private async Task WriteServiceAsync()

in AdlsDotNetSDK/AdlsOutputStream.cs [397:443]
40 lines of code
13 McCabe index (conditional complexity)

        private async Task WriteServiceAsync(SyncFlag flag, CancellationToken cancelToken)
        {
            if (BufferSize == 0 && (flag == SyncFlag.DATA || (MetaDataSynced && flag == SyncFlag.METADATA)))
            {
                return;
            }
            if (OutStreamLog.IsTraceEnabled)
            {
                OutStreamLog.Trace($"ADLFileOutputStream, Stream flush of size {BufferSize} at offset {FilePointer} for file {Filename} for client {Client.ClientId}");
            }
            OperationResponse resp = new OperationResponse();
            await Core.AppendAsync(Filename, LeaseId, LeaseId, flag, FilePointer, Buffer, 0, BufferSize, Client, new RequestOptions(Client.GetPerRequestTimeout(), new ExponentialRetryPolicy()), resp, cancelToken).ConfigureAwait(false);
            if (!resp.IsSuccessful)
            {
                // if this was a retry and we get bad offset, then this might be because we got a transient
                // failure on first try, but request succeeded on back-end. In that case, the retry would fail
                // with bad offset. To detect that, we check if there was a retry done, and if the current error we
                // have is bad offset.
                // If so, do a zero-length append at the current expected Offset, and if that succeeds,
                // then the file length must be good - swallow the error. If this append fails, then the last append
                // did not succeed and we have some other offset on server - bubble up the error.
                if (resp.Retries > 0 && resp.HttpStatus == HttpStatusCode.BadRequest &&
                    resp.RemoteExceptionName.Equals("BadOffsetException"))
                {
                    bool zeroAppendIsSuccesful = await PerformZeroLengthAppendAsync(FilePointer + BufferSize, flag, cancelToken).ConfigureAwait(false);
                    if (zeroAppendIsSuccesful)
                    {
                        if (OutStreamLog.IsDebugEnabled)
                        {
                            OutStreamLog.Debug($"ADLFileOutputStream, Zero size Append succeded and the expected FileSize is {FilePointer + BufferSize}, ignoring BadOffsetException for session {LeaseId} for file {Filename} for client {Client.ClientId}");
                        }
                        FilePointer += BufferSize;
                        BufferSize = 0;
                        MetaDataSynced = flag == SyncFlag.METADATA;
                        return;
                    }
                    if (OutStreamLog.IsDebugEnabled)
                    {
                        OutStreamLog.Debug($"ADLFileOutputStream, Append failed at offset {FilePointer} for session {LeaseId} for file {Filename} for client {Client.ClientId}");
                    }
                }
                throw Client.GetExceptionFromResponse(resp, $"Error in appending for file {Filename} at offset {FilePointer}.");
            }
            MetaDataSynced = flag == SyncFlag.METADATA;//Make sure if metadata is already updated, then do not try to update metada again unless data has been written
            FilePointer += BufferSize;//Update the filepointer as data is written to server
            BufferSize = 0;//Resets buffersize since all data in buffer is flushed to server
        }