using Deal.Grpc.Storage;
using Deal.Storage.Services;
using Grpc.Core;

namespace Deal.Storage;

/// <summary>
/// Реализация сервиса данных.
/// </summary>
public sealed class StorageServiceImpl : StorageService.StorageServiceBase
{
    private const int HeadSize = 512;
    private const int DownloadChunkSize = 64 * 1024;

    private readonly MinioObjectStore _store;
    private readonly ILogger<StorageServiceImpl> _logger;

    /// <summary>
    /// Создаёт реализацию поверх хранилища.
    /// </summary>
    public StorageServiceImpl(MinioObjectStore store, ILogger<StorageServiceImpl> logger)
    {
        ArgumentNullException.ThrowIfNull(store);
        ArgumentNullException.ThrowIfNull(logger);
        _store = store;
        _logger = logger;
    }

    /// <inheritdoc />
    public override async Task<UploadReply> Upload(
        IAsyncStreamReader<UploadRequest> requestStream,
        ServerCallContext context)
    {
        CancellationToken ct = context.CancellationToken;
        await using MemoryStream buffer = new();
        byte[] head = new byte[HeadSize];
        int headLength = 0;
        UploadMeta? meta = null;

        while (await requestStream.MoveNext(ct))
        {
            UploadRequest message = requestStream.Current;
            if (meta is null && message.Meta is not null)
            {
                meta = message.Meta;
            }

            if (message.Data.Length == 0)
            {
                continue;
            }

            if (headLength < HeadSize)
            {
                int take = Math.Min(HeadSize - headLength, message.Data.Length);
                message.Data.Span[..take].CopyTo(head.AsSpan(headLength));
                headLength += take;
            }

            await buffer.WriteAsync(message.Data.Memory, ct);
        }

        if (meta is null || string.IsNullOrWhiteSpace(meta.TenantId))
        {
            throw new RpcException(new Status(StatusCode.InvalidArgument, "tenant_id обязателен"));
        }

        (string kind, string mimeType) = FileKindSniffer.Detect(head.AsSpan(0, headLength), meta.ContentType);
        string key = $"{meta.TenantId.Trim()}/{Guid.NewGuid():N}";
        buffer.Position = 0;
        long size = await _store.PutAsync(key, buffer, mimeType, ct);

        _logger.LogInformation("Объект сохранён: {Key} ({Kind}, {Size} байт)", key, kind, size);

        return new UploadReply
        {
            Id = key,
            Ref = key,
            Kind = kind,
            MimeType = mimeType,
            FileName = meta.FileName ?? string.Empty,
            Size = size,
        };
    }

    /// <inheritdoc />
    public override async Task Download(
        DownloadRequest request,
        IServerStreamWriter<DownloadChunk> responseStream,
        ServerCallContext context)
    {
        CancellationToken ct = context.CancellationToken;
        await using Stream? content = await _store.GetAsync(request.Id, ct);
        if (content is null)
        {
            throw new RpcException(new Status(StatusCode.NotFound, "объект не найден"));
        }

        byte[] chunk = new byte[DownloadChunkSize];
        int read;
        while ((read = await content.ReadAsync(chunk, ct)) > 0)
        {
            await responseStream.WriteAsync(new DownloadChunk { Data = Google.Protobuf.ByteString.CopyFrom(chunk, 0, read) }, ct);
        }
    }

    /// <inheritdoc />
    public override async Task<StatReply> Stat(StatRequest request, ServerCallContext context)
    {
        (long Size, string ContentType)? stat = await _store.StatAsync(request.Id, context.CancellationToken);
        if (stat is null)
        {
            return new StatReply { Found = false };
        }

        return new StatReply
        {
            Found = true,
            Info = new UploadReply
            {
                Id = request.Id,
                Ref = request.Id,
                MimeType = stat.Value.ContentType,
                Size = stat.Value.Size,
            },
        };
    }

    /// <inheritdoc />
    public override async Task<DeleteReply> Delete(DeleteRequest request, ServerCallContext context)
    {
        await _store.DeleteAsync(request.Id, context.CancellationToken);
        return new DeleteReply();
    }
}