps> descriptors = new();
        foreach (var url in VERSION_MANIFEST_URLS)
        {
            try
            {
                var manifestText = await http.GetStringAsync(url);
                var catalog = JsonConvert.DeserializeObject<VersionCatalog>(manifestText);
                if (catalog != null)
                    descriptors.AddRange(catalog.versions);
            }
            catch (Exception ex)
            {
                Приложение.Логгер.LogWarn(nameof(Сеть), ex);
            }
        }

        return descriptors;
    }

    private static List<GameVersionProps>? _versionPropsList;

    /// <returns>empty list if couldn't find any remote versions</returns>
    public static async Task<IReadOnlyList<GameVersionProps>> GetDownloadableVersions()
    {
        if (_versionPropsList == null)
        {
            _versionPropsList = new();
            var rvdlist = await GetRemoteVersionDescriptorsAsync();
            foreach (var r in rvdlist)
            {
                if (r.type == "release")
                    _versionPropsList.Add(new GameVersionProps(r.id, r.url));
            }
        }

        return _versionPropsList;
    }
}