Merge pull request #15604 from dkanada/opf-metadata

extract local metadata from OPF and EPUB files

5 files changed, 676 insertions, 0 deletions

diff --git a/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubImageProvider.cs b/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubImageProvider.cs
new file mode 100644
index 000000000..33d2823de
--- /dev/null
+++ b/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubImageProvider.cs
@@ -0,0 +1,118 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.IO.Compression;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Xml;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Providers;
+using MediaBrowser.Model.Entities;
+using Microsoft.Extensions.Logging;
+
+namespace MediaBrowser.Providers.Books.OpenPackagingFormat
+{
+    /// <summary>
+    /// Provides the primary image for EPUB items that have embedded covers.
+    /// </summary>
+    public class EpubImageProvider : IDynamicImageProvider
+    {
+        private readonly ILogger<EpubImageProvider> _logger;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EpubImageProvider"/> class.
+        /// </summary>
+        /// <param name="logger">Instance of the <see cref="ILogger{EpubImageProvider}"/> interface.</param>
+        public EpubImageProvider(ILogger<EpubImageProvider> logger)
+        {
+            _logger = logger;
+        }
+
+        /// <inheritdoc />
+        public string Name => "EPUB Metadata";
+
+        /// <inheritdoc />
+        public bool Supports(BaseItem item)
+        {
+            return item is Book;
+        }
+
+        /// <inheritdoc />
+        public IEnumerable<ImageType> GetSupportedImages(BaseItem item)
+        {
+            yield return ImageType.Primary;
+        }
+
+        /// <inheritdoc />
+        public Task<DynamicImageResponse> GetImage(BaseItem item, ImageType type, CancellationToken cancellationToken)
+        {
+            if (string.Equals(Path.GetExtension(item.Path), ".epub", StringComparison.OrdinalIgnoreCase))
+            {
+                return GetFromZip(item);
+            }
+
+            return Task.FromResult(new DynamicImageResponse { HasImage = false });
+        }
+
+        private async Task<DynamicImageResponse> LoadCover(ZipArchive epub, XmlDocument opf, string opfRootDirectory)
+        {
+            var utilities = new OpfReader<EpubImageProvider>(opf, _logger);
+            var coverReference = utilities.ReadCoverPath(opfRootDirectory);
+            if (coverReference == null)
+            {
+                return new DynamicImageResponse { HasImage = false };
+            }
+
+            var cover = coverReference.Value;
+            var coverFile = epub.GetEntry(cover.Path);
+
+            if (coverFile == null)
+            {
+                return new DynamicImageResponse { HasImage = false };
+            }
+
+            var memoryStream = new MemoryStream();
+            using (var coverStream = coverFile.Open())
+            {
+                await coverStream.CopyToAsync(memoryStream).ConfigureAwait(false);
+            }
+
+            memoryStream.Position = 0;
+
+            var response = new DynamicImageResponse { HasImage = true, Stream = memoryStream };
+            response.SetFormatFromMimeType(cover.MimeType);
+
+            return response;
+        }
+
+        private async Task<DynamicImageResponse> GetFromZip(BaseItem item)
+        {
+            using var epub = ZipFile.OpenRead(item.Path);
+
+            var opfFilePath = EpubUtils.ReadContentFilePath(epub);
+            if (opfFilePath == null)
+            {
+                return new DynamicImageResponse { HasImage = false };
+            }
+
+            var opfRootDirectory = Path.GetDirectoryName(opfFilePath);
+            if (opfRootDirectory == null)
+            {
+                return new DynamicImageResponse { HasImage = false };
+            }
+
+            var opfFile = epub.GetEntry(opfFilePath);
+            if (opfFile == null)
+            {
+                return new DynamicImageResponse { HasImage = false };
+            }
+
+            using var opfStream = opfFile.Open();
+
+            var opfDocument = new XmlDocument();
+            opfDocument.Load(opfStream);
+
+            return await LoadCover(epub, opfDocument, opfRootDirectory).ConfigureAwait(false);
+        }
+    }
+}
diff --git a/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubProvider.cs b/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubProvider.cs
new file mode 100644
index 000000000..bc77e5928
--- /dev/null
+++ b/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubProvider.cs
@@ -0,0 +1,100 @@
+using System;
+using System.IO;
+using System.IO.Compression;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Xml;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Providers;
+using MediaBrowser.Model.IO;
+using Microsoft.Extensions.Logging;
+
+namespace MediaBrowser.Providers.Books.OpenPackagingFormat
+{
+    /// <summary>
+    /// Provides book metadata from OPF content in an EPUB item.
