using Google.Protobuf;
using Grpc.Core;
using TestGrpc;

namespace TestGrpc.Services;

public class GreeterService : Greeter.GreeterBase
{
    private readonly ILogger<GreeterService> _logger;
    public GreeterService(ILogger<GreeterService> logger)
    {
        _logger = logger;
    }

    public override async Task DownloadFile(FileRequest request, IServerStreamWriter<ChunkMsg> responseStream, ServerCallContext context)
    {
        string filePath = request.FilePath;

        if (!File.Exists(filePath))
        {
            return;
        }

        var fileInfo = new FileInfo(filePath);

        var chunk = new ChunkMsg
        {
            FileName = Path.GetFileName(filePath),
            FileSize = fileInfo.Length
        };

        int fileChunkSize = 64 * 1024;

        byte[] fileByteArray = File.ReadAllBytes(filePath);
        byte[] fileChunk = new byte[fileChunkSize];
        int fileOffset = 0;

        while (fileOffset < fileByteArray.Length && !context.CancellationToken.IsCancellationRequested)
        {
            int length = Math.Min(fileChunkSize, fileByteArray.Length - fileOffset);
            Buffer.BlockCopy(fileByteArray, fileOffset, fileChunk, 0, length);
            fileOffset += length;
            ByteString byteString = ByteString.CopyFrom(fileChunk);

            chunk.Chunk = byteString;
            await responseStream.WriteAsync(chunk).ConfigureAwait(false);
        }
    }
}