// File: Services/RomArchiveReader.cs
using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Text.RegularExpressions;
using SharpCompress.Archives;
using SharpCompress.Archives.Rar;
using SharpCompress.Common;
using SharpCompress.IO;
using SharpCompress.Readers;
using TinfoilVibeServer.Utilities;

namespace TinfoilVibeServer.Services
{
    /// <summary>
    /// Reads a ROM archive (zip / 7z / rar) from a stream.
    /// </summary>
    public sealed class RomArchiveReader : IDisposable
    {
        private readonly ZipArchive?   _zipArchive;
        private readonly IArchive?    _archive;
        private readonly Stream?      _archiveStream;   // the stream actually handed to SharpCompress
        private readonly ICollection<Stream>? _partStreams;

        public RomArchiveReader(string path)
        {
            _archive = DetectAndWrap(path);
        }
        /// <summary>
        /// Opens an archive from a stream.
        /// The *fileName* parameter is only used to decide which archive format
        /// to open; it can be <c>null</c> if the caller already knows the format.
        /// </summary>
        public RomArchiveReader(string path, Stream stream)
        {
            if (stream == null) throw new ArgumentNullException(nameof(stream));

            var fileInfo = new FileInfo(path);

            switch (fileInfo.Extension)
            {
                case ".zip":
                    // System.IO.Compression can use the stream directly
                    _zipArchive = new ZipArchive(stream, ZipArchiveMode.Read, leaveOpen: false);
                    break;

                case ".7z":
                case ".rar":
                    // SharpCompress requires a seekable stream; copy if necessary
                    if (!stream.CanSeek)
                    {
                        var ms = new MemoryStream();
                        stream.CopyTo(ms);
                        ms.Position = 0;
                        _archiveStream = ms;
                        stream.Dispose();          // original non‑seekable stream no longer needed
                    }
                    else
                    {
                        _archiveStream = stream;
                    }

                    _archive = ArchiveFactory.Open(_archiveStream, new ReaderOptions() { LeaveStreamOpen = false, BufferSize = 10 * 1024 * 1024});
                    break;

                default:
                    throw new NotSupportedException($"Archive type '{fileInfo.Extension}' is not supported.");
            }
        }

        // Detect whether the file is a multi‑part RAR and wrap it if necessary
        private static IArchive DetectAndWrap(string path)
        {
            string ext = Path.GetExtension(path).ToLowerInvariant();

            if (ext == ".rar" || ext == ".r00" || ext == ".r01" || ext == ".r02")
            {
                var dir        = Path.GetDirectoryName(path)!;
                var fileName   = Path.GetFileName(path);

                // ----- 1️⃣  Determine the base name (everything before the first ".rar" or ".partNN") -----
                string baseName = MultiPartRarHelper.GetBaseNameForRarVolume(fileName);

                // Any file that ends with .rar or .rNN could be the start of a multi‑part set
                // Let MultiPartRarStream decide which parts belong together.
                var volumes = MultiPartRarHelper.DiscoverVolumes(dir, baseName);
                if (volumes.Count is 0 or 1)
                {
                    return ArchiveFactory.Open(path);
                }

                var streams = new List<Stream>(volumes.Count);
                foreach (var volume in volumes)
                {
                    streams.Add(new FileStream(volume, FileMode.Open, FileAccess.Read, FileShare.Read));
                }

                return ArchiveFactory.Open(streams, new ReaderOptions { LeaveStreamOpen = false });
            }

            // Normal single‑file archive (zip, 7z, single‑rar, etc.)
            using var archiveStream = File.OpenRead(path);
            return ArchiveFactory.Open(archiveStream);
        }

        private static Stream? GetPart(int arg)
        {
            throw new NotImplementedException();
        }

        public Stream? GetEntryStream(string entryName)
        {
            var entry = _archive?.Entries
                .Single(e => e.Key != null && e.Key.Equals(entryName, StringComparison.OrdinalIgnoreCase));
            return entry?.OpenEntryStream();
        }
        /// <summary>
        /// Enumerates every file entry inside the archive.
        /// </summary>
        public IEnumerable<RomArchiveEntry> GetEntries()
        {
            if (_zipArchive != null)
            {
                foreach (var entry in _zipArchive.Entries)
                {
                    if (entry.FullName.EndsWith("/", StringComparison.Ordinal))
                        continue;   // skip directories

                    yield return new RomArchiveEntry(entry.FullName, entry.Open());
                }
            }
            else if (_archive != null)
            {
                foreach (var entry in _archive.Entries)
                {
                    if (entry.IsDirectory)
                        continue;

                    // SharpCompress gives us a stream that must be disposed by the caller
                    if (!entry.Archive.IsComplete)
                    {
                        if (entry.Key != null)
                        {
                            var entryStream = GetEntryStream(entry.Key);
                            if (entryStream != null) yield return new RomArchiveEntry(entry.Key, entryStream);
                        }
                    }
                    else
                    {
                        if (entry.Key != null) yield return new RomArchiveEntry(entry.Key, entry.OpenEntryStream());
                    }
                }
            }
        }

        /// <summary>
        /// Back‑compat wrapper used by SnapshotService.
        /// </summary>
        public IEnumerable<RomArchiveEntry> GetContentInfos() => GetEntries();

        /// <summary>
        /// Disposes the underlying archive objects and the stream(s).
        /// </summary>
        public void Dispose()
        {
            _zipArchive?.Dispose();
            _archive?.Dispose();
            _archiveStream?.Dispose();
        }

        /// <summary>
        /// Lightweight container that holds the entry name and the opened stream.
        /// The caller must dispose <c>Stream</c> after it is done.
        /// </summary>
        public sealed record RomArchiveEntry(string Name, Stream Stream);
    }
}