+    /// </summary>
+    public class EpubProvider : ILocalMetadataProvider<Book>
+    {
+        private readonly IFileSystem _fileSystem;
+        private readonly ILogger<EpubProvider> _logger;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EpubProvider"/> class.
+        /// </summary>
+        /// <param name="fileSystem">Instance of the <see cref="IFileSystem"/> interface.</param>
+        /// <param name="logger">Instance of the <see cref="ILogger{EpubProvider}"/> interface.</param>
+        public EpubProvider(IFileSystem fileSystem, ILogger<EpubProvider> logger)
+        {
+            _fileSystem = fileSystem;
+            _logger = logger;
+        }
+
+        /// <inheritdoc />
+        public string Name => "EPUB Metadata";
+
+        /// <inheritdoc />
+        public Task<MetadataResult<Book>> GetMetadata(ItemInfo info, IDirectoryService directoryService, CancellationToken cancellationToken)
+        {
+            var path = GetEpubFile(info.Path)?.FullName;
+
+            if (path is null)
+            {
+                return Task.FromResult(new MetadataResult<Book> { HasMetadata = false });
+            }
+
+            var result = ReadEpubAsZip(path, cancellationToken);
+
+            if (result is null)
+            {
+                return Task.FromResult(new MetadataResult<Book> { HasMetadata = false });
+            }
+            else
+            {
+                return Task.FromResult(result);
+            }
+        }
+
+        private FileSystemMetadata? GetEpubFile(string path)
+        {
+            var fileInfo = _fileSystem.GetFileSystemInfo(path);
+
+            if (fileInfo.IsDirectory)
+            {
+                return null;
+            }
+
+            if (!string.Equals(Path.GetExtension(fileInfo.FullName), ".epub", StringComparison.OrdinalIgnoreCase))
+            {
+                return null;
+            }
+
+            return fileInfo;
+        }
+
+        private MetadataResult<Book>? ReadEpubAsZip(string path, CancellationToken cancellationToken)
+        {
+            using var epub = ZipFile.OpenRead(path);
+
+            var opfFilePath = EpubUtils.ReadContentFilePath(epub);
+            if (opfFilePath == null)
+            {
+                return null;
+            }
+
+            var opf = epub.GetEntry(opfFilePath);
+            if (opf == null)
+            {
+                return null;
+            }
+
+            using var opfStream = opf.Open();
+
+            var opfDocument = new XmlDocument();
+            opfDocument.Load(opfStream);
+
+            var utilities = new OpfReader<EpubProvider>(opfDocument, _logger);
+            return utilities.ReadOpfData(cancellationToken);
+        }
+    }
+}
diff --git a/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubUtils.cs b/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubUtils.cs
new file mode 100644
index 000000000..e5d298731
--- /dev/null
+++ b/MediaBrowser.Providers/Books/OpenPackagingFormat/EpubUtils.cs
@@ -0,0 +1,35 @@
+using System.IO;
+using System.IO.Compression;
+using System.Linq;
+using System.Xml.Linq;
+
+namespace MediaBrowser.Providers.Books.OpenPackagingFormat
+{
+    /// <summary>
+    /// Utilities for EPUB files.
+    /// </summary>
+    public static class EpubUtils
+    {
+        /// <summary>
+        /// Attempt to read content from ZIP archive.
