archived-discord-bot/CompatBot/EventHandlers/LogParsing/ArchiveHandlers/RarHandler.cs

using System;
using System.IO;
using System.IO.Pipelines;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using CompatBot.Utils;
using SharpCompress.Readers.Rar;

namespace CompatBot.EventHandlers.LogParsing.ArchiveHandlers
{
    internal sealed class RarHandler: IArchiveHandler
    {
        private static readonly byte[] Header = {0x52, 0x61, 0x72, 0x21, 0x1A, 0x07};

        public long LogSize { get; private set; }
        public long SourcePosition { get; private set; }

        public (bool result, string? reason) CanHandle(string fileName, int fileSize, ReadOnlySpan<byte> header)
        {
            if (header.Length >= Header.Length && header.Slice(0, Header.Length).SequenceEqual(Header)
                || fileName.EndsWith(".rar", StringComparison.InvariantCultureIgnoreCase))
            {
                var firstEntry = Encoding.ASCII.GetString(header);
                if (!firstEntry.Contains(".log", StringComparison.InvariantCultureIgnoreCase))
                    return (false, "Archive doesn't contain any logs.");

                return (true, null);
            }

            return (false, null);
        }

        public async Task FillPipeAsync(Stream sourceStream, PipeWriter writer, CancellationToken cancellationToken)
        {
            try
            {
                await using var statsStream = new BufferCopyStream(sourceStream);
                using var rarReader = RarReader.Open(statsStream);
                while (rarReader.MoveToNextEntry())
                {
                    if (!rarReader.Entry.IsDirectory
                        && rarReader.Entry.Key.EndsWith(".log", StringComparison.InvariantCultureIgnoreCase)
                        && !rarReader.Entry.Key.Contains("tty.log", StringComparison.InvariantCultureIgnoreCase))
                    {
                        LogSize = rarReader.Entry.Size;
                        await using var rarStream = rarReader.OpenEntryStream();
                        int read;
                        FlushResult flushed;
                        do
                        {
                            var memory = writer.GetMemory(Config.MinimumBufferSize);
                            read = await rarStream.ReadAsync(memory, cancellationToken);
                            writer.Advance(read);
                            SourcePosition = statsStream.Position;
                            flushed = await writer.FlushAsync(cancellationToken).ConfigureAwait(false);
                            SourcePosition = statsStream.Position;
                        } while (read > 0 && !(flushed.IsCompleted || flushed.IsCanceled || cancellationToken.IsCancellationRequested));
                        await writer.CompleteAsync();
                        return;
                    }
                    SourcePosition = statsStream.Position;
                }
                Config.Log.Warn("No rar entries that match the log criteria");
            }
            catch (Exception e)
            {
                Config.Log.Error(e, "Error filling the log pipe");
            }
            await writer.CompleteAsync();
        }
    }
}