using System;
using System.Threading.Tasks;

using Grpc.Core;

using FrostFS.Object;

namespace FrostFS.SDK.ClientV2;

internal class ObjectReader(AsyncServerStreamingCall<GetResponse> call) : IDisposable
{
    public AsyncServerStreamingCall<GetResponse> Call { get; private set; } = call;

    public async Task<Object.Object> ReadHeader()
    {
        if (!await Call.ResponseStream.MoveNext())
            throw new InvalidOperationException("unexpected end of stream");
        
        var response = Call.ResponseStream.Current;
        Verifier.CheckResponse(response);
        
        if (response.Body.ObjectPartCase != GetResponse.Types.Body.ObjectPartOneofCase.Init)
            throw new InvalidOperationException("unexpected message type");
        
        return new Object.Object
        {
            ObjectId = response.Body.Init.ObjectId,
            Header = response.Body.Init.Header,
        };
    }

    public async Task<byte[]?> ReadChunk()
    {
        if (!await Call.ResponseStream.MoveNext())
            return null;
        
        var response = Call.ResponseStream.Current;
        Verifier.CheckResponse(response);
        
        if (response.Body.ObjectPartCase != GetResponse.Types.Body.ObjectPartOneofCase.Chunk)
            throw new InvalidOperationException("unexpected message type");

        return response.Body.Chunk.ToByteArray();
    }

    public void Dispose()
    {
        Call.Dispose();
    }
}