+        /// </summary>
+        /// <param name="epub">The ZIP archive.</param>
+        /// <returns>The content file path.</returns>
+        public static string? ReadContentFilePath(ZipArchive epub)
+        {
+            var container = epub.GetEntry(Path.Combine("META-INF", "container.xml"));
+            if (container == null)
+            {
+                return null;
+            }
+
+            using var containerStream = container.Open();
+
+            XNamespace containerNamespace = "urn:oasis:names:tc:opendocument:xmlns:container";
+            var containerDocument = XDocument.Load(containerStream);
+            var element = containerDocument.Descendants(containerNamespace + "rootfile").FirstOrDefault();
+
+            return element?.Attribute("full-path")?.Value;
+        }
+    }
+}
diff --git a/MediaBrowser.Providers/Books/OpenPackagingFormat/OpfProvider.cs b/MediaBrowser.Providers/Books/OpenPackagingFormat/OpfProvider.cs
new file mode 100644
index 000000000..6e678802c
--- /dev/null
+++ b/MediaBrowser.Providers/Books/OpenPackagingFormat/OpfProvider.cs
@@ -0,0 +1,94 @@
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Xml;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Providers;
+using MediaBrowser.Model.IO;
+using Microsoft.Extensions.Logging;
+
+namespace MediaBrowser.Providers.Books.OpenPackagingFormat
+{
+    /// <summary>
+    /// Provides metadata for book items that have an OPF file in the same directory. Supports the standard
+    /// content.opf filename, bespoke metadata.opf name from Calibre libraries, and OPF files that have the
+    /// same name as their respective books for directories with several books.
+    /// </summary>
+    public class OpfProvider : ILocalMetadataProvider<Book>, IHasItemChangeMonitor
+    {
+        private const string StandardOpfFile = "content.opf";
+        private const string CalibreOpfFile = "metadata.opf";
+
+        private readonly IFileSystem _fileSystem;
+
+        private readonly ILogger<OpfProvider> _logger;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="OpfProvider"/> class.
+        /// </summary>
+        /// <param name="fileSystem">Instance of the <see cref="IFileSystem"/> interface.</param>
+        /// <param name="logger">Instance of the <see cref="ILogger{OpfProvider}"/> interface.</param>
+        public OpfProvider(IFileSystem fileSystem, ILogger<OpfProvider> logger)
+        {
+            _fileSystem = fileSystem;
+            _logger = logger;
+        }
+
+        /// <inheritdoc />
+        public string Name => "Open Packaging Format";
+
+        /// <inheritdoc />
+        public bool HasChanged(BaseItem item, IDirectoryService directoryService)
+        {
+            var file = GetXmlFile(item.Path);
+
+            return file.Exists && _fileSystem.GetLastWriteTimeUtc(file) > item.DateLastSaved;
+        }
+
+        /// <inheritdoc />
+        public Task<MetadataResult<Book>> GetMetadata(ItemInfo info, IDirectoryService directoryService, CancellationToken cancellationToken)
+        {
+            var path = GetXmlFile(info.Path).FullName;
+
+            try
+            {
+                return Task.FromResult(ReadOpfData(path, cancellationToken));
+            }
+            catch (FileNotFoundException)
+            {
+                return Task.FromResult(new MetadataResult<Book> { HasMetadata = false });
+            }
+        }
+
+        private FileSystemMetadata GetXmlFile(string path)
+        {
+            var fileInfo = _fileSystem.GetFileSystemInfo(path);
+            var directoryInfo = fileInfo.IsDirectory ? fileInfo : _fileSystem.GetDirectoryInfo(Path.GetDirectoryName(path)!);
+
+            // check for OPF with matching name first since it's the most specific filename
+            var specificFile = Path.Combine(directoryInfo.FullName, Path.GetFileNameWithoutExtension(path) + ".opf");
+            var file = _fileSystem.GetFileInfo(specificFile);
+
+            if (file.Exists)
+            {
+                return file;
+            }
+
+            file = _fileSystem.GetFileInfo(Path.Combine(directoryInfo.FullName, StandardOpfFile));
+
+            // check metadata.opf last since it's really only used by Calibre
+            return file.Exists ? file : _fileSystem.GetFileInfo(Path.Combine(directoryInfo.FullName, CalibreOpfFile));
+        }
+
+        private MetadataResult<Book> ReadOpfData(string file, CancellationToken cancellationToken)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+
+            var doc = new XmlDocument();
+            doc.Load(file);
+
+            var utilities = new OpfReader<OpfProvider>(doc, _logger);
+            return utilities.ReadOpfData(cancellationToken);
+        }
+    }
+}
diff --git a/MediaBrowser.Providers/Books/OpenPackagingFormat/OpfReader.cs b/MediaBrowser.Providers/Books/OpenPackagingFormat/OpfReader.cs
new file mode 100644
index 000000000..5d202c59e
--- /dev/null
+++ b/MediaBrowser.Providers/Books/OpenPackagingFormat/OpfReader.cs
@@ -0,0 +1,329 @@
+using System;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Xml;
+using Jellyfin.Data.Enums;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Providers;
+using MediaBrowser.Model.Entities;
+using MediaBrowser.Model.Net;
+using Microsoft.Extensions.Logging;
+
+namespace MediaBrowser.Providers.Books.OpenPackagingFormat
+{
+    /// <summary>
+    /// Methods used to pull metadata and other information from Open Packaging Format in XML objects.
+    /// </summary>
+    /// <typeparam name="TCategoryName">The type of category.</typeparam>
+    public class OpfReader<TCategoryName>
+    {
+        private const string DcNamespace = @"http://purl.org/dc/elements/1.1/";
+        private const string OpfNamespace = @"http://www.idpf.org/2007/opf";
+
+        private readonly XmlNamespaceManager _namespaceManager;
+        private readonly XmlDocument _document;
+
+        private readonly ILogger<TCategoryName> _logger;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="OpfReader{TCategoryName}"/> class.
+        /// </summary>
+        /// <param name="document">The XML document to parse.</param>
+        /// <param name="logger">Instance of the <see cref="ILogger{TCategoryName}"/> interface.</param>
+        public OpfReader(XmlDocument document, ILogger<TCategoryName> logger)
+        {
+            _document = document;
+            _logger = logger;
+            _namespaceManager = new XmlNamespaceManager(_document.NameTable);
+
+            _namespaceManager.AddNamespace("dc", DcNamespace);
+            _namespaceManager.AddNamespace("opf", OpfNamespace);
+        }
+
+        /// <summary>
+        /// Checks for the existence of a cover image.
+        /// </summary>
+        /// <param name="opfRootDirectory">The root directory in which the OPF file is located.</param>
+        /// <returns>Returns the found cover and its type or null.</returns>
+        public (string MimeType, string Path)? ReadCoverPath(string opfRootDirectory)
+        {
+            var coverImage = ReadEpubCoverInto(opfRootDirectory, "//opf:item[@properties='cover-image']");
+            if (coverImage is not null)
+            {
+                return coverImage;
+            }
+
+            var coverId = ReadEpubCoverInto(opfRootDirectory, "//opf:item[@id='cover' and @media-type='image/*']");
+            if (coverId is not null)
+            {
+                return coverId;
+            }
+
+            var coverImageId = ReadEpubCoverInto(opfRootDirectory, "//opf:item[@id='*cover-image']");
+            if (coverImageId is not null)
+            {
+                return coverImageId;
+            }
+
+            var metaCoverImage = _document.SelectSingleNode("//opf:meta[@name='cover']", _namespaceManager);
+            var content = metaCoverImage?.Attributes?["content"]?.Value;
+            if (string.IsNullOrEmpty(content) || metaCoverImage is null)
+            {
+                return null;
+            }
+
+            var coverPath = Path.Combine("Images", content);
+            var coverFileManifest = _document.SelectSingleNode($"//opf:item[@href='{coverPath}']", _namespaceManager);
+            var mediaType = coverFileManifest?.Attributes?["media-type"]?.Value;
+            if (coverFileManifest?.Attributes is not null && !string.IsNullOrEmpty(mediaType) && IsValidImage(mediaType))
+            {
+                return (mediaType, Path.Combine(opfRootDirectory, coverPath));
+            }
+
+            var coverFileIdManifest = _document.SelectSingleNode($"//opf:item[@id='{content}']", _namespaceManager);
+            if (coverFileIdManifest is not null)
+            {
+                return ReadManifestItem(coverFileIdManifest, opfRootDirectory);
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Read all supported OPF data from the file.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns>The metadata result to update.</returns>
+        public MetadataResult<Book> ReadOpfData(CancellationToken cancellationToken)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+
+            var book = CreateBookFromOpf();
+            var result = new MetadataResult<Book> { Item = book, HasMetadata = true };
+
+            FindAuthors(result);
+            ReadStringInto("//dc:language", language => result.ResultLanguage = language);
+
+            return result;
+        }
+
+        private Book CreateBookFromOpf()
+        {
+            var book = new Book
+            {
+                Name = FindMainTitle(),
+                ForcedSortName = FindSortTitle(),
+            };
+
+            ReadStringInto("//dc:description", summary => book.Overview = summary);
+            ReadStringInto("//dc:publisher", publisher => book.AddStudio(publisher));
+            ReadStringInto("//dc:identifier[@opf:scheme='AMAZON']", amazon => book.SetProviderId("Amazon", amazon));
+            ReadStringInto("//dc:identifier[@opf:scheme='GOOGLE']", google => book.SetProviderId("GoogleBooks", google));
+            ReadStringInto("//dc:identifier[@opf:scheme='ISBN']", isbn => book.SetProviderId("ISBN", isbn));
+
+            ReadStringInto("//dc:date", date =>
+            {
+                if (DateTime.TryParse(date, out var dateValue))
+                {
+                    book.PremiereDate = dateValue.Date;
+                    book.ProductionYear = dateValue.Date.Year;
+                }
+            });
+
+            var genreNodes = _document.SelectNodes("//dc:subject", _namespaceManager);
+
+            if (genreNodes?.Count > 0)
+            {
+                foreach (var node in genreNodes.Cast<XmlNode>().Where(node => !string.IsNullOrEmpty(node.InnerText) && !book.Genres.Contains(node.InnerText)))
+                {
+                    // specification has no rules about content and some books combine every genre into a single element
+                    foreach (var item in node.InnerText.Split(["/", "&", ",", ";", " - "], StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries))
+                    {
+                        book.AddGenre(item);
+                    }
+                }
+            }
+
+            ReadInt32AttributeInto("//opf:meta[@name='calibre:series_index']", index => book.IndexNumber = index);
+            ReadInt32AttributeInto("//opf:meta[@name='calibre:rating']", rating => book.CommunityRating = rating);
+
+            var seriesNameNode = _document.SelectSingleNode("//opf:meta[@name='calibre:series']", _namespaceManager);
+
+            if (!string.IsNullOrEmpty(seriesNameNode?.Attributes?["content"]?.Value))
+            {
+                try
+                {
+                    book.SeriesName = seriesNameNode.Attributes["content"]?.Value;
+                }
+                catch (Exception)
+                {
+                    _logger.LogError("error parsing Calibre series name");
+                }
+            }
+
+            return book;
+        }
+
+        private string FindMainTitle()
+        {
+            var title = string.Empty;
+            var titleTypes = _document.SelectNodes("//opf:meta[@property='title-type']", _namespaceManager);
+
+            if (titleTypes is not null && titleTypes.Count > 0)
+            {
+                foreach (XmlElement titleNode in titleTypes)
+                {
+                    string refines = titleNode.GetAttribute("refines").TrimStart('#');
+                    string titleType = titleNode.InnerText;
+
+                    var titleElement = _document.SelectSingleNode($"//dc:title[@id='{refines}']", _namespaceManager);
+                    if (titleElement is not null && string.Equals(titleType, "main", StringComparison.OrdinalIgnoreCase))
+                    {
+                        title = titleElement.InnerText;
+                    }
+                }
+            }
+
+            // fallback in case there is no main title definition
+            if (string.IsNullOrEmpty(title))
+            {
+                ReadStringInto("//dc:title", titleString => title = titleString);
+            }
+
+            return title;
+        }
+
+        private string? FindSortTitle()
+        {
+            var titleTypes = _document.SelectNodes("//opf:meta[@property='file-as']", _namespaceManager);
+
+            if (titleTypes is not null && titleTypes.Count > 0)
+            {
+                foreach (XmlElement titleNode in titleTypes)
+                {
+                    string refines = titleNode.GetAttribute("refines").TrimStart('#');
+                    string sortTitle = titleNode.InnerText;
+
+                    var titleElement = _document.SelectSingleNode($"//dc:title[@id='{refines}']", _namespaceManager);
+                    if (titleElement is not null)
+                    {
+                        return sortTitle;
+                    }
+                }
+            }
+
+            // search for OPF 2.0 style title_sort node
+            var resultElement = _document.SelectSingleNode("//opf:meta[@name='calibre:title_sort']", _namespaceManager);
+            var titleSort = resultElement?.Attributes?["content"]?.Value;
+
+            return titleSort;
+        }
+
+        private void FindAuthors(MetadataResult<Book> book)
+        {
+            var resultElement = _document.SelectNodes("//dc:creator", _namespaceManager);
+
+            if (resultElement != null && resultElement.Count > 0)
+            {
+                foreach (XmlElement creator in resultElement)
+                {
+                    var creatorName = creator.InnerText;
+                    var role = creator.GetAttribute("opf:role");
+                    var person = new PersonInfo { Name = creatorName, Type = GetRole(role) };
+
+                    book.AddPerson(person);
+                }
+            }
+        }
+
+        private PersonKind GetRole(string? role)
+        {
+            switch (role)
+            {
+                case "arr":
+                    return PersonKind.Arranger;
+                case "art":
+                    return PersonKind.Artist;
+                case "aut":
+                case "aqt":
+                case "aft":
+                case "aui":
+                default:
+                    return PersonKind.Author;
+                case "edt":
+                    return PersonKind.Editor;
+                case "ill":
+                    return PersonKind.Illustrator;
+                case "lyr":
+                    return PersonKind.Lyricist;
+                case "mus":
+                    return PersonKind.AlbumArtist;
+                case "oth":
+                    return PersonKind.Unknown;
+                case "trl":
+                    return PersonKind.Translator;
+            }
+        }
+
+        private void ReadStringInto(string xmlPath, Action<string> commitResult)
+        {
+            var resultElement = _document.SelectSingleNode(xmlPath, _namespaceManager);
+            if (resultElement is not null && !string.IsNullOrWhiteSpace(resultElement.InnerText))
+            {
+                commitResult(resultElement.InnerText);
+            }
+        }
+
+        private void ReadInt32AttributeInto(string xmlPath, Action<int> commitResult)
+        {
+            var resultElement = _document.SelectSingleNode(xmlPath, _namespaceManager);
+            var resultValue = resultElement?.Attributes?["content"]?.Value;
+
+            if (!string.IsNullOrEmpty(resultValue))
+            {
+                try
+                {
+                    commitResult(Convert.ToInt32(Convert.ToDouble(resultValue, CultureInfo.InvariantCulture)));
+                }
+                catch (Exception e)
+                {
+                    _logger.LogError(e, "error converting to Int32");
+                }
+            }
+        }
+
+        private (string MimeType, string Path)? ReadEpubCoverInto(string opfRootDirectory, string xmlPath)
+        {
+            var resultElement = _document.SelectSingleNode(xmlPath, _namespaceManager);
+
+            if (resultElement is not null)
+            {
+                return ReadManifestItem(resultElement, opfRootDirectory);
+            }
+
+            return null;
+        }
+
+        private (string MimeType, string Path)? ReadManifestItem(XmlNode manifestNode, string opfRootDirectory)
+        {
+            var href = manifestNode.Attributes?["href"]?.Value;
+            var mediaType = manifestNode.Attributes?["media-type"]?.Value;
+
+            if (string.IsNullOrEmpty(href) || string.IsNullOrEmpty(mediaType) || !IsValidImage(mediaType))
+            {
+                return null;
+            }
+
+            var coverPath = Path.Combine(opfRootDirectory, href);
+
+            return (MimeType: mediaType, Path: coverPath);
+        }
+
+        private static bool IsValidImage(string? mimeType)
+        {
+            return !string.IsNullOrEmpty(mimeType) && !string.IsNullOrWhiteSpace(MimeTypes.ToExtension(mimeType));
+        }
+    }
